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NASA Technical Reports Server (NTRS)
Wells, Dennis L. (Inventor)
This invention relates to techniques for fabricating hour glass throat or convergent divergent nozzle shapes, and more particularly to new and improved techniques for forming rocket nozzles from electrically conductive material and forming cooling channels in the wall thereof. The concept of positioning a block of electrically conductive material so that its axis is set at a predetermined skew angle with relation to a travelling electron discharge machine electrode and thereafter revolving the body about its own axis to generate a hyperbolic surface of revolution, either internal or external is novel. The method will generate a rocket nozzle which may be provided with cooling channels using the same control and positioning system. The configuration of the cooling channels so produced are unique and novel. Also the method is adaptable to nonmetallic material using analogous cutting tools, such as, water jet, laser, abrasive wire and hot wire.
NASA Technical Reports Server (NTRS)
Wells, Dennis L. (Inventor)
A block of electrically conductive material which is to be formed into a body with internal and/or external surfaces that approximate hyperboloids of one sheet is placed so that its axis is set at a predetermined skew angle with relation to a traveling EDM electrode wire. The electrode wire is then moved into cutting proximity of the body wire. Thereafter, by revolving the body about its own axis, the external and/or internal surfaces of the body will be cut into an approximate hyperbolic surface of revolution depending upon whether the body is positioned with the cutting wire outside of the body or in a previously formed longitudinal passage in the body. As an alternative technique, elongated channels can also be cut into the wall of the body by successively orienting the body to a selected number of angular positions, with the electrode wire being either outside of the body or in a previously formed passage in the body. At each of these angular positions, the electrode wire is moved orthogonally with respect to the axis of the wire, while both the body axis skew angle and the rotational position about that axis is controlled by cutting a channel or groove in the body to relieve stresses in the body material or to convey a coolant fluid.
NASA Technical Reports Server (NTRS)
Wells, Dennis L. (Inventor)
A block of electrically-conductive material which is to be formed into a body with internal and/or external surfaces that approximate hyperboloids of one sheet is placed so that its axis is set at a predetermined skew angle with relation to a travelling EDM electrode wire and the electrode wire is then moved into cutting proximity of the body. Thereafter, by revolving the body about its own axis, the external and/or internal surfaces of the body will be cut into an approximate hyperbolic surface of revolution depending upon whether the body is positioned with the cutting wire outside of the body or in a previously-formed longitudinal passage in the body. As an alternative technique, elongated channels can also be cut into the walls of the body by successively orienting the body to a selected number of angular positions with the electrode wire being either outside of the body or in a previously-formed passage in the body. At each of these angular positions, the electrode wire is moved orthogonally with respect to the axis of the wire while both the body axis skew angle and the rotational position about that axis are controlled for cutting a channel or groove in the body as required to relieve stresses in the material of the body or to convey a coolant fluid.
Micro-fabrication Techniques for Target Components
Miles, R; Hamilton, J; Crawford, J; Ratti, S; Trevino, J; Graff, T; Stockton, C; Harvey, C
Micro-fabrication techniques, derived from the semi-conductor industry, can be used to make a variety of useful mechanical components for targets. A selection of these components including supporting cooling arms for prototype cryogenic inertial confinement fusion targets, stepped and graded density targets for materials dynamics experiments are described. Micro-fabrication enables cost-effective, simultaneous fabrication of multiple high-precision components with complex geometries. Micro-fabrication techniques such as thin-film deposition, photo-lithographic patterning and etch processes normally used in the semi-conductor manufacture industry, can be exploited to make useful mechanical target components. Micro-fabrication processes have in recent years been used to create a number of micro-electro-mechanical systems (MEMS) components such as pressure sensors, accelerometers, ink jet printer heads, microfluidics platforms and the like. These techniques consist primarily of deposition of thin films of material, photo-lithographic patterning and etching processes performed sequentially to produce three dimensional structures using essentially planar processes. While the planar technology can be limiting in terms of the possible geometries of the final product, advantages of using these techniques include the ability to make multiple complex structures simultaneously and cost-effectively. Target components fabricated using these techniques include the supporting cooling arms for cryogenic prototype fusion ignition targets, stepped targets for equation-of-state experiments, and graded density reservoirs for material strength experiments.
Fabrication techniques for very fast diffractive lenses
NASA Technical Reports Server (NTRS)
Tai, Anthony M.; Marron, Joseph C.
Aspheric lenses with arbitrary phase functions can be fabricated on thin light weight substrates via the binary optics fabrication technique. However, it is difficult and costly to fabricate a fast lens (f/number less than 1) for use as the shorter wavelengths. The pitch of the masks and the alignment accuracy must be very fine. For a large lens, the space-bandwidth product of the element can also become impractically large. In this paper, two alternate approaches for the fabrication of fast aspheric diffractive lenses are described. The first approach fabricates the diffractive lens interferometrically, utilizing a spherical wavefront to provide the optical power of the lens and a computer generated hologram to create the aspheric components. The second approach fabricates the aspheric diffractive lens in the form if a higher order kinoform which trades groove profile fidelity for coarser feature size. The design and implementation issues for these two fabrication techniques are discussed.
Monitoring by Control Technique - Fabric Filters
Stationary source emissions monitoring is required to demonstrate that a source is meeting the requirements in Federal or state rules. This page is about fabric filter control techniques used to reduce pollutant emissions.
Comparison of fabrication techniques for hollow retroreflectors
NASA Astrophysics Data System (ADS)
Preston, Alix; Merkowitz, Stephen
Despite the wide usage of hollow retroreflectors, there is limited literature involving their fabrication techniques and only two documented construction methods could be found. One consists of an adjustable fixture that allows for the independent alignment of each mirror, while the other consists of a modified solid retroreflector that is used as a mandrel. Although both methods were shown to produce hollow retroreflectors with arc second dihedral angle errors, a comparison and analysis of each method could not be found, which makes it difficult to ascertain which method would be better suited to use for precision-aligned retroreflectors. Although epoxy bonding is generally the preferred method to adhere the three mirrors, a relatively new method known as hydroxide-catalysis bonding (HCB) presents several potential advantages over epoxy bonding. HCB has been used to bond several optical components for space-based missions, but has never been applied for construction of hollow retroreflectors. We examine the benefits and limitations of each bonding fixture as well as the present results and analysis of hollow retroreflectors made using both epoxy and HCB techniques.
A photolithographic fabrication technique for magnetohydrodynamic micropumps
NASA Astrophysics Data System (ADS)
Kuenstner, Stephen; Baylor, Martha-Elizabeth
Magnetohydrodynamic (MHD) devices use perpendicular electric and magnetic fields to exert a Lorentz body force on a conducting fluid. Miniaturized MHD devices have been used to create pumps, stirrers, heat exchangers, and microfluidic networks. Compared to mechanical micropumps, MHD micropumps are appealing because they require no moving parts, which simplifies fabrication, and because they are amenable to electronic control. This abstract reports the fabrication and testing of a centimeter-scale MHD pump using a thiol-ene/methacrylate-based photopolymer and mask-based photolithographic technique. Pumps like this one could simplify the fabrication of sophisticated optofluidic devices, including liquid-core, liquid cladding (L2) waveguides, which are usually created with PDMS using stamps, or etched into silicon wafers. The photolithographic technique demonstrated here requires only one masking step to create fluid channels with complex geometries.
Technology development of fabrication techniques for advanced solar dynamic concentrators
NASA Technical Reports Server (NTRS)
Richter, Scott W.
The objective of the advanced concentrator program is to develop the technology that will lead to lightweight, highly reflective, accurate, scaleable, and long lived space solar dynamic concentrators. The advanced concentrator program encompasses new and innovative concepts, fabrication techniques, materials selection, and simulated space environmental testing. Fabrication techniques include methods of fabricating the substrates and coating substrate surfaces to produce high quality optical surfaces, acceptable for further coating with vapor deposited optical films. The selected materials to obtain a high quality optical surface include microsheet glass and Eccocoat EP-3 epoxy, with DC-93-500 selected as a candidate silicone adhesive and levelizing layer. The following procedures are defined: cutting, cleaning, forming, and bonding microsheet glass. Procedures are also defined for surface cleaning, and EP-3 epoxy application. The results and analyses from atomic oxygen and thermal cycling tests are used to determine the effects of orbital conditions in a space environment.
Electrohydrodynamics: A facile technique to fabricate drug delivery systems
Chakraborty, Syandan; Liao, I-Chien; Adler, Andrew; Leong, Kam W.
Electrospinning and electrospraying are facile electrohydrodynamic fabrication methods that can generate drug delivery systems (DDS) through a one-step process. The nano-structured fiber and particle morphologies produced by these techniques offer tunable release kinetics applicable to diverse biomedical applications. Coaxial-electrospinning/electrospraying, a relatively new technique of fabricating core-shell fibers/particles have added to the versatility of these DDS by affording a near zero-order drug release kinetics, dampening of burst release, and applicability to a wider range of bioactive agents. Controllable electrospinning/spraying of fibers and particles and subsequent drug release from these chiefly polymeric vehicles depends on well-defined solution and process parameters. The additional drug delivery capability from electrospun fibers can further enhance the material's functionality in tissue engineering applications. This review discusses the state-of-the-art of using electrohydrodynamic technique to generate nano-fiber/particles as drug delivery devices. PMID:19651167
Biomolecule immobilization techniques for bioactive paper fabrication.
Kong, Fanzhi; Hu, Yim Fun
Research into paper-based sensors or functional materials that can perform analytical functions with active recognition capabilities is rapidly expanding, and significant research effort has been made into the design and fabrication of bioactive paper at the biosensor level to detect potential health hazards. A key step in the fabrication of bioactive paper is the design of the experimental and operational procedures for the immobilization of biomolecules such as antibodies, enzymes, phages, cells, proteins, synthetic polymers and DNA aptamers on a suitably prepared paper membrane. The immobilization methods are concisely categorized into physical absorption, bioactive ink entrapment, bioaffinity attachment and covalent chemical bonding immobilization. Each method has individual immobilization characteristics. Although every biomolecule-paper combination has to be optimized before use, the bioactive ink entrapment method is the most commonly used approach owing to its general applicability and biocompatibility. Currently, there are four common applications of bioactive paper: (1) paper-based bioassay or paper-based analytical devices for sample conditioning; (2) counterfeiting and countertempering in the packaging and construction industries; (3) pathogen detection for food and water quality monitoring; and (4) deactivation of pathogenic bacteria using antimicrobial paper. This article reviews and compares the different biomolecule immobilization techniques and discusses current trends. Current, emerging and future applications of bioactive paper are also discussed.
Advanced fabrication techniques for cooled engine structures
NASA Technical Reports Server (NTRS)
Buchmann, O. A.
An improved design for regeneratively cooled engine structures was identified. This design uses photochemically machined (PCM) coolant passages. It permits the braze joint to be placed in a relatively cool area, remote from the critical hot face sheet. The geometry of the passages at the face sheet also minimizes stress concentration and, therefore, enhances the low cycle fatigue performance. The two most promising alloys identified for this application are Inconel 617 and Nickel 201. Inconel 617 was selected because it has excellent creep rupture properties, while Nickel 201 was selected because of its predicted good performance under low cycle fatigue loading. The fabrication of the PCM coolant passages in both Inconel 617 and Nickel 201 was successfully developed. During fabrication of Inconel 617, undesirable characteristics were observed in the braze joints. A development program to resolve this condition was undertaken and led to definition of an isothermal solidification process for joining Inconel 617 panels. This process produced joints which approach parent metal strength and homogeneity.
Investigation of electroforming techniques. [fabrication of regeneratively cooled thrust chambers
NASA Technical Reports Server (NTRS)
Malone, G. A.
Copper and nickel electroforming was examined for the purpose of establishing the necessary processes and procedures for repeatable, successful fabrication of the outer structures of regeneratively cooled thrust chambers. The selection of electrolytes for copper and nickel deposition is described. The development studies performed to refine and complete the processes necessary for successful chamber shell fabrication and the testing employed to verify the applicability of the processes and procedures to small scale hardware are described. Specifications were developed to afford a guideline for the electroforming of high quality outer shells on regeneratively cooled thrust chamber liners. Test results indicated repeatable mechanical properties could be produced in copper deposits from the copper sulfate electrolyte with periodic current reversal and in nickel deposits from the sulfamate solution. Use of inert, removable channel fillers and the conductivizing of such is described. Techniques (verified by test) which produce high integrity bonds to copper and copper alloy liners are discussed.
High volume fabrication of laser targets using MEMS techniques
NASA Astrophysics Data System (ADS)
Spindloe, C.; Arthur, G.; Hall, F.; Tomlinson, S.; Potter, R.; Kar, S.; Green, J.; Higginbotham, A.; Booth, N.; Tolley, M. K.
The latest techniques for the fabrication of high power laser targets, using processes developed for the manufacture of Micro-Electro-Mechanical System (MEMS) devices are discussed. These laser targets are designed to meet the needs of the increased shot numbers that are available in the latest design of laser facilities. Traditionally laser targets have been fabricated using conventional machining or coarse etching processes and have been produced in quantities of 10s to low 100s. Such targets can be used for high complexity experiments such as Inertial Fusion Energy (IFE) studies and can have many complex components that need assembling and characterisation with high precision. Using the techniques that are common to MEMS devices and integrating these with an existing target fabrication capability we are able to manufacture and deliver targets to these systems. It also enables us to manufacture novel targets that have not been possible using other techniques. In addition, developments in the positioning systems that are required to deliver these targets to the laser focus are also required and a system to deliver the target to a focus of an F2 beam at 0.1Hz is discussed.
48 CFR 252.236-7013 - Requirement for competition opportunity for American steel producers, fabricators, and...
Code of Federal Regulations, 2012 CFR
... competition opportunity for American steel producers, fabricators, and manufacturers. 252.236-7013 Section 252....236-7013 Requirement for competition opportunity for American steel producers, fabricators, and... for American Steel Producers, Fabricators, and Manufacturers (JAN 2009) (a) Definition....
48 CFR 252.236-7013 - Requirement for competition opportunity for American steel producers, fabricators, and...
Code of Federal Regulations, 2013 CFR
... competition opportunity for American steel producers, fabricators, and manufacturers. 252.236-7013 Section 252....236-7013 Requirement for competition opportunity for American steel producers, fabricators, and... for American Steel Producers, Fabricators, and Manufacturers (JUN 2013JAN 2009) (a)...
48 CFR 252.236-7013 - Requirement for competition opportunity for american steel producers, fabricators, and...
Code of Federal Regulations, 2011 CFR
... competition opportunity for american steel producers, fabricators, and manufacturers. 252.236-7013 Section 252....236-7013 Requirement for competition opportunity for american steel producers, fabricators, and... FOR AMERICAN STEEL PRODUCERS, FABRICATORS, AND MANUFACTURERS (JAN 2009) (a) Definition....
48 CFR 252.236-7013 - Requirement for competition opportunity for American steel producers, fabricators, and...
Code of Federal Regulations, 2014 CFR
... competition opportunity for American steel producers, fabricators, and manufacturers. 252.236-7013 Section 252....236-7013 Requirement for competition opportunity for American steel producers, fabricators, and... for American Steel Producers, Fabricators, and Manufacturers (JUN 2013) (a) Definition....
48 CFR 252.236-7013 - Requirement for competition opportunity for american steel producers, fabricators, and...
Code of Federal Regulations, 2010 CFR
... competition opportunity for american steel producers, fabricators, and manufacturers. 252.236-7013 Section 252....236-7013 Requirement for competition opportunity for american steel producers, fabricators, and... FOR AMERICAN STEEL PRODUCERS, FABRICATORS, AND MANUFACTURERS (JAN 2009) (a) Definition....
Development of a Direct Fabrication Technique for Full-Shell X-Ray Optics
NASA Technical Reports Server (NTRS)
Gubarev, M.; Kolodziejczak, J. K.; Griffith, C.; Roche, J.; Smith, W. S.; Kester, T.; Atkins, C.; Arnold, W.; Ramsey, B.
Future astrophysical missions will require fabrication technology capable of producing high angular resolution x-ray optics. A full-shell direct fabrication approach using modern robotic polishing machines has the potential for producing high resolution, light-weight and affordable x-ray mirrors that can be nested to produce large collecting area. This approach to mirror fabrication, based on the use of the metal substrates coated with nickel phosphorous alloy, is being pursued at MSFC. The design of the polishing fixtures for the direct fabrication, the surface figure metrology techniques used and the results of the polishing experiments are presented.
Design for producing fiberglass fabric in a lunar environment
NASA Technical Reports Server (NTRS)
Dorrity, J. Lewis; Patel, Suneer; Benson, Rafer M.; Johnson, Michael C.; Storey, Mark A.; Tran, Dai T.; Zahr, Thomas A.; Causby, Dana R.
The purpose of this project was to design a method of producing a fabric material on the lunar surface from readily available glass fibers. Various methods for forming fabrics were analyzed to determine which methods were appropriate for the lunar conditions. A nonwoven process was determined to be the most suitable process for making a fabric material out of fiberglass under these conditions. Various resins were considered for adhering the fibers. A single thermoplastic resin (AURUM) was found to be the only applicable resin. The end product of the process was determined to be suitable for use as a roadway surfacing material, canopy materials, reflective material, or packaging material. A cost analysis of the lunar process versus shipping the end-product from the earth suggests that the lunar formation is highly feasible. A design for a lunar, nonwoven process was determined and included in the following document.
Design for producing fiberglass fabric in a lunar environment
NASA Technical Reports Server (NTRS)
Benson, Rafer M.; Causby, Dana R.; Johnson, Michael C.; Storey, Mark A.; Tran, Dal T.; Zahr, Thomas A.
The purpose of this project was to design a method of producing a fabric material on the lunar surface from readily available glass fibers. Various methods for forming fabrics were analyzed to determine which methods were appropriate for the lunar conditions. A nonwoven process was determined to be the most suitable process for making a fabric material out of fiberglass under these conditions. Various resins were considered for adhering the fibers. A single thermoplastic resin (AURUM) was found to be the only applicable resin. The end product of the process was determined to be suitable for use as a roadway surfacing material, canopy material, reflective material, or packaging material. A cost analysis of the lunar process versus shipping the end-product from the Earth suggests that the lunar formation is highly feasible. A design for a lunar, nonwoven process was determined and is included.
Electromagnetic levitation coil fabrication technique for MSFC containerless processing facilities
NASA Technical Reports Server (NTRS)
Ethridge, E. C.; Theiss, J.; Curreri, P. A.; Abbaschian, G. J.
A technique is described for more reproducible fabrication of electromagnetic levitation coils. A split mandrel was developed upon which the coil is wound. After fabrication the mandrel can be disassembled to remove it from the coil. Previously, a full day was required to fabricate a levitation coil and the success rate for a functional coil was only 50 percent. About eight coils may be completed in one day using the technique developed and 95 percent of them are good levitation coils.
Contact-eutectic-lens fabrication technique
NASA Technical Reports Server (NTRS)
Allen, F. G.; Yue, A. S.; Yu, J. G.
Method enables use of crystal or semiconductor materials with selective spectral-response characteristics (ultraviolet, visible, or infrared wavelengths) in fabrication of contact lenses, reading glasses, and photographic processing equipment.
Fabrication techniques developed for small- diameter, thin-wall tungsten and tungsten alloy tubing
NASA Technical Reports Server (NTRS)
Brillhart, D. C.; Burt, W. R.; Karasek, F. J.; Mayfield, R. M.
Report describes methods for the fabrication of tungsten and tungsten alloys into small-diameter, thin-wall tubing of nuclear quality. The tungsten, or tungsten alloy tube blanks are produced by double extrusion. Plug-drawing has emerged as an excellent secondary fabrication technique for the reduction of the overall tube dimensions.
Fabrication of a wearable fabric tactile sensor produced by artificial hollow fiber
NASA Astrophysics Data System (ADS)
Hasegawa, Yoshihiro; Shikida, Mitsuhiro; Ogura, Daisuke; Suzuki, Yoshitaka; Sato, Kazuo
An artificial-hollow-fiber structure as a new material for MEMS was developed and applied to a novel type of fabric tactile sensor. The artificial hollow fiber was fabricated by uniformly deposited metal and insulation layers on the surface of an elastic tube. A special rotating mechanism for uniformly depositing a metal layer on the tube surface during sputtering was developed. A rectangular-shaped fabric tactile sensor was produced by combining artificial hollow fibers and typical cotton yarns, like a cloth. The sensor can detect a contact force by measuring changes in capacitance at all intersection points of the artificial hollow fibers. Two different types of wearable-tactile-sensor glove, a patched type and a direct knit type, were also fabricated, and it was confirmed that both types can detect a normal load by measuring the capacitance change.
Improved fabrication techniques for infrared bolometers
NASA Technical Reports Server (NTRS)
Lange, A. E.; Mcbride, S. E.; Richards, P. L.; Haller, E. E.; Kreysa, E.
Ion implantation and sputter metallization are used to produce ohmic electrical contacts to Ge:Ga chips. The method is shown to give a high yield of small monolithic bolometers with very little low-frequency noise. It is noted that when one of the chips is used as the thermometric element of a composite bolometer it must be bonded to a dielectric substrate. The thermal resistance of the conventional epoxy bond is measured and found to be undesirably large. A procedure for soldering the chip to a metallized portion of the substrate in such a way as to reduce this resistance is outlined. An evaluation is made of the contribution of the metal film absorber to the heat capacity of a composite bolometer. It is found that the heat capacity of a NiCr absorber at 1.3 K can dominate the bolometer performance. A Bi absorber possesses significantly lower heat capacity. A low-temperature blackbody calibrator is built to measure the optical responsivity of bolometers. A composite bolometer system with a throughput of approximately 0.1 sr sq cm is constructed using the new techniques. The noise in this bolometer is white above 2.5 Hz and is slightly below the value predicted by thermodynamic equilibrium theory.
Composite material fabrication techniques. CRADA final report
Frame, B J; Paulauskas, F L; Miller, J; Parzych, W
This report describes a low cost method of fabricating components for mockups and training simulators used in the transportation industry. This technology was developed jointly by the Oak Ridge National Laboratory (ORNL) and Metters Industries, Incorporated (MI) as part of a Cooperative Research and Development Agreement (CRADA) ORNL94-0288 sponsored by the Department of Energy (DOE) Office of Economic Impace and Diversity Minority Business Technology Transfer Consortium. The technology involves fabricating component replicas from fiberglass/epoxy composites using a resin transfer molding (RTM) process. The original components are used as masters to fabricate the molds. The molding process yields parts that duplicate the significant dimensional requirements of the original component while still parts that duplicate the significant dimensional requirements of the original component while still providing adequate strength and stiffness for use in training simulators. This technology permits MI to overcome an acute shortage in surplus military hardware available to them for use in manufacturing training simulators. In addition, the cost of the molded fiberglass components is expected to be less than that of procuring the original components from the military.
Advanced Manufacturing Techniques Demonstrated for Fabricating Developmental Hardware
NASA Technical Reports Server (NTRS)
Redding, Chip
NASA Glenn Research Center's Engineering Development Division has been working in support of innovative gas turbine engine systems under development by Glenn's Combustion Branch. These one-of-a-kind components require operation under extreme conditions. High-temperature ceramics were chosen for fabrication was because of the hostile operating environment. During the designing process, it became apparent that traditional machining techniques would not be adequate to produce the small, intricate features for the conceptual design, which was to be produced by stacking over a dozen thin layers with many small features that would then be aligned and bonded together into a one-piece unit. Instead of using traditional machining, we produced computer models in Pro/ENGINEER (Parametric Technology Corporation (PTC), Needham, MA) to the specifications of the research engineer. The computer models were exported in stereolithography standard (STL) format and used to produce full-size rapid prototype polymer models. These semi-opaque plastic models were used for visualization and design verification. The computer models also were exported in International Graphics Exchange Specification (IGES) format and sent to Glenn's Thermal/Fluids Design & Analysis Branch and Applied Structural Mechanics Branch for profiling heat transfer and mechanical strength analysis.
Fabrication techniques for septum magnets at the APS.
Jaski, M.; Thompson, K.; Kim, S.; Friedsam, H.; Toter, W.; Humbert, J.
The design, construction, and installation of pulsed septum magnets for particle accelerators presents many challenges for the magnet engineer. Issues associated with magnet core structure design, component alignment, weldment design, and electrical insulation choices are among those requiring careful attention. The designs of the six septum magnets required for the APS facility have evolved since operation began in 1996. Improvements in the designs have provided better injection/extraction performance parameters and extended the machine reliability to meet the requirements of a world-class, third-generation synchrotron radiation facility. Details of the techniques used to address issues involved in producing septum magnets at the APS are described here to aid magnet engineers in the fabrication of future septum magnets.
Fabrication of a Bronze Age Sword using Ancient Techniques
NASA Astrophysics Data System (ADS)
Sapiro, David; Webler, Bryan
A khopesh was cast and forged for the TMS 2016 Bladesmithing Symposium. The khopesh was the first sword style, originating during the Bronze Age in the Near East. The manufacturing process used in this study closely followed Bronze Age techniques to determine the plausibility of open mold casting coupled with cold work and annealing cycles. Forging and annealing cycles substantially increased blade strength and diminished intergranular δ-phase inclusions. While a functional blade was not completed due to casting defects, the process gives valuable insight into the effort required to fabricate a khopesh during the Bronze Age. Forging and annealing cycles following casting were necessary to produce the mechanical properties desired in a sword.
Advanced fabrication techniques for hydrogen-cooled engine structures
NASA Technical Reports Server (NTRS)
Buchmann, O. A.; Arefian, V. V.; Warren, H. A.; Vuigner, A. A.; Pohlman, M. J.
Described is a program for development of coolant passage geometries, material systems, and joining processes that will produce long-life hydrogen-cooled structures for scramjet applications. Tests were performed to establish basic material properties, and samples constructed and evaluated to substantiate fabrication processes and inspection techniques. Results of the study show that the basic goal of increasing the life of hydrogen-cooled structures two orders of magnitude relative to that of the Hypersonic Research Engine can be reached with available means. Estimated life is 19000 cycles for the channels and 16000 cycles for pin-fin coolant passage configurations using Nickel 201. Additional research is required to establish the fatigue characteristics of dissimilar-metal coolant passages (Nickel 201/Inconel 718) and to investigate the embrittling effects of the hydrogen coolant.
High-throughput plastic microlenses fabricated using microinjection molding techniques
NASA Astrophysics Data System (ADS)
Appasamy, Sreeram; Li, Weizhuo; Lee, Se Hwan; Boyd, Joseph T.; Ahn, Chong H.
A novel fabrication scheme to develop high-throughput plastic microlenses using injection-molding techniques is realized. The initial microlens mold is fabricated using the well-known reflow technique. The reflow process is optimized to obtain reliable and repeatable microlens patterns. The master mold insert for the injection-molding process is fabricated using metal electroforming. The electroplating process is optimized for obtaining a low stress electroform. Two new plastic materials, cyclo olefin copolymer (COC) and Poly IR 2 are introduced in this work for fabricating microlenses. The plastic microlenses have been characterized for their focal lengths that range from 200 µm to 1.9 mm. This technique enables high-volume production of plastic microlenses with cycle times for a single chip being of the order of 60 s.
NASA Technical Reports Server (NTRS)
Angel, Roger; Helms, Richard; Bilbro, Jim; Brown, Norman; Eng, Sverre; Hinman, Steve; Hull-Allen, Greg; Jacobs, Stephen; Keim, Robert; Ulmer, Melville
What aspects of optical fabrication technology need to be developed so as to facilitate existing planned missions, or enable new ones? Throughout the submillimeter to UV wavelengths, the common goal is to push technology to the limits to make the largest possible apertures that are diffraction limited. At any one wavelength, the accuracy of the surface must be better than lambda/30 (rms error). The wavelength range is huge, covering four orders of magnitude from 1 mm to 100 nm. At the longer wavelengths, diffraction limited surfaces can be shaped with relatively crude techniques. The challenge in their fabrication is to make as large as possible a reflector, given the weight and volume constraints of the launch vehicle. The limited cargo diameter of the shuttle has led in the past to emphasis on deployable or erectable concepts such as the Large Deployable Reflector (LDR), which was studied by NASA for a submillimeter astrophysics mission. Replication techniques that can be used to produce light, low-cost reflecting panels are of great interest for this class of mission. At shorter wavelengths, in the optical and ultraviolet, optical fabrication will tax to the limit the most refined polishing methods. Methods of mechanical and thermal stabilization of the substrate will be severely stressed. In the thermal infrared, the need for large aperture is tempered by the even stronger need to control the telescope's thermal emission by cooled or cryogenic operation. Thus, the SIRTF mirror at 1 meter is not large and does not require unusually high accuracy, but the fabrication process must produce a mirror that is the right shape at a temperature of 4 K. Future large cooled mirrors will present more severe problems, especially if they must also be accurate enough to work at optical wavelengths. At the very shortest wavelengths accessible to reflecting optics, in the x-ray domain, the very low count fluxes of high energy photons place a premium on the collecting area. It is
NASA Astrophysics Data System (ADS)
Angel, Roger; Helms, Richard; Bilbro, Jim; Brown, Norman; Eng, Sverre; Hinman, Steve; Hull-Allen, Greg; Jacobs, Stephen; Keim, Robert; Ulmer, Melville
What aspects of optical fabrication technology need to be developed so as to facilitate existing planned missions, or enable new ones? Throughout the submillimeter to UV wavelengths, the common goal is to push technology to the limits to make the largest possible apertures that are diffraction limited. At any one wavelength, the accuracy of the surface must be better than lambda/30 (rms error). The wavelength range is huge, covering four orders of magnitude from 1 mm to 100 nm. At the longer wavelengths, diffraction limited surfaces can be shaped with relatively crude techniques. The challenge in their fabrication is to make as large as possible a reflector, given the weight and volume constraints of the launch vehicle. The limited cargo diameter of the shuttle has led in the past to emphasis on deployable or erectable concepts such as the Large Deployable Reflector (LDR), which was studied by NASA for a submillimeter astrophysics mission. Replication techniques that can be used to produce light, low-cost reflecting panels are of great interest for this class of mission. At shorter wavelengths, in the optical and ultraviolet, optical fabrication will tax to the limit the most refined polishing methods. Methods of mechanical and thermal stabilization of the substrate will be severely stressed. In the thermal infrared, the need for large aperture is tempered by the even stronger need to control the telescope's thermal emission by cooled or cryogenic operation. Thus, the SIRTF mirror at 1 meter is not large and does not require unusually high accuracy, but the fabrication process must produce a mirror that is the right shape at a temperature of 4 K. Future large cooled mirrors will present more severe problems, especially if they must also be accurate enough to work at optical wavelengths. At the very shortest wavelengths accessible to reflecting optics, in the x-ray domain, the very low count fluxes of high energy photons place a premium on the collecting area. It is
Fabrication and characterization of oxide fibrous monoliths produced by coextrusion.
Polzin, B. J.
Unidirectional fibrous monoliths (FMs) based on dense, strong ZrSiO{sub 4} cells that were surrounded by a porous, weaker ZrSiO{sub 4} cell-boundary phase were fabricated. A duplex filament was coextruded, sectioned, bundled, and the resulting bundle was extruded to form a new filament. This filament was cut and packed into plate and bar dies to produce FM test specimens. Four-point flexural tests were conducted on the cell material, cell-boundary material, and FMs. After testing, fracture surfaces and cross sections were examined by scanning electron microscopy. The FMs exhibited graceful failure in flexural testing, and the fracture surfaces exhibited clear evidence of crack deflection and delamination.
A Comparison of Fabrication Techniques for Hollow Retroreflectors
NASA Technical Reports Server (NTRS)
Preston, Alix; Merkowitz, Stephen
Despite the wide usage of hollow retroreflectors, there is limited literature involving their fabrication techniques and only two documented construction methods could be found. One consists of an adjustable fixture that allows for the independent alignment of each mirror, while the other consists of a modified solid retroreflector that is used as a mandrel. Although both methods were shown to produce hollow retroreflectors with arcsecond dihedral angle errors, a comparison and analysis of each method could not be found which makes it difficult to ascertain which method would be better suited to use for precision-aligned retroreflectors. Although epoxy bonding is generally the preferred method to adhere the three mirrors, a relatively new method known as hydroxide-catalysis bonding (HCB) presents several potential advantages over epoxy bonding. HCB has been used to bond several optical components for space-based missions, but has never been applied for construction of hollow retroreflectors. In this paper we examine the benefits and limitations of each bonding fixture as well as present results and analysis of hollow retroreflectors made using both epoxy and HCB techniques.
Fabricating an Accurate Implant Master Cast: A Technique Report.
Balshi, Thomas J; Wolfinger, Glenn J; Alfano, Stephen G; Cacovean, Jeannine N; Balshi, Stephen F
The technique for fabricating an accurate implant master cast following the 12-week healing period after Teeth in a Day® dental implant surgery is detailed. The clinical, functional, and esthetic details captured during the final master impression are vital to creating an accurate master cast. This technique uses the properties of the all-acrylic resin interim prosthesis to capture these details. This impression captures the relationship between the remodeled soft tissue and the interim prosthesis. This provides the laboratory technician with an accurate orientation of the implant replicas in the master cast with which a passive fitting restoration can be fabricated.
Development of a Fluid Structures Interaction Test Technique for Fabrics
NASA Technical Reports Server (NTRS)
Zilliac, Gregory G.; Heineck, James T.; Schairer, Edward T.; Mosher, Robert N.; Garbeff, Theodore Joseph
Application of fluid structures interaction (FSI) computational techniques to configurations of interest to the entry, descent and landing (EDL) community is limited by two factors - limited characterization of the material properties for fabrics of interest and insufficient experimental data to validate the FSI codes. Recently ILC Dover Inc. performed standard tests to characterize the static stress-strain response of four candidate fabrics for use in EDL applications. The objective of the tests described here is to address the need for a FSI dataset for CFD validation purposes. To reach this objective, the structural response of fabrics was measured in a very simple aerodynamic environment with well controlled boundary conditions. Two test series were undertaken. The first series covered a range of tunnel conditions and the second focused on conditions that resulted in fabric panel buckling.
Rapid Fabrication Techniques for Liquid Rocket Channel Wall Nozzles
NASA Technical Reports Server (NTRS)
Gradl, Paul R.
The functions of a regeneratively-cooled nozzle are to (1) expand combustion gases to increase exhaust gas velocity while, (2) maintaining adequate wall temperatures to prevent structural failure, and (3) transfer heat from the hot gases to the coolant fluid to promote injector performance and stability. Regeneratively-cooled nozzles are grouped into two categories: tube-wall nozzles and channel wall nozzles. A channel wall nozzle is designed with an internal liner containing a series of integral coolant channels that are closed out with an external jacket. Manifolds are attached at each end of the nozzle to distribute coolant to and away from the channels. A variety of manufacturing techniques have been explored for channel wall nozzles, including state of the art laser-welded closeouts and pressure-assisted braze closeouts. This paper discusses techniques that NASA MSFC is evaluating for rapid fabrication of channel wall nozzles that address liner fabrication, slotting techniques and liner closeout techniques. Techniques being evaluated for liner fabrication include large-scale additive manufacturing of freeform-deposition structures to create the liner blanks. Abrasive water jet milling is being evaluated for cutting the complex coolant channel geometries. Techniques being considered for rapid closeout of the slotted liners include freeform deposition, explosive bonding and Cold Spray. Each of these techniques, development work and results are discussed in further detail in this paper.
Organic compounds produced during the thermal decomposition of cotton fabrics.
Moltó, Julia; Conesa, Juan A; Font, Rafael; Martin-Gullón, Ignacio
Used cotton fabrics, which can be considered a biomass according to its origin, were descomposed thermically in a laboratory scale reactor through a set of runs carried out in inert and air atmospheres, with temperatures between 650 and 1050 degrees C. More than 90 compounds, including carbon oxides, light hydrocarbons, and PAHs, have been identified and quantified. In the gas phase some of the main components obtained were methane, ethene, and benzene. The main semivolatile compounds detected were styrene, phenol, naphthalene, acenaphthylene, and phenanthrene. Furthermore, analyses of PCDD/Fs in the material tested and in the semivolatile compounds produced during the combustion at 850 degrees C were also performed, obtaining values of 14.5 (sample) and 7.2 pg I-TEQ/g (combustion). The congener that mostly contributes to the total I-TEQ was 2,3,4,7,8-PeCDF. The results obtained show that this waste could be used as biomass, and in this way, it is a valid alternative to disposal in landfills.
Toner and paper-based fabrication techniques for microfluidic applications.
Coltro, Wendell Karlos Tomazelli; de Jesus, Dosil Pereira; da Silva, José Alberto Fracassi; do Lago, Claudimir Lucio; Carrilho, Emanuel
The interest in low-cost microfluidic platforms as well as emerging microfabrication techniques has increased considerably over the last years. Toner- and paper-based techniques have appeared as two of the most promising platforms for the production of disposable devices for on-chip applications. This review focuses on recent advances in the fabrication techniques and in the analytical/bioanalytical applications of toner and paper-based devices. The discussion is divided in two parts dealing with (i) toner and (ii) paper devices. Examples of miniaturized devices fabricated by using direct-printing or toner transfer masking in polyester-toner, glass, PDMS as well as conductive platforms as recordable compact disks and printed circuit board are presented. The construction and the use of paper-based devices for off-site diagnosis and bioassays are also described to cover this emerging platform for low-cost diagnostics.
Recent Developments in Microsystems Fabricated by the Liga-Technique
NASA Technical Reports Server (NTRS)
Schulz, J.; Bade, K.; El-Kholi, A.; Hein, H.; Mohr, J.
As an example of microsystems fabricated by the LIGA-technique (x-ray lithography, electroplating and molding), three systems are described and characterized: a triaxial acceleration sensor system, a micro-optical switch, and a microsystem for the analysis of pollutants. The fabrication technologies are reviewed with respect to the key components of the three systems: an acceleration sensor, and electrostatic actuator, and a spectrometer made by the LIGA-technique. Aa micro-pump and micro-valve made by using micromachined tools for molding and optical fiber imaging are made possible by combining LIGA and anisotropic etching of silicon in a batch process. These examples show that the combination of technologies and components is the key to complex microsystems. The design of such microsystems will be facilitated is standardized interfaces are available.
Advanced Fibre Bragg Grating and Microfibre Bragg Grating Fabrication Techniques
NASA Astrophysics Data System (ADS)
Chung, Kit Man
Fibre Bragg gratings (FBGs) have become a very important technology for communication systems and fibre optic sensing. Typically, FBGs are less than 10-mm long and are fabricated using fused silica uniform phase masks which become more expensive for longer length or non-uniform pitch. Generally, interference UV laser beams are employed to make long or complex FBGs, and this technique introduces critical precision and control issues. In this work, we demonstrate an advanced FBG fabrication system that enables the writing of long and complex gratings in optical fibres with virtually any apodisation profile, local phase and Bragg wavelength using a novel optical design in which the incident angles of two UV beams onto an optical fibre can be adjusted simultaneously by moving just one optical component, instead of two optics employed in earlier configurations, to vary the grating pitch. The key advantage of the grating fabrication system is that complex gratings can be fabricated by controlling the linear movements of two translation stages. In addition to the study of advanced grating fabrication technique, we also focus on the inscription of FBGs written in optical fibres with a cladding diameter of several ten's of microns. Fabrication of microfibres was investigated using a sophisticated tapering method. We also proposed a simple but practical technique to filter out the higher order modes reflected from the FBG written in microfibres via a linear taper region while the fundamental mode re-couples to the core. By using this technique, reflection from the microfibre Bragg grating (MFBG) can be effectively single mode, simplifying the demultiplexing and demodulation processes. MFBG exhibits high sensitivity to contact force and an MFBG-based force sensor was also constructed and tested to investigate their suitability for use as an invasive surgery device. Performance of the contact force sensor packaged in a conforming elastomer material compares favourably to one
New Advanced Fabrication Technique for Millimeter-Wave Planar Components based on Fluororesin Substrates using Graft Polymerization
NASA Astrophysics Data System (ADS)
Ito, Naoki; Mase, Atsushi; Kogi, Yuichiro; Seko, Noriaki; Tamada, Masao; Sakata, Eiji
As the importance of advanced millimeter-wave diagnostics increases, a reliable and accurate fabrication technique for high-performance devices and relevant components is essential. We describe a new improved fabrication technique for millimeter-wave planar components, such as antennas using low-loss fluororesin substrates. A fragile adhesion between the copper foil and fluororesin substrate and the accuracy of the device pattern using conventional fabrication techniques have been prime suspects in the failure of the devices. In order to solve these problems, surface treatment of fluororesin films and a fabrication method using electro-fine-forming (EF2) are proposed. The peel adhesion strength between the metal and fluororesin films and the value of the dielectric constant of the fluororesin films before and after grafting are reported. A prototype antenna using conventional fluororesin substrates and grafted-poly(tetrafluoroethylene) (PTFE) films produced using the EF2 fabrication technique are also introduced.
FY-87 packing fabrication techniques (commercial waste form) results
Werry, E.V.; Gates, T.E.; Cabbage, K.S.; Eklund, J.D.
This report covers the investigation of fabrication techniques associated with the development of suitable materials and methods to provide a prefabricated packing for waste packages for the Basalt Waste Isolation Project (BWIP). The principal functions of the packing are to minimize container corrosion during the 300 to 1000 years following repository closure and provide long-term control of the release of radionuclides from the waste package. The investigative work, discussed in this report, was specifically conceived to develop the design criteria for production of full-scale prototypical packing rings. The investigative work included the preparation of procedures, the preparation of fabrication materials, physical properties, and the determination of the engineering properties. The principal activities were the preparation of the materials and the determination of the physical properties. 21 refs., 20 figs., 14 tabs.
Innovative sputtering techniques for CIS and CdTe submodule fabrication
Armstrong, J.M.; Misra, M.S.; Lanning, B. . Astronautics Group)
This report describes work done during Phase 1 of the subject subcontract. The subcontract was designed to study innovative deposition techniques, such as the rotating cylindrical magnetron sputtering system and electrodeposition for large-area, low-cost copper indium diselenide (CIS) and cadmium telluride (CdTe) devices. A key issue for photovoltaics (PV) in terrestrial and future space applications is producibility, particularly for applications using a large quantity of PV. Among the concerns for fabrication of polycrystalline thin-film PV, such as CIS and CdTe, are production volume, cost, and minimization of waste. Both rotating cylindrical magnetron (C-Mag[trademark]) sputtering and electrodeposition have tremendous potential for the fabrication of polycrystalline thin-film PV due to scaleability, efficient utilization of source materials, and inherently higher deposition rates. In the case of sputtering, the unique geometry of the C-Mae facilitates innovative cosputtering and reactive sputtering that could lead to greater throughput reduced health and safety risks, and, ultimately, lower fabrication cost. Electrodeposited films appear to be adherent and comparable with low-cost fabrication techniques. Phase I involved the initial film and device fabrication using the two techniques mentioned herein. Devices were tested by both internal facilities, as well as NREL and ISET.
Method for producing fabrication material for constructing micrometer-scaled machines, fabrication material for micrometer-scaled machines
Stevens, F.J.
A method for producing fabrication material for use in the construction of nanometer-scaled machines is provided whereby similar protein molecules are isolated and manipulated at predetermined residue positions so as to facilitate noncovalent interaction, but without compromising the folding configuration or native structure of the original protein biomodules. A fabrication material is also provided consisting of biomodules systematically constructed and arranged at specific solution parameters.
The occlusal guard: a simplified technique for fabrication and equilibration.
Antonelli, John; Hottel, Timothy L; Siegel, Sharon C; Brandt, Robert; Silva, Gladston
Hard occlusal guards have been used effectively to treat myofacial pain originating from parafunctional activities. Also, they can protect the natural dentition when it opposes porcelain restorations, help to evaluate changes in occlusal vertical dimension during full mouth rehabilitation, minimize further tooth loss in patients with abfraction lesions, and redirect occlusal loads more favorably onto dental implant-supported prostheses. A simplified technique is described to fabricate a properly designed wax model of an occlusal guard that can be processed in acrylic in the same manner used to construct a complete denture.
General technique for fabricating large arrays of nanowires
NASA Astrophysics Data System (ADS)
Jorritsma, J.; Gijs, M. A. M.; Kerkhof, J. M.; Stienen, J. G. H.
Large arrays of parallel metallic nanowires ranging from 20 - 120 nm in width are fabricated using a general and relatively simple technique. Holographic laser interference exposure of photoresist and anisotropic etching are used to pattern the surface of InP(001) substrates into V-shaped grooves of 200 nm period. Subsequently metal is evaporated at an angle onto the V-grooved substrates, naturally resulting in thousands of ultra-narrow metallic wires in parallel. Resistance measurements proof that as-prepared wires are electrically continuous.
Novel fabrication technique for improving the figure-of-merit of thermoelectric materials
NASA Technical Reports Server (NTRS)
Beaty, J. S.; Masters, R.; Vandersande, J. W.; Wood, C.
Reduction of the thermal conductivity of thermoelectric materials in order to improve the figure of merit and, hence, the conversion efficiency is discussed. A novel fabrication technique that reduces the thermal conductivity without too adverse an effect on the electrical properties is reported. This is achieved by producing an oxygen-free, very-fine-grain SiGe alloy with very small (on the order of 50 A) precipitates.
A modified technique for fabricating a mirror image wax pattern for an auricular prosthesis.
Gajdhar, Shaiq; Gajdhar, Sajda Khan; Salakalakonda, Srikanth Reddy; Vasthare, Abubakkar
This article describes a technique for fabricating a wax pattern for an auricular prosthesis by tracing the shape of a sliced cast of the contralateral ear at an interval of 1-mm and transferring the shape of each 1-mm slice to a similar dimension modeling wax sheet. In this way, slices of modeling wax are obtained, which can be reversed and placed over the previous slice to produce a mirror image wax pattern of the contralateral ear.
Advanced Materials and Fabrication Techniques for the Orion Attitude Control Motor
NASA Technical Reports Server (NTRS)
Gorti, Sridhar; Holmes, Richard; O'Dell, John; McKechnie, Timothy; Shchetkovskiy, Anatoliy
Rhenium, with its high melting temperature, excellent elevated temperature properties, and lack of a ductile-to-brittle transition temperature (DBTT), is ideally suited for the hot gas components of the ACM (Attitude Control Motor), and other high-temperature applications. However, the high cost of rhenium makes fabricating these components using conventional fabrication techniques prohibitive. Therefore, near-net-shape forming techniques were investigated for producing cost-effective rhenium and rhenium alloy components for the ACM and other propulsion applications. During this investigation, electrochemical forming (EL-Form ) techniques were evaluated for producing the hot gas components. The investigation focused on demonstrating that EL-Form processing techniques could be used to produce the ACM flow distributor. Once the EL-Form processing techniques were established, a representative rhenium flow distributor was fabricated, and samples were harvested for material properties testing at both room and elevated temperatures. As a lower cost and lighter weight alternative to an all-rhenium component, rhenium- coated graphite and carbon-carbon were also evaluated. The rhenium-coated components were thermal-cycle tested to verify that they could withstand the expected thermal loads during service. High-temperature electroforming is based on electrochemical deposition of compact layers of metals onto a mandrel of the desired shape. Mandrels used for electro-deposition of near-net shaped parts are generally fabricated from high-density graphite. The graphite mandrel is easily machined and does not react with the molten electrolyte. For near-net shape components, the inner surface of the electroformed part replicates the polished graphite mandrel. During processing, the mandrel itself becomes the cathode, and scrap or refined refractory metal is the anode. Refractory metal atoms from the anode material are ionized in the molten electrolytic solution, and are deposited
Novel immobilization techniques in the fabrication of efficient electrochemical biosensors
NASA Astrophysics Data System (ADS)
Alva, Shridhara; Marx, Kenneth A.; Samuelson, Lynne A.; Kumar, Jayant; Tripathy, Sukant K.; Kaplan, David L.
The development of enzyme electrodes plays a major role in the performance of an electrochemical biosensor. In this paper, we describe two generic methods for efficient immobilization of enzymes or biomolecules at the electrode surface. These methods are based on physical entrapment of the enzymes during biochemical polymerization of phenols and electrochemical copolymerization of aromatic diamines with enzymes that are covalently coupled to the monomer. Both of these techniques have proven to be chemically mild and provide efficient polymer matrices for the fabrication of enzyme electrodes. Enzymes including horseradish peroxidase, alkaline phosphatase and glucose oxidase have been immobilized in these polymeric matrices and used for electrochemical as well as colorimetric detection of various substrates. Response times of the order of 5 - 10 seconds and sensitivities of the order of mM have been achieved with these electrodes. The use of these immobilization techniques towards the development of microelectrode arrays for multianalyte sensors is also discussed.
A hybrid sequential deposition fabrication technique for micro fuel cells
NASA Astrophysics Data System (ADS)
Stanley, Kevin G.; Czyzewska, Eva K.; Vanderhoek, Tom P. K.; Fan, Lilian L. Y.; Abel, Keith A.; Wu, Q. M. Jonathan; Parameswaran, M. Ash
Micro fuel cell systems have elicited significant interest due to their promise for instantly rechargeable, longer duration and portable power. Most micro fuel cell systems are either built as miniaturized plate-and-frame or silicon-based microelectromechanical systems (MEMS). Plate-and-frame systems are difficult to fabricate smaller than 20 cm3. Existing micro fuel cell designs cannot meet the cost, scale and power requirements of some portable power markets. Traditional MEMS scaling advantages do not apply to fuel cells because the minimum area for the fuel cell is fixed by the catalyst area required for a given power output, and minimum volume set by mass transport limitations. We have developed a new hybrid technique that borrows from both micro and macro machining techniques to create fuel cells in the 1-20 cm3 range, suitable for cell phones, PDAs and smaller devices.
Method of producing catalytic materials for fabricating nanostructures
Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei
Methods of fabricating nano-catalysts are described. In some embodiments the nano-catalyst is formed from a powder-based substrate material and is some embodiments the nano-catalyst is formed from a solid-based substrate material. In some embodiments the substrate material may include metal, ceramic, or silicon or another metalloid. The nano-catalysts typically have metal nanoparticles disposed adjacent the surface of the substrate material. The methods typically include functionalizing the surface of the substrate material with a chelating agent, such as a chemical having dissociated carboxyl functional groups (--COO), that provides an enhanced affinity for metal ions. The functionalized substrate surface may then be exposed to a chemical solution that contains metal ions. The metal ions are then bound to the substrate material and may then be reduced, such as by a stream of gas that includes hydrogen, to form metal nanoparticles adjacent the surface of the substrate.
Micro cycloid-gear system fabricated by multiexposure LIGA technique
NASA Astrophysics Data System (ADS)
Hirata, Toru; Chung, Song-Jo; Hein, Herbert; Akashi, Tomoyuki; Mohr, Juergen
In this paper, a prototype of 2 mm-diameter micro-cycloid gear system fabricated by the multi-exposure LIGA technique is presented. The entire gear system consists of a casing and three vertically stacked disks and gears. Each part is composed of three different levels. The first level, 40 micrometers high, was fabricated by UV-lithography, and the second as well as the third level, 195 micrometers and 250 micrometers high respectively, were processed by aligned deep X-ray lithography (DXL). The alignment error between two DXL- processed layers was measured, and the results have turned out to be within +/- 5 micrometers range. As a result of the height control process by the mechanical surface machining, the deviation of structural height has been maintained within +/- 3 micrometers range for the UV-lithography-processed structures, and +/- 10 micrometers for the DXL-processed structures. Further the tests of gear assembly were implemented with 125 micrometers -diameter glass fiber, by using a die-bonding machine with vacuum gripper under stereo- microscope. Finally the dynamic tests of the gear system were successfully conducted with the mechanical torque input by an electrical motor. A proper rotational speed reduction was observed in the operational input range of 3 to 1500 rpm with the designed gear ratio of 18.
Chromatic changes to artificial irises produced using different techniques
NASA Astrophysics Data System (ADS)
Bannwart, Lisiane Cristina; Goiato, Marcelo Coelho; dos Santos, Daniela Micheline; Moreno, Amália; Pesqueira, Aldiéris Alves; Haddad, Marcela Filié; Andreotti, Agda Marobo; de Medeiros, Rodrigo Antonio
Ocular prostheses are important determinants of their users' aesthetic recovery and self-esteem. Because of use, ocular prostheses longevity is strongly affected by instability of the iris color due to polymerization. The goal of this study is to examine how the color of the artificial iris button is affected by different techniques of artificial wear and by the application of varnish following polymerization of the colorless acrylic resin that covers the colored paint. We produce 60 samples (n=10) according to the wear technique applied: conventional technique without varnish (PE); conventional technique with varnish (PEV); technique involving a prefabricated cap without varnish (CA); technique involving a prefabricated cap with varnish (CAV); technique involving inverted painting without varnish (PI); and technique involving inverted painting with varnish (PIV). Color readings using a spectrophotometer are taken before and after polymerization. We submitted the data obtained to analyses of variance and Tukey's test (P<0.05). The color test shows significant changes after polymerization in all groups. The PE and PI techniques have clinically acceptable values of ΔE, independent of whether we apply varnish to protect the paint. The PI technique produces the least color change, whereas the PE and CA techniques significantly improve color stability.
Characterization of a Viking Blade Fabricated by Traditional Forging Techniques
NASA Astrophysics Data System (ADS)
Vo, H.; Frazer, D.; Bailey, N.; Traylor, R.; Austin, J.; Pringle, J.; Bickel, J.; Connick, R.; Connick, W.; Hosemann, P.
A team of students from the University of California, Berkeley, participated in a blade-smithing competition hosted by the Minerals, Metals, and Materials Society at the TMS 2015 144th annual meeting and exhibition. Motivated by ancient forging methods, the UC Berkeley team chose to fabricate our blade from historical smithing techniques utilizing naturally-occurring deposits of iron ore. This approach resulted in receiving the "Best Example of a Traditional Blade Process/Ore Smelting Technique" award for our blade named "Berkelium." First, iron-enriched sand was collected from local beaches. Magnetite (Fe3O4) was then extracted from the sand and smelted into individual high- and low-carbon steel ingots. Layers of high- and low-carbon steels were forge-welded together, predominantly by hand, to form a composite material. Optical microscopy, energy dispersive spectroscopy, and Vickers hardness mechanical testing were conducted at different stages throughout the blade-making process to evaluate the microstructure and hardness evolution during formation. It was found that the pre-heat-treated blade microstructure was composed of ferrite and pearlite, and contained many nonmetallic inclusions. A final heat treatment was performed, which caused the average hardness of the blade edge to increase by more than a factor of two, indicating a martensitic transformation.
Fabrication technique for the production of on- and off-axis conic surfaces of revolution (WAGNER)
NASA Astrophysics Data System (ADS)
Faehnle, Oliver W.; van Brug, Hedser H.; Frankena, Hans J.
A new fabrication technique, derived from an earlier development to produce on- and off-axis optical surfaces of revolution is presented. Although based on a shape copying method, it is possible to generate different types of surfaces with the same machine tool. Load controlled point- contact machining is applied using a small tool which is guided along a pre-determined tool-path, not requiring an in-process tool-path control. This fabrication technique employs a self-correcting process and is characterized by an advantageous error propagation between tool and workpiece. The characteristics of this fabrication technique are discussed together with its application for the generation of on- and off-axis surfaces with conic sections as generators. The design of a first set-up for production of conic surfaces is presented with which it is possible to generate all kinds of conic surfaces on the same machine, featuring a pantograph enabling the production of different scales of the surfaces, together with the discussion of fist experimental data.
Fabrication of a microreactor by proton beam writing technique
NASA Astrophysics Data System (ADS)
Huszank, R.; Szilasi, S. Z.; Vad, K.; Rajta, I.
Microreactors are innovative and promising tools in technology nowadays because of their advantages compared to the conventional-scale reactors. These advantages include vast improvements in surface to volume ratio, energy efficiency, reaction speed and yield and increased control of reaction conditions, to name a few examples. The high resolution capability of the micromachining technique utilizing accelerated ion beams in the fabrication technology of microreactors has not yet been taken advantage of. In this work we present the design of a prototype micro-electrochemical cell of 1.5 μL volume (2.5 × 2.5 × 0.240 mm) created with a 3 MeV proton microbeam. The cell can be separated into two half-cells with a suitable membrane applicable to galvanic or fuel cells as well. We deposited gold electrodes on both of the half-cells. The operability of the device was demonstrated by electric current flow between the two electrodes in this micro-electrochemical cell containing a simple electrolyte solution. We used a polycapillary film to separate the two half-cells, hindering the mixing of the anolyte and catholyte solutions. As a result of the minimal mixing caused by the polycapillary film, this cell design can be suitable for electro-synthesis. Due to the high resolution of proton beam writing, it is planned to reduce the dimensions of this kind of microreactor.
Thermocapillary Technique for Shaping and Fabricating Optical Ribbon Waveguides
NASA Astrophysics Data System (ADS)
Fiedler, Kevin; Troian, Sandra
The demand for ever increasing bandwidth and higher speed communication has ushered the next generation optoelectronic integrated circuits which directly incorporate polymer optical waveguide devices. Polymer melts are very versatile materials which have been successfully cast into planar single- and multimode waveguides using techniques such as embossing, photolithography and direct laser writing. In this talk, we describe a novel thermocapillary patterning method for fabricating waveguides in which the free surface of an ultrathin molten polymer film is exposed to a spatially inhomogeneous temperature field via thermal conduction from a nearby cooled mask pattern held in close proximity. The ensuring surface temperature distribution is purposely designed to pool liquid selectively into ribbon shapes suitable for optical waveguiding, but with rounded and not rectangular cross sectional areas due to capillary forces. The solidified waveguide patterns which result from this non-contact one step procedure exhibit ultrasmooth interfaces suitable for demanding optoelectronic applications. To complement these studies, we have also conducted finite element simulations for quantifying the influence of non-rectangular cross-sectional shapes on mode propagation and losses. Kf gratefully acknowledges support from a NASA Space Technology Research Fellowship.
Effect of fabrication technique on direct methanol fuel cells designed to operate at low airflow
NASA Technical Reports Server (NTRS)
Valdez, T. I.; Narayanan, S. R.
This study investigates the effects of catalyst ink constituents and MEA fabrication techniques on improving cell performance. Particular attention was focused on increasing the overall cell efficiency.
UV-transmitting step-index fluorophosphate glass fiber fabricated by the crucible technique
NASA Astrophysics Data System (ADS)
Galleani, Gustavo; Ledemi, Yannick; de Lima Filho, Elton Soares; Morency, Steeve; Delaizir, Gaëlle; Chenu, Sébastien; Duclere, Jean René; Messaddeq, Younes
In this study, we report on the fabrication process of highly pure step-index fluorophosphate glass optical fibers by a modified crucible technique. High-purity fluorophosphate glasses based on 10 mol% of barium metaphosphate and 90 mol% of metal fluorides (AlF3sbnd CaF2sbnd MgF2sbnd SrF2) have been studied in order to produce step-index optical fibers transmitting in the deep-ultraviolet (DUV) region. The characteristic temperatures, viscosity around softening temperature and optical transmission in the UV-visible region of the prepared bulk glasses were characterized in a first step. The selected glass compositions were then used to prepare core-cladding optical preforms by using a modified built-in casting technique. While uncontrolled crystallization of the fiber was observed during the preform stretching by using the conventional method, we successfully obtained crystal-free fiber by using a modified crucible technique. In this alternative approach, the produced core-cladding preforms were inserted into a home-designed fused silica crucible assembly and heated at 643 °C to allow glass flowing throughout the crucible, preventing the formation of crystals. Single index fluorophosphate glass fibers were fabricated following the same process as well. The optical attenuation at 244 nm and in the interval 350-1750 nm was measured on both single index and step-index optical fibers. Their potential for using in DUV applications is discussed.
Improved ceramic slip casting technique. [application to aircraft model fabrication
NASA Technical Reports Server (NTRS)
Buck, Gregory M. (Inventor); Vasquez, Peter (Inventor)
A primary concern in modern fluid dynamics research is the experimental verification of computational aerothermodynamic codes. This research requires high precision and detail in the test model employed. Ceramic materials are used for these models because of their low heat conductivity and their survivability at high temperatures. To fabricate such models, slip casting techniques were developed to provide net-form, precision casting capability for high-purity ceramic materials in aqueous solutions. In previous slip casting techniques, block, or flask molds made of plaster-of-paris were used to draw liquid from the slip material. Upon setting, parts were removed from the flask mold and cured in a kiln at high temperatures. Casting detail was usually limited with this technique -- detailed parts were frequently damaged upon separation from the flask mold, as the molded parts are extremely delicate in the uncured state, and the flask mold is inflexible. Ceramic surfaces were also marred by 'parting lines' caused by mold separation. This adversely affected the aerodynamic surface quality of the model as well. (Parting lines are invariably necessary on or near the leading edges of wings, nosetips, and fins for mold separation. These areas are also critical for flow boundary layer control.) Parting agents used in the casting process also affected surface quality. These agents eventually soaked into the mold, the model, or flaked off when releasing the case model. Different materials were tried, such as oils, paraffin, and even an algae. The algae released best, but some of it remained on the model and imparted an uneven texture and discoloration on the model surface when cured. According to the present invention, a wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell
Fabrication of bowtie aperture antennas for producing sub-20 nm optical spots.
Chen, Yang; Chen, Jianfeng; Xu, Xianfan; Chu, Jiaru
Bowtie aperture antennas are known to generate sub-diffraction limited optical spots in the visible and near-infrared frequencies, which can be applied to many areas. Regular bowtie apertures fabricated by FIB suffer from tapered sidewall and rounded corner, which degrade its optical enhancement and localization. In this work, a new fabrication method is demonstrated to manufacture bowtie aperture antennas which can produce optical spots with lateral size smaller than 20 nm. We also employ numerical simulations to compute the near-field distribution on the surface of the bowtie aperture with topography extracted from the fabrication antennas. The near-field distribution measured by s-NSOM agrees well with the simulation and confirms the improved near-field localization of our bowtie aperture. This new fabrication method can be applied to other types of ridged apertures, which promises wide applications of deep sub-diffraction limited optical spots in many areas.
Synthesis of nano silver on cellulosic denim fabric producing yellow colored garment with antibacterial properties.
Maryan, Ali Sadeghian; Montazer, Majid; Harifi, Tina
In this study, an aged-look denim fabric with antibacterial property was prepared in one single step process. For this purpose, the simultaneous antibacterial finishing and discoloration of denim fabric was carried out through reduction of indigo dye and silver nitrate by glucose in alkaline media using a conventional garment washing machine. The uniform distribution of silver nanoparticles on the fiber surface was confirmed by scanning electron microscope and energy dispersive X-ray spectroscopy. The treated fabrics were also characterized by X-ray diffraction (XRD) and Raman spectroscopy. Due to the color changes during the process, the color coordinates of the treated samples were also measured. Findings suggest the potential of the proposed method in producing old-look denim fabric with desirable yellow appearance and reasonable antibacterial activity against Staphylococcus aureus and Escherichia coli with low toxicity for human.
A low-cost, high-yield fabrication method for producing optimized biomimetic dry adhesives
NASA Astrophysics Data System (ADS)
Sameoto, D.; Menon, C.
We present a low-cost, large-scale method of fabricating biomimetic dry adhesives. This process is useful because it uses all photosensitive polymers with minimum fabrication costs or complexity to produce molds for silicone-based dry adhesives. A thick-film lift-off process is used to define molds using AZ 9260 photoresist, with a slow acting, deep UV sensitive material, PMGI, used as both an adhesion promoter for the AZ 9260 photoresist and as an undercutting material to produce mushroom-shaped fibers. The benefits to this process are ease of fabrication, wide range of potential layer thicknesses, no special surface treatment requirements to demold silicone adhesives and easy stripping of the full mold if process failure does occur. Sylgard® 184 silicone is used to cast full sheets of biomimetic dry adhesives off 4" diameter wafers, and different fiber geometries are tested for normal adhesion properties. Additionally, failure modes of the adhesive during fabrication are noted and strategies for avoiding these failures are discussed. We use this fabrication method to produce different fiber geometries with varying cap diameters and test them for normal adhesion strengths. The results indicate that the cap diameters relative to post diameters for mushroom-shaped fibers dominate the adhesion properties.
A direct technique to fabricate an intraoral shield for unilateral head and neck radiation.
Khan, Zafrulla; Abdel-Azim, Tamer
A radiation oncologist may ask the prosthodontist to fabricate an intraoral shield when ipsilateral fields are used for patients with head and neck cancer. A technique for its fabrication is described that can be accomplished with materials and equipment that are readily available in the dental office. Baseplate wax is used intraorally to fabricate a pattern, which is duplicated with irreversible hydrocolloid material. Autopolymerizing acrylic resin is then used to make the shield. This simple technique can be completed in a single visit.
The hydroentanglement system of producing nonwoven fabrics of certain specific attributes and functionalities
Technology Transfer Automated Retrieval System (TEKTRAN)
Although the traditional technologies and processes of producing fabric structures, via yarn spinning, weaving, knitting, lacing, tufting, or the like, continue to be the 'major league' players in textile manufacturing today, the modern hydroentanglement system, commonly known as "spunlacing," has a...
Physical and combustion properties of nonwoven fabrics produced from conventional and naturally colored cottons
Technology Transfer Automated Retrieval System (TEKTRAN)
A comparative study was conducted to identify the effects of processing parameters on physical and combustion properties of needlepunched (NP) and hydroentangled (H-E) nonwoven fabrics produced from fibers of a standard Mid-South white fiber cotton and a naturally colored brown fiber cotton. The fl...
Technique for the efficient and reproducible fabrication of electromagnetic levitation coils
NASA Technical Reports Server (NTRS)
Ethridge, E. C.; Curreri, P. A.; Theiss, J.; Abbaschian, G. J.
A technique has been developed for fabricating electromagnetic induction coils in a reproducible manner. The process utilizes a split mandrel that can be disassembled to remove the mandrel from the coil. The technique has increased coil production rates by a factor of 8 over the freehand winding method. The success rate for producing a functional levitation coil has been increased from 50 percent to 95 percent. The levitation coil designed during this work has successfully levitated and melted a variety of alloys including Cu, Ag, Ag-Ni, Cu-Fe, Fe-C, and Nb-Ge. W was also levitated but not melted at temperatures as high as 2700 C. The highest sample melt temperature achieved was 2400 C for the Nb-Ge samples.
New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques
Tang, W.; Zhou, L.; Kassen, A. G.; ...
Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (Hcj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology. Asmore » a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.« less
New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques
Tang, W.; Zhou, L.; Kassen, A. G.; Palasyuk, A.; White, E. M.; Dennis, K. W.; Kramer, M. J.; McCallum, R. W.; Anderson, I. E.
Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (Hcj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology. As a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.
Structural design and fabrication techniques of composite unmanned aerial vehicles
NASA Astrophysics Data System (ADS)
Hunt, Daniel Stephen
Popularity of unmanned aerial vehicles has grown substantially in recent years both in the private sector, as well as for government functions. This growth can be attributed largely to the increased performance of the technology that controls these vehicles, as well as decreasing cost and size of this technology. What is sometimes forgotten though, is that the research and advancement of the airframes themselves are equally as important as what is done with them. With current computer-aided design programs, the limits of design optimization can be pushed further than ever before, resulting in lighter and faster airframes that can achieve longer endurances, higher altitudes, and more complex missions. However, realization of a paper design is still limited by the physical restrictions of the real world and the structural constraints associated with it. The purpose of this paper is to not only step through current design and manufacturing processes of composite UAVs at Oklahoma State University, but to also focus on composite spars, utilizing and relating both calculated and empirical data. Most of the experience gained for this thesis was from the Cessna Longitude project. The Longitude is a 1/8 scale, flying demonstrator Oklahoma State University constructed for Cessna. For the project, Cessna required dynamic flight data for their design process in order to make their 2017 release date. Oklahoma State University was privileged enough to assist Cessna with the mission of supporting the validation of design of their largest business jet to date. This paper will detail the steps of the fabrication process used in construction of the Longitude, as well as several other projects, beginning with structural design, machining, molding, skin layup, and ending with final assembly. Also, attention will be paid specifically towards spar design and testing in effort to ease the design phase. This document is intended to act not only as a further development of current
Wire electric-discharge machining and other fabrication techniques
NASA Technical Reports Server (NTRS)
Morgan, W. H.
Wire electric discharge machining and extrude honing were used to fabricate a two dimensional wing for cryogenic wind tunnel testing. Electric-discharge cutting is done with a moving wire electrode. The cut track is controlled by means of a punched-tape program and the cutting feed is regulated according to the progress of the work. Electric-discharge machining involves no contact with the work piece, and no mechanical force is exerted. Extrude hone is a process for honing finish-machined surfaces by the extrusion of an abrasive material (silly putty), which is forced through a restrictive fixture. The fabrication steps are described and production times are given.
Microemulsion extrusion technique: a new method to produce lipid nanoparticles
NASA Astrophysics Data System (ADS)
de Jesus, Marcelo Bispo; Radaic, Allan; Zuhorn, Inge S.; de Paula, Eneida
Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) have been intensively investigated for different applications, including their use as drug and gene delivery systems. Different techniques have been employed to produce lipid nanoparticles, of which high pressure homogenization is the standard technique that is adopted nowadays. Although this method has a high efficiency, does not require the use of organic solvents, and allows large-scale production, some limitations impede its application at laboratory scale: the equipment is expensive, there is a need of huge amounts of surfactants and co-surfactants during the preparation, and the operating conditions are energy intensive. Here, we present the microemulsion extrusion technique as an alternative method to prepare lipid nanoparticles. The parameters to produce lipid nanoparticles using microemulsion extrusion were established, and the lipid particles produced (SLN, NLC, and liposomes) were characterized with regard to size (from 130 to 190 nm), zeta potential, and drug (mitoxantrone) and gene (pDNA) delivery properties. In addition, the particles' in vitro co-delivery capacity (to carry mitoxantrone plus pDNA encoding the phosphatase and tensin homologue, PTEN) was tested in normal (BALB 3T3 fibroblast) and cancer (PC3 prostate and MCF-7 breast) cell lines. The results show that the microemulsion extrusion technique is fast, inexpensive, reproducible, free of organic solvents, and suitable for small volume preparations of lipid nanoparticles. Its application is particularly interesting when using rare and/or costly drugs or ingredients (e.g., cationic lipids for gene delivery or labeled lipids for nanoparticle tracking/diagnosis).
Planar techniques for fabricating X-ray diffraction gratings and zone plates
NASA Technical Reports Server (NTRS)
Smith, H. I.; Anderson, E. H.; Hawryluk, A. M.; Schattenburg, M. L.
The state of current planar techniques in the fabrication of Fresnel zone plates and diffraction gratings is reviewed. Among the fabrication techniques described are multilayer resist techniques; scanning electron beam lithography; and holographic lithography. Consideration is also given to: X-ray lithography; ion beam lithography; and electroplating. SEM photographs of the undercut profiles obtained in a type AZ 135OB photoresistor by holographic lithography are provided.
Retention of denture bases fabricated by three different processing techniques – An in vivo study
Chalapathi Kumar, V. H.; Surapaneni, Hemchand; Ravikiran, V.; Chandra, B. Sarat; Balusu, Srilatha; Reddy, V. Naveen
Aim: Distortion due to Polymerization shrinkage compromises the retention. To evaluate the amount of retention of denture bases fabricated by conventional, anchorized, and injection molding polymerization techniques. Materials and Methods: Ten completely edentulous patients were selected, impressions were made, and master cast obtained was duplicated to fabricate denture bases by three polymerization techniques. Loop was attached to the finished denture bases to estimate the force required to dislodge them by retention apparatus. Readings were subjected to nonparametric Friedman two-way analysis of variance followed by Bonferroni correction methods and Wilcoxon matched-pairs signed-ranks test. Results: Denture bases fabricated by injection molding (3740 g), anchorized techniques (2913 g) recorded greater retention values than conventional technique (2468 g). Significant difference was seen between these techniques. Conclusions: Denture bases obtained by injection molding polymerization technique exhibited maximum retention, followed by anchorized technique, and least retention was seen in conventional molding technique. PMID:27382542
Porous titanium scaffolds fabricated using a rapid prototyping and powder metallurgy technique.
Ryan, Garrett E; Pandit, Abhay S; Apatsidis, Dimitrios P
One of the main issues in orthopaedic implant design is the fabrication of scaffolds that closely mimic the biomechanical properties of the surrounding bone. This research reports on a multi-stage rapid prototyping technique that was successfully developed to produce porous titanium scaffolds with fully interconnected pore networks and reproducible porosity and pore size. The scaffolds' porous characteristics were governed by a sacrificial wax template, fabricated using a commercial 3D-printer. Powder metallurgy processes were employed to generate the titanium scaffolds by filling around the wax template with titanium slurry. In the attempt to optimise the powder metallurgy technique, variations in slurry concentration, compaction pressure and sintering temperature were investigated. By altering the wax design template, pore sizes ranging from 200 to 400 microm were achieved. Scaffolds with porosities of 66.8 +/- 3.6% revealed compression strengths of 104.4+/-22.5 MPa in the axial direction and 23.5 +/- 9.6 MPa in the transverse direction demonstrating their anisotropic nature. Scaffold topography was characterised using scanning electron microscopy and microcomputed tomography. Three-dimensional reconstruction enabled the main architectural parameters such as pore size, interconnecting porosity, level of anisotropy and level of structural disorder to be determined. The titanium scaffolds were compared to their intended designs, as governed by their sacrificial wax templates. Although discrepancies in architectural parameters existed between the intended and the actual scaffolds, overall the results indicate that the porous titanium scaffolds have the properties to be potentially employed in orthopaedic applications.
Development of Ultraviolet (UV) Radiation Protective Fabric Using Combined Electrospinning and Electrospraying Technique
NASA Astrophysics Data System (ADS)
Sinha, Mukesh Kumar; Das, B. R.; Kumar, Kamal; Kishore, Brij; Prasad, N. Eswara
The article reports a novel technique for functionization of nanoweb to develop ultraviolet (UV) radiation protective fabric. UV radiation protection effect is produced by combination of electrospinning and electrospraying technique. A nanofibrous web of polyvinylidene difluoride (PVDF) coated on polypropylene nonwoven fabric is produced by latest nanospider technology. Subsequently, web is functionalized by titanium dioxide (TiO2). The developed web is characterized for evaluation of surface morphology and other functional properties; mechanical, chemical, crystalline and thermal. An optimal (judicious) nanofibre spinning condition is achieved and established. The produced web is uniformly coated by defect free functional nanofibres in a continuous form of useable textile structural membrane for ultraviolet (UV) protective clothing. This research initiative succeeds in preparation and optimization of various nanowebs for UV protection. Field Emission Scanning Electron Microscope (FESEM) result reveals that PVDF webs photo-degradative behavior is non-accelerated, as compared to normal polymeric grade fibres. Functionalization with TiO2 has enhanced the photo-stability of webs. The ultraviolet protection factor of functionalized and non-functionalized nanowebs empirically evaluated to be 65 and 24 respectively. The developed coated layer could be exploited for developing various defence, para-military and civilian UV protective light weight clothing (tent, covers and shelter segments, combat suit, snow bound camouflaging nets). This research therefore, is conducted in an attempt to develop a scientific understanding of PVDF fibre coated webs for photo-degradation and applications for defence protective textiles. This technological research in laboratory scale could be translated into bulk productionization.
A technique to produce aluminum color bands for avian research
Koronkiewicz, T.J.; Paxton, E.H.; Sogge, M.K.
We developed a technique to produce metal (aluminum) color bands, in response to concerns about leg injuries caused by celluloid-plastic color bands applied to Willow Flycatchers (Empidonax traillii). The technique involves color-anodized aluminum bands (unnumbered blanks and federal numbered bands), with auto pin-striping tape and flexible epoxy sealant, to create a variety of solid, half- and triple-split colors. This allows for hundreds of unique, high-contrast color combinations. During six consecutive years of application, these colored metal bands have resisted color fade compared to conventional celluloid-plastic bands, and have reduced leg injuries in the flycatcher. Although not necessarily warranted for all color-banding studies, these metal bands may provide a lower-impact option for studies of species known to be impacted by plastic color bands.
Epoxy nanodielectrics fabricated with in situ and ex situ techniques
Tuncer, Enis; Polyzos, Georgios; Sauers, Isidor; James, David Randy; Ellis, Alvin R; More, Karren Leslie
In this study, we report fabrication and characterisation of a nanocomposite system composed of a commercial resin and extremely small (several nanometres in diameter) titanium dioxide particles. Nanoparticles were synthesised in situ with particle nucleation occurring inside the resin matrix. In this nanodielectric fabrication method, the nanoparticle precursor was mixed to the resin solution, and the nanoparticles were in situ precipitated. Note that no high shear mixing equipment was needed to improve particle dispersion - nanoparticles were distributed in the polymer matrix uniformly since particle nucleation occurs uniformly throughout the matrix. The properties of in situ nanodielectrics are compared to the unfilled resin and an ex situ nanocomposite. We anticipate that the presented in situ nanocomposite would be employed in high-temperature superconductivity applications. In additions, the improvement shown in the dielectric breakdown indicates that conventional high-voltage components and systems can be reduced in size with novel nanodielectrics.
Development of a direct fabrication technique for full-shell x-ray optics
NASA Astrophysics Data System (ADS)
Gubarev, M.; Kolodziejczak, J. K.; Griffith, C.; Roche, J.; Smith, W. S.; Kester, T.; Atkins, C.; Arnold, W.; Ramsey, B.
Future astrophysical missions will require fabrication technology capable of producing high angular resolution x-ray optics. A full-shell direct fabrication approach using modern robotic polishing machines has the potential for producing high resolution, light-weight and affordable x-ray mirrors that can be nested to produce large collecting area. This approach to mirror fabrication, based on the use of the metal substrates coated with nickel phosphorous alloy, is being pursued at MSFC. A model of the wear pattern as a function of numerous physical parameters is developed and verified using a mandrel sample. The results of the polishing experiments are presented.
A novel porous scaffold fabrication technique for epithelial and endothelial tissue engineering.
McHugh, Kevin J; Tao, Sarah L; Saint-Geniez, Magali
Porous scaffolds have the ability to minimize transport barriers for both two- (2D) and three-dimensional tissue engineering. However, current porous scaffolds may be non-ideal for 2D tissues such as epithelium due to inherent fabrication-based characteristics. While 2D tissues require porosity to support molecular transport, pores must be small enough to prevent cell migration into the scaffold in order to avoid non-epithelial tissue architecture and compromised function. Though electrospun meshes are the most popular porous scaffolds used today, their heterogeneous pore size and intense topography may be poorly-suited for epithelium. Porous scaffolds produced using other methods have similar unavoidable limitations, frequently involving insufficient pore resolution and control, which make them incompatible with 2D tissues. In addition, many of these techniques require an entirely new round of process development in order to change material or pore size. Herein we describe "pore casting," a fabrication method that produces flat scaffolds with deterministic pore shape, size, and location that can be easily altered to accommodate new materials or pore dimensions. As proof-of-concept, pore-cast poly(ε-caprolactone) (PCL) scaffolds were fabricated and compared to electrospun PCL in vitro using canine kidney epithelium, human colon epithelium, and human umbilical vein endothelium. All cell types demonstrated improved morphology and function on pore-cast scaffolds, likely due to reduced topography and universally small pore size. These results suggest that pore casting is an attractive option for creating 2D tissue engineering scaffolds, especially when the application may benefit from well-controlled pore size or architecture.
Two-step fabrication technique of gold tips for use in point-contact spectroscopy
Narasiwodeyar, S.; Dwyer, M.; Liu, M.; Park, W. K. Greene, L. H.
For a successful point-contact spectroscopy (PCS) measurement, metallic tips of proper shape and smoothness are essential to ensure the ballistic nature of a point-contact junction. Until recently, the fabrication of Au tips suitable for use in point-contact spectroscopy has remained more of an art involving a trial and error method rather than an automated scientific process. To address these issues, we have developed a technique with which one can prepare high quality Au tips reproducibly and systematically. It involves an electronic control of the driving voltages used for an electrochemical etching of a gold wire in a HCl-glycerol mixture or a HCl solution. We find that a stopping current, below which the circuit is set to shut off, is a single very important parameter to produce an Au tip of desired shape. We present detailed descriptions for a two-step etching process for Au tips and also test results from PCS measurements using them.
Advanced fabrication techniques for hydrogen-cooled engine structures. Final report, October 1975-June 1982
Buchmann, O.A.; Arefian, V.V.; Warren, H.A.; Vuigner, A.A.; Pohlman, M.J.
Described is a program for development of coolant passage geometries, material systems, and joining processes that will produce long-life hydrogen-cooled structures for scramjet applications. Tests were performed to establish basic material properties, and samples constructed and evaluated to substantiate fabrication processes and inspection techniques. Results of the study show that the basic goal of increasing the life of hydrogen-cooled structures two orders of magnitude relative to that of the Hypersonic Research Engine can be reached with available means. Estimated life is 19000 cycles for the channels and 16000 cycles for pin-fin coolant passage configurations using Nickel 201. Additional research is required to establish the fatigue characteristics of dissimilar-metal coolant passages (Nickel 201/Inconel 718) and to investigate the embrittling effects of the hydrogen coolant.
Two-beam laser fabrication technique and the application for fabricating conductive silver nanowire on flexible substrate
NASA Astrophysics Data System (ADS)
He, Gui-Cang; Zheng, Mei-Ling; Dong, Xian-Zi; Liu, Jie; Duan, Xuan-Ming; Zhao, Zhen-Sheng
In this study, a two-beam laser fabrication technique is proposed to fabricate silver nanowire (AgNW) on the polyethylene terephthalate (PET) substrate. The femtosecond pulse laser in the technique plays a role in generating Ag nanoparticles from the silver aqueous solution by multiphoton photoreduction. The continuous wave (CW) laser of the technique works as optical tweezers, and make the Ag nanoparticles gather to a continuous AgNW by the optical trapping force. The optical trapping force of the CW laser was calculated under our experimental condition. The flexibility and the resistance stability of the AgNW that fabricated by this technique are very excellent. Compared to the resistance of the AgNW without bending, the decreasing rate of the AgNW resistance is about 16% under compressed bending condition at the radius of 1 mm, and the increasing rate of the AgNW resistance is only 1.3% after the AgNW bended about 3500 times at the bending radius of 1 mm. The study indicates that the AgNW is promising for achieving flexible device and would promote the development of the flexible electronics.
Fabrication of an Implant-Supported Fixed Interim Prosthesis Using a Duplicate Denture: An Alternative Technique.
Al-Thobity, Ahmad M
The fabrication of an implant-supported fixed complete denture prosthesis involves multiple clinical and laboratory steps. One of the main steps is to provide the patient with an interim fixed prosthesis to evaluate the patient's esthetic and functional needs as well as to enhance the patient's psychology before proceeding to the definitive prosthesis. Different techniques for fabricating interim prostheses have been described in the literature. This report describes an alternative technique that uses a duplicate denture made of self-curing acrylic resin to fabricate an implant-supported fixed interim prosthesis. The interim prosthesis was later used as a blueprint for the definitive implant-supported hybrid prosthesis.
A blanket design, apparatus, and fabrication techniques for the mass production of multilayer insulation blankets for the Superconducting Super Collider
Gonczy, J.D.; Boroski, W.N.; Niemann, R.C.; Otavka, J.G.; Ruschman, M.K.; Schoo, C.J.
The multilayer insulation (MLI) system for the Superconducting Super Collider (SSC) consists of full cryostat length assemblies of aluminized polyester film fabricated in the form of blankets and installed as blankets to the 4.5K cold mass and the 20K and 80K thermal radiation shields. Approximately 40,000 MLI blankets will be required in the 10,000 cryogenic devices comprising the SSC accelerator. Each blanket is nearly 17 meters long and 1.8 meters wide. This paper reports the blanket design, an apparatus, and the fabrication method used to mass produce pre-fabricated MLI blankets. Incorporated in the blanket design are techniques which automate quality control during installation of the MLI blankets in the SSC cryostat. The apparatus and blanket fabrication method insure consistency in the mass produced blankets by providing positive control of the dimensional parameters which contribute to the thermal performance of the MLI blanket. By virtue of the fabrication process, the MLI blankets have inherent features of dimensional stability three-dimensional uniformity, controlled layer density, layer-to-layer registration, interlayer cleanliness, and interlayer material to accommodate thermal contraction differences. 11 refs., 6 figs., 1 tab.
High Contrast Internal and External Coronagraph Masks Produced by Various Techniques
NASA Technical Reports Server (NTRS)
Balasubramanian, Kunjithapatha; Wilson, Daniel; White, Victor; Muller, Richard; Dickie, Matthew; Yee, Karl; Ruiz, Ronald; Shaklan, Stuart; Cady, Eric; Kern, Brian; Belikov, Ruslan; Guyon, Olivier; Kasdin, N. Jeremy
Masks for high contrast internal and external coronagraphic imaging require a variety of masks depending on different architectures to suppress star light. Various fabrication technologies are required to address a wide range of needs including gradient amplitude transmission, tunable phase profiles, ultra-low reflectivity, precise small scale features, and low-chromaticity. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks, and lab-scale external occulter type masks by various techniques including electron beam, ion beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each. Further development is in progress to produce circular masks of various kinds for obscured aperture telescopes.
Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures
NASA Technical Reports Server (NTRS)
Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali
Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.
Archerfish use their shooting technique to produce adaptive underwater jets.
Dewenter, Jana; Gerullis, Peggy; Hecker, Alexander; Schuster, Stefan
Archerfish are renowned for dislodging aerial prey using well-aimed shots of water. Recently it has been shown that these fish can shape their aerial jets by adjusting the dynamics of their mouth opening and closing. This allows the fish to adjust their jet to target distance so that they can forcefully hit prey over considerable distances. Here, we suggest that archerfish use the same technique to also actively control jets under water. Fired from close range, the underwater jets are powerful enough to lift up buried food particles, which the fish then can pick up. We trained fish so that we could monitor their mouth opening and closing maneuvers during underwater shooting and compare them with those employed in aerial shooting. Our analysis suggests that the fish use the same dynamic mechanism to produce aerial and underwater jets and that they employ the same basic technique to adjust their jets in both conditions. When food is buried in substrate that consists of large particles, the fish use a brief pulse, but they use a longer one when the substrate is more fine-grained. These findings extend the notion that archerfish can flexibly shape their jets to be appropriate in different contexts and suggest that archerfish shooting might have been shaped both by constraints in aerial and underwater shooting.
Fabrication of poly-DL-lactide/polyethylene glycol scaffolds using the gas foaming technique.
Ji, Chengdong; Annabi, Nasim; Hosseinkhani, Maryam; Sivaloganathan, Sobana; Dehghani, Fariba
The aim of this study was to prepare poly-DL-lactide/polyethylene glycol (PDLLA/PEG) blends to improve medium absorption and cell proliferation in the three-dimensional (3-D) structure of their scaffolds. Carbon dioxide (CO2) was used as a foaming agent to create porosity in these blends. The results of Fourier transform infrared (FTIR) spectroscopy demonstrated that the blends were homogeneous mixtures of PDLLA and PEG. The peak shifts at 1092 and 1744 cm(-1) confirmed the presence of molecular interactions between these two compounds. Increasing the PEG weight ratio enhanced the relative crystallinity and hydrophilicity. The PDLLA/PEG blends (especially 80/20 and 70/30 weight ratios) exhibited linear degradation profiles over an incubation time of 8 weeks. The mechanical properties of PDLLA/PEG blends having less than 30 wt.% PEG were suitable for the fabrication of porous scaffolds. Increasing the concentration of PEG to above 50% resulted in blends that were brittle and had low mechanical integrity. Highly porous scaffolds with controllable pore size were produced for 30 wt.% PEG samples using the gas foaming technique at temperatures between 25 and 55 °C and pressures between 60 and 160 bar. The average pore diameters achieved by gas foaming process were between 15 and 150 μm, and had an average porosity of 84%. The medium uptake and degradation rate of fabricated PDLLA/PEG scaffolds were increased compared with neat PDLLA film due to the presence of PEG and porosity. The porous scaffolds also demonstrated a lower modulus of elasticity and a higher elongation at break compared to the non-porous film. The fabricated PDLLA/PEG scaffolds have high potential for various tissue-engineering applications.
Simple multimask technique for fabrication of high-resolution polymer structures
NASA Astrophysics Data System (ADS)
Cowin, Michael A.; Penty, Richard V.; White, Ian H.
The performance of many integrated photonic deices is often determined by the accuracy by which the structure can be defined and ultimately fabricated. However the manufacture of highly defined vertices in photonic structures is often limited by the mask quality and by the limited resolution obtainable by standard photolithography. A simplified fabrication technique is presented here, that offers advantages over previously reported methods for the fabrication of highly defined vertices in polymeric integrated optical components so overcoming these limiting factors. The application of this technique for the fabrication of 2D integrated optical wavelength division multiplexing components is demonstrated. The possible application of this component to the low cost datacom market is also reviewed and compared to competitive technologies. The advantages of the technique is discussed and the improved resolution obtainable in comparison to standard single mask photolithography is illustrated.
Artificial submicron or nanometer speckle fabricating technique and electron microscope speckle photography
Liu Zhanwei; Xie Huimin; Fang Daining; Dai Fulong; Wang Weining; Fang Yan
In this article, a novel artificial submicro- or nanometer speckle fabricating technique is proposed by taking advantage of submicro or nanometer particles. In the technique, submicron or nanometer particles were adhered to an object surface by using ultrasonic dispersing technique. The particles on the object surface can be regarded as submicro or nanometer speckle by using a scanning electronic microscope at a special magnification. In addition, an electron microscope speckle photography (EMSP) method is developed to measure in-plane submicron or nanometer deformation of the object coated with the artificial submicro or nanometer speckles. The principle of artificial submicro or nanometer speckle fabricating technique and the EMSP method are discussed in detail in this article. Some typical applications of this method are offered. The experimental results verified that the artificial submicro or nanometer speckle fabricating technique and EMSP method is feasible.
Structures and fabrication techniques for solid state electrochemical devices
Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.
Low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures provide solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one aspect the invention provides techniques for co-firing of device substrate (often an electrode) with an electrolyte or membrane layer to form densified electrolyte/membrane films 5 to 20 microns thick. In another aspect, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe and Cu, or alloys thereof.
Current techniques in CAD/CAM denture fabrication.
Baba, Nadim Z; AlRumaih, Hamad S; Goodacre, Brian J; Goodacre, Charles J
Recently, the use of computer-aided design/computer-aided manufacturing (CAD/CAM) to produce complete dentures has seen exponential growth in the dental market, and the number of commercially available CAD/CAM denture systems grows every year. The purpose of this article is to describe the clinical and laboratory procedures of 5 CAD/CAM denture systems.
MEMS pressure sensor fabricated by advanced bulk micromachining techniques
NASA Astrophysics Data System (ADS)
Vanko, Gabriel; Hudek, Peter; Zehetner, Johann; Dzuba, Jaroslav; Choleva, Pavlina; Vallo, Martin; Rýger, Ivan; Lalinský, Tibor
We present the design and implementation of a MEMS pressure sensor with an operation potential under harsh conditions at high temperatures (T = 300 - 800°C). The sensor consists of a circular HEMT (C-HEMT) integrated on a circular AlGaN/GaN membrane. In order to realize MEMS for extreme conditions using AlGaN/GaN material system, two key issues should be solved: (a) realization of MEMS structures by etching of the substrate material and (b) formation of metallic contacts (both ohmic and Schottky) to be able to withstand high thermal loads. In this design concept the piezoresistive and piezoelectric effect of AlGaN/GaN heterostructure is used to sense the pressure under static and/or dynamic conditions. The backside bulk micromachining of our SiC wafer in the first experiment started with FS-laser ablation down to ~200 -270μm deep holes of 500μm in diameter. Because no additional intermediate layer can stop the ablation process, the number of laser pulses has to be optimized in order to reach the required ablation depth. 2D structural-mechanical and piezoelectric analyses were performed to verify the mechanical and piezoelectric response of the circular membrane pressure sensor to static pressure load (in the range between 20 and 100kPa). We suggested that suppressing the residual stress in the membrane can improve the sensor response. The parameters of the same devices previously fabricated on bulk substrates and/or membranes were compared. The maxima of drain currents of our C-HEMT devices on SiC exhibit more than four times higher values compared to those measured on silicon substrates.
Levofloxacin implants with predefined microstructure fabricated by three-dimensional printing technique.
Huang, Weidong; Zheng, Qixin; Sun, Wangqiang; Xu, Huibi; Yang, Xiangliang
A novel three-dimensional (3D) printing technique was utilized in the preparation of drug implants that can be designed to have complex drug release profiles. The method we describe is based on a lactic acid polymer matrix with a predefined microstructure that is amenable to rapid prototyping and fabrication. We describe how the process parameters, especially selection of the binder, were optimized. Implants containing levofloxacin (LVFX) with predefined microstructures using an optimized binder solution of ethanol and acetone (20:80, v/v) were prepared by a 3D printing process that achieved a bi-modal profile displaying both pulsatile and steady state LVFX release from a single implant. The pulse release appeared from day 5 to 25, followed by a steady state phase of 25 days. The next pulse release phase then began at the 50th day and ended at the 80th day. To evaluate the drug implants structurally and analytically, the microscopic morphologies and the in vitro release profiles of the implants fabricated by both the 3D printing technique and the conventional lost mold technique were assessed using environmental scanning electron microscopy (ESEM) and UV absorbance spectrophotometry. The results demonstrate that the 3D printing technology can be used to fabricate drug implants with sophisticated micro- and macro-architecture in a single device that may be rapidly prototyped and fabricated. We conclude that drug implants with predefined microstructure fabricated by 3D printing techniques can have clear advantages compared to implants fabricated by conventional compressing methods.
A technique to facilitate the fabrication of provisional restorations for ITI solid abutments.
Kurt, Murat; Güler, Ahmet Umut; Erkoçak, Ayça; Sanal, Fatma Ayşe
The aim of this technique report was to present a procedure for the fabrication of provisional restorations for ITI solid abutments using impression caps in the laboratory with a number of advantages over intraoral techniques. There may be no need for cementation, and elimination of cementation may assist tissue healing.
A direct technique for fabricating esthetic anterior fixed provisional restorations using polycarbonate veneers.
Bidra, Avinash S; Manzotti, Anna
Fabrication of esthetic interim restorations by a chairside technique often challenges the clinician with regard to the required time and skills, as well as meeting the expectations of the patient. Autopolymerizing polymethyl methacrylate resin has been reported to be the most popular material for fabricating provisional restorations. However, this material does not routinely yield esthetic provisional restorations via a chairside technique. This article describes a simple technique to overcome some of the disadvantages of this material by using prefabricated polycarbonate facings backed with autopolymerizing acrylic resin. This technique can be used chairside for fabricating esthetic anterior interim restorations, utilizing the beneficial properties of both materials. It exploits the manufactured smooth-surface finish, superior esthetics, color stability, and durability of polycarbonate facings, as well as the marginal adaptation, strength, and low cost of autopolymerizing acrylic resin.
Mass-producible and efficient optical antennas with CMOS-fabricated nanometer-scale gap.
Seok, Tae Joon; Jamshidi, Arash; Eggleston, Michael; Wu, Ming C
Optical antennas have been widely used for sensitive photodetection, efficient light emission, high resolution imaging, and biochemical sensing because of their ability to capture and focus light energy beyond the diffraction limit. However, widespread application of optical antennas has been limited due to lack of appropriate methods for uniform and large area fabrication of antennas as well as difficulty in achieving an efficient design with small mode volume (gap spacing < 10nm). Here, we present a novel optical antenna design, arch-dipole antenna, with optimal radiation efficiency and small mode volume, 5 nm gap spacing, fabricated by CMOS-compatible deep-UV spacer lithography. We demonstrate strong surface-enhanced Raman spectroscopy (SERS) signal with an enhancement factor exceeding 108 from the arch-dipole antenna array, which is two orders of magnitude stronger than that from the standard dipole antenna array fabricated by e-beam lithography. Since the antenna gap spacing, the critical dimension of the antenna, can be defined by deep-UV lithography, efficient optical antenna arrays with nanometer-scale gap can be mass-produced using current CMOS technology.
New fabrication techniques for high dynamic range tunneling sensors
NASA Astrophysics Data System (ADS)
Chang, David T.; Stratton, Fred P.; Kubena, Randall L.; Vickers-Kirby, Deborah J.; Joyce, Richard J.; Schimert, Thomas R.; Gooch, Roland W.
We have developed high dynamic range (105-106 g's) tunneling accelerometers1,2 that may be ideal for smart munitions applications by employing both surface and bulk micromachining processing techniques. The highly miniaturized surface-micromachined devices can be manufactured at very low cost and integrated on chip with the control electronics. Bulk-micromachined devices with Si as the cantilever material should have reduced long-term bias drift as well as better stability at higher temperatures. Fully integrated sensors may provide advantages in minimizing microphonics for high-g applications. Previously, we described initial test results using electrostatic forces generated by a self-test electrode located under a Au cantilever3. In this paper, we describe more recent testing of Ni and Au cantilever devices on a shaker table using a novel, low input voltage (5 V) servo controller on both printed wiring board and surface-mount control circuitry. In addition, we report our initial test results for devices packaged using a low-temperature wafer-level vacuum packaging technique for low-cost manufacturing.
Strategic design and recent fabrication techniques for bioengineered tissue scaffolds to improve peripheral nerve regeneration.
Rajaram, Ajay; Chen, Xiong-Biao; Schreyer, David J
Bioengineered tissue scaffolds are a potential tool for improving regenerative repair of damaged peripheral nerves. Novel modes of fabrication coupled with scaffold design strategies that are based on an understanding of the biology of nerve injury offer the prospect of intervention at a more sophisticated level. We review the etiology and incidence of peripheral nerve injury and the biological events that unfold during nerve regeneration after an injury. Newly available tissue scaffold fabrication technologies using bioplotting and laser-based techniques are described. Scaffold design strategies are also discussed, including the incorporation of living cells during scaffold fabrication, inclusion of neurotrophic gradients, use of electric stimulation, inclusion of antioxidant compounds to counteract neural apotosis, and promotion of angiogenesis. Use of these advanced fabrication techniques and incorporation of one or more of these active biological strategies may eventually lead to a greater success in peripheral nerve tissue engineering.
Combinatorial-mold imprint lithography: A versatile technique for fabrication of three-dimensional polymer structures
NASA Astrophysics Data System (ADS)
Low, Hong Yee; Zhao, Wei; Dumond, Jarrett
A two-step fabrication technique based on nanoimprint lithography is described for the fabrication of three-dimensional micro- and nanostructures. By combining simple two-dimensional geometries from two molds, complex and useful three-dimensional structures are obtained. The careful selection of mold geometries constitutes a simplified and efficient approach toward building up desirable three-dimensional structures without resorting to the use of a sacrificial process or components. Three-dimensional structures fabricated for a variety of specific applications are presented using both thermoplastic and cross-linked polymer materials.
Rapid vacuum sintering: a novel technique for fabricating fluorapatite ceramic scaffolds for bone tissue engineering.
Denry, Isabelle; Goudouri, Ourania-Menti; Harless, Jeffrey; Holloway, Julie A
Macroporous bioceramic scaffolds are often fabricated via the foam replica technique, based on polymeric foam impregnation with a glass slurry, followed by slow heat treatment to allow for drying, polymeric burnout, and sintering of the glass particles. As a consequence, the process is time consuming and complicated by concurrent crystallization of the glass, often leading to incomplete sintering. Our goal was to investigate the effect of heating rate on sintering behavior, architecture, and mechanical properties of fluorapatite-based glass and glass-ceramic scaffolds. Glass scaffolds were prepared and sintered by rapid vacuum sintering (RVS) at 785°C under vacuum at a fast heating rate (55°C/min.) or without vacuum at a slow heating rate (2°C/min.). Two additional groups were further crystallized at 775°C/1 h. XRD confirmed the presence of fluorapatite for crystallized scaffolds. All groups presented interconnected porosity with a pore size in the 500 μm range. Scaffolds produced by RVS exhibited an excellent degree of sintering while scaffolds produced by slow sintering were incompletely sintered. The mean compressive strength was significantly higher for the RVS groups (1.52 ± 0.55 and 1.72 ± 0.61 MPa) compared to the slow-sintered groups (0.54 ± 0.30 and 0.45 ± 0.26 MPa). Meanwhile, the total production time was reduced by more than 12 h by using the RVS technique. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017.
Fabrication of ultra-fine grained aluminium tubes by RTES technique
Jafarzadeh, H. Abrinia, K.
Recently, repetitive tube expansion and shrinking have been exploited as a means for producing ultra-fine grained and nano-crystalline microstructures for magnesium alloy tubes. This method includes two different half-cycles and was based on pressing a tubular part through an angular channel die with two shear zones. Since the aluminium alloys are the most widely used materials in industries, in this study, repetitive tube expansion and shrinking as a new severe plastic deformation technique was applied to commercially pure aluminium for fabricating ultra-fine grained aluminium tubes for the first time and the ability of this process in significant grain refinement is determined even after single cycle. Transmission electron microscopy and X-ray diffraction were used to evaluate the microstructure of the repetitive tube expansion and shrinking processed materials and the examinations showed ultra-fine grains with the average grain size of 320 nm after one cycle of repetitive tube expansion and shrinking. The yield strength, ultimate tensile strength increased notably by the factor of 2.17 and 1.27 respectively, after one cycle of repetitive tube expansion and shrinking, whereas the elongation to failure as well as the uniform elongation decreased. Furthermore, micro-hardness distribution through the part's section proposed the hardness increasing to ~ 55 HV from the initial value of ~ 28 HV after one cycle of repetitive tube expansion and shrinking. - Highlights: • RTES was introduced for fabricating the UFGed AA1050 tubes for the first time. • Nano-grained AA1050 tube was obtained by RTES process. • Grain size of ~ 320 nm was obtained after two half-cycles of RTES process. • Yield and ultimate strength increased by the factor of 2.17 and 1.27 respectively. • The microhardness increased to ~ 55 HV from the initial value of ~ 28 HV.
Biofabrication Under Fluorocarbon: A Novel Freeform Fabrication Technique to Generate High Aspect Ratio Tissue-Engineered Constructs
Blaeser, Andreas; Duarte Campos, Daniela F.; Weber, Michael; Neuss, Sabine; Theek, Benjamin; Fischer, Horst
Abstract Bioprinting is a recent development in tissue engineering, which applies rapid prototyping techniques to generate complex living tissues. Typically, cell-containing hydrogels are dispensed layer-by-layer according to a computer-generated three-dimensional model. The lack of mechanical stability of printed hydrogels hinders the fabrication of high aspect ratio constructs. Here we present submerged bioprinting, a novel technique for freeform fabrication of hydrogels in liquid fluorocarbon. The high buoyant density of fluorocarbons supports soft hydrogels by floating. Hydrogel constructs of up to 30-mm height were generated. Using 3% (w/v) agarose as the hydrogel and disposable syringe needles as nozzles, the printer produced features down to 570-μm diameter with a lateral dispensing accuracy of 89 μm. We printed thin-walled hydrogel cylinders measuring 4.8 mm in height, with an inner diameter of ∼2.9 mm and a minimal wall thickness of ∼650 μm. The technique was successfully applied in printing a model of an arterial bifurcation. We extruded under fluorocarbon, cellularized alginate tubes with 5-mm outer diameter and 3-cm length. Cells grew vigorously and formed clonal colonies within the 7-day culture period. Submerged bioprinting thus seems particularly suited to fabricate hollow structures with a high aspect ratio like vascular grafts for cardiovascular tissue engineering as well as branching or cantilever-like structures, obviating the need for a solid support beneath the overhanging protrusions. PMID:24083093
Development of core cladding fabrication techniques for phase I fission propulsion systems
NASA Astrophysics Data System (ADS)
Salvail, Patrick G.; Reid, Robert S.; Ring, Peter J.
Phase I fission propulsion systems focus on safety, timely development, and affordability. Prototype and flight units can be tested at full thrust, using resistance heaters to closely simulate heat from a fission reaction. In Phase I ground testing, one goal is to establish a reliable and affordable manufacturing technique for fabricating a flight-like core. A refractory metal (Mo) has been suggested for the core substrate, primarily due to the existence of a significant database for Mo/UO2 fuel. The core can be fabricated by bundling Mo tubes with a bonding system that meets preliminary test goals. These criteria include materials compatibility, ability to maintain thermal and structural integrity during 10,000 hours of operation, and fabrication with existing facilities. This paper describes an effort to investigate several fabrication techniques in a cost-effective manner. First, inexpensive materials were tested at low temperatures to determine the relative effectiveness of such techniques as welding, brazing, plating, and vacuum plasma spraying (VPSing). Promising techniques were chosen for further evaluation, including thermal and structural studies, using ceramic tubing at intermediate temperatures. The most desirable technique will be tested on actual Mo tubing at anticipated operating temperatures. This work is being performed by the National Aeronautics & Space Administration (NASA) at George C. Marshall Space Flight Center (MSFC), Los Alamos National Laboratory (LANL), and Advanced Methods & Materials (AMM), Inc. .
Fabric phase sorptive extraction: Two practical sample pretreatment techniques for brominated flame retardants in water.
Huang, Guiqi; Dong, Sheying; Zhang, Mengfei; Zhang, Haihan; Huang, Tinglin
Sample pretreatment is the critical section for residue monitoring of hazardous pollutants. In this paper, using the cellulose fabric as host matrix, three extraction sorbents such as poly (tetrahydrofuran) (PTHF), poly (ethylene glycol) (PEG) and poly (dimethyldiphenylsiloxane) (PDMDPS), were prepared on the surface of the cellulose fabric. Two practical extraction techniques including stir bar fabric phase sorptive extraction (stir bar-FPSE) and magnetic stir fabric phase sorptive extraction (magnetic stir-FPSE) have been designed, which allow stirring of fabric phase sorbent during the whole extraction process. In the meantime, three brominated flame retardants (BFRs) [tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bisallylether (TBBPA-BAE), tetrabromobisphenol A bis(2,3-dibromopropyl)ether (TBBPA-BDBPE)] in the water sample were selected as model analytes for the practical evaluation of the proposed two techniques using high-performance liquid chromatography (HPLC). Moreover, various experimental conditions affecting extraction process such as the type of fabric phase, extraction time, the amount of salt and elution conditions were also investigated. Due to the large sorbent loading capacity and unique stirring performance, both techniques possessed high extraction capability and fast extraction equilibrium. Under the optimized conditions, high recoveries (90-99%) and low limits of detection (LODs) (0.01-0.05 μg L(-1)) were achieved. In addition, the reproducibility was obtained by evaluating the intraday and interday precisions with relative standard deviations (RSDs) less than 5.1% and 6.8%, respectively. The results indicated that two pretreatment techniques were promising and practical for monitoring of hazardous pollutants in the water sample. Due to low solvent consumption and high repeated use performance, proposed techniques also could meet green analytical criteria.
New finishing possibilities for producing durable multifunctional cotton/wool and viscose/wool blended fabrics.
Ibrahim, N A; El-Zairy, M R; Eid, B M; El-Zairy, E M R; Emam, E M
This research work focuses on the development of a one-bath functional finishing procedure for imparting durable multifunctional properties such as easy care, soft-hand, antibacterial and/or ultra violet (UV) protection to cotton/wool and viscose/wool blends using diverse finishing combinations and formulations. In this study finishing agents such as reactant resin, silicon softeners, 4-hydroxybenzophenone, triclosan, and pigment colorant were selected using magnesium chloride/citric acid as a mixed catalyst and the pad-dry microwave fixation technique. The results reveal that enhancement in the imparted functional properties are governed by type of the finished substrate as well as nature and concentration of finishing formulation components. The finished fabrics still retained high level of functionalities even after 15 consecutive laundering. Surface morphology and composition of selected samples were investigated using scan electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. The mode of interactions was also investigated. Practical applications for multifunctionlization of cellulose/wool blended fabrics are possible using these sorts of proper finishing formulations and unique finishing application method.
High frequency PMN-PT single crystal focusing transducer fabricated by a mechanical dimpling technique.
Chen, Y; Lam, K H; Zhou, D; Cheng, W F; Dai, J Y; Luo, H S; Chan, H L W
High frequency (∼30MHz and ∼80MHz) focusing ultrasound transducers were fabricated using a PMN-0.28PT single crystal by a mechanical dimpling technique. The dimpled single crystal was used as an active element for the focusing transducer. Compared with a plane transducer, the focusing transducer fabricated with a dimpled active element exhibits much broader bandwidth and higher sensitivity. Besides, a high quality image can be obtained by the 30MHz focusing transducer, in which the -6dB axial and lateral resolution is 27μm and 139μm, respectively. These results prove that the dimpling technique is capable to fabricate the high frequency focusing transducers with excellent performance for imaging applications.
Nano-fabricated superconducting radio-frequency composites, method for producing nano-fabricated superconducting rf composites
Norem, James H.; Pellin, Michael J.
Superconducting rf is limited by a wide range of failure mechanisms inherent in the typical manufacture methods. This invention provides a method for fabricating superconducting rf structures comprising coating the structures with single atomic-layer thick films of alternating chemical composition. Also provided is a cavity defining the invented laminate structure.
A new fabrication technique for back-to-back varactor diodes
NASA Technical Reports Server (NTRS)
Smith, R. Peter; Choudhury, Debabani; Martin, Suzanne; Frerking, Margaret A.; Liu, John K.; Grunthaner, Frank A.
A new varactor diode process has been developed in which much of the processing is done from the back of an extremely thin semiconductor wafer laminated to a low-dielectric substrate. Back-to-back BNN diodes were fabricated with this technique; excellent DC and low-frequency capacitance measurements were obtained. Advantages of the new technique relative to other techniques include greatly reduced frontside wafer damage from exposure to process chemicals, improved capability to integrate devices (e.g. for antenna patterns, transmission lines, or wafer-scale grids), and higher line yield. BNN diodes fabricated with this technique exhibit approximately the expected capacitance-voltage characteristics while showing leakage currents under 10 mA at voltages three times that needed to deplete the varactor. This leakage is many orders of magnitude better than comparable Schottky diodes.
Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.
Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao
In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.
Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties
Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao
In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546
An innovative impression technique for fabrication of a custom made ocular prosthesis
Tripuraneni, Sunil Chandra; Vadapalli, Sriharsha Babu; Ravikiran, P; Nirupama, N
Various impression and fitting techniques have been described in the past for restoring ocular defects. The present article describes a new direct impression technique for recording and rehabilitating ocular defects, by custom-made ocular prosthesis. All the techniques described in the history, mainly concentrated in recording the tissue surface of the defect, which made it difficult to contour the palpebral surface resulting in the poor esthetics of the prosthesis. The present impression technique uses heavy bodied polyvinyl siloxane impression material, which facilitates accurate recording of the tissue surface and the palpebral surface of the defect, resulting in the fabrication of functionally and esthetically acceptable prosthesis. PMID:26265651
Fabrication of Ultrasensitive Field-Effect Transistor DNA Biosensors by a Directional Transfer Technique Based on CVD-Grown Graphene.
Zheng, Chao; Huang, Le; Zhang, Hong; Sun, Zhongyue; Zhang, Zhiyong; Zhang, Guo-Jun
Most graphene field-effect transistor (G-FET) biosensors are fabricated through a routine process, in which graphene is transferred onto a Si/SiO2 substrate and then devices are subsequently produced by micromanufacture processes. However, such a fabrication approach can introduce contamination onto the graphene surface during the lithographic process, resulting in interference for the subsequent biosensing. In this work, we have developed a novel directional transfer technique to fabricate G-FET biosensors based on chemical-vapor-deposition- (CVD-) grown single-layer graphene (SLG) and applied this biosensor for the sensitive detection of DNA. A FET device with six individual array sensors was first fabricated, and SLG obtained by the CVD-growth method was transferred onto the sensor surface in a directional manner. Afterward, peptide nucleic acid (PNA) was covalently immobilized on the graphene surface, and DNA detection was realized by applying specific target DNA to the PNA-functionalized G-FET biosensor. The developed G-FET biosensor was able to detect target DNA at concentrations as low as 10 fM, which is 1 order of magnitude lower than those reported in a previous work. In addition, the biosensor was capable of distinguishing the complementary DNA from one-base-mismatched DNA and noncomplementary DNA. The directional transfer technique for the fabrication of G-FET biosensors is simple, and the as-constructed G-FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential application in disease diagnostics as a point-of-care tool.
TiB 2/TiSi 2 bilayer fabrication by various techniques: Structure and contact properties
NASA Astrophysics Data System (ADS)
Pelleg, Joshua; Sade, G.
TiB 2/TiSi 2 films were produced by several techniques in an attempt to evaluate the most appropriate method to fabricate this system. Analysis by X-ray diffraction, Auger electron spectroscopy, transmission and high-resolution transmission electron microscopy indicate that the best method to obtain the above system is by sequential cosputtering of the layers without exposure to air between the two cosputtering sequences. Post-deposition annealing was performed to obtain a low resistive bilayer. Schottky diodes fabricated by this method provided an average barrier height of ∼0.68 V with an ideality factor in the range of 1.0-1.04 (excluding the as-deposited specimen). In specimens fabricated by silicidation of TiB 2/Ti films formation of TiSi 2 was Ti thickness dependent [G. Sade, Ph.D. Thesis, Ben Gurion University of the Negev, Beer Sheva, Israel, 1999]. Small amounts of Ti 5Si 3 were observed at 1123 K. The attempts to obtain a TiB 2/TiSi 2 bilayer from (Ti+B) enriched with Ti at 1073 K resulted in the formation of small amounts of Ti 5Si 3, and some crystallization of the amorphous TiB 2 also occurred. Diodes fabricated by this technique showed Ohmic rather than rectifying character. The shift from rectifying to Ohmic behavior is the result of B out-diffusion to the Si and the consequent change of the substrate from an n- to a p-type Si. The results place the Fermi level of TiB 2 about 0.9 eV below the silicon conduction band. A remedy to this problem could result in a challenging method of fabricating a TiB 2/TiSi 2 bilayer structure in a one-step process.
Photographic and drafting techniques simplify method of producing engineering drawings
NASA Technical Reports Server (NTRS)
Provisor, H.
Combination of photographic and drafting techniques has been developed to simplify the preparation of three dimensional and dimetric engineering drawings. Conventional photographs can be converted to line drawings by making copy negatives on high contrast film.
Application of Optical Measurement Techniques During Fabrication and Testing of Liquid Rocket Nozzles
NASA Technical Reports Server (NTRS)
Gradl, Paul R.
This paper presents a series of optical measurement techniques that were developed for use during large-scale fabrication and testing of nozzle components. A thorough understanding of hardware throughout the fabrication cycle and hotfire testing is critical to meet component design intent. Regeneratively cooled nozzles and associated tooling require tight control of tolerances during the fabrication process to ensure optimal performance. Additionally, changes in geometry during testing can affect performance of the nozzle and mating components. Structured light scanning and digital image correlation techniques were used to collect data during the fabrication and test of nozzles, in addition to other engine components. This data was used to analyze deformations data during machining, heat treatment, assembly and testing operations. A series of feasibility experiments were conducted for these techniques that led to use on full scale nozzles during the J-2X upper stage engine program in addition to other engine development programs. This paper discusses the methods and results of these measurement techniques throughout the nozzle life cycle and application to other components.
ORNL Demonstrates Large-Scale Technique to Produce Quantum Dots
Graham, David; Moon, Ji-Won
A method to produce significant amounts of semiconducting nanoparticles for light-emitting displays, sensors, solar panels and biomedical applications has gained momentum with a demonstration by researchers at Oak Ridge National Laboratory.
ORNL Demonstrates Large-Scale Technique to Produce Quantum Dots
Graham, David; Moon, Ji-Won
A method to produce significant amounts of semiconducting nanoparticles for light-emitting displays, sensors, solar panels and biomedical applications has gained momentum with a demonstration by researchers at Oak Ridge National Laboratory.
Low-cost epitaxial techniques for solar-cell fabrication. Final report, 25 September 1979-24 September 1980
D'Aiello, R.V.; Robinson, P.H.
This research and development effort was designed to investigate epitaxial growth processes which will allow the use of low-cost forms of silicon for fabricating high-efficiency, cost-effective solar cells. This report covers the results of a 1-y effort which involved characterization of potentially low-cost silicon substrates, epitaxial growth studies, and the fabrication and evaluation of solar cells made in the epitaxial layers. Silicon substrates prepared from metallurgical grade silicon by potentially low-cost purification and growth techniques form satisfactory substrates for epitaxial growth and the fabrication of 10 to 12% efficient solar cells. The allowable range of variation in the key parameters of the epitaxial process and cell structures was determined and it was found that a greater variation in these parameters is possible for solar cells compared with those required for epitaxial devices now produced in the semiconductor industry. Thin-film epitaxially grown solar cells were reproducibly demonstrated with efficiencies of over 10%. A scale-up to practical sized cells was shown to be feasible by fabricating cells of 10-cm/sup 2/ area with almost 10% efficiency.
Rapid Prototyping Technique for the Fabrication of Millifluidic Devices for Polymer Formulations
NASA Astrophysics Data System (ADS)
Cabral, Joao; Harrison, Christopher; Eric, Amis; Karim, Alamgir
We describe a rapid prototyping technique for the fabrication of 600 micron deep fluidic channels in a solvent-resistant polymeric matrix. Using a conventional illumination source, a laser-jet printed mask, and a commercially available thioelene-based adhesive, we demonstrate the fabrication of fluidic channels which are impervious to a wide range of solvents. The fabrication of channels with this depth by conventional lithography would be both challenging and time-consuming. We demonstrate two lithography methods: one which fabricates channels sealed between glass plates (closed face) and one which fabricates structures on a single plate (open-faced). Furthermore, we demonstrate that this technology can be used to fabricate channels with a depth which varies linearly with distance. The latter is completely compatible with silicone replication technniques. Additionally, we demonstrate that siloxane-based elastomer molds of these channels can be readily made for aqueous applications. Applications to on-line phase mapping of polymer solutions (PEO-Water-Salt) and off line phase separation studies will be discussed.
Nacre-like materials using a simple doctor blading technique: Fabrication, testing and modeling.
Mirkhalaf, M; Barthelat, F
The remarkable mechanical performance of biological materials such as bone, nacre, and spider silk stems from their staggered microstructure in which stiff and strong reinforcements are elongated in the direction of loading, separated by softer interfaces, and shifted relative to each other. This structure results in useful combinations of modulus, strength and toughness and therefore is increasingly mimicked in bio-inspired engineering composites. Here, we report the use of a simple and versatile technique based on doctor-blading to fabricate staggered composites of microscopic alumina tablets with high alignment in a chitosan matrix. Tensile tests on these nacre-like materials show that the modulus and strength of the composite films are enhanced by the incorporation of ceramic tablets, but only up to 15vol% after which all properties degrade. This phenomenon, also reported in the past for most of nacre-like materials, composed of micro/nano tablets, obtained from different techniques, has been limiting our ability to produce large volumes of high-performance nacre-like materials. Examination of the structure of the films revealed that at lower tablet concentrations the tablets are well-aligned and well dispersed thorough the volume of the film. At 15vol% and beyond, we observed tablet misalignment and clustering. In order to investigate the impact of these imperfections on material performance we developed large scale finite element models representative of the structure of the composite films. These models show that the mechanical performance significantly degrades with tablet misalignment, and especially at high tablet concentrations. The simulations along with the SEM images therefore quantitatively explain the experimental trends, e.g. the degradation of mechanical properties at high tablet contents.
Er3+-activated photonic structures fabricated by sol-gel and rf-sputtering techniques
NASA Astrophysics Data System (ADS)
Ferrari, M.; Alombert-Goget, G.; Armellini, C.; Berneschi, S.; Bhaktha, S. N. B.; Boulard, B.; Brenci, M.; Chiappini, A.; Chiasera, A.; Duverger-Arfuso, C.; Féron, P.; Gonçalves, R. R.; Jestin, Y.; Minati, L.; Moser, E.; Nunzi Conti, G.; Pelli, S.; Rao, D. N.; Retoux, R.; Righini, G. C.; Speranza, G.
The realization of photonic structures operating at visible and near infrared frequencies is a highly attractive scientific and technological challenge. Since optical fiber innovation, a huge of activity has been performed leading to interesting results, such as optical waveguides and planar lightwave circuits, microphotonic devices, optical microcavities, nanowires, plasmonic structures, and photonic crystals. These systems have opened new possibilities in the field of both basic and applied physics, in a large area covering Information Communication Technologies, Health and Biology, Structural Engineering, and Environment Monitoring Systems. Several materials and techniques are employed to successfully fabricate photonic structures. Concerning materials, Er3+-activated silica-based glasses still play an important role, although recently interesting results have been published about fluoride glass-ceramic waveguides. As far as regards the fabrication methods sol-gel route and rf sputtering have proved to be versatile and reliable techniques. In this article we will present a review of some Er3+-activated photonic structures fabricated by sol gel route and rf sputtering deposition. In the discussion on the sol-gel approach we focus our attention on the silica-hafnia binary system presenting an overview concerning fabrication protocols and structural, optical and spectroscopic assessment of SiO2-HfO2 waveguides activated by Er3+ ions. In order to put in evidence the reliability and versatility of the sol-gel route for photonics applications four different confined structures are briefly presented: amorphous waveguides, coated microspheres, monolithic waveguide laser, and core-shell nanospheres. As examples of rf sputtering technique, we will discuss Er3+-activated silica-hafnia and silica-germania waveguides, the latter system allowing fabrication of integrated optics structures by UV photo-imprinting. Finally, two examples of photonic crystal structures, one
Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique
Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu
Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin–avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin–biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area. PMID:24770668
High T(sub c) superconductors fabricated by plasma aerosol mist deposition technique
NASA Technical Reports Server (NTRS)
Wang, X. W.; Vuong, K. D.; Leone, A.; Shen, C. Q.; Williams, J.; Coy, M.
We report new results on high T(sub c) superconductors fabricated by a plasma aerosol mist deposition technique, in atmospheric environment. Materials fabricated are YBaCuO, BiPbSrCaCuO, BaCaCuO precursor films for TlBaCaCuO, and other buffers such as YSZ. Depending on processing conditions, sizes of crystallites and/or particles are between dozens of nano-meters and several micrometers. Superconductive properties and other material characteristics can also be tailored.
Instantly AgNPs deposition through facile solventless technique for poly-functional cotton fabrics.
Emam, Hossam E; Saleh, N H; Nagy, Khaled S; Zahran, M K
Nowadays, functional clothes are employed for human body protection in addition to be fashionable clothes. Hence functionalization of clothes increases the attention of scientists and business. In the current study, poly-functional cotton fabric was carried out by instantly deposition of AgNPs using two solventless techniques namely; sorption and padding. Sorption technique was exhibited extremely high efficiency than padding one by ca. 10 times. By using the same concentrations of AgNO3, Ag content was ranged 69.3-6094.8 mg/kg and 33.8-609.3 mg/kg for sorption and padding, respectively. After AgNPs deposition, fabrics color was turned to gray-reddish yellow. By applying 5912.3 mgAg/kg fabric, bacterial reduction and UPF value were reached 99% and 12.59. Bacterial reduction and UPF were lessened to 90% and 10.19 after 20 washings. These findings proved that the direct AgNPs deposition into cotton using solventless/sorption technique is applicable in manufacturing of antibacterial/UV resistant fabrics with acquired decorative color.
A Novel Technique for Performing PID Susceptibility Screening during the Solar Cell Fabrication Process
Oh, Jaewon; Dahal, Som; Dauksher, Bill; Bowden, Stuart; Tamizhmani, Govindasamy; Hacke, Peter
Various characterization techniques have historically been developed in order to screen potential induced degradation (PID)-susceptible cells, but those techniques require final solar cells. We present a new characterization technique for screening PID-susceptible cells during the cell fabrication process. Illuminated Lock-In Thermography (ILIT) was used to image PID shunting of the cell without metallization and clearly showed PID-affected areas. PID-susceptible cells can be screened by ILIT, and the sample structure can advantageously be simplified as long as the sample has the silicon nitride antireflection coating and an aluminum back surface field.
Fabrication of Metal Oxide Thin Films Using the Langmuir-Blodgett Deposition Technique.
NASA Astrophysics Data System (ADS)
Johnson, David John
The Langmuir Blodgett (LB) deposition of metal arachidates was investigated as a technique for fabrication of metal oxides with emphasis placed on the lanthanide arachidates. Traditionally, these materials are difficult to deposit via the LB process, due to the rigidity of the floating monolayer. Studies on yttrium arachidate have shown that the quality of deposition of these materials is highly dependent on the concentration of the metal salt and the pH of the subphase. Yttrium arachidate was thus deposited at 10^{-5} M YCl_3 over a pH range of 4.0 to 6.9. Uniform multilayer films were produced with films at the higher pH's showing 100% yttrium arachidate. A pK_{rm a} value of 4.9 +/- 0.2 was obtained under these conditions. Fourier transform infrared spectroscopy, Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy data indicate that the metal is being incorporated into the arachidic acid predominantly as Y(OH) ^{2+}. A saturation areal density of (2.0 +/- 0.1) times 10^{14} Y/cm ^2 was measured for one layer of yttrium arachidate. Ellipsometric measurements were performed on films of yttrium arachidate to study order-disorder transitions. Upon heating the films were observed to undergo two transitions at 65^circC and 100 ^circC. At room temperature, the as -deposited films were found to be anisotropic with indices of refraction of N_{rm x} = 1.503 +/- 0.005 and N _{rm z} = 1.554 +/- 0.005 and a monolayer spacing of 2.73 +/- 0.03 nm. Above 100^ circC the films were isotropic with N = 1.440 +/- 0.005 and a thickness of 3.13 +/- 0.03 nm per original layer. The films showed no desorption below 100^circ C. In contrast to films of cadium arachidate, the yttrium arachidate films were observed to undergo supercooling by 35^circC. This may point to a lack of nucleation sites in the yttrium arachidate films explaining why they maintain areal integrity at high temperature while cadmium arachidate films do not. The decomposition of LB films was
Electroless-plating technique for fabricating thin-wall convective heat-transfer models
NASA Technical Reports Server (NTRS)
Avery, D. E.; Ballard, G. K.; Wilson, M. L.
A technique for fabricating uniform thin-wall metallic heat-transfer models and which simulates a Shuttle thermal protection system tile is described. Two 6- by 6- by 2.5-in. tiles were fabricated to obtain local heat transfer rates. The fabrication process is not limited to any particular geometry and results in a seamless thin-wall heat-transfer model which uses a one-wire thermocouple to obtain local cold-wall heat-transfer rates. The tile is relatively fragile because of the brittle nature of the material and the structural weakness of the flat-sided configuration; however, a method was developed and used for repairing a cracked tile.
Wearable strain sensors fabricated by silver nanowire patterning method based on parylene stencil technique.
Namsun Chou; Sohee Kim
This paper describes a fabrication method of the silver nanowire (AgNW) patterns on PDMS substrate using a parylene stencil technique. The AgNW electrodes with the straight line and serpentine line traces were fabricated and characterized in terms of electromechanical properties. The sensitivity of the AgNW patterns was measured using a custom-designed stretch test module, resulting in gauge factors from 55.2 to 2.7 at 2% strain for two different 100 um-wide AgNW patterns. The wearable sensor based on AgNW patterns was designed and fabricated to epidermally detect the respiration and heart rate from the abdomen and neck. The respiration was continuously recorded for 10 min successfully. The heart rate from the carotid artery was also recorded without applying external pressure.
Systems and Methods for Fabricating Objects Including Amorphous Metal Using Techniques Akin to Additive Manufacturing
NASA Technical Reports Server (NTRS)
Hofmann, Douglas (Inventor)
Systems and methods in accordance with embodiments of the invention fabricate objects including amorphous metals using techniques akin to additive manufacturing. In one embodiment, a method of fabricating an object that includes an amorphous metal includes: applying a first layer of molten metallic alloy to a surface; cooling the first layer of molten metallic alloy such that it solidifies and thereby forms a first layer including amorphous metal; subsequently applying at least one layer of molten metallic alloy onto a layer including amorphous metal; cooling each subsequently applied layer of molten metallic alloy such that it solidifies and thereby forms a layer including amorphous metal prior to the application of any adjacent layer of molten metallic alloy; where the aggregate of the solidified layers including amorphous metal forms a desired shape in the object to be fabricated; and removing at least the first layer including amorphous metal from the surface.
CAD/CAM machining Vs pre-sintering in-lab fabrication techniques of Y-TZP ceramic specimens: Effects on their mechanical fatigue behavior.
Zucuni, C P; Guilardi, L F; Fraga, S; May, L G; Pereira, G K R; Valandro, L F
This study evaluated the effects of different pre-sintering fabrication processing techniques of Y-TZP ceramic (CAD/CAM Vs. in-lab), considering surface characteristics and mechanical performance outcomes. Pre-sintered discs of Y-TZP ceramic (IPS e.max ZirCAD, Ivoclar Vivadent) were produced using different pre-sintering fabrication processing techniques: Machined- milling with a CAD/CAM system; Polished- fabrication using a cutting device followed by polishing (600 and 1200 SiC papers); Xfine- fabrication using a cutting machine followed by grinding with extra-fine diamond bur (grit size 30 μm); Fine- fabrication using a cutting machine followed by grinding with fine diamond bur (grit size 46 μm); SiC- fabrication using a cutting machine followed by grinding with 220 SiC paper. Afterwards, the discs were sintered and submitted to roughness (n=35), surface topography (n=2), phase transformation (n=2), biaxial flexural strength (n=20), and biaxial flexural fatigue strength (fatigue limit) (n=15) analyses. No monoclinic-phase content was observed in all processing techniques. It can be observed that obtaining a surface with similar characteristics to CAD/CAM milling is essential for the observation of similar mechanical performance. On this sense, grinding with fine diamond bur before sintering (Fine group) was the best mimic protocol in comparison to the CAD/CAM milling.
Techniques used to fabricate all-ceramic restorations in the dental practice.
Puri, Sameer
Porcelain is an increasingly popular material to use for restorations. This article will discuss the 3 main ways to fabricate porcelain restorations. The first method involves waxing up the restoration to the proper form and casting it in molten porcelain similar to the lost wax technique for gold. The second technique requires the use of porcelain in a powder form to be stacked on top of a refractory die or a platinum foil and then fired in the oven. The third main technique is the use of a CAD/CAM system to mill the porcelain restoration from a solid block of porcelain. All 3 techniques are valid and the clinician should have a thorough understanding of which techniques are appropriate in various clinical situations.
Investigation of etching techniques for superconductive Nb/Al-Al2O3/Nb fabrication processes
NASA Technical Reports Server (NTRS)
Lichtenberger, A. W.; Lea, D. M.; Lloyd, F. L.
Wet etching, CF4 and SF6 reactive ion etching (RIE), RIE/wet hybrid etching, Cl-based RIE, ion milling, and liftoff techniques have been investigated for use in superconductive Nb/Al-Al2O3/Nb fabrication processes. High-quality superconductor-insulator-superconductor (SIS) junctions have been fabricated using a variety of these etching methods; however, each technique offers distinct tradeoffs for a given process an wafer design. In particular, it was shown that SF6 provides an excellent RIE chemistry for low-voltage anisotropic etching of Nb with high selectivity to Al. The SF6 tool has greatly improved the trilevel resist junction insulation process. Excellent repeatability, selectivity with respect to quartz, and submicron resolution make Cl2 + BCl3 + CHCl3 RIE a very attractive process for trilayer patterning.
Fabrication of advanced electrochemical energy materials using sol-gel processing techniques
NASA Technical Reports Server (NTRS)
Chu, C. T.; Chu, Jay; Zheng, Haixing
Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.
Analytical and experimental evaluation of techniques for the fabrication of thermoplastic hologram storage devices
NASA Technical Reports Server (NTRS)
Rogers, J. W.
The results of an experimental investigation on recording information on thermoplastic are given. A description was given of a typical fabrication configuration, the recording sequence, and the samples which were examined. There are basically three configurations which can be used for the recording of information on thermoplastic. The most popular technique uses corona which furnishes free charge. The necessary energy for deformation is derived from a charge layer atop the thermoplastic. The other two techniques simply use a dc potential in place of the corona for deformation energy.
Technique for fabricating individualized dentures with a gingiva-shade composite resin.
Park, Beom-Woo; Kim, Nam-Jin; Lee, Jonghyuk; Lee, Hae-Hyoung
More natural dental esthetics have been sought by patients who wear conventional complete or partial dentures. Recently, gingiva-shade composite resins (GSCRs) have become available for replicating soft tissue for both fixed and removable prostheses. The technique presented is for fabricating individualized complete dentures. First the acrylic resin is mixed with a coloring agent and processed to modify the base shade of the denture. GSCRs are light polymerized onto a prepared space on the buccal surfaces of denture base to replicate the appearance of gingival tissues including blood vessels. The technique provides an outstanding natural, gingiva-like, appearance and allows complete dentures to harmonize with the individual patient's surrounding oral tissues.
Microstructural Examination to Aid in Understanding Friction Bonding Fabrication Technique for Monolithic Nuclear Fuel
Karen L. Shropshire
Monolithic nuclear fuel is currently being developed for use in research reactors, and friction bonding (FB) is a technique being developed to help in this fuel's fabrication. Since both FB and monolithic fuel are new concepts, research is needed to understand the impact of varying FB fabrication parameters on fuel plate characteristics. This thesis research provides insight into the FB process and its application to the monolithic fuel design by recognizing and understanding the microstructural effects of varying fabrication parameters (a) FB tool load, and (b) FB tool face alloy. These two fabrication parameters help drive material temperature during fabrication, and thus the material properties, bond strength, and possible formation of interface reaction layers. This study analyzed temperatures and tool loads measured during those FB processes and examined microstructural characteristics of materials and bonds in samples taken from the resulting fuel plates. This study shows that higher tool load increases aluminum plasticization and forging during FB, and that the tool face alloy helps determine the tool's heat extraction efficacy. The study concludes that successful aluminum bonds can be attained in fuel plates using a wide range of FB tool loads. The range of tool loads yielding successful uranium-aluminum bonding was not established, but it was demonstrated that such bonding can be attained with FB tool load of 48,900 N (11,000 lbf) when using a FB tool faced with a tungsten alloy. This tool successfully performed FB, and with better results than tools faced with other materials. Results of this study correlate well with results reported for similar aluminum bonding techniques. This study's results also provide support and validation for other nuclear fuel development studies and conclusions. Recommendations are offered for further research.
Extrusion based rapid prototyping technique: an advanced platform for tissue engineering scaffold fabrication.
Hoque, M Enamul; Chuan, Y Leng; Pashby, Ian
Advances in scaffold design and fabrication technology have brought the tissue engineering field stepping into a new era. Conventional techniques used to develop scaffolds inherit limitations, such as lack of control over the pore morphology and architecture as well as reproducibility. Rapid prototyping (RP) technology, a layer-by-layer additive approach offers a unique opportunity to build complex 3D architectures overcoming those limitations that could ultimately be tailored to cater for patient-specific applications. Using RP methods, researchers have been able to customize scaffolds to mimic the biomechanical properties (in terms of structural integrity, strength, and microenvironment) of the organ or tissue to be repaired/replaced quite closely. This article provides intensive description on various extrusion based scaffold fabrication techniques and review their potential utility for TE applications. The extrusion-based technique extrudes the molten polymer as a thin filament through a nozzle onto a platform layer-by-layer and thus building 3D scaffold. The technique allows full control over pore architecture and dimension in the x- and y- planes. However, the pore height in z-direction is predetermined by the extruding nozzle diameter rather than the technique itself. This review attempts to assess the current state and future prospects of this technology.
Carbon MEMS from the nanoscale to the macroscale: Novel fabrication techniques and applications in electrochemistry
NASA Astrophysics Data System (ADS)
Zaouk, Rabih Bachir
Micro electromechanical systems (MEMS) have strongly impacted our way of life in the last two decades. From accelerometers and gyroscopes that ensure your driving safety, to inkjet printer cartridges that transpose your ideas onto paper, to micromirrors that enable your small projectors. MEMS have become more and more ubiquitous. Silicon, the material on which the semiconductor industry based its revolution, has so far been the material of choice for MEMS. While silicon is a great platform for constructing electronics, it is less than ideal for applications that involve electrodes exposed to aggressive liquid and gaseous environments. Carbon is one of the most commonly used materials when it comes to electrochemical applications, it is therefore the best candidate to carry over the trend of miniaturization in arenas such as smart chemical sensing, biological microdevices, miniature power, etc. Recent advances in engineering nanoscale structures show great promise towards delivering higher performance sensors, detectors, transistors, displays, etc. In order to leverage the power of nanostructures in general, new manufacturing processes that can bridge between the nanoscale and the macroscale are needed. Such integrated fabrication methods are essential in enabling the transfer of the advantages boasted by nanostructures from the research labs towards mass manufacturing. The present work starts by introducing the basic photolithography technique that has been used so far to fabricate Carbon MEMS (C-MEMS). Several novel techniques stemming for the original process are then described in details and lithium-ion microbattery anodes are presented as an example application of these novel fabrication methods. These Carbon MEMS anodes are characterized through a combination of cyclic voltammetry and electrochemical impedance spectroscopy (OS). A new finite element analysis (FEA) technique is then proposed to more accurately model the current density distributions of 3
A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication
Bilgin, Mehmet Selim; Baytaroğlu, Ebru Nur; Erdem, Ali; Dilber, Erhan
The aim of this review was to investigate usage of computer-aided design/computer-aided manufacture (CAD/CAM) such as milling and rapid prototyping (RP) technologies for removable denture fabrication. An electronic search was conducted in the PubMed/MEDLINE, ScienceDirect, Google Scholar, and Web of Science databases. Databases were searched from 1987 to 2014. The search was performed using a variety of keywords including CAD/CAM, complete/partial dentures, RP, rapid manufacturing, digitally designed, milled, computerized, and machined. The identified developments (in chronological order), techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication are summarized. Using a variety of keywords and aiming to find the topic, 78 publications were initially searched. For the main topic, the abstract of these 78 articles were scanned, and 52 publications were selected for reading in detail. Full-text of these articles was gained and searched in detail. Totally, 40 articles that discussed the techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication and the articles were incorporated in this review. Totally, 16 of the papers summarized in the table. Following review of all relevant publications, it can be concluded that current innovations and technological developments of CAD/CAM and RP allow the digitally planning and manufacturing of removable dentures from start to finish. As a result according to the literature review CAD/CAM techniques and supportive maxillomandibular relationship transfer devices are growing fast. In the close future, fabricating removable dentures will become medical informatics instead of needing a technical staff and procedures. However the methods have several limitations for now. PMID:27095912
A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication.
Bilgin, Mehmet Selim; Baytaroğlu, Ebru Nur; Erdem, Ali; Dilber, Erhan
The aim of this review was to investigate usage of computer-aided design/computer-aided manufacture (CAD/CAM) such as milling and rapid prototyping (RP) technologies for removable denture fabrication. An electronic search was conducted in the PubMed/MEDLINE, ScienceDirect, Google Scholar, and Web of Science databases. Databases were searched from 1987 to 2014. The search was performed using a variety of keywords including CAD/CAM, complete/partial dentures, RP, rapid manufacturing, digitally designed, milled, computerized, and machined. The identified developments (in chronological order), techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication are summarized. Using a variety of keywords and aiming to find the topic, 78 publications were initially searched. For the main topic, the abstract of these 78 articles were scanned, and 52 publications were selected for reading in detail. Full-text of these articles was gained and searched in detail. Totally, 40 articles that discussed the techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication and the articles were incorporated in this review. Totally, 16 of the papers summarized in the table. Following review of all relevant publications, it can be concluded that current innovations and technological developments of CAD/CAM and RP allow the digitally planning and manufacturing of removable dentures from start to finish. As a result according to the literature review CAD/CAM techniques and supportive maxillomandibular relationship transfer devices are growing fast. In the close future, fabricating removable dentures will become medical informatics instead of needing a technical staff and procedures. However the methods have several limitations for now.
Review of high-throughput techniques for detecting solid phase Transformation from material libraries produced by combinatorial methods
NASA Technical Reports Server (NTRS)
Lee, Jonathan A.
High-throughput measurement techniques are reviewed for solid phase transformation from materials produced by combinatorial methods, which are highly efficient concepts to fabricate large variety of material libraries with different compositional gradients on a single wafer. Combinatorial methods hold high potential for reducing the time and costs associated with the development of new materials, as compared to time-consuming and labor-intensive conventional methods that test large batches of material, one- composition at a time. These high-throughput techniques can be automated to rapidly capture and analyze data, using the entire material library on a single wafer, thereby accelerating the pace of materials discovery and knowledge generation for solid phase transformations. The review covers experimental techniques that are applicable to inorganic materials such as shape memory alloys, graded materials, metal hydrides, ferric materials, semiconductors and industrial alloys.
Fabrication of Converging and Diverging Polymeric Microlens Arrays By A Thermocapillary Replication Technique
NASA Astrophysics Data System (ADS)
Lim, Soon Wei Daniel; Fiedler, Kevin; Troian, Sandra
Thermocapillary forces offer a powerful method for sculpting interfaces at microscale dimensions. Here we demonstrate how periodic arrays of cooled pins placed in close proximity to the surface of a molten polymer nanofilm can be used to fabricate various large area microlens arrays, which when solidified exhibit ultrasmooth surfaces and excellent focusing capability. This technique was used to fabricate both homogeneous converging and diverging microlens shapes by application of various thermal distributions. The converging arrays were incorporated into a Shack-Hartmann wavefront sensor able to image moving currents of airborne spray droplets. Feature overlap was also used to achieve hierarchical arrays comprising two superimposed patterns. By varying the width of the cooled pins, it was also possible to fabricate converging microlens structures featuring a caldera-like depression at the vertex able to focus collimated light into a sharp annulus. These demonstrations prove that with suitable microscale control over the thermal distributions projected onto molten nanofilms, a diverse set of micro-optical components can be fabricated by thermocapillary replication from a nearby mask without contact and in a single step. S. W. D. Lim acknowledges funding from the Toshi Kubota SURF fellowship. KRF is supported by a NASA Science and Technology Research Fellowship.
Novel fabrication techniques for low-mass composite structures in silicon particle detectors
NASA Astrophysics Data System (ADS)
Hartman, Neal; Silber, Joseph; Anderssen, Eric; Garcia-Sciveres, Maurice; Gilchriese, Murdock; Johnson, Thomas; Cepeda, Mario
The structural design of silicon-based particle detectors is governed by competing demands of reducing mass while maximizing stability and accuracy. These demands can only be met by fiber reinforced composite laminates (CFRP). As detecting sensors and electronics become lower mass, the motivation to reduce structure as a proportion of overall mass pushes modern detector structures to the lower limits of composite ply thickness, while demanding maximum stiffness. However, classical approaches to composite laminate design require symmetric laminates and flat structures, in order to minimize warping during fabrication. This constraint of symmetry in laminate design, and a "flat plate" approach to fabrication, results in more massive structures. This study presents an approach to fabricating stable and accurate, geometrically complex composite structures by bonding warped, asymmetric, but ultra-thin component laminates together in an accurate tool, achieving final overall precision normally associated with planar structures. This technique has been used to fabricate a prototype "I-beam" that supports two layers of detecting elements, while being up to 20 times stiffer and up to 30% lower mass than comparable, independent planar structures (typically known as "staves").
Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization
NASA Astrophysics Data System (ADS)
Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi
Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.
Novel fabrication technique of hybrid structure lens array for 3D images
NASA Astrophysics Data System (ADS)
Lee, Junsik; Kim, Junoh; Kim, Cheoljoong; Shin, Dooseub; Koo, Gyohyun; Won, Yong Hyub
Tunable liquid lens arrays can produce three dimensional images by using electrowetting principle that alters surface tensions by applying voltage. This method has advantages of fast response time and low power consumption. However, it is challenging to fabricate a high fill factor liquid lens array and operate three dimensional images which demand high diopter. This study describes a hybrid structure lens array which has not only a liquid lens array but a solid lens array. A concave-shape lens array is unavoidable when using only the liquid lens array and some voltages are needed to make the lens flat. By placing the solid lens array on the liquid lens array, initial diopter can be positive. To fabricate the hybrid structure lens array, a conventional lithographic process in semiconductor manufacturing is needed. A negative photoresist SU-8 was used as chamber master molds. PDMS and UV adhesive replica molding are done sequentially. Two immiscible liquids, DI water and dodecane, are injected in the fabricated chamber, followed by sealing. The fabricated structure has a 20 by 20 pattern of cylindrical shaped circle array and the aperture size of each lens is 1mm. The thickness of the overall hybrid structure is about 2.8mm. Hybrid structure lens array has many advantages. Solid lens array has almost 100% fill factor and allow high efficiency. Diopter can be increased by more than 200 and negative diopter can be shifted to the positive region. This experiment showed several properties of the hybrid structure and demonstrated its superiority.
A Novel Bio-carrier Fabricated Using 3D Printing Technique for Wastewater Treatment
NASA Astrophysics Data System (ADS)
Dong, Yang; Fan, Shu-Qian; Shen, Yu; Yang, Ji-Xiang; Yan, Peng; Chen, You-Peng; Li, Jing; Guo, Jin-Song; Duan, Xuan-Ming; Fang, Fang; Liu, Shao-Yang
The structure of bio-carriers is one of the key operational characteristics of a biofilm reactor. The goal of this study is to develop a series of novel fullerene-type bio-carriers using the three-dimensional printing (3DP) technique. 3DP can fabricate bio-carriers with more specialized structures compared with traditional fabrication processes. In this research, three types of fullerene-type bio-carriers were fabricated using the 3DP technique and then compared with bio-carrier K3 (from AnoxKaldnes) in the areas of physicochemical properties and biofilm growth. Images acquired by 3D profiling and SEM indicated that the surface roughness of the 3DP bio-carrier was greater than that of K3. Furthermore, contact angle data indicated that the 3DP bio-carriers were more hydrophilic than K3. The biofilm on the 3DP bio-carriers exhibited higher microbial activity and stronger adhesion ability. These findings were attributed to excellent mass transfer of the substrate (and oxygen) between the vapour-liquid-solid tri-phase system and to the surface characteristics. It is concluded that the novel 3DP fullerene-type bio-carriers are ideal carriers for biofilm adherence and growth.
Fabrication of dielectrophoretic microfluidic chips using a facile screen-printing technique for microparticle trapping
NASA Astrophysics Data System (ADS)
Wee, Wei Hong; Li, Zedong; Hu, Jie; Adib Kadri, Nahrizul; Xu, Feng; Li, Fei; Pingguan-Murphy, Belinda
Trapping of microparticles finds wide applications in numerous fields. Microfluidic chips based on a dielectrophoresis (DEP) technique hold several advantages for trapping microparticles, such as fast result processing, a small amount of sample required, high spatial resolution, and high accuracy of target selection. There is an unmet need to develop DEP microfluidic chips on different substrates for different applications in a low cost, facile, and rapid way. This study develops a new facile method based on a screen-printing technique for fabrication of electrodes of DEP chips on three types of substrates (i.e. polymethyl-methacrylate (PMMA), poly(ethylene terephthalate) and A4 paper). The fabricated PMMA-based DEP microfluidic chip was selected as an example and successfully used to trap and align polystyrene microparticles in a suspension and cardiac fibroblasts in a cell culture solution. The developed electrode fabrication method is compatible with different kinds of DEP substrates, which could expand the future application field of DEP microfluidic chips, including new forms of point-of care diagnostics and trapping circulating tumor cells.
Surface properties and corrosion behavior of Co-Cr alloy fabricated with selective laser melting technique.
Xin, Xian-zhen; Chen, Jie; Xiang, Nan; Wei, Bin
We sought to study the corrosion behavior and surface properties of a commercial cobalt-chromium (Co-Cr) alloy which was fabricated with selective laser melting (SLM) technique. For this purpose, specimens were fabricated using different techniques, such as SLM system and casting methods. Surface hardness testing, microstructure observation, surface analysis using X-ray photoelectron spectroscopy (XPS) and electrochemical corrosion test were carried out to evaluate the corrosion properties and surface properties of the specimens. We found that microstructure of SLM specimens was more homogeneous than that of cast specimens. The mean surface hardness values of SLM and cast specimens were 458.3 and 384.8, respectively; SLM specimens showed higher values than cast ones in hardness. Both specimens exhibited no differences in their electrochemical corrosion properties in the artificial saliva through potentiodynamic curves and EIS, and no significant difference via XPS. Therefore, we concluded that within the scope of this study, SLM-fabricated restorations revealed good surface properties, such as proper hardness, homogeneous microstructure, and also showed sufficient corrosion resistance which could meet the needs of dental clinics.
Fabrication of superconducting MgB2 nanostructures by an electron beam lithography-based technique
NASA Astrophysics Data System (ADS)
Portesi, C.; Borini, S.; Amato, G.; Monticone, E.
In this work, we present the results obtained in fabrication and characterization of magnesium diboride nanowires realized by an electron beam lithography (EBL)-based method. For fabricating MgB2 thin films, an all in situ technique has been used, based on the coevaporation of B and Mg by means of an e-gun and a resistive heater, respectively. Since the high temperatures required for the fabrication of good quality MgB2 thin films do not allow the nanostructuring approach based on the lift-off technique, we structured the samples combining EBL, optical lithography, and Ar milling. In this way, reproducible nanowires 1 μm long have been obtained. To illustrate the impact of the MgB2 film processing on its superconducting properties, we measured the temperature dependence of the resistance on a nanowire and compared it to the original magnesium diboride film. The electrical properties of the films are not degraded as a consequence of the nanostructuring process, so that superconducting nanodevices may be obtained by this method.
A Novel Bio-carrier Fabricated Using 3D Printing Technique for Wastewater Treatment
Dong, Yang; Fan, Shu-Qian; Shen, Yu; Yang, Ji-Xiang; Yan, Peng; Chen, You-Peng; Li, Jing; Guo, Jin-Song; Duan, Xuan-Ming; Fang, Fang; Liu, Shao-Yang
The structure of bio-carriers is one of the key operational characteristics of a biofilm reactor. The goal of this study is to develop a series of novel fullerene-type bio-carriers using the three-dimensional printing (3DP) technique. 3DP can fabricate bio-carriers with more specialized structures compared with traditional fabrication processes. In this research, three types of fullerene-type bio-carriers were fabricated using the 3DP technique and then compared with bio-carrier K3 (from AnoxKaldnes) in the areas of physicochemical properties and biofilm growth. Images acquired by 3D profiling and SEM indicated that the surface roughness of the 3DP bio-carrier was greater than that of K3. Furthermore, contact angle data indicated that the 3DP bio-carriers were more hydrophilic than K3. The biofilm on the 3DP bio-carriers exhibited higher microbial activity and stronger adhesion ability. These findings were attributed to excellent mass transfer of the substrate (and oxygen) between the vapour-liquid-solid tri-phase system and to the surface characteristics. It is concluded that the novel 3DP fullerene-type bio-carriers are ideal carriers for biofilm adherence and growth. PMID:26202477
A Novel Bio-carrier Fabricated Using 3D Printing Technique for Wastewater Treatment.
Dong, Yang; Fan, Shu-Qian; Shen, Yu; Yang, Ji-Xiang; Yan, Peng; Chen, You-Peng; Li, Jing; Guo, Jin-Song; Duan, Xuan-Ming; Fang, Fang; Liu, Shao-Yang
The structure of bio-carriers is one of the key operational characteristics of a biofilm reactor. The goal of this study is to develop a series of novel fullerene-type bio-carriers using the three-dimensional printing (3DP) technique. 3DP can fabricate bio-carriers with more specialized structures compared with traditional fabrication processes. In this research, three types of fullerene-type bio-carriers were fabricated using the 3DP technique and then compared with bio-carrier K3 (from AnoxKaldnes) in the areas of physicochemical properties and biofilm growth. Images acquired by 3D profiling and SEM indicated that the surface roughness of the 3DP bio-carrier was greater than that of K3. Furthermore, contact angle data indicated that the 3DP bio-carriers were more hydrophilic than K3. The biofilm on the 3DP bio-carriers exhibited higher microbial activity and stronger adhesion ability. These findings were attributed to excellent mass transfer of the substrate (and oxygen) between the vapour-liquid-solid tri-phase system and to the surface characteristics. It is concluded that the novel 3DP fullerene-type bio-carriers are ideal carriers for biofilm adherence and growth.
Fabrication of flex sensors through direct ink write technique and its electrical characterization
NASA Astrophysics Data System (ADS)
Abas, Muhammad; Rahman, Khalid
The present work is intended to fabricate low-cost flex sensor from conductive carbon paste using direct ink write (DIW) technique. DIW method is one of the additive manufacturing processes, which is capable to deposit a variety of material on a variety of substrates by a different mechanism to feature resolution at a microns level. It is widely used in the electronic industry for fabrication of PCBS and electrodes for different electronic devices. The DIW system in present study extrudes material stored in the syringe barrel through nozzle using compressed air. This mechanism will assist in creating patterns on a variety of substrates. Pneumatic controller is employed to control deposition of material, while computer-controlled X-Y stage is employed to control pattern generation. For effective and control patterning, printing parameters were optimized using Taguchi design optimization technique. The conductive carbon paste is used as ink for pattern generation on flexible PET substrate. Samples of flex sensor having different dimensions are prepared through DIW. The fabricated sensors were used as flexion sensor, and its electrical characteristic was evaluated. The obtained sensors are stable and reliable in performance.
Modelling, Simulation, Fabrication, Experiments and Real-Time Linear State Variable Feedback Control of Cuk Converter using Pole Placement Technique
NASA Astrophysics Data System (ADS)
Nanda, S.; Sengupta, M.; Sengupta, A.
Using a suitable combination of some of the basic converter topologies representing the Buck, the Boost and the Buck-Boost converters, one may obtain some other useful dc-to-dc converters. A typical example is the cascade connection of the Boost and the Buck converter which produces the well known Cuk converter. This work emphasises on the modelling, real-time simulations, fabrication and closed-loop control of a Cuk converter. For the modelling and real time simulation, FPGA platform has been used. Small signal modelling and conventional control aspects (compensator) of Cuk converter are discussed. A 200W, 10kHz Cuk converter is designed, fabricated and tested in the laboratory. The converter model is of fourth order. The transfer function being a non-minimum phase one with two right-half plane zeroes, a limited work has been done on this. For such systems, conventional control methods are demonstrated to fail. Pole placement technique, which is envisaged to be a suitable control technique for a higher order non-minimum phase system has been adopted. Excellent correlation between off-line and real-time simulation results establishes the accuracy of the work. Agreement between open-loop results obtained from the experimental set-up under steady state vis-a-vis those obtained from simulation is also a major highlight of the paper.
Focused ion beam techniques for fabricating geometrically-complex components and devices.
Mayer, Thomas Michael; Adams, David Price; Hodges, V. Carter; Vasile, Michael J.
We have researched several new focused ion beam (FIB) micro-fabrication techniques that offer control of feature shape and the ability to accurately define features onto nonplanar substrates. These FIB-based processes are considered useful for prototyping, reverse engineering, and small-lot manufacturing. Ion beam-based techniques have been developed for defining features in miniature, nonplanar substrates. We demonstrate helices in cylindrical substrates having diameters from 100 {micro}m to 3 mm. Ion beam lathe processes sputter-define 10-{micro}m wide features in cylindrical substrates and tubes. For larger substrates, we combine focused ion beam milling with ultra-precision lathe turning techniques to accurately define 25-100 {micro}m features over many meters of path length. In several cases, we combine the feature defining capability of focused ion beam bombardment with additive techniques such as evaporation, sputter deposition and electroplating in order to build geometrically-complex, functionally-simple devices. Damascene methods that fabricate bound, metal microcoils have been developed for cylindrical substrates. Effects of focused ion milling on surface morphology are also highlighted in a study of ion-milled diamond.
Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants
NASA Astrophysics Data System (ADS)
Chan, Kwai S.; Koike, Marie; Mason, Robert L.; Okabe, Toru
Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.
Curved grating fabrication techniques for concentric-circle grating, surface-emitting semiconductor lasers
NASA Technical Reports Server (NTRS)
Jordan, Rebecca H.; King, Oliver; Wicks, Gary W.; Hall, Dennis G.; Anderson, Erik H.; Rooks, Michael J.
We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a concentric-circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each concentric-circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, concentric-circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.
Resonant marker design and fabrication techniques for device visualization during interventional magnetic resonance imaging.
Kaiser, Mandy; Detert, Markus; Rube, Martin A; El-Tahir, Abubakr; Elle, Ole Jakob; Melzer, Andreas; Schmidt, Bertram; Rose, Georg H
Magnetic resonance imaging (MRI) has great potential as an imaging modality for guiding minimally invasive interventions because of its superior soft tissue contrast and the possibility of arbitrary slice positioning while avoiding ionizing radiation and nephrotoxic iodine contrast agents. The major constraints are: limited patient access, the insufficient assortment of compatible instruments and the difficult device visualization compared to X-ray based techniques. For the latter, resonant MRI markers, fabricated by using the wire-winding technique, have been developed. This fabrication technique serves as a functional model but has no clinical use. Thus, the aim of this study is to illustrate a four-phase design process of resonant markers involving microsystems technologies. The planning phase comprises the definition of requirements and the simulation of electromagnetic performance of the MRI markers. The following technologies were considered for the realization phase: aerosol-deposition process, hot embossing technology and thin film technology. The subsequent evaluation phase involves several test methods regarding electrical and mechanical characterization as well as MRI visibility aspects. The degree of fulfillment of the predefined requirements is determined within the analysis phase. Furthermore, an exemplary evaluation of four realized MRI markers was conducted, focusing on the performance within the MRI environment.
Antiwetting Fabric Produced by a Combination of Layer-by-Layer Assembly and Electrophoretic Deposition of Hydrophobic Nanoparticles.
Joung, Young Soo; Buie, Cullen R
This work describes a nanoparticle coating method to produce durable antiwetting polyester fabric. Electrophoretic deposition is used for fast modification of polyester fabric with silica nanoparticles embedded in polymeric networks for high durability coatings. Typically, electrophoretic deposition (EPD) is utilized on electrically conductive substrates due to its dependence on an applied electrical field. EPD on nonconductive materials has been attempted but are limited by weak adhesion, cracks, and other irregularities. To resolve these issues, we coat polyester fabric with thin polymer layers using electrostatic self-assembly (layer-by-layer self-assembly). Next, silica nanoparticles are uniformly dispersed on the polymer layers. Finally, polymerically stabilized silica nanoparticles are deposited by EPD on the fabric, followed by heat treatment. The modified fabric shows high static contact angle and low contact angle hysteresis, while keeping its original color, flexibility, and air permeability. During a skin fiction resistance test, the hydrophobicity of the coating layer was maintained over 500 h. Furthermore, we also show that this approach facilitates patterned regions of wettability by modifying the electric field in EPD.
Fabrication of a novel biosensor for macromolecules detection through molecular imprinting technique
NASA Astrophysics Data System (ADS)
Yu, Yingjie
There is an increasing need for precise molecular detection as a diagnostic tool for early identification of diseases, pathogens, and abnormal protein levels in the body. Typical chemical analytical methods are generally costly, unstable, and time-consuming. Molecular imprinting (MI) technique, based on the "lock and key model", could be a simple method to overcome those shortcomings. In this study, a self-assembled monolayer (SAM) was employed as a platform to fabricate MI biosensor for detection of macromolecules. I demonstrated that, when the monolayer was formed on a rough surface, this method was in fact templating molecules in three dimensions, and hence was not limited by the height of the monolayer, but rather by the height of the roughness. This hypothesis was tested on biomolecules of multiple length scales. The SAM is assembled on the walls of the niche, forming a 3D pattern of the analyte uniquely molded to its contour. The surfaces with multi-scale roughness were prepared by evaporation of gold onto electropolished (smooth) and unpolished (rough) Si wafers, where the native roughness was found to have a normal distribution centered around 5 and 90 nm respectively. Our studies, using molecules, such as proteins, i.e., hemoglobin, ranging from a few nanometers, to viruses (i.e. polio, adenovirus), ranging from several tens of nanometers, and protein complexes ranging from several hundred nanometers, showed that when the size of the analyte matched the roughness of the gold surface, this method was very effective and could detect even small changes in the configuration, such as those induced by changes in the pH of the system. The detection method was further quantified by applying it to the detection of CEA in pancreatic cyst fluid obtained from 18 patients under IRB 95867-6. The results of the MI biosensor were directly compared with those obtained using ELISA in the hospital pathology laboratory with excellent agreement, except that the MI biosensor
Sensing and identification of carbon monoxide using carbon films fabricated by methane arc discharge decomposition technique
Carbonaceous materials have recently received attention in electronic applications and measurement systems. In this work, we demonstrate the electrical behavior of carbon films fabricated by methane arc discharge decomposition technique. The current-voltage (I-V) characteristics of carbon films are investigated in the presence and absence of gas. The experiment reveals that the current passing through the carbon films increases when the concentration of CO2 gas is increased from 200 to 800 ppm. This phenomenon which is a result of conductance changes can be employed in sensing applications such as gas sensors. PMID:25177219
Electrohydrodynamic direct-writing lithography: An alternative maskless technique for microstructure fabrication
NASA Astrophysics Data System (ADS)
He, Jiankang; Xu, Fangyuan; Cao, Yi; Liu, Yaxiong; Li, Dichen; Jin, Zhongmin
A maskless electrohydrodynamic direct-writing lithographic strategy was presented to flexibly fabricate user-specific micropatterns on silicon substrates. By optimizing the operating parameters, parallel lines as well as lattices with line width of about 2 μm could be stably deposited. The printed micropatterns were found to function as sacrificial template to transfer microstructures into silicon substrates and the etching processes had little effect on the predefined size. It is envisioned that this simple approach provides an alternative to the existing microfabrication techniques, which might enable the wide accessibility of microscale technologies to advance various research fields such as microfluidics, biomedical chips, and microscale tissue engineering.
An Innovative and Simple Technique of Hollow Maxillary Complete Denture Fabrication
Aras, Meena Ajay; Chitre, Vidya; Mysore, Ashwin; Da Costa, Godwin Clovis
Prosthetic rehabilitation of severely atrophic ridges has always been an ordeal for the clinician due to decreased support, stability and retention. Because of severe resorption the restorative space between maxillary and mandibular residual ridges is increased. Rehabilitation in such cases may result in increased height and weight of the prosthesis further compromising its retention and stability. This in turn overloads the underlying hard and soft tissues exacerbating ridge resorption so, in order to break this vicious cycle, the weight of the prosthesis needs to be reduced which can be achieved by making hollow prosthesis. This article describes a novel technique of fabricating a hollow maxillary complete denture. PMID:27656580
One-step fabrication of multifunctional silica microbelt with the novel stacked structure by electrospinning technique
NASA Astrophysics Data System (ADS)
Yao, Yongtao; Lu, Haibao; Leng, Jinsong; Li, Jianjun
In this study, novel route for the preparation of novel stacked structure and one-step fabrication of electrospun silica microbelt with controllable wettability by a combination of sol-gel chemistry and electrospinning techniques. The application field of the one-dimensional silica in different environmental conditions was controlled by functionalization of the hydroxyl groups and non-polar groups on the backbone. Experimental results reveal that the formation of one-dimensional stacked structure is strongly related to the conductive properties of collective substrate. The exploration of the one-dimensional stacked structure mechanism was also conducted.
A Simple Technique for Fabricating a Screw-Retained/Cemented Implant-Supported Crown.
Helvey, Gregg A
Many factors figure into the long-term success of an implant-supported restoration. While some are uncontrollable, others are manageable. The cement-retained implant-supported restoration is easier to fabricate, while the screw-retained implant-supported restoration involves more complicated, timeconsuming laboratory procedures. Most research has found the screw-retained restoration has had more minimal complications than the cement-retained counterpart. This article describes a simple, low-cost technique of converting a cement-retained implant crown to a screw-retained implant crown, which allows for easy retrievability and eliminates a number of laboratory steps and costs.
Comparison of quartz crystallographic preferred orientations identified with optical fabric analysis, electron backscatter and neutron diffraction techniques.
Hunter, N J R; Wilson, C J L; Luzin, V
Three techniques are used to measure crystallographic preferred orientations (CPO) in a naturally deformed quartz mylonite: transmitted light cross-polarized microscopy using an automated fabric analyser, electron backscatter diffraction (EBSD) and neutron diffraction. Pole figure densities attributable to crystal-plastic deformation are variably recognizable across the techniques, particularly between fabric analyser and diffraction instruments. Although fabric analyser techniques offer rapid acquisition with minimal sample preparation, difficulties may exist when gathering orientation data parallel with the incident beam. Overall, we have found that EBSD and fabric analyser techniques are best suited for studying CPO distributions at the grain scale, where individual orientations can be linked to their source grain or nearest neighbours. Neutron diffraction serves as the best qualitative and quantitative means of estimating the bulk CPO, due to its three-dimensional data acquisition, greater sample area coverage, and larger sample size. However, a number of sampling methods can be applied to FA and EBSD data to make similar approximations.
Characterization of fabricated three dimensional scaffolds of bioceramic-polymer composite via microstereolithography technique
NASA Astrophysics Data System (ADS)
Talib, Marina; Covington, James A.; Bolarinwa, Aminat
Microstereolithography is a method used for rapid prototyping of polymeric and ceramic components. This technique converts a computer-aided design (CAD) to a three dimensional (3D) model, and enables layer per layer fabrication curing a liquid resin with UV-light or laser source. The aim of this project was to formulate photocurable polymer reinforced with synthesized calcium pyrophosphate (CPP), and to fabricate a 3D scaffolds with optimum mechanical properties for specific tissue engineering applications. The photocurable ceramic suspension was prepared with acrylate polyester, multifunctional acrylate monomer with the addition of 50-70wt% of CPP, photoinitiators and photoinhibitors. The 3D structure of disc (5 mm height × 4 mm diameter) was successfully fabricated using Envisiontec Perfactory3® . They were then sintered at high temperature for polymer removal, to obtain a ceramic of the desired porosity. The density increased to more than 35% and the dimensional shrinkage after sintering were 33%. The discs were then subjected compressive measurement, biodegradation and bioactivity test. Morphology and CPP content of the sintered polymer was investigated with SEM and XRD, respectively. The addition of CPP coupled with high temperature sintering, had a significant effect on the compressive strength exhibited by the bioceramic. The values are in the range of cancellous bone (2-4 MPa). In biodegradation and bioactivity test, the synthesized CPP induced the formation of apatite layer and its nucleation onto the composite surface.
Fabrication of low-cost, cementless femoral stem 316L stainless steel using investment casting technique.
Baharuddin, Mohd Yusof; Salleh, Sh-Hussain; Suhasril, Andril Arafat; Zulkifly, Ahmad Hafiz; Lee, Muhammad Hisyam; Omar, Mohd Afian; Abd Kader, Ab Saman; Mohd Noor, Alias; A Harris, Arief Ruhullah; Abdul Majid, Norazman
Total hip arthroplasty is a flourishing orthopedic surgery, generating billions of dollars of revenue. The cost associated with the fabrication of implants has been increasing year by year, and this phenomenon has burdened the patient with extra charges. Consequently, this study will focus on designing an accurate implant via implementing the reverse engineering of three-dimensional morphological study based on a particular population. By using finite element analysis, this study will assist to predict the outcome and could become a useful tool for preclinical testing of newly designed implants. A prototype is then fabricated using 316L stainless steel by applying investment casting techniques that reduce manufacturing cost without jeopardizing implant quality. The finite element analysis showed that the maximum von Mises stress was 66.88 MPa proximally with a safety factor of 2.39 against endosteal fracture, and micromotion was 4.73 μm, which promotes osseointegration. This method offers a fabrication process of cementless femoral stems with lower cost, subsequently helping patients, particularly those from nondeveloped countries.
Comparison of the fit of cast gold crowns fabricated from the digital and the conventional impression techniques
Jeon, Young-Chan; Jeong, Chang-Mo
PURPOSE The purpose of this study was to compare the fit of cast gold crowns fabricated from the conventional and the digital impression technique. MATERIALS AND METHODS Artificial tooth in a master model and abutment teeth in ten patients were restored with cast gold crowns fabricated from the digital and the conventional impression technique. The forty silicone replicas were cut in three sections; each section was evaluated in nine points. The measurement was carried out by using a measuring microscope and I-Soultion. Data from the silicone replica were analyzed and all tests were performed with α-level of 0.05. RESULTS 1. The average gaps of cast gold crowns fabricated from the digital impression technique were larger than those of the conventional impression technique significantly. 2. In marginal and internal axial gap of cast gold crowns, no statistical differences were found between the two impression techniques. 3. The internal occlusal gaps of cast gold crowns fabricated from the digital impression technique were larger than those of the conventional impression technique significantly. CONCLUSION Both prostheses presented clinically acceptable results with comparing the fit. The prostheses fabricated from the digital impression technique showed more gaps, in respect of occlusal surface. PMID:28243386
Fabrication techniques and properties of multifilamentary Nb/sub 3/Sn conductors
Suenaga, M; Sampson, W B; Luhman, T S
Various processing techniques for multifilamentary Nb/sub 3/Sn and V/sub 3/Ga are reviewed. The critical current of commercially produced Nb/sub 3/Sn wires manufactured by both the bronze and external diffusion techniques are compared. Critical currents for in situ and powder processed Nb/sub 3/Sn are also included. New developments which promise improvements in J/sub c/ are discussed.
Polymer microfluidic bioreactor fabrication by means of gray scale lithography technique
NASA Astrophysics Data System (ADS)
Sierakowski, Andrzej; Prokaryn, Piotr; Dobrowolski, Rafał; Malinowska, Anna; Szmigiel, Dariusz; Grabiec, Piotr; Trojanowski, Damian; Jakimowicz, Dagmara; Zakrzewska-Czerwinska, Jolanta
In this paper we present a new method of polymer microfluidic bioreactor fabrication by means of a gray scale lithography technique. As a result of the gray scale lithography process the 3D model of the bioreactor is defined in photoresist. The obtained model serves as a sacrificial layer for the subsequent transfer of the 3D shape into the polymer material. The proposed method allows simultaneous definition of both the overall bioreactor geometry and the multi steps cell traps in a single photolithography step. Such microfluidic structure can be used for sorting cells based on their size. The developed solution significantly simplifies the production technology and reduces its costs in comparison to standard photolithography techniques.
PMN-PT single crystal focusing transducer fabricated using a mechanical dimpling technique.
Lam, K H; Chen, Y; Cheung, K F; Dai, J Y
A ∼5MHz focusing PMN-PT single crystal ultrasound transducer has been fabricated utilizing a mechanical dimpling technique, where the dimpled crystal wafer was used as an active element of the focusing transducer. For the dimpled focusing transducer, the effective electromechanical coupling coefficient was enhanced significantly from 0.42 to 0.56. The dimpled transducer also yields a -6dB bandwidth of 63.5% which is almost double the bandwidth of the plane transducer. An insertion loss of the dimpled transducer (-18.1dB) is much lower than that of the plane transducer. Finite element simulation also reveals specific focused beam from concave crystal surface. These promising results show that the dimpling technique can be used to develop high-resolution focusing single crystal transducers.
Fabrication of capacitive acoustic resonators combining 3D printing and 2D inkjet printing techniques.
Haque, Rubaiyet Iftekharul; Ogam, Erick; Loussert, Christophe; Benaben, Patrick; Boddaert, Xavier
A capacitive acoustic resonator developed by combining three-dimensional (3D) printing and two-dimensional (2D) printed electronics technique is described. During this work, a patterned bottom structure with rigid backplate and cavity is fabricated directly by a 3D printing method, and then a direct write inkjet printing technique has been employed to print a silver conductive layer. A novel approach has been used to fabricate a diaphragm for the acoustic sensor as well, where the conductive layer is inkjet-printed on a pre-stressed thin organic film. After assembly, the resulting structure contains an electrically conductive diaphragm positioned at a distance from a fixed bottom electrode separated by a spacer. Measurements confirm that the transducer acts as capacitor. The deflection of the diaphragm in response to the incident acoustic single was observed by a laser Doppler vibrometer and the corresponding change of capacitance has been calculated, which is then compared with the numerical result. Observation confirms that the device performs as a resonator and provides adequate sensitivity and selectivity at its resonance frequency.
Fabrication of a highly sensitive penicillin sensor based on charge transfer techniques.
Lee, Seung-Ro; Rahman, M M; Sawada, Kazuaki; Ishida, Makoto
A highly sensitive penicillin biosensor based on a charge-transfer technique (CTTPS) has been fabricated and demonstrated in this paper. CTTPS comprised a charge accumulation technique for penicilloic acid and H(+) ions perception system. With the proposed CTTPS, it is possible to amplify the sensing signals without external amplifier by using the charge accumulation cycles. The fabricated CTTPS exhibits excellent performance for penicillin detection and exhibit a high-sensitivity (47.852 mV/mM), high signal-to-noise ratio (SNR), large span (1445 mV), wide linear range (0-25 mM), fast response time (<3s), and very good reproducibility. A very lower detection limit of about 0.01 mM was observed from the proposed sensor. Under optimum conditions, the proposed CTTPS outstripped the performance of the widely used ISFET penicillin sensor and exhibited almost eight times greater sensitivity as compared to ISFET (6.56 mV/mM). The sensor system is implemented for the measurement of the penicillin concentration in penicillin fermentation broth.
Fabrication of Capacitive Acoustic Resonators Combining 3D Printing and 2D Inkjet Printing Techniques
Haque, Rubaiyet Iftekharul; Ogam, Erick; Loussert, Christophe; Benaben, Patrick; Boddaert, Xavier
A capacitive acoustic resonator developed by combining three-dimensional (3D) printing and two-dimensional (2D) printed electronics technique is described. During this work, a patterned bottom structure with rigid backplate and cavity is fabricated directly by a 3D printing method, and then a direct write inkjet printing technique has been employed to print a silver conductive layer. A novel approach has been used to fabricate a diaphragm for the acoustic sensor as well, where the conductive layer is inkjet-printed on a pre-stressed thin organic film. After assembly, the resulting structure contains an electrically conductive diaphragm positioned at a distance from a fixed bottom electrode separated by a spacer. Measurements confirm that the transducer acts as capacitor. The deflection of the diaphragm in response to the incident acoustic single was observed by a laser Doppler vibrometer and the corresponding change of capacitance has been calculated, which is then compared with the numerical result. Observation confirms that the device performs as a resonator and provides adequate sensitivity and selectivity at its resonance frequency. PMID:26473878
A new method of fabricating a blend scaffold using an indirect three-dimensional printing technique.
Jung, Jin Woo; Lee, Hyungseok; Hong, Jung Min; Park, Jeong Hun; Shim, Jung Hee; Choi, Tae Hyun; Cho, Dong-Woo
Due to its simplicity and effectiveness, the physical blending of polymers is considered to be a practical strategy for developing a versatile scaffold having desirable mechanical and biochemical properties. In the present work, an indirect three-dimensional (i3D) printing technique was proposed to fabricate a 3D free-form scaffold using a blend of immiscible materials, such as polycaprolactone (PCL) and gelatin. The i3D printing technique includes 3D printing of a mold and a sacrificial molding process. PCL/chloroform and gelatin/water were physically mixed to prepare the blend solution, which was subsequently injected into the cavity of a 3D printed mold. After solvent removal and gelatin cross-linking, the mold was dissolved to obtain a PCL-gelatin (PG) scaffold, with a specific 3D structure. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis indicated that PCL masses and gelatin fibers in the PG scaffold homogenously coexisted without chemical bonding. Compression tests confirmed that gelatin incorporation into the PCL enhanced its mechanical flexibility and softness, to the point of being suitable for soft-tissue engineering, as opposed to pure PCL. Human adipose-derived stem cells, cultured on a PG scaffold, exhibited enhanced in vitro chondrogenic differentiation and tissue formation, compared with those on a PCL scaffold. The i3D printing technique can be used to blend a variety of materials, facilitating 3D scaffold fabrication for specific tissue regeneration. Furthermore, this convenient and versatile technique may lead to wider application of 3D printing in tissue engineering.
Mass-producible microtags for security applications: calculated fabrication tolerances by rigorous coupled-wave analysis
Descour, M.R.; Sweatt, W.C.; Krenz, K.D.
We develop a method for encoding phase and amplitude in microscopic computer-generated holograms (microtags) for security applications. An 8{times}8 cell phase-only and an 8{times}8 cell phase-and-amplitude microtag design are fabricated in photoresist using an extreme ultraviolet (13.4-nm) lithography (EUVL) tool. Each microtag measures 80{times}160{mu}m and contains features 0.2 {mu}m wide. Fraunhofer-zone diffraction patterns can be obtained from fabricated microtags without any intervening optics and compare very favorably with predicted diffraction patterns [Descour {ital et al.} (1996)]. We present the results of a rigorous coupled-wave analysis (RCWA) of microtags. Microtags are modeled as consisting of subwavelength gratings of a trapezoidal profile. Transverse-electric (TE) and TM readout polarizations are modeled. The analysis concerns the determination of optimal microtag-grating design parameter values and tolerances on those parameters. The parameters are grating wall-slope angle, grating duty cycle, grating depth, and metal coating thickness. Optimal microtag-grating parameter values result in maximum diffraction efficiency, which is calculated at 16{percent} for microtag gratings in air and 12{percent} for microtag gratings underneath a protective dielectric coating, within fabrication constraints. TM-polarized readout illumination is diffracted with higher efficiency than TE-polarized illumination by microtag gratings. {copyright} {ital 1998 Society of Photo-Optical Instrumentation Engineers.}{ital Key words:} computer-generated holograms; security and anticounterfeiting devices; grating fabrication tolerances; rigorous coupled-wave analysis. {copyright} {ital 1998} {ital Society of Photo-Optical Instrumentation Engineers}
Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced by Electron Beam Freeform Fabrication
NASA Technical Reports Server (NTRS)
Domack, Marcia S.; Tainger, Karen M.
The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties demonstrated for electron beam deposited aluminum and titanium alloys are comparable to wrought products, although the microstructures of the deposits exhibit cast features. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. Tensile mechanical properties and microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains with interior dendritic structures, described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.
Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced By Electron Beam Freeform Fabrication
NASA Technical Reports Server (NTRS)
Domack, Marcia S.; Taminger, Karen M. B.; Begley, Matthew
The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties have been demonstrated for electron beam deposited aluminum and titanium alloys that are comparable to wrought products, although the microstructures of the deposits exhibit features more typical of cast material. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. In the current study, mechanical properties and resulting microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Material performance was evaluated based on tensile properties and results were compared with properties of Al 2219 wrought products. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains, typically with interior dendritic structures, which were described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.
Analysis of Translucency Parameter of Glass-Ceramics Fabricated by Different Techniques
Ledić, Karla; Majnarić, Igor; Milardović, Slađana; Ortolan; Špalj, Stipe; Štefančić, Sanja
The purpose of the study was to analyse translucency parameter (TP values) of glass-ceramics fabricated by different techniques and investigate the effect of the corrosive medium on TP values. Materials and methods Three specimens of each type of IPS e.max ceramics (Ivoclar Vivadent, Schaan, Liechtenstein) were made in three colours (A2, C2 and B3) by three fabrication techniques (layering – e.max Ceram Dentin; heat-pressing – e.max Press; CAD/CAM – e.max CAD). Specimens were made in the form of plates (10 mm x 12 mm x 0.8 mm). CIE L*a*b* values were measured by a spectrophotometer (X-Rite DTP 20 Pulse, Neu Isenburg, Germany) before and after exposure to 4% acetic acid at 80 °C for 16 hours (ISO 6872) to calculate translucency parameter (TP values). Statistical data were analysed using the IBM SPSS 22 software. Results IPS e.max Ceram Dentin had significantly the lowest TP values, and IPS e.max Press the highest TP values of all colours (A2, C2, B3), both prior and after exposure to acid (p<0.001). The difference in TP values among colours was evident in the IPS e.max Ceram Dentin material, both before and after exposure to acid with a great effect size (p<0.001; η2 = 0.702 and 0.741), and in the IPS e.max Press material (p<0.001, effect size 0.547 and 0.576). CAD/CAD specimens showed uniform TP values between three colours. Further, exposure to a corrosive medium did not result in a statistically significant change of TP values in any of the materials tested. Conclusions Different types of glass-ceramics showed significant difference in TP values both with respect to the fabrication technique and colour. Exposure to a corrosive medium did not result in a statistically significant change of TP values. PMID:27688383
Wearable Atmospheric Pressure Plasma Fabrics Produced by Knitting Flexible Wire Electrodes for the Decontamination of Chemical Warfare Agents
NASA Astrophysics Data System (ADS)
Jung, Heesoo; Seo, Jin Ah; Choi, Seungki
One of the key reasons for the limited use of atmospheric pressure plasma (APP) is its inability to treat non-flat, three-dimensional (3D) surface structures, such as electronic devices and the human body, because of the rigid electrode structure required. In this study, a new APP system design—wearable APP (WAPP)—that utilizes a knitting technique to assemble flexible co-axial wire electrodes into a large-area plasma fabric is presented. The WAPP device operates in ambient air with a fully enclosed power electrode and grounded outer electrode. The plasma fabric is flexible and lightweight, and it can be scaled up for larger areas, making it attractive for wearable APP applications. Here, we report the various plasma properties of the WAPP device and successful test results showing the decontamination of toxic chemical warfare agents, namely, mustard (HD), soman (GD), and nerve (VX) agents.
Wearable Atmospheric Pressure Plasma Fabrics Produced by Knitting Flexible Wire Electrodes for the Decontamination of Chemical Warfare Agents.
Jung, Heesoo; Seo, Jin Ah; Choi, Seungki
One of the key reasons for the limited use of atmospheric pressure plasma (APP) is its inability to treat non-flat, three-dimensional (3D) surface structures, such as electronic devices and the human body, because of the rigid electrode structure required. In this study, a new APP system design-wearable APP (WAPP)-that utilizes a knitting technique to assemble flexible co-axial wire electrodes into a large-area plasma fabric is presented. The WAPP device operates in ambient air with a fully enclosed power electrode and grounded outer electrode. The plasma fabric is flexible and lightweight, and it can be scaled up for larger areas, making it attractive for wearable APP applications. Here, we report the various plasma properties of the WAPP device and successful test results showing the decontamination of toxic chemical warfare agents, namely, mustard (HD), soman (GD), and nerve (VX) agents.
Wearable Atmospheric Pressure Plasma Fabrics Produced by Knitting Flexible Wire Electrodes for the Decontamination of Chemical Warfare Agents
Jung, Heesoo; Seo, Jin Ah; Choi, Seungki
One of the key reasons for the limited use of atmospheric pressure plasma (APP) is its inability to treat non-flat, three-dimensional (3D) surface structures, such as electronic devices and the human body, because of the rigid electrode structure required. In this study, a new APP system design—wearable APP (WAPP)—that utilizes a knitting technique to assemble flexible co-axial wire electrodes into a large-area plasma fabric is presented. The WAPP device operates in ambient air with a fully enclosed power electrode and grounded outer electrode. The plasma fabric is flexible and lightweight, and it can be scaled up for larger areas, making it attractive for wearable APP applications. Here, we report the various plasma properties of the WAPP device and successful test results showing the decontamination of toxic chemical warfare agents, namely, mustard (HD), soman (GD), and nerve (VX) agents. PMID:28098192
A technique for fabricating single screw-retained implant-supported interim crowns in conjunction with implant surgery.
McRory, M Eric; Cagna, David R
This article presents an intraoral technique for fabricating single screw-retained implant-supported interim crowns immediately after surgical implant placement in extraction sites. The technique may be used with any implant system that provides a provisional abutment or an open-tray impression coping that can be modified for use as a provisional abutment.
Study on fabrication of scaffold using three-dimensional electrohydrodynamic ink-jet technique
NASA Astrophysics Data System (ADS)
Ko, Han Seo; Lee, Soo-Hong; Lee, Pil-Ho; Kim, Dae-Hoon; Yu, Chiang Wei; Lee, Sang Won
The EHD ink-jet technique uses the electrostatic force by applied voltage between a nozzle and an electrode to fabricate a three-dimensional scaffold by accumulating layers. In this study, a PLA (Polylactide) which is a polymer material was used to make the biodegradable scaffold. The experiment was performed by various inks with different solvent ratios because the layer thickness and width on the substrate are influenced by the ink properties such as the solvent ratio and boiling point. The cone-jet mode which looks cone-shaped on the meniscus was used for the EHD jetting by various stage velocities and solvent ratios of the PCL material. The micro-zoom lens and the LED lamp were used to visualize the jetting performance. The three-dimensional printing was completed by the movement of the stages using the Gentry structure. The optimum condition was selected for the fabrication of the scaffold after investigating the width of the pattern and the thickness of the multiple layers. This work supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean government (MEST) (No. S-2011-0023457).
Fabrication of Al-Cu alloy with elongated pores by continuous casting technique
NASA Astrophysics Data System (ADS)
Suzuki, S.; Kim, T.-B.; Nakajima, H.
A1-4.5wt%Cu was unidirectionally solidified by continuous casting technique under hydrogen pressure of 0.1MPa at the transference velocities ranging from 1 to 50 mmmidmin-1. The fabricated slabs have microstructures of columnar α-dendrite and eutectic, which are typical for hypo-eutectic Al-Cu alloys. Elongated pores are observed in the eutectic region surrounded by several columnar α-dendrites. The shapes of the pores are affected by that of the surrounding α-dendrites. The average pores diameter is several ten μm smaller than the average dendrite arm spacing, which decreases with increasing solidification rate. Therefore, the pore diameter varies from about 200 μm to 30 μm with increasing transference velocity from 1 to 50 mmmidmin-1. The porosity of the fabricated samples is in the range between 2 ~ 6 %. There is not significant dependence of the porosity on the transference velocity in the range of the present study. The porosity is similar to the reported value of Al-Si, where the area fraction of eutectic region is smaller than that of α-dendrite.
Fabrication of Converging and Diverging Polymeric Microlens Arrays By A Thermocapillary Replication Technique
NASA Astrophysics Data System (ADS)
Lim, Soon Wei Daniel; Fiedler, Kevin R.; Troian, Sandra M.
Thermocapillary forces offer a powerful method for sculpting air/liquid interfaces at microscale dimensions. Here we demonstrate how square arrays of slender chilled pins in close proximity to a molten nanofilm enforce periodic distributions of thermocapillary stresses suitable for fabricating microlens arrays with ultrasmooth surfaces and excellent focusing capability. We applied this technique to shape and then solidify polystyrene films on quartz to form converging and diverging microlens arrays. By adjusting the growth time, width of the chilled pins, and pin pitch, we created simple convex, simple concave, caldera-like and even hierarchical microarray components. The latter two tend to form when the pitch and pin width are comparable in size. The diverging arrays were incorporated into a Shack-Hartmann wavefront sensor for imaging spatial fluctuations in refractive index caused by bursts of cooled spray. The caldera-like arrays were used to collimate an incident beam into annuli. These demonstrations illustrate how spatiotemporal control over thermocapillary distributions can be used to fabricate a multiplicity of micro-optical components in a single, non-contact step. This work was supported by the Kiyo and Eiko Tomiyasu SURF scholarship (SWDL) and an NSTRF fellowship (KRF).
Elastomeric PDMS Planoconvex Lenses Fabricated by a Confined Sessile Drop Technique.
Ekgasit, S; Kaewmanee, N; Jangtawee, P; Thammacharoen, C; Donphoongpri, M
The ubiquity of high quality smartphones at affordable prices not only accelerated the social penetration in the global population but also promoted nontraditional usage of smartphones as point-of-care medical diagnostic devices, sensors, and portable digital microscopes. This paper reveals a simple, rapid, cost-effective, and template-free technique for mass-scale production of an elastomeric PDMS (ePDMS) planoconvex lens capable of converting a smartphone into a portable digital microscope. By taking advantage of the resistance to spreading of liquid by a sharp edge, highly stable spherical cap of viscous liquid PDMS (lPDMS) on a smooth PMMA circular disk was fabricated. The axisymmetric spreading of lPDMS under the gravitational force and interfacial tension force enable the formation of spherical cap with a certain radius of curvature. A thermal treatment at 80 °C for 30 min cured the spherical cap lPDMS into a bubble-free ePDMS planoconvex lens. Lenses with focal lengths of 55.2-3.4 mm could be reproducibly fabricated by adjusting the volume of dispensed lPDMSs and diameter of PMMA disks. High-resolution panoramic microscope images without a distortion of small cylindrical object could be constructed on-the-fly using the imbedded smartphone app. Applications of the smartphone digital microscope equipped with an ePDMS planoconvex lens for imaging of micro printings, gun shot residues, cylindrical objects, and bullet toolmarks were explored.
Hemoglobin protein hollow shells fabricated through covalent layer-by-layer technique
Duan Li; He Qiang; Cui Yue; Wang Kewei; Li Junbai . E-mail: firstname.lastname@example.com
Hemoglobin (Hb) protein microcapsules held together by cross-linker, glutaraldehyde (GA), were successfully fabricated by covalent layer-by-layer (LbL) technique. The Schiff base reaction occurred on the colloid templates between the aldehyde groups of GA and free amino sites of Hb results in the formation of GA/Hb microcapsules after the removal of the templates. The structure of obtained monodisperse protein microcapsule was characterized by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The UV-Vis spectra measurements demonstrate the existence of Hb in the assembled capsules. Cyclic voltammetry (CV) and potential-controlled amperometric measurements (I-t curve) confirm that hemoglobin microcapsules after fabrication remain their heme electroactivity. Moreover, direct electron transfer process from protein to electrode surface was performed to detect the heme electrochemistry without using any mediator or promoter. The experiments of fluorescence recovery after photobleaching (FRAP) by CLSM demonstrate that the hemoglobin protein microcapsules have an improved permeability comparing to the conventional polyelectrolyte microcapsules.
Toxicity study in blood and tumor cells of laser produced medicines for application in fabrics.
Morán, M Carmen; Tozar, Tatiana; Simon, Agota; Dinache, Andra; Smarandache, Adriana; Andrei, Ionut Relu; Boni, Mihai; Pascu, Mihail Lucian; Cirisano, Francesca; Ferrari, Michele
Phenothiazine derivatives are non-antibiotics with antimicrobial, fungistatic and fungicidal effects. We exposed to a high energy UV laser beam phenothiazines solutions in water at 20mg/mL concentration to increase antibacterial activity of resulting mixtures. Compared to previous results obtained on bacteria, more research is needed about UV laser irradiated phenothiazines applications on cancer cell cultures to evidence possible anticancerous properties. Evaluation of the safety of the newly obtained photoproducts in view of use on humans is also needed. Due to expensive animal testing in toxicology and pressure from general public and governments to develop alternatives to in vivo testing, in vitro cell-based models are attractive for preliminary testing of new materials. Cytotoxicity screening reported here shows that laser irradiated (4h exposure time length) chlorpromazine and promazine are more efficient against some cell cultures. Interaction of laser irradiated phenothiazines with fabrics show that promethazine and chlorpromazine have improved wetting properties. Correlation of these two groups of properties shows that chlorpromazine appears to be more recommended for applications on tissues using fabrics as transport vectors. The reported results concern stability study of phenothiazines water solutions to know the time limits within which they are stable and may be used.
Materials and Techniques for the Femtosecond Laser Fabrication of Optical Devices in Glass
NASA Astrophysics Data System (ADS)
Troy, Neil William
Focused femtosecond laser pulses can be used to permanently modify the refractive index of glasses. If the change in the refractive index of the laser-modified material is positive, the material can be easily used to create optical waveguiding structures. Unfortunately, few materials are known to exhibit this property. In prior research we found a unique zinc phosphate glass composition, 60ZnO ∘ 40P2O5, that exhibits this property and we have used it as a launching point to create more robust glasses as well as optical devices using the femtosecond laser writing technique. In particular, the research presented in this dissertation verifies our claim that the oxygen to phosphorus ratio (O/P) in the glass is responsible for the glass's ability to create high index regions when modified. This O/P ratio of 3.25 has allowed us to create waveguides in zinc phosphate glasses with the inclusion of rare-earth doping, magnesium doping, and aluminum doping. After the creation of these waveguides Raman spectroscopy showed that there were distinct changes to the phosphate glass network such that longer phosphate chains were broken up into smaller chains by the modification process. We were able to show that by mapping the ratio of differently bonded phosphate tetrahedra (denoted by their Qi species) we could precisely map out all laser-modified material. In a separate study we investigated the use of cylindrical vector beams for femtosecond laser writing. By using cylindrical vector beams, in which the polarization state varies across the beam profile, it is possible to create torus-shaped foci, which possibly yield new waveguide geometries. After creation of these beams with a twisted nematic liquid crystal device we modified torus-shaped regions on and inside glasses. In glasses we attempted to use this torus modified shape to induce optical guiding by producing a low index region around a high index core but were unable to, likely due to the self-focusing of the laser deep
Modified technique to improve fabrication and outcome of definitive orbital prosthesis.
Aggarwal, Himanshi; Kumar, Pradeep; Singh, Saumyendra V
Facial prostheses are generally fabricated from silicones, which provide life-like appearance and flexibility. The longevity of silicone, however, is limited because of its tendency to support fungal growth, absorb oils and grease, and edge-tearing susceptibility. Polyurethane (PU) liners have been used on the tissue-bearing surface of such prosthesis to improve tear resistance and fungal resistance. Technique sensitivity, discoloration and metamerism are significant limitations of urethane lining. Further, this liner is incorporated during processing of definitive prosthesis, which precludes try-in of tissue surface of prosthesis. This article describes an alternative lining material for fitting surface of definitive orbital prostheses, which could overcome limitations associated with all silicone or PU lined silicone prostheses.
Zinc Oxide Thin Films Fabricated with Direct Current Magnetron Sputtering Deposition Technique
Hoon, Jian-Wei; Chan, Kah-Yoong; Krishnasamy, Jegenathan; Tou, Teck-Yong
Zinc oxide (ZnO) is a very promising material for emerging large area electronic applications including thin-film sensors, transistors and solar cells. We fabricated ZnO thin films by employing direct current (DC) magnetron sputtering deposition technique. ZnO films with different thicknesses ranging from 100 nm to 1020 nm were deposited on silicon (Si) substrate. The deposition pressure was varied from 12 mTorr to 25 mTorr. The influences of the film thickness and the deposition pressure on structural properties of the ZnO films were investigated using Mahr surface profilometer and atomic force microscopy (AFM). The experimental results reveal that the film thickness and the deposition pressure play significant role in the structural formation of the deposited ZnO thin films. ZnO films deposited on Si substrates are promising for variety of thin-film sensor applications.
A post-fabrication selective magnetic annealing technique in standard MEMS processes
NASA Astrophysics Data System (ADS)
Mohammadi, A.; Karmakar, N. C.; Yuce, M. R.
A selective electrothermal magnetic annealing technique is introduced that provides programming capabilities for mechanical micro-resonators. In the proposed approach, the magnetic properties of resonators can be locally tuned in a post-fabrication batch-compatible process step. A prototype is implemented in a standard microfabrication process, where resonating ferromagnetic elements are suspended on top of a polysilicon resistive heater. The ferromagnetic elements consist of electroplated Nickel (Ni) with minor Iron (Fe) impurities. The electro-thermo-mechanical heating phenomenon is simulated for design purposes. The magnetization of micro-resonators with and without magnetic annealing is measured. The resulting magnetic property enhancement is illustrated by hysteresis (M-H) loop variations.
Unconventional low-cost fabrication and patterning techniques for point of care diagnostics.
Sharma, Himanshu; Nguyen, Diep; Chen, Aaron; Lew, Valerie; Khine, Michelle
The potential of rapid, quantitative, and sensitive diagnosis has led to many innovative 'lab on chip' technologies for point of care diagnostic applications. Because these chips must be designed within strict cost constraints to be widely deployable, recent research in this area has produced extremely novel non-conventional micro- and nano-fabrication innovations. These advances can be leveraged for other biological assays as well, including for custom assay development and academic prototyping. The technologies reviewed here leverage extremely low-cost substrates and easily adoptable ways to pattern both structural and biological materials at high resolution in unprecedented ways. These new approaches offer the promise of more rapid prototyping with less investment in capital equipment as well as greater flexibility in design. Though still in their infancy, these technologies hold potential to improve upon the resolution, sensitivity, flexibility, and cost-savings over more traditional approaches.
Fabrication of multi-well chips for spheroid cultures and implantable constructs through rapid prototyping techniques.
Lopa, Silvia; Piraino, Francesco; Kemp, Raymond J; Di Caro, Clelia; Lovati, Arianna B; Di Giancamillo, Alessia; Moroni, Lorenzo; Peretti, Giuseppe M; Rasponi, Marco; Moretti, Matteo
Three-dimensional (3D) culture models are widely used in basic and translational research. In this study, to generate and culture multiple 3D cell spheroids, we exploited laser ablation and replica molding for the fabrication of polydimethylsiloxane (PDMS) multi-well chips, which were validated using articular chondrocytes (ACs). Multi-well ACs spheroids were comparable or superior to standard spheroids, as revealed by glycosaminoglycan and type-II collagen deposition. Moreover, the use of our multi-well chips significantly reduced the operation time for cell seeding and medium refresh. Exploiting a similar approach, we used clinical-grade fibrin to generate implantable multi-well constructs allowing for the precise distribution of multiple cell types. Multi-well fibrin constructs were seeded with ACs generating high cell density regions, as shown by histology and cell fluorescent staining. Multi-well constructs were compared to standard constructs with homogeneously distributed ACs. After 7 days in vitro, expression of SOX9, ACAN, COL2A1, and COMP was increased in both constructs, with multi-well constructs expressing significantly higher levels of chondrogenic genes than standard constructs. After 5 weeks in vivo, we found that despite a dramatic size reduction, the cell distribution pattern was maintained and glycosaminoglycan content per wet weight was significantly increased respect to pre-implantation samples. In conclusion, multi-well chips for the generation and culture of multiple cell spheroids can be fabricated by low-cost rapid prototyping techniques. Furthermore, these techniques can be used to generate implantable constructs with defined architecture and controlled cell distribution, allowing for in vitro and in vivo investigation of cell interactions in a 3D environment.
Fabrication of porous polymeric matrix drug delivery devices using the selective laser sintering technique.
Leong, K F; Phua, K K; Chua, C K; Du, Z H; Teo, K O
New techniques in solid freeform fabrication (SFF) have prompted research into methods of manufacturing and controlling porosity. The strategy of this research is to integrate computer aided design (CAD) and the SFF technique of selective laser sintering (SLS) to fabricate porous polymeric matrix drug delivery devices (DDDs). This study focuses on the control of the porosity of a matrix by manipulating the SLS process parameters of laser beam power and scan speed. Methylene blue dye is used as a drug model to infiltrate the matrices via a degassing method; visual inspection of dye penetration into the matrices is carried out. Most notably, the laser power matrices show a two-stage penetration process. The matrices are sectioned along the XZ planes and viewed under scanning electron microscope (SEM). The morphologies of the samples reveal a general increase in channel widths as laser power decreases and scan speed increases. The fractional release profiles of the matrices are determined by allowing the dye to diffuse out in vitro within a controlled environment. The results show that laser power and scan speed matrices deliver the dye for 8-9 days and have an evenly distributed profile. Mercury porosimetry is used to analyse the porosity of the matrices. Laser power matrices show a linear relationship between porosity and variation in parameter values. However, the same relationship for scan speed matrices turns out to be rather inconsistent. Relationships between the SLS parameters and the experimental results are developed using the fractional release rate equation for the infinite slab porous matrix DDD as a basis for correlation.
Demonstration of Logic Operations in High-Performance RRAM Crossbar Array Fabricated by Atomic Layer Deposition Technique
NASA Astrophysics Data System (ADS)
Han, Runze; Huang, Peng; Zhao, Yudi; Chen, Zhe; Liu, Lifeng; Liu, Xiaoyan; Kang, Jinfeng
In this paper, resistive random access memory (RRAM)-based crossbar arrays with the cell structure of Pt/[AlO y /HfO x ] m /TiN were fabricated by using atomic layer deposition (ALD) technique. The RRAM devices in the arrays show excellent performances such as good uniformity and high reliability. Based on the fabricated RRAM array, a complete set of basic logic operations including NOR and XNOR were successfully demonstrated.
Process for fabricating polycrystalline semiconductor thin-film solar cells, and cells produced thereby
Wu, Xuanzhi; Sheldon, Peter
A novel, simplified method for fabricating a thin-film semiconductor heterojunction photovoltaic device includes initial steps of depositing a layer of cadmium stannate and a layer of zinc stannate on a transparent substrate, both by radio frequency sputtering at ambient temperature, followed by the depositing of dissimilar layers of semiconductors such as cadmium sulfide and cadmium telluride, and heat treatment to convert the cadmium stannate to a substantially single-phase material of a spinel crystal structure. Preferably, the cadmium sulfide layer is also deposited by radio frequency sputtering at ambient temperature, and the cadmium telluride layer is deposited by close space sublimation at an elevated temperature effective to convert the amorphous cadmium stannate to the polycrystalline cadmium stannate with single-phase spinel structure.
A Novel Supercritical Fluid-Assisted Fabrication Technique for Producing Transparent Nanocomposites
Contractors (DD882) Inventions (DD882) Scientific Progress Three types of studies were conducted : 1. Transparent nanocomposites based on poly(methyl...methacrylate) (PMMA) and cellulose nanocrystals (CNC) nanocomposites 2. Transparent green polymer blends based on polylactic acid (PLA) and polypropylene ...carbonate (PPC) 3. Transparent green nanocomposites based on polylactic acid (PLA), polypropylene carbonate (PPC) and nanofibrillated cellulose (NFC
Chemical Fabrication Used to Produce Thin-Film Materials for High Power-to- Weight-Ratio Space Photovoltaic Arrays
NASA Technical Reports Server (NTRS)
Hepp, Aloysius F.; Rybicki, George C.; Raffaelle, Ryne P.; Harris, Jerry D.; Hehemann, David G.; Junek, William; Gorse, Joseph; Thompson, Tracy L.; Hollingsworth, Jennifer A.; Buhro, William E.
The key to achieving high specific power (watts per kilogram) space solar arrays is the development of a high-efficiency, thin-film solar cell that can be fabricated directly on a flexible, lightweight, space-qualified durable substrate such as Kapton (DuPont) or other polyimide or suitable polymer film. Cell efficiencies approaching 20 percent at AM0 (air mass zero) are required. Current thin-film cell fabrication approaches are limited by either (1) the ultimate efficiency that can be achieved with the device material and structure or (2) the requirement for high-temperature deposition processes that are incompatible with all presently known flexible polyimide or other polymer substrate materials. Cell fabrication processes must be developed that will produce high-efficiency cells at temperatures below 400 degrees Celsius, and preferably below 300 degress Celsius to minimize the problems associated with the difference between the coefficients of thermal expansion of the substrate and thin-film solar cell and/or the decomposition of the substrate.
A modified SAG technique for the fabrication of DWDM DFB laser arrays with highly uniform wavelength spacings.
Zhang, Can; Liang, Song; Zhu, Hongliang; Wang, Baojun; Wang, Wei
A modified selective area growth (SAG) technique, in which the effective index of only the upper separate confinement heterostructure (SCH) layer are modulated to obtain different emission wavelengths, is reported for the fabrication of dense wavelength division multiplexing (DWDM) multi-wavelength laser arrays (MWLAs). InP based 1.5 μm distributed feedback (DFB) laser arrays with 0.8 nm, 0.42 nm, and 0.19 nm channel separations are demonstrated, all showing highly uniform wavelength spacings. The standard deviation of the distribution of the wavelength residues with respect to the corresponding linear fitting values is 0.0672 nm, which is a lot smaller than those of the MWLAs fabricated by other techniques including electron beam lithography. These results indicate that our SAG technique which needs only a simple procedure is promising for the fabrication of low cost DWDM MWLAs.
Quantification of Changes in Mulberry Silk Fabrics due to Different Laundering: Using WAXS Technique
NASA Astrophysics Data System (ADS)
Parameswara, P.; Nivedita, S.; Somashekar, R.
Loom finished mulberry silk fabrics (Taffeta) were machine laundered and hand laundered several times. X-ray diffractograms of pure and laundered fabrics were used to calculate microstructural parameters like average crystallite size (D) and lattice strain (Vegr) employing Williamson-Hall plot. Microstructural parameters were compared with measured mechanical properties like breaking load, tenacity, and elongation of warp yarns unraveled from fabrics. Surface morphology and texture of silk fabrics changed upon washing is evident from SEM images.
Applications of Semiconductor Fabrication Methods to Nanomedicine: A Review of Recent Inventions and Techniques
Rajasekhar, Achanta; Gimi, Barjor; Hu, Walter
We live in a world of convergence where scientific techniques from a variety of seemingly disparate fields are being applied cohesively to the study and solution of biomedical problems. For instance, the semiconductor processing field has been primarily developed to cater to the needs of the ever decreasing transistor size and cost while increasing functionality of electronic circuits. In recent years, pioneers in this field have equipped themselves with a powerful understanding of how the same techniques can be applied in the biomedical field to develop new and efficient systems for the diagnosis, analysis and treatment of various conditions in the human body. In this paper, we review the major inventions and experimental methods which have been developed for nano/micro fluidic channels, nanoparticles fabricated by top-down methods, and in-vivo nanoporous microcages for effective drug delivery. This paper focuses on the information contained in patents as well as the corresponding technical publications. The goal of the paper is to help emerging scientists understand and improvise over these inventions. PMID:24312161
Research on subsurface defects of potassium dihydrogen phosphate crystals fabricated by single point diamond turning technique
NASA Astrophysics Data System (ADS)
Tie, Guipeng; Dai, Yifan; Guan, Chaoliang; Chen, Shaoshan; Song, Bing
Potassium dihydrogen phosphate (KDP) crystals, which are widely used in high-power laser systems, are required to be free of defects on fabricated subsurfaces. The depth of subsurface defects (SSD) of KDP crystals is significantly influenced by the parameters used in the single point diamond turning technique. In this paper, based on the deliquescent magnetorheological finishing technique, the SSD of KDP crystals is observed and the depths under various cutting parameters are detected and discussed. The results indicate that no SSD is generated under small parameters and with the increase of cutting parameters, SSD appears and the depth rises almost linearly. Although the ascending trends of SSD depths caused by cutting depth and feed rate are much alike, the two parameters make different contributions. Taking the same material removal efficiency as a criterion, a large cutting depth generates shallower SSD depth than a large feed rate. Based on the experiment results, an optimized cutting procedure is obtained to generate defect-free surfaces.
Applications of Semiconductor Fabrication Methods to Nanomedicine: A Review of Recent Inventions and Techniques.
Rajasekhar, Achanta; Gimi, Barjor; Hu, Walter
We live in a world of convergence where scientific techniques from a variety of seemingly disparate fields are being applied cohesively to the study and solution of biomedical problems. For instance, the semiconductor processing field has been primarily developed to cater to the needs of the ever decreasing transistor size and cost while increasing functionality of electronic circuits. In recent years, pioneers in this field have equipped themselves with a powerful understanding of how the same techniques can be applied in the biomedical field to develop new and efficient systems for the diagnosis, analysis and treatment of various conditions in the human body. In this paper, we review the major inventions and experimental methods which have been developed for nano/micro fluidic channels, nanoparticles fabricated by top-down methods, and in-vivo nanoporous microcages for effective drug delivery. This paper focuses on the information contained in patents as well as the corresponding technical publications. The goal of the paper is to help emerging scientists understand and improvise over these inventions.
Fabrication of nanostructure by physical vapor deposition with glancing angle deposition technique and its applications
NASA Astrophysics Data System (ADS)
Horprathum, M.; Eiamchai, P.; Kaewkhao, J.; Chananonnawathorn, C.; Patthanasettakul, V.; Limwichean, S.; Nuntawong, N.; Chindaudom, P.
A nanostructural thin film is one of the highly exploiting research areas particularly in applications in sensor, photocatalytic, and solar-cell technologies. In the past two decades, the integration of glancing-angle deposition (GLAD) technique to physical vapor deposition (PVD) process has gained significant attention for well-controlled multidimensional nanomorphologies because of fast, simple, cost-effective, and mass-production capability. The performance and functional properties of the coated thin films generally depend upon their nanostructural compositions, i.e., large aspect ratio, controllable porosity, and shape. Such structural platforms make the fabricated thin films very practical for several realistic applications. We therefore present morphological and nanostructural properties of various deposited materials, which included metals, i.e., silver (Ag), and oxide compounds, i.e., tungsten oxide (WO3), titanium dioxide (TiO2), and indium tin oxide (ITO). Different PVD techniques based on DC magnetron sputtering and electron-beam evaporation, both with the integrated GLAD component, were discussed. We further explore engineered nanostructures which enable controls of optical, electrical, and mechanical properties. These improvements led to several practical applications in surface-enhanced Raman, smart windows, gas sensors, self-cleaning materials and transparent conductive oxides (TCO).
Creating tissues from textiles: scalable nonwoven manufacturing techniques for fabrication of tissue engineering scaffolds.
Tuin, S A; Pourdeyhimi, B; Loboa, E G
Electrospun nonwovens have been used extensively for tissue engineering applications due to their inherent similarities with respect to fibre size and morphology to that of native extracellular matrix (ECM). However, fabrication of large scaffold constructs is time consuming, may require harsh organic solvents, and often results in mechanical properties inferior to the tissue being treated. In order to translate nonwoven based tissue engineering scaffold strategies to clinical use, a high throughput, repeatable, scalable, and economic manufacturing process is needed. We suggest that nonwoven industry standard high throughput manufacturing techniques (meltblowing, spunbond, and carding) can meet this need. In this study, meltblown, spunbond and carded poly(lactic acid) (PLA) nonwovens were evaluated as tissue engineering scaffolds using human adipose derived stem cells (hASC) and compared to electrospun nonwovens. Scaffolds were seeded with hASC and viability, proliferation, and differentiation were evaluated over the course of 3 weeks. We found that nonwovens manufactured via these industry standard, commercially relevant manufacturing techniques were capable of supporting hASC attachment, proliferation, and both adipogenic and osteogenic differentiation of hASC, making them promising candidates for commercialization and translation of nonwoven scaffold based tissue engineering strategies.
A novel wet extrusion technique to fabricate self-assembled microfiber scaffolds for controlled drug delivery.
Lavin, Danya M; Harrison, Michael W; Tee, Louis Y; Wei, Karen A; Mathiowitz, Edith
We have developed a novel wet extrusion process to fabricate nonwoven self-assembled microfiber scaffolds with uniform diameters less than 5 μm and without any postmanipulation. In this method, a poly(L-lactic acid) solution flows dropwise into a stirring nonsolvent bath, deforming into liquid polymer streams that self-assemble into a nonwoven microfiber scaffold. The ability to tune fiber diameter was achieved by decreasing polymer spin dope concentration and increasing the silicon oil to petroleum ether ratio of the nonsolvent spin bath. To demonstrate the drug delivery capabilities of scaffolds, heparin was encapsulated using a conventional water-in-oil (W/O) emulsion technique and a cryogenic emulsion technique developed in our laboratory. Spin dope preparation was found to significantly effect the release kinetics of self-assembled scaffolds by altering the interconnectivity of pores within the precipitating filaments. After 35 days, scaffolds prepared from W/O emulsions released up to 45% encapsulated heparin, whereas nearly 80% release of heparin was observed from cryogenic emulsion formulations. The versatility of our system, combined with the prolonged release of small molecules and the ability to control the homogeneity of self-assembling scaffolds, could be beneficial for many tissue regeneration and engineering applications.
Comparison of three-dimensional printing and vacuum freeze-dried techniques for fabricating composite scaffolds.
Sun, Kai; Li, Ruixin; Jiang, Wenxue; Sun, Yufu; Li, Hui
In this study, the performances of different preparation methods of the scaffolds were analyzed for chondrocyte tissue engineering. Silk fibroin/collagen (SF/C) was fabricated using a vacuum freeze-dried technique and by 3D printing. The porosity, water absorption expansion rates, mechanical properties, and pore sizes of the resulting materials were evaluated. The proliferation and metabolism of the cells was detected at different time points using an MTT assay. Cell morphologies and distributions were observed by histological analysis and scanning electron microscopy (SEM). The porosity, water absorption expansion rate, and Young's modulus of the material obtained via 3D printing were significantly higher than those obtained by the freeze-dried method, while the pore size did not differ significantly between the two methods. MTT assay results showed that the metabolism of cells seeded on the 3D printed scaffolds was more viable than the metabolism on the freeze-dried material. H&E staining of the scaffolds revealed that the number of cells in the 3D printed scaffold was higher in comparison to a similar measurement on the freeze-dried material. Consequently, stem cells grew well inside the 3D printed scaffolds, as measured by SEM, while the internal structure of the freeze-dried scaffold was disordered. Compared with the freeze-dried technique, the 3D printed scaffold exhibited better overall performance and was more suitable for cartilage tissue engineering.
Fabrication of nanostructure by physical vapor deposition with glancing angle deposition technique and its applications
Horprathum, M. Eiamchai, P. Patthanasettakul, V.; Limwichean, S.; Nuntawong, N.; Chindaudom, P.; Kaewkhao, J.; Chananonnawathorn, C.
A nanostructural thin film is one of the highly exploiting research areas particularly in applications in sensor, photocatalytic, and solar-cell technologies. In the past two decades, the integration of glancing-angle deposition (GLAD) technique to physical vapor deposition (PVD) process has gained significant attention for well-controlled multidimensional nanomorphologies because of fast, simple, cost-effective, and mass-production capability. The performance and functional properties of the coated thin films generally depend upon their nanostructural compositions, i.e., large aspect ratio, controllable porosity, and shape. Such structural platforms make the fabricated thin films very practical for several realistic applications. We therefore present morphological and nanostructural properties of various deposited materials, which included metals, i.e., silver (Ag), and oxide compounds, i.e., tungsten oxide (WO{sub 3}), titanium dioxide (TiO{sub 2}), and indium tin oxide (ITO). Different PVD techniques based on DC magnetron sputtering and electron-beam evaporation, both with the integrated GLAD component, were discussed. We further explore engineered nanostructures which enable controls of optical, electrical, and mechanical properties. These improvements led to several practical applications in surface-enhanced Raman, smart windows, gas sensors, self-cleaning materials and transparent conductive oxides (TCO)
3D-Cultivation of bone marrow stromal cells on hydroxyapatite scaffolds fabricated by dispense-plotting and negative mould technique.
Detsch, R; Uhl, F; Deisinger, U; Ziegler, G
The main principle of a bone tissue engineering (BTE) strategy is to cultivate osteogenic cells in an osteoconductive porous scaffold. Ceramic implants for osteogenesis are based mainly on hydroxyapatite (HA), since this is the inorganic component of bone. Rapid Prototyping (RP) is a new technology in research for producing ceramic scaffolds. This technology is particularly suitable for the fabrication of individually and specially tailored single implants. For tissue engineering these scaffolds are seeded with osteoblast or osteoblast precursor cells. To supply the cultured osteoblastic cells efficiently with nutrition in these 3D-geometries a bioreactor system can be used. The aim of this study was to analyse the influence of differently fabricated HA-scaffolds on bone marrow stromal cells. For this, two RP-techniques, dispense-plotting and a negative mould method, were used to produce porous ceramics. The manufactured HA-scaffolds were then cultivated in a dynamic system (bioreactor) with an osteoblastic precursor cell line. In our study, the applied RP-techniques give the opportunity to design and process HA-scaffolds with defined porosity, interconnectivity and 3D pore distribution. A higher differentiation of bone marrow stromal cells could be detected on the negative mould fabricated scaffolds, while cell proliferation was higher on the dispense-plotted scaffolds. Nevertheless, both scaffold types can be used in tissue engineering applications.
Development of Hot Pressing as a Low Cost Processing Technique for Fuel Cell Fabrication
Sarin, V
Dependable, plentiful, and economical energy has been the driving force for financial, industrial, and political growth in the US since the mid 19th century. For a country whose progress is so deeply rooted in abundant energy and whose current political agenda involves stabilizing world fossil fuel prices, the development of a reliable, efficient and environmentally friendly power generating source seems compulsory. The maturing of high technology fuel cells may be the panacea the country will find indispensable to free itself from foreign dependence. Fuel cells offer an efficient, combustion-less, virtually pollution-free power source, capable of being sited in downtown urban areas or in remote regions. Fuel cells have few moving parts and run almost silently. Fuel cells are electrochemical devices that convert the chemical energy of a fuel directly to electrical energy. Unlike batteries, which store a finite amount of energy, fuel cells will generate electricity continuously, as long as fuel and oxidant are available to the electrodes. Additionally, fuel cells offer clean, efficient, and reliable power and they can be operated using a variety of fuels. Hence, the fuel cell is an extremely promising technology. Over the course of this research, the fundamental knowledge related to ceramic processing, sintering, and hot pressing to successfully hot press a single operational SOFC in one step has been developed. Ceramic powder processing for each of the components of an SOFC has bene tailored towards this goal. Processing parameter for the electrolyte and cathode have been studied and developed until they converted. Several anode fabrication techniques have been developed. Additionally, a novel anode structured has been developed and refined. These individual processes have been cultivated until a single cell SOFC has been fabricated in one step.
Application of powder metallurgy techniques to produce improved bearing elements for liquid rocket engines
NASA Technical Reports Server (NTRS)
Moracz, D. J.; Shipley, R. J.; Moxson, V. S.; Killman, R. J.; Munson, H. E.
The objective was to apply powder metallurgy techniques for the production of improved bearing elements, specifically balls and races, for advanced cryogenic turbopump bearings. The materials and fabrication techniques evaluated were judged on the basis of their ability to improve fatigue life, wear resistance, and corrosion resistance of Space Shuttle Main Engine (SSME) propellant bearings over the currently used 440C. An extensive list of candidate bearing alloys in five different categories was considered: tool/die steels, through hardened stainless steels, cobalt-base alloys, and gear steels. Testing of alloys for final consideration included hardness, rolling contact fatigue, cross cylinder wear, elevated temperature wear, room and cryogenic fracture toughness, stress corrosion cracking, and five-ball (rolling-sliding element) testing. Results of the program indicated two alloys that showed promise for improved bearing elements. These alloys were MRC-2001 and X-405. 57mm bearings were fabricated from the MRC-2001 alloy for further actual hardware rig testing by NASA-MSFC.
Novel Engineering and Fabrication Techniques Tested in Low-Noise- Research Fan Blades
NASA Technical Reports Server (NTRS)
Cunningham, Cameron C.
A major source of fan noise in commercial turbofan engines is the interaction of the wake from the fan blades with the stationary vanes (stators) directly behind them. The Trailing Edge Blowing (TEB) project team at the NASA Glenn Research Center designed and fabricated new fan blades to study the effects of fan trailing edge blowing as a potential noise-reduction concept. The intent is to fill the rotor wake by supplying air to the rotor blade trailing edge at the proper conditions to minimize the wake deficit, and thus generate less noise. The TEB hardware is designed for the Active Noise Control Fan (ANCF) test rig in Glenn's Aeroacoustic Propulsion Laboratory. For this test, the air is fed from an external supply through the shaft of the rig. It is distributed to the base of each blade through an impeller, where it is forced into a plenum at the core of each blade. In actual engine configuration, air would most likely be bled from the compressor, but only at times when noise is an issue, such as takeoffs and landings. Glenn researchers designed and manufactured the blades in-house, using new techniques and concepts. The skins, which were designed for maximum strength in the directions of highest stress, were molded from multiple layers of carbon fiber. Considerable use was made of rapid prototyping techniques, such as laser sintering. The core was sintered from a lightweight polymer, and the retainer was CNC-machined (computer numerical control machined) from aluminum. All the components were joined with a cold-cure aerospace adhesive. These techniques and processes reduced the overall cost and allowed the new concept to be studied much sooner than would be possible using traditional fabrication methods. Since this test rig did not support the use of blade-monitoring techniques such as strain gauges, extensive bench testing was required to qualify the design. The blades were examined using a variety of methods including holography, pull tests (cyclic and
High-Quality Large-Magnification Polymer Lens from Needle Moving Technique and Thermal Assisted Moldless Fabrication Process
Pongsoon, Prasit; Jarujareet, Ungkarn; Chaitavon, Kosom; Porntheeraphat, Supanit; Sumriddetchkajorn, Sarun; Koanantakool, Thaweesak
The need of mobile microscope is escalating as well as the demand of high quality optical components in low price. We report here a novel needle moving technique to fabricate milli-size lens together with thermal assist moldless method. Our proposed protocol is able to create a high tensile strength structure of the lens and its base which is beneficial for exploiting in convertinga smart phone to be a digital microscope. We observe that no bubble trapped in a lens when this technique is performed which can overcome a challenge problem found in a typical dropping technique. We demonstrate the symmetry, smoothness and micron-scale resolution of the fabricated structure. This proposed technique is promising to serve as high quality control mass production without any expensive equipment required. PMID:26765524
Michigan state upgrade to produce intense radioactive ion beams by fragmentation technique
Lubkin, G.B.
This article describes the planned upgrading of accelerator facilities to produce intense radioactive ion beams, by a fragmentation technique, for experimental simulation of nucleosynthesis in novas and supernovas. (AIP) {ital 1997 American Institute of Physics.} {copyright} {ital 1997} {ital American Institute of Physics}
Fabrication of YSZ buffer layer by single source MOCVD technique for YBCO coated conductor
NASA Astrophysics Data System (ADS)
Jun, Byung-Hyuk; Sun, Jong-Won; Kim, Ho-Jin; Lee, Dong-Wook; Jung, Choong-Hwan; Park, Soon-Dong; Kim, Chan-Joong
Yttria stabilized zirconia (YSZ) buffer layers were deposited by a metal organic chemical vapor deposition technique using a single liquid source for the application of YBa 2Cu 3O 7- δ (YBCO) coated conductor. Y:Zr mole ratio was 0.2:0.8, and tetrahydrofuran (THF) was used as a solvent. The (1 0 0) single crystal MgO substrate was used for searching the deposition conditions. Bi-axially oriented CeO 2 and NiO films were fabricated on {1 0 0} <0 0 1> textured Ni substrate by the same method and used as templates. At a constant working pressure of 10 Torr, the deposition temperatures (660-800 °C) and oxygen flow rates (100-500 sccm) were changed to find the optimum deposition condition. The best (1 0 0) oriented YSZ film on MgO was obtained at 740 °C and O 2 flow rate of 300 sccm. For a YSZ buffer layer with this deposition condition on a CeO 2/Ni template, full width half maximum values of the in-plane ( ϕ-scan) and out-of-plane ( ω-scan) alignments were 10.6° and 9.8°, respectively. The SEM image of YSZ film on CeO 2/Ni showed surface morphologies without microcracks. The film deposition rate was about 100 nm/min.
Fabrication of Lotus-Type Porous Al-Si Alloys Using the Continuous Casting Technique
NASA Astrophysics Data System (ADS)
Park, J. S.; Hyun, S. K.; Suzuki, S.; Nakajima, H.
Lotus-type porous Al-Si (4, 8, 12, 14, and 18 wt pct) alloys were fabricated using the continuous casting technique under a hydrogen gas pressure of 0.1 MPa at various transference velocities, and the effects of the silicon content level and transference velocity on the pore morphology and porosity were investigated. Both the porosity and the average pore diameter increase as the silicon content level increases and decrease as the transference velocity increases. In particular, the velocity dependence is obviously exhibited at a silicon content level higher than 12 wt pct. The pore shape is changed from irregular in the higher-dendrite fraction to nearly circular in the lower-dendrite fraction. The porosity and the pore morphology are influenced by the silicon content level and transference velocity. In the model, these results can be understood with the explanation that the pores, which contribute to the increase in porosity, are generated at the eutectic fronts. This indicated that the porosity and the pore size in lotus-type porous Al-Si alloys can be well controlled by varying the silicon content level and the transference velocity.
Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques
NASA Astrophysics Data System (ADS)
Chan, Kwai S.
Rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) were fabricated by layer-by-layer deposition techniques that included electron beam melting (EBM) and laser beam melting (LBM). The surface conditions of these plates were characterized using x-ray micro-computed tomography. The depth and radius of surface notch-like features on the LBM and EBM plates were measured from sectional images of individual virtual slices of the rectangular plates. The stress concentration factors of individual surface notches were computed and analyzed statistically to determine the appropriate distributions for the notch depth, notch radius, and stress concentration factor. These results were correlated with the fatigue life of the Ti-6Al-4V ELI alloys from an earlier investigation. A surface notch analysis was performed to assess the debit in the fatigue strength due to the surface notches. The assessment revealed that the fatigue lives of the additively manufactured plates with rough surface topographies and notch-like features are dominated by the fatigue crack growth of large cracks for both the LBM and EBM materials. The fatigue strength reduction due to the surface notches can be as large as 60%-75%. It is concluded that for better fatigue performance, the surface notches on EBM and LBM materials need to be removed by machining and the surface roughness be improved to a surface finish of about 1 μm.
Organic Lasers: Recent Developments on Materials, Device Geometries, and Fabrication Techniques.
Kuehne, Alexander J C; Gather, Malte C
Organic dyes have been used as gain medium for lasers since the 1960s, long before the advent of today's organic electronic devices. Organic gain materials are highly attractive for lasing due to their chemical tunability and large stimulated emission cross section. While the traditional dye laser has been largely replaced by solid-state lasers, a number of new and miniaturized organic lasers have emerged that hold great potential for lab-on-chip applications, biointegration, low-cost sensing and related areas, which benefit from the unique properties of organic gain materials. On the fundamental level, these include high exciton binding energy, low refractive index (compared to inorganic semiconductors), and ease of spectral and chemical tuning. On a technological level, mechanical flexibility and compatibility with simple processing techniques such as printing, roll-to-roll, self-assembly, and soft-lithography are most relevant. Here, the authors provide a comprehensive review of the developments in the field over the past decade, discussing recent advances in organic gain materials, which are today often based on solid-state organic semiconductors, as well as optical feedback structures, and device fabrication. Recent efforts toward continuous wave operation and electrical pumping of solid-state organic lasers are reviewed, and new device concepts and emerging applications are summarized.
Recognition of Prior Learning as a Technique for Fabricating the Adult Learner: A Genealogical Analysis on Swedish Adult Education Policy
ERIC Educational Resources Information Center
Andersson, Per; Fejes, Andreas
This article focuses on the recognition of prior learning and the figure of thought it represents in Swedish policy on adult education. It can be seen as a technique for governing the adult learner and a way of fabricating the subject. We are tracing this thought back in time to see how it has changed and what it consists of. The material analysed…
Fabrication and characterization of SiC f/SiC composites produced by the slurry infiltration process
NASA Astrophysics Data System (ADS)
Lee, S. P.; Lee, M. H.; Lee, J. K.; Byun, J. H.; Kohyama, A.
The mechanical properties of SiC f/SiC composites have been investigated, based on detailed analyses of their microstructure. SiC f/SiC composites were prepared from fiber preforms by a slurry infiltration technique, in which a mixture with SiC, Al 2O 3, and Y 2O 3 particles was impregnated into the fabric structure. SiC f/SiC composites were consolidated by liquid phase sintering process, associated with the creation of secondary phases by the addition of Al 2O 3 and Y 2O 3 particles. The reinforcing material was a plain weave Tyranno SA SiC fabric with a carbon interfacial layer. The sintered density and the pore volume fraction of SiC f/SiC composites were about 3.0 Mg/m 3 and about 10%, respectively. These SiC f/SiC composites had an average flexural strength of about 250 MPa at room temperature. They exhibited pseudo-ductile fracture behavior, due to the carbon interfacial layer. The introduction of the carbon interfacial layer greatly improved the fracture energy of SiC f/SiC composites.
Template-free synthesis and encapsulation technique for layer-by-layer polymer nanocarrier fabrication.
Qi, Aisha; Chan, Peggy; Ho, Jenny; Rajapaksa, Anushi; Friend, James; Yeo, Leslie
The encapsulation of therapeutic molecules within multiple layers of biocompatible and biodegradable polymeric excipients allows exquisite design of their release profile, to the extent the drug can be selectively delivered to a specific target location in vivo. Here, we develop a novel technique for the assembly of multilayer polyelectrolyte nanocarriers based on surface acoustic wave atomization as a rapid and efficient alternative to conventional layer-by-layer assembly, which requires the use of a sacrificial colloidal template over which consecutive polyelectrolyte layers are deposited. Polymer nanocarriers are synthesized by atomizing a polymer solution and suspending them within a complementary polymer solution of opposite charge subsequent to their solidification in-flight as the solvent evaporates; reatomizing this suspension produces nanocarriers with a layer of the second polymer deposited over the initial polymer core. Successive atomization-suspension layering steps can then be repeated to produce as many additional layers as desired. Specifically, we synthesize nanocarriers comprising two and three, and up to eight, alternating layers of chitosan (or polyethyleneimine) and carboxymethyl cellulose within which plasmid DNA is encapsulated and show in vitro DNA release profiles over several days. Evidence that the plasmid's viability is preserved and hence the potential of the technique for gene delivery is illustrated through efficient in vitro transfection of the encapsulated plasmid in human mesenchymal progenitor and COS-7 cells.
Fit accuracy of metal partial removable dental prosthesis frameworks fabricated by traditional or light curing modeling material technique: An in vitro study
Anan, Mohammad Tarek M.; Al-Saadi, Mohannad H.
Objective The aim of this study was to compare the fit accuracies of metal partial removable dental prosthesis (PRDP) frameworks fabricated by the traditional technique (TT) or the light-curing modeling material technique (LCMT). Materials and methods A metal model of a Kennedy class III modification 1 mandibular dental arch with two edentulous spaces of different spans, short and long, was used for the study. Thirty identical working casts were used to produce 15 PRDP frameworks each by TT and by LCMT. Every framework was transferred to a metal master cast to measure the gap between the metal base of the framework and the crest of the alveolar ridge of the cast. Gaps were measured at three points on each side by a USB digital intraoral camera at ×16.5 magnification. Images were transferred to a graphics editing program. A single examiner performed all measurements. The two-tailed t-test was performed at the 5% significance level. Results The mean gap value was significantly smaller in the LCMT group compared to the TT group. The mean value of the short edentulous span was significantly smaller than that of the long edentulous span in the LCMT group, whereas the opposite result was obtained in the TT group. Conclusion Within the limitations of this study, it can be concluded that the fit of the LCMT-fabricated frameworks was better than the fit of the TT-fabricated frameworks. The framework fit can differ according to the span of the edentate ridge and the fabrication technique for the metal framework. PMID:26236129
Fabrication of three-dimensional porous scaffolds with controlled filament orientation and large pore size via an improved E-jetting technique.
Li, Jin Lan; Cai, Yan Li; Guo, Yi Lin; Fuh, Jerry Ying Hsi; Sun, Jie; Hong, Geok Soon; Lam, Ruey Na; Wong, Yoke San; Wang, Wilson; Tay, Bee Yen; Thian, Eng San
Biodegradable polymeric scaffolds have been widely used in tissue engineering as a platform for cell proliferation and subsequent tissue regeneration. Conventional microextrusion methods for three-dimensional (3D) scaffold fabrication were limited by their low resolution. Electrospinning, a form of electrohydrodynamic (EHD) printing, is an attractive method due to its capability of fabricating high-resolution scaffolds at the nanometer/micrometer scale level. However, the scaffold was composed of randomly orientated filaments which could not guide the cells in a specific direction. Furthermore, the pores of the electrospun scaffold were small, thus preventing cell infiltration. In this study, an alternative EHD jet printing (E-jetting) technique has been developed and employed to fabricate 3D polycaprolactone (PCL) scaffolds with desired filament orientation and pore size. The effect of PCL solution concentration was evaluated. Results showed that solidified filaments were achieved at concentration >70% (w/v). Uniform filaments of diameter 20 μm were produced via the E-jetting technique, and X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopic analyses revealed that there was no physicochemical changes toward PCL. Scaffold with a pore size of 450 μm and porosity level of 92%, was achieved. A preliminary in vitro study illustrated that live chondrocytes were attaching on the outer and inner surfaces of collagen-coated E-jetted PCL scaffolds. E-jetted scaffolds increased chondrocytes extracellular matrix secretion, and newly formed matrices from chondrocytes contributed significantly to the mechanical strength of the scaffolds. All these results suggested that E-jetting is an alternative scaffold fabrication technique, which has the capability to construct 3D scaffolds with aligned filaments and large pore sizes for tissue engineering applications.
A comparison of marginal fit of glass infiltrated alumina copings fabricated using two different techniques and the effect of firing cycles over them
Parkhedkar, Rambhao
PURPOSE This study evaluated marginal fit of glass infiltrated alumina cores fabricated using two techniques and their marginal stability after firing cycles of veneering porcelain. MATERIALS AND METHODS Fifteen standardized all-ceramic crowns were fabricated on a metal die using each technique: slip cast technique of VITA In-Ceram sprint Alumina (Group A as control) and plastic foil matrix technique of Turkom-Cera fused alumina core system (Group B). Copings were compared between groups and within groups at coping stage and after firing each layer of veneering porcelain. A device was used to standardize seating of copings on the metal die and positioning of the specimens under the microscope after each stage of fabrication. The specimens were not cemented and marginal gap was measured using an image analyzing software (Imagepro Express) on the photographs captured under an optical microscope. Two tailed unpaired 't test' was used to compare marginal gaps in two groups and one way ANOVA was used to analyze marginal distortion within each group at 95% confidence interval. RESULTS The marginal gap was smaller at the coping stage in group B (60 + 30 µm) than group A (81 + 21 µm) with statistical significance. After firing of veneering porcelain the difference was insignificant. At the final stage, both groups exhibited lower mean marginal gaps than at the initial coping stage with the difference of 11.75 µm for group A and 11.94 µm for group B, but it was statistically insignificant due to high value of standard deviation. CONCLUSION Within the limitations of this study, it was concluded that both techniques produced copings with comparable and acceptable marginal fit and marginal stability on firing veneering porcelain. PMID:22259703
Fabrication of ultra-thin diamond films using hydrogen implantation and Lift-off technique
NASA Astrophysics Data System (ADS)
Popov, V. P.; Antonov, V. A.; Safronov, L. N.; Kupriyanov, I. N.; Pal'yanov, Yu. N.; Rubanov, S.
The Lift-off technique based on high fluence (>3×1016cm-2) implantation of hydrogen (H-) ions has been developed to increase the structural quality and electro-optical properties of the diamond thin membranes. According to the XTEM study the Vacuum Pressure - High Temperature (VPHT) treatment of the H2+ implanted (111) diamond plates at 1200-1600°C and 10-3Pa forms buried glassy like graphite layers in the implanted areas. High Pressure - High Temperature (HPHT) annealing at the same temperatures but under the pressure 4-8 GPa leads to the epitaxial growth of graphite in the buried implanted layers, which could not be etched chemically, but could be easily removed by etching in the anodic cell. Visible light Raman spectroscopy has shown that the H-Lift-off technique is suitable for formation of ultra-thin (down to 30 nm) high quality single crystal diamond membranes and heterostructures. High concentration of nitrogen-vacancy NV- centres (˜1020cm-3) was observed under graphite contacts in thin layer (≤100 nm). Thin, 30 nm single crystal diamond films are the thinnest and largest area single crystal diamond structure produced to date by the Lift-off technique.
Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds
Hockett, Kevin L.; Baltrus, David A.
The soft-agar overlay technique was originally developed over 70 years ago and has been widely used in several areas of microbiological research, including work with bacteriophages and bacteriocins, proteinaceous antibacterial agents. This approach is relatively inexpensive, with minimal resource requirements. This technique consists of spotting supernatant from a donor strain (potentially harboring a toxic compound(s)) onto a solidified soft agar overlay that is seeded with a bacterial test strain (potentially sensitive to the toxic compound(s)). We utilized this technique to screen a library of Pseudomonas syringae strains for intraspecific killing. By combining this approach with a precipitation step and targeted gene deletions, multiple toxic compounds produced by the same strain can be differentiated. The two antagonistic agents commonly recovered using this technique are bacteriophages and bacteriocins. These two agents can be differentiated using two simple additional tests. Performing a serial dilution on a supernatant containing bacteriophage will result in individual plaques becoming less in number with greater dilution, whereas serial dilution of a supernatant containing bacteriocin will result a clearing zone that becomes uniformly more turbid with greater dilution. Additionally, a bacteriophage will produce a clearing zone when spotted onto a fresh soft agar overlay seeded with the same strain, whereas a bacteriocin will not produce a clearing zone when transferred to a fresh soft agar lawn, owing to the dilution of the bacteriocin. PMID:28117830
Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds.
Hockett, Kevin L; Baltrus, David A
The soft-agar overlay technique was originally developed over 70 years ago and has been widely used in several areas of microbiological research, including work with bacteriophages and bacteriocins, proteinaceous antibacterial agents. This approach is relatively inexpensive, with minimal resource requirements. This technique consists of spotting supernatant from a donor strain (potentially harboring a toxic compound(s)) onto a solidified soft agar overlay that is seeded with a bacterial test strain (potentially sensitive to the toxic compound(s)). We utilized this technique to screen a library of Pseudomonas syringae strains for intraspecific killing. By combining this approach with a precipitation step and targeted gene deletions, multiple toxic compounds produced by the same strain can be differentiated. The two antagonistic agents commonly recovered using this technique are bacteriophages and bacteriocins. These two agents can be differentiated using two simple additional tests. Performing a serial dilution on a supernatant containing bacteriophage will result in individual plaques becoming less in number with greater dilution, whereas serial dilution of a supernatant containing bacteriocin will result a clearing zone that becomes uniformly more turbid with greater dilution. Additionally, a bacteriophage will produce a clearing zone when spotted onto a fresh soft agar overlay seeded with the same strain, whereas a bacteriocin will not produce a clearing zone when transferred to a fresh soft agar lawn, owing to the dilution of the bacteriocin.
Computer-Assisted Mandibular Reconstruction using a Patient-Specific Reconstruction Plate Fabricated with Computer-Aided Design and Manufacturing Techniques.
Wilde, Frank; Cornelius, Carl-Peter; Schramm, Alexander
We investigated the workflow of computer-assisted mandibular reconstruction that was performed with a patient-specific mandibular reconstruction plate fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) techniques and a fibula flap. We assessed the feasibility of this technique from virtual planning to the completion of surgery. Computed tomography (CT) scans of a cadaveric skull and fibula were obtained for the virtual simulation of mandibular resection and reconstruction using ProPlan CMF software (Materialise(®)/DePuy Synthes(®)). The virtual model of the reconstructed mandible provided the basis for the computer-aided design of a patient-specific reconstruction plate that was milled from titanium using a five-axis milling machine and CAM techniques. CAD/CAM techniques were used for producing resection guides for mandibular resection and cutting guides for harvesting a fibula flap. Mandibular reconstruction was simulated in a cadaveric wet laboratory. No problems were encountered during the procedure. The plate was fixed accurately to the residual bone without difficulty. The fibula segments were attached to the plate rapidly and reliably. The fusion of preoperative and postoperative CT datasets demonstrated high reconstruction precision. Computer-assisted mandibular reconstruction with CAD/CAM-fabricated patient-specific reconstruction plates appears to be a promising approach for mandibular reconstruction. Clinical trials are required to determine whether these promising results can be translated into successful practice and what further developments are needed.
Wafer-level fabrication of nanocone forests by plasma repolymerization technique for surface-enhanced Raman scattering devices
NASA Astrophysics Data System (ADS)
Mao, Haiyang; Huang, Chengjun; Wu, Wengang; Xue, Mei; Yang, Yudong; Xiong, Jijun; Ming, Anjie; Wang, Weibing
This work presents a novel type of surface-enhanced Raman scattering (SERS) devices based on nanocone forests. The nanocone forests are fabricated by using a plasma repolymerization technique, which is a simple and parallel approach that has high reproducibility in wafer-level fabrication. The nanocone forest-based SERS devices exhibit an averaged enhancement factor at the order of 3 × 106, meanwhile, the relative standard deviation of Raman intensity over large areas is around 7%. These experimental results demonstrate great potential of the nanocone forest-based SERS devices in wide applications.
Fabricating sub-collimating grids for an x-ray solar imaging spectrometer using LIGA techniques
Brennen, R.A.; Hecht, M.H.; Wiberg, D.V.
The HESSI mission proposes to perform high resolution imaging and spectroscopy observations in the soft X-ray, hard X-ray, and gamma-ray regimes, with finer angular resolution (nearly 2 arcseconds) and finer energy resolution (approximately 1 keV) than has been previously possible. This combination of imaging and spectroscopy is achieved with a set of Rotating Modulation Collimators placed in front of an array of cooled germanium and silicon detectors. A set of 12 bi-grid collimators, each of which consists of a pair of identically pitched, widely-separated grids, is used to provide the imaging. Each grid consists of a planar array of equally-spaced, parallel, X-ray opaque slats separated by X-ray transparent slits. If the slits of each grid are parallel to each other and the pitch is identical for the two grids, then the transmission through the grid pair depends on the direction of incidence of the incoming X-rays. For slits and slats of equal width, the transmission varies between zero and 50% depending on whether the shadows of the slats in the top grid fall on the slits or slats of the lower grid. A complete transmission cycle from zero to 50% and back to zero corresponds to a change in source direction that is given by p/L, where L is the separation between the grids. The authors describe a deep etch lithography technique developed to fabricate the grids which have pitches below 100 {micro}m. They use a free standing sheet of PMMA as a base for the process, and use the ALS facility to perform the exposures of the PMMA.
Transformation of eutectic emulsion to nanosuspension fabricating with solvent evaporation and ultrasonication technique
Phaechamud, Thawatchai; Tuntarawongsa, Sarun
Eutectic solvent can solubilize high amount of some therapeutic compounds. Volatile eutectic solvent is interesting to be used as solvent in the preparation of nanosuspension with emulsion solvent evaporation technique. The mechanism of transformation from the eutectic emulsion to nanosuspension was investigated in this study. The 30% w/w ibuprofen eutectic solution was used as the internal phase, and the external phase is composed of Tween 80 as emulsifier. Ibuprofen nanosuspension was prepared by eutectic emulsion solvent evaporating method followed with ultrasonication. During evaporation process, the ibuprofen concentration in emulsion droplets was increased leading to a drug supersaturation but did not immediately recrystallize because of low glass transition temperature (Tg) of ibuprofen. The contact angle of the internal phase on ibuprofen was apparently lower than that of the external phase at all times of evaporation, indicating that the ibuprofen crystals were preferentially wetted by the internal phase than the external phase. From calculated dewetting value ibuprofen crystallization occurred in the droplet. Crystallization of the drug was initiated with external mechanical force, and the particle size of the drug was larger due to Ostwald ripening. Cavitation force from ultrasonication minimized the ibuprofen crystals to the nanoscale. Particle size and zeta potential of formulated ibuprofen nanosuspension were 330.87±51.49 nm and −31.1±1.6 mV, respectively, and exhibited a fast dissolution. Therefore, the combination of eutectic emulsion solvent evaporation method with ultrasonication was favorable for fabricating an ibuprofen nanosuspension, and the transformation mechanism was attained successfully. PMID:27366064
Transformation of eutectic emulsion to nanosuspension fabricating with solvent evaporation and ultrasonication technique.
Phaechamud, Thawatchai; Tuntarawongsa, Sarun
Eutectic solvent can solubilize high amount of some therapeutic compounds. Volatile eutectic solvent is interesting to be used as solvent in the preparation of nanosuspension with emulsion solvent evaporation technique. The mechanism of transformation from the eutectic emulsion to nanosuspension was investigated in this study. The 30% w/w ibuprofen eutectic solution was used as the internal phase, and the external phase is composed of Tween 80 as emulsifier. Ibuprofen nanosuspension was prepared by eutectic emulsion solvent evaporating method followed with ultrasonication. During evaporation process, the ibuprofen concentration in emulsion droplets was increased leading to a drug supersaturation but did not immediately recrystallize because of low glass transition temperature (T g) of ibuprofen. The contact angle of the internal phase on ibuprofen was apparently lower than that of the external phase at all times of evaporation, indicating that the ibuprofen crystals were preferentially wetted by the internal phase than the external phase. From calculated dewetting value ibuprofen crystallization occurred in the droplet. Crystallization of the drug was initiated with external mechanical force, and the particle size of the drug was larger due to Ostwald ripening. Cavitation force from ultrasonication minimized the ibuprofen crystals to the nanoscale. Particle size and zeta potential of formulated ibuprofen nanosuspension were 330.87±51.49 nm and -31.1±1.6 mV, respectively, and exhibited a fast dissolution. Therefore, the combination of eutectic emulsion solvent evaporation method with ultrasonication was favorable for fabricating an ibuprofen nanosuspension, and the transformation mechanism was attained successfully.
Suspended micro/nanofiber hierarchical biological scaffolds fabricated using non-electrospinning STEP technique.
Wang, Ji; Nain, Amrinder S
Extracellular matrix (ECM) is a fibrous natural cell environment, possessing complicated micro- and nanoarchitectures, which provide extracellular signaling cues and influence cell behaviors. Mimicking this three-dimensional microenvironment in vitro is a challenge in developmental and disease biology. Here, suspended multilayer hierarchical nanofiber assemblies (diameter from micrometers to less than 100 nm) with accurately controlled fiber orientation and spacing are demonstrated as biological scaffolds fabricated using the non-electrospinning STEP (Spinneret based Tunable Engineered Parameter) fiber manufacturing technique. Micro/nanofiber arrays were manufactured with high parallelism (relative angles between fibers were maintained less than 6°) and well controlled interfiber spacing (<15%). Using these controls, we demonstrate a bottom up hierarchical assembly of suspended six layer structures of progressively reduced diameters and spacing from several polymer systems. We then demonstrate use of STEP scaffolds to study single and multicell arrangement at high magnifications. Specifically, using double layer divergent (0°-90°) suspended nanofibers assemblies, we show precise quantitative control of cell geometry (change in shape index from 0.15 to 0.57 at similar cell areas), and through design of scaffold porosity (80 × 80 μm(2) to 5 × 5 μm(2)) quadruple the cell attachment density. Furthermore, using unidirectional or crisscross patterns of sparse and dense fiber arrays, we are able to control the cell spread area from ∼400 to ∼700 μm(2), while the nucleus shape index increases from 0.75 to 0.99 with cells nearly doubling their focal adhesion cluster lengths (∼15 μm) on widely spaced nanofiber arrays. The platform developed in this study allows a wide parametric investigation of biophysical cues which influence cell behaviors with implications in tissue engineering, developmental biology, and disease biology.
Double-Step Image Superimposition Technique for Fabricating a Drilling Guide to Access the Abutment Screw in Implant Prostheses.
Mai, Hang-Nga; Kim, Kyung-Rok; Lee, Du-Hyeong
Limited retrievability is a major disadvantage of cement-retained implant restorations. Despite great progress in locating the abutment screw within crowns, the existing techniques are based on prior data or prefabricated devices and require significant work. This study introduces a new procedure for fabricating a guide template to drill a screw access hole using a double-step superimposition technique that incorporates intraoral optical scanning, cone beam computed tomography, and dental design software. The double-step superimposition technique with computer-aided design/computer-assisted manufacturing technology can enhance the convenience and accuracy of drilling the screw-access hole.
Fabrication of high sensitivity 3D nanoSQUIDs based on a focused ion beam sculpting technique
NASA Astrophysics Data System (ADS)
De Leo, Natascia; Fretto, Matteo; Lacquaniti, Vincenzo; Granata, Carmine; Vettoliere, Antonio
In this paper a nanofabrication process, based on a focused ion beam (FIB) nanosculpting technique, for high sensitivity three-dimensional nanoscale superconducting quantum interference devices (nanoSQUIDs) is reported. The crucial steps of the fabrication process are described, as are some peculiar features of the superconductor-normal metal-insulator-superconductor (SNIS) Josephson junctions, which may useful for applications in cryocooler systems. This fabrication procedure is employed to fabricate sandwich nanojunctions and high sensitivity nanoSQUIDs. Specifically, the superconductive nanosensors have a rectangular loop of 1 × 0.2-0.4 μm2 interrupted by two square Nb/Al-AlO x /Nb SNIS Josephson junctions with side lengths of 0.3 μm. The characterization of a typical nanoSQUID has been carried out and a spectral density of magnetic flux noise as low as 0.8 μΦ0 Hz-1/2 has been measured.
Gelatin porous scaffolds fabricated using a modified gas foaming technique: characterisation and cytotoxicity assessment.
Poursamar, S Ali; Hatami, Javad; Lehner, Alexander N; da Silva, Cláudia L; Ferreira, Frederico Castelo; Antunes, A P M
The current study presents an effective and simple strategy to obtain stable porous scaffolds from gelatin via a gas foaming method. The technique exploits the intrinsic foaming ability of gelatin in the presence of CO2 to obtain a porous structure stabilised with glutaraldehyde. The produced scaffolds were characterised using physical and mechanical characterisation methods. The results showed that gas foaming may allow the tailoring of the 3-dimensional structure of the scaffolds with an interconnected porous structure. To assess the effectiveness of the preparation method in mitigating the potential cytotoxicity risk of using glutaraldehyde as a crosslinker, direct and in-direct cytotoxicity assays were performed at different concentrations of glutaraldehyde. The results indicate the potential of the gas foaming method, in the preparation of viable tissue engineering scaffolds.
Fiber microaxicons fabricated by a polishing technique for the generation of Bessel-like beams.
Grosjean, Thierry; Saleh, Said Sadat; Suarez, Miguel Angel; Ibrahim, Idriss Abdoulkader; Piquerey, Vincent; Charraut, Daniel; Sandoz, Patrick
We report a simple method for generating microaxicons at the extremity of commercial optical fibers. The proposed solution, based on a polishing technique, can readily produce any desired microaxicon cone angle and is independent of the nature of the fiber. An optical study of microaxicon performance, in terms of confinement ability and length of the generated Bessel-like beams, is presented as a function of the microaxicon angle. This study, made possible by the experimental acquisition of the 3D light distribution of the Bessel-like beams, reveals the relationship between the Bessel-like beam confinement zone and the beam length. Finally, the effect of diffraction of the Bessel-like beams, induced by the limited lateral extent of the incident fiber mode, is studied and discussed.
3D printed electromagnetic transmission and electronic structures fabricated on a single platform using advanced process integration techniques
NASA Astrophysics Data System (ADS)
Deffenbaugh, Paul Issac
3D printing has garnered immense attention from many fields including in-office rapid prototyping of mechanical parts, outer-space satellite replication, garage functional firearm manufacture, and NASA rocket engine component fabrication. 3D printing allows increased design flexibility in the fabrication of electronics, microwave circuits and wireless antennas and has reached a level of maturity which allows functional parts to be printed. Much more work is necessary in order to perfect the processes of 3D printed electronics especially in the area of automation. Chapter 1 shows several finished prototypes of 3D printed electronics as well as newly developed techniques in fabrication. Little is known about the RF and microwave properties and applications of the standard materials which have been developed for 3D printing. Measurement of a wide variety of materials over a broad spectrum of frequencies up to 10 GHz using a variety of well-established measurement methods is performed throughout chapter 2. Several types of high frequency RF transmission lines are fabricated and valuable model-matched data is gathered and provided in chapter 3 for future designers' use. Of particular note is a fully 3D printed stripline which was automatically fabricated in one process on one machine. Some core advantages of 3D printing RF/microwave components include rapid manufacturing of complex, dimensionally sensitive circuits (such as antennas and filters which are often iteratively tuned) and the ability to create new devices that cannot be made using standard fabrication techniques. Chapter 4 describes an exemplary fully 3D printed curved inverted-F antenna.
Spray-on technique simplifies fabrication of complex thermal insulation blanket
NASA Technical Reports Server (NTRS)
Bond, W. E. G.; Raymond, R.
Spray-on process constructs molds used in forming sections of thermal insulation blankets. The process simplifies the fabrication of blankets by eliminating much of the equipment formerly required and decreasing the time involved.
Development of fabrication techniques for NR150B2-S5X graphite/polyimide high temperature composites. [applicable to space shuttle orbiter aft body flap
NASA Technical Reports Server (NTRS)
Scheck, W. G.; Smith, C. W.; Harrison, E.
Fabrication techniques for NR-150B2-S5X graphite/polyimide composites are described. The development of fabrication, tooling, and quality assurance techniques used for the composites is discussed. Processing information and preliminary mechanical property data are presented along with long term aging data.
Ex Vivo Produced Oral Mucosa Equivalent by Using the Direct Explant Cell Culture Technique
Bayar, Gürkan Raşit; Aydıntuğ, Yavuz Sinan; Günhan, Ömer; Öztürk, Kamile; Gülses, Aydın
Objective: The aim of this study is the histological and immunohistochemical evaluation of ex vivo produced oral mucosal equivalents using keratinocytes cultured by direct explant technique. Material and Methods: Oral mucosa tissue samples were obtained from the keratinized gingival tissues of 14 healthy human subjects. Human oral mucosa keratinocytes from an oral mucosa biopsy specimen were dissociated by the explant technique. Once a sufficient population of keratinocytes was reached, they were seeded onto the type IV collagen coated "AlloDerm" and taken for histological and immunohistochemical examinations at 11 days postseeding of the keratinocytes on the cadaveric human dermal matrix. Results: Histopathologically and immunohistochemically, 12 out of 14 successful ex vivo produced oral mucosa equivalents (EVPOME) that consisted of a stratified epidermis on a dermal matrix have been developed with keratinocytes cultured by the explant technique. Conclusion: The technical handling involved in the direct explant method at the beginning of the process has fewer steps than the enzymatic method and use of the direct explant technique protocol for culturing of human oral mucosa keratinocyte may be more adequate for EVPOME production. PMID:25207018
A review of experimental techniques to produce a nacre-like structure.
Corni, I; Harvey, T J; Wharton, J A; Stokes, K R; Walsh, F C; Wood, R J K
The performance of man-made materials can be improved by exploring new structures inspired by the architecture of biological materials. Natural materials, such as nacre (mother-of-pearl), can have outstanding mechanical properties due to their complicated architecture and hierarchical structure at the nano-, micro- and meso-levels which have evolved over millions of years. This review describes the numerous experimental methods explored to date to produce composites with structures and mechanical properties similar to those of natural nacre. The materials produced have sizes ranging from nanometres to centimetres, processing times varying from a few minutes to several months and a different range of mechanical properties that render them suitable for various applications. For the first time, these techniques have been divided into those producing bulk materials, coatings and free-standing films. This is due to the fact that the material's application strongly depends on its dimensions and different results have been reported by applying the same technique to produce materials with different sizes. The limitations and capabilities of these methodologies have been also described.
Techniques for Producing Coastal Land Water Masks from Landsat and Other Multispectral Satellite Data
NASA Technical Reports Server (NTRS)
Spruce, Joseph P.; Hall, Callie
Coastal erosion and land loss continue to threaten many areas in the United States. Landsat data has been used to monitor regional coastal change since the 1970s. Many techniques can be used to produce coastal land water masks, including image classification and density slicing of individual bands or of band ratios. Band ratios used in land water detection include several variations of the Normalized Difference Water Index (NDWI). This poster discusses a study that compares land water masks computed from unsupervised Landsat image classification with masks from density-sliced band ratios and from the Landsat TM band 5. The greater New Orleans area is employed in this study, due to its abundance of coastal habitats and its vulnerability to coastal land loss. Image classification produced the best results based on visual comparison to higher resolution satellite and aerial image displays. However, density sliced NDWI imagery from either near infrared (NIR) and blue bands or from NIR and green bands also produced more effective land water masks than imagery from the density-sliced Landsat TM band 5. NDWI based on NIR and green bands is noteworthy because it allows land water masks to be generated from multispectral satellite sensors without a blue band (e.g., ASTER and Landsat MSS). NDWI techniques also have potential for producing land water masks from coarser scaled satellite data, such as MODIS.
Techniques for Producing Coastal Land Water Masks from Landsat and Other Multispectral Satellite Data
NASA Technical Reports Server (NTRS)
Spruce, Joe; Hall, Callie
Coastal erosion and land loss continue to threaten many areas in the United States. Landsat data has been used to monitor regional coastal change since the 1970's. Many techniques can be used to produce coastal land water masks, including image classification and density slicing of individual bands or of band ratios. Band ratios used in land water detection include several variations of the Normalized Difference Water Index (NDWI). This poster discusses a study that compares land water masks computed from unsupervised Landsat image classification with masks from density-sliced band ratios and from the Landsat TM band 5. The greater New Orleans area is imployed in this study, due to its abundance of coastal habitats and ist vulnerability to coastal land loss. Image classification produced the best results based on visual comparison to higher resolution satellite and aerial image displays. However, density-sliced NDWI imagery from either near infrared (NIR) and blue bands or from NIR and green bands also produced more effective land water masks than imagery from the density-sliced Landsat TM band 5. NDWI based on NIR and green bands is noteworthy because it allows land water masks to be generated form multispectral satellite sensors without a blue band (e.g., ASTER and Landsat MSS). NDWI techniques also have potential for producing land water masks from coarser scaled satellite data, such as MODIS.
Mechanical characterization of TiO{sub 2} nanofibers produced by different electrospinning techniques
Vahtrus, Mikk; Šutka, Andris; Vlassov, Sergei; Šutka, Anna; Polyakov, Boris; Saar, Rando; Dorogin, Leonid; Lõhmus, Rünno
In this work TiO{sub 2} nanofibers produced by needle and needleless electrospinning processes from the same precursor were characterized and compared using Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and in situ SEM nanomechanical testing. Phase composition, morphology, Young's modulus and bending strength values were found. Weibull statistics was used to evaluate and compare uniformity of mechanical properties of nanofibers produced by two different methods. It is shown that both methods yield nanofibers with very similar properties. - Graphical abstract: Display Omitted - Highlights: • TiO{sub 2} nanofibers were produced by needle and needleless electrospinning processes. • Structure was studied by Raman spectroscopy and electron microscopy methods. • Mechanical properties were measured using advanced in situ SEM cantilevered beam bending technique. • Both methods yield nanofibers with very similar properties.
Surface Modification and Characterisation of Silk Fibroin Fabric Produced by the Layer-by-Layer Self-Assembly of Multilayer Alginate/Regenerated Silk Fibroin
Shen, Gaotian; Hu, Xingyou; Guan, Guoping; Wang, Lu
Silk-based medical products have a long history of use as a material for surgical sutures because of their desirable mechanical properties. However, silk fibroin fabric has been reported to be haemolytic when in direct contact with blood. The layer-by-layer self-assembly technique provides a method for surface modification to improve the biocompatibility of silk fibroin fabrics. Regenerated silk fibroin and alginate, which have excellent biocompatibility and low immunogenicity, are outstanding candidates for polyelectrolyte deposition. In this study, silk fabric was degummed and positively charged to create a silk fibroin fabric that could undergo self-assembly. The multilayer self-assembly of the silk fibroin fabric was achieved by alternating the polyelectrolyte deposition of a negatively charged alginate solution (pH = 8) and a positively charged regenerated silk fibroin solution (pH = 2). Finally, the negatively charged regenerated silk fibroin solution (pH = 8) was used to assemble the outermost layer of the fabric so that the surface would be negatively charged. A stable structural transition was induced using 75% ethanol. The thickness and morphology were characterised using atomic force microscopy. The properties of the self-assembled silk fibroin fabric, such as the bursting strength, thermal stability and flushing stability, indicated that the fabric was stable. In addition, the cytocompatibility and haemocompatibility of the self-assembled silk fibroin fabrics were evaluated. The results indicated that the biocompatibility of the self-assembled multilayers was acceptable and that it improved markedly. In particular, after the self-assembly, the fabric was able to prevent platelet adhesion. Furthermore, other non-haemolytic biomaterials can be created through self-assembly of more than 1.5 bilayers, and we propose that self-assembled silk fibroin fabric may be an attractive candidate for anticoagulation applications and for promoting endothelial cell
A novel 2D silicon nano-mold fabrication technique for linear nanochannels over a 4 inch diameter substrate.
Yin, Zhifu; Qi, Liping; Zou, Helin; Sun, Lei
A novel low-cost 2D silicon nano-mold fabrication technique was developed based on Cu inclined-deposition and Ar(+) (argon ion) etching. With this technique, sub-100 nm 2D (two dimensional) nano-channels can be etched economically over the whole area of a 4 inch n-type <100> silicon wafer. The fabricating process consists of only 4 steps, UV (Ultraviolet) lithography, inclined Cu deposition, Ar(+) sputter etching, and photoresist &Cu removing. During this nano-mold fabrication process, we investigated the influence of the deposition angle on the width of the nano-channels and the effect of Ar(+) etching time on their depth. Post-etching measurements showed the accuracy of the nanochannels over the whole area: the variation in width is 10%, in depth it is 11%. However, post-etching measurements also showed the accuracy of the nanochannels between chips: the variation in width is 2%, in depth it is 5%. With this newly developed technology, low-cost and large scale 2D nano-molds can be fabricated, which allows commercial manufacturing of nano-components over large areas.
A novel 2D silicon nano-mold fabrication technique for linear nanochannels over a 4 inch diameter substrate
Yin, Zhifu; Qi, Liping; Zou, Helin; Sun, Lei
A novel low-cost 2D silicon nano-mold fabrication technique was developed based on Cu inclined-deposition and Ar+ (argon ion) etching. With this technique, sub-100 nm 2D (two dimensional) nano-channels can be etched economically over the whole area of a 4 inch n-type <100> silicon wafer. The fabricating process consists of only 4 steps, UV (Ultraviolet) lithography, inclined Cu deposition, Ar+ sputter etching, and photoresist & Cu removing. During this nano-mold fabrication process, we investigated the influence of the deposition angle on the width of the nano-channels and the effect of Ar+ etching time on their depth. Post-etching measurements showed the accuracy of the nanochannels over the whole area: the variation in width is 10%, in depth it is 11%. However, post-etching measurements also showed the accuracy of the nanochannels between chips: the variation in width is 2%, in depth it is 5%. With this newly developed technology, low-cost and large scale 2D nano-molds can be fabricated, which allows commercial manufacturing of nano-components over large areas. PMID:26752559
Marginal fit of all-ceramic crowns fabricated using two extraoral CAD/CAM systems in comparison with the conventional technique
Alqahtani, Fawaz
Objective The purpose of this study was to determine the effect of two extraoral computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, in comparison with conventional techniques, on the marginal fit of monolithic CAD/CAM lithium disilicate ceramic crowns. Study design This is an in vitro interventional study. Place and duration of study The study was carried out at the Department of Prosthodontics, School of Dentistry, Prince Sattam Bin Abdul-Aziz University, Saudi Arabia, from December 2015 to April 2016. Methodology A marginal gap of 60 lithium disilicate crowns was evaluated by scanning electron microscopy. In total, 20 pressable lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) ceramic crowns were fabricated using the conventional lost-wax technique as a control group. The experimental all-ceramic crowns were produced based on a scan stone model and milled using two extraoral CAD/CAM systems: the Cerec group was fabricated using the Cerec CAD/CAM system, and the Trios group was fabricated using Trios CAD and milled using Wieland Zenotec CAM. One-way analysis of variance (ANOVA) and the Scheffe post hoc test were used for statistical comparison of the groups (α=0.05). Results The mean (±standard deviation) of the marginal gap of each group was as follows: the Control group was 91.15 (±15.35) µm, the Cerec group was 111.07 (±6.33) µm, and the Trios group was 60.17 (±11.09) µm. One-way ANOVA and the Scheffe post hoc test showed a statistically significant difference in the marginal gap between all groups. Conclusion It can be concluded from the current study that all-ceramic crowns, fabricated using the CAD/CAM system, show a marginal accuracy that is acceptable in clinical environments. The Trios CAD group displayed the smallest marginal gap. PMID:28352204
Modified technique to fabricate a hollow light-weight facial prosthesis for lateral midfacial defect: a clinical report
Large oro-facial defects result from cancer treatment consequences in serious functional as well as cosmetic deformities. Acceptable cosmetic results usually can be obtained with a facial prosthesis. However, retention of a large facial prosthesis can be challenging because of its size and weight. This article describes prosthetic rehabilitation of a 57-year-old man having a right lateral mid-facial defect with intraoral-extraoral combination prosthesis. A modified technique to fabricate a hollow substructure in heat-polymerizing polymethyl-methacrylate to support silicone facial prosthesis was illustrated. The resultant facial prosthesis was structurally durable and light in weight facilitating the retention with magnets satisfactorily. This technique is advantageous as there is no need to fabricate the whole prosthesis again in case of damage of the silicone layer because the outer silicone layer can be removed and re-packed on the substructure if the gypsum-mold is preserved. PMID:21165271
Comparative study on structural and optical properties of CdS films fabricated by three different low-cost techniques
NASA Astrophysics Data System (ADS)
Ravichandran, K.; Philominathan, P.
Highly crystalline and transparent cadmium sulphide films were fabricated at relatively low temperature by employing an inexpensive, simplified spray technique using perfume atomizer (generally used for cosmetics). The structural, surface morphological and optical properties of the films were studied and compared with that prepared by conventional spray pyrolysis using air as carrier gas and chemical bath deposition. The films deposited by the simplified spray have preferred orientation along (1 0 1) plane. The lattice parameters were calculated as a = 4.138 Å and c = 6.718 Å which are well agreed with that obtained from the other two techniques and also with the standard data. The optical transmittance in the visible range and the optical band gap were found as 85% and 2.43 eV, respectively. The structural and optical properties of the films fabricated by the simplified spray are found to be desirable for opto-electronic applications.
Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique
NASA Astrophysics Data System (ADS)
Li, Zhenhao; Wong, Lawrence L. P.; Chen, Albert I. H.; Na, Shuai; Sun, Jame; Yeow, John T. W.
This paper reports the fabrication process of wafer bonded capacitive micromachined ultrasonic transducers (CMUTs) using photosensitive benzocyclobutene as a polymer adhesive. Compared with direct bonding and anodic bonding, polymer adhesive bonding provides good tolerance to wafer surface defects and contamination. In addition, the low process temperature of 250 °C is compatible with standard CMOS processes. Single-element CMUTs consisting of cells with a diameter of 46 µm and a cavity depth of 323 nm were fabricated. In-air and immersion acoustic characterizations were performed on the fabricated CMUTs, demonstrating their capability for transmitting and receiving ultrasound signals. An in-air resonance frequency of 5.47 MHz was measured by a vibrometer under a bias voltage of 300 V.
A miniature rigid/flex salinity measurement device fabricated using printed circuit processing techniques
NASA Astrophysics Data System (ADS)
Broadbent, H. A.; Ketterl, T. P.; Reid, C. S.
The design, fabrication and initial performance of a single substrate, miniature, low-cost conductivity, temperature, depth (CTD) sensor board with interconnects are presented. In combination these sensors measure ocean salinity. The miniature CTD device board was designed and fabricated as the main component of a 50 mm × 25 mm × 25 mm animal-attached biologger. The board was fabricated using printed circuit processes and consists of two distinct regions on a continuous single liquid crystal polymer substrate: an 18 mm × 28 mm rigid multi-metal sensor section and a 72 mm long flexible interconnect section. The 95% confidence intervals for the conductivity, temperature and pressure sensors were demonstrated to be ±0.083 mS cm-1, 0.01 °C, and ±0.135 dbar, respectively.
Rapid fabrication of microdevices using laser direct writing and replica moulding technique
NASA Astrophysics Data System (ADS)
Antończak, A. J.; Stepak, B. D.; Abramski, K. M.
This paper presents a method that enables fast and low-cost fabrication of microchannels with oval cross-section. The procedure is based on formation of a concave meniscus at the interface between an initially cured PDMS and a polymeric mould fabricated using excimer laser. The replica is formed by expanding gas trapped within the structures of the mould during thermal curing. A second shaping factor is connected with surface phenomena at the interface between the mould, gas and partially cured PDMS. The final shape of the meniscus is determined when the PDMS reaches the high cure extent.
Diagnostics of glass fiber reinforced polymers and comparative analysis of their fabrication techniques with the use of acoustic emission
NASA Astrophysics Data System (ADS)
Bashkov, O. V.; Bryansky, A. A.; Panin, S. V.; Zaikov, V. I.
Strength properties of the glass fiber reinforced polymers (GFRP) fabricated by vacuum and vacuum autoclave molding techniques were analyzed. Measurements of porosity of the GFRP parts manufactured by various molding techniques were conducted with the help of optical microscopy. On the basis of experimental data obtained by means of acoustic emission hardware/software setup, the technique for running diagnostics and forecasting the bearing capacity of polymeric composite materials based on the result of three-point bending tests has been developed. The operation principle of the technique is underlined by the evaluation of the power function index change which takes place on the dependence of the total acoustic emission counts versus the loading stress.
A xenograft mantle transplantation technique for producing a novel pearl in an akoya oyster host.
Fukushima, Ei; Iwai, Toshiharu; Miura, Chiemi; Celino, Fritzie T; Urasaki, Shintarou; Miura, Takeshi
The brightness and color of pearls varies among different pearl-producing shellfish and have been a source of human fascination since ancient times. When produced through cultivation, the characteristics and quality of a pearl depend on the kind of shellfish used and also the transplanted mantle graft. This suggests that the Akoya pearl oyster, which is generally used in Japan for pearl culturing, can produce different kinds of pearl through the use of mantles from different species of shellfish. However, a transplanted heterogeneous mantle would be rejected by the immune system of the Akoya oyster. We have therefore developed a new method to suppress the Akoya immune system that archives immune tolerance to other shellfish. It is generally known that small quantities of antigens can be used to produce archived immunological tolerance in a clinical setting. We successfully suppressed the Akoya pearl oyster immune response against a Mabé pearl oyster graft through repeat injections of mantle homogenates. We then transplanted a Mabé pearl oyster mantle graft into the immunologically tolerant Akoya pearl oyster and obtained a Mabé pearl from an Akoya pearl oyster. Our new technique thus makes the production of novel and different pearls in the Akoya possible. We believe that this has significant future potential for the advancement of the pearl industry.
Assessing the Applicability of Digital Image Correlation (DIC) Technique in Tensile Testing of Fabric Composites
used for vacuum assisted resin transfer molding process ( VARTM )/Scrimp processing. The fibers were oriented in a plain woven fabric (orthogonally...infused with matrix using a VARTM . After infusion, the sample was cured in an oven. After curing, specimens were extracted from the panel from the flow
Consolidation and fabrication techniques for vanadium-20 w/o titanium /TV-20/
NASA Technical Reports Server (NTRS)
Burt, W. R.; Karasek, F. J.; Kramer, W. C.; Mayfield, R. M.; Mc Gowan, R. D.
Tests of the mechanical properties, fuel compatibility, sodium corrosion and irradiation behavior were made for vanadium and vanadium alloy. Improved methods for consolidation and fabrication of bar, rod, sheet, and high-quality, small diameter, thin-wall tubing of vanadium-20 without titanium are reported.
Fabrication of silk fibroin film using centrifugal casting technique for corneal tissue engineering.
Lee, Min Chae; Kim, Dong-Kyu; Lee, Ok Joo; Kim, Jung-Ho; Ju, Hyung Woo; Lee, Jung Min; Moon, Bo Mi; Park, Hyun Jung; Kim, Dong Wook; Kim, Su Hyeon; Park, Chan Hum
Films prepared from silk fibroin have shown potential as biomaterials in tissue engineering applications for the eye. Here, we present a novel process for fabrication of silk fibroin films for corneal application. In this work, fabrication of silk fibroin films was simply achieved by centrifugal force. In contrast to the conventional dry casting method, we carried out the new process in a centrifuge with a rotating speed of 4000 rpm, where centrifugal force was imposed on an aluminum tube containing silk fibroin solution. In the present study, we also compared the surface roughness, mechanical properties, transparency, and cell proliferation between centrifugal and dry casting method. In terms of surface morphology, films fabricated by the centrifugal casting have less surface roughness than those by the dry casting. For elasticity and transparency, silk fibroin films obtained from the centrifugal casting had favorable results compared with those prepared by dry casting. Furthermore, primary human corneal keratocytes grew better in films prepared by the centrifugal casting. Therefore, our results suggest that this new fabrication process for silk fibroin films offers important potential benefits for corneal tissue regeneration.
Fabrication of microlens array on silicon surface using electrochemical wet stamping technique
NASA Astrophysics Data System (ADS)
Lai, Lei-Jie; Zhou, Hang; Zhu, Li-Min
This paper focuses on the fabrication of microlens array (MLA) on silicon surface by taking advantage of a novel micromachining approach, the electrochemical we stamping (E-WETS). The E-WETS allows the direct imprinting of MLA on an agarose stamp into the substrate through a selective anodic dissolution process. The pre-patterned agarose stamp can direct and supply the solution preferentially on the contact area between the agarose stamp and the substrate, to which the electrochemical reaction is confined. The anodic potential vs. saturated calomel electrode is optimized and 1.5 V is chosen as the optimum value for the electrochemical polishing of p-Si. A refractive MLA on a PMMA mold is successfully transferred onto the p-Si surface. The machining deviations of the fabricated MLA from those on the mold are 0.44% in diameter and 2.1% in height respectively, and the machining rate in HF is around 1.1 μm/h. The surface roughness of the fabricated MLA is less than 12 nm owing to the electrochemical polishing process. The results demonstrate that E-WETS is a promising approach to fabricate MLA on p-Si surface with high accuracy and efficiency.
Periodically tapered photonic crystal fibre based strain sensor fabricated by a CO2 laser technique
NASA Astrophysics Data System (ADS)
Farrell, Gerald; Bo, Lin; Guan, Chunying; Semenova, Yuliya; Wang, Pengfei
A focused CO2 laser beam has been previously used to successfully fabricate both symmetric and asymmetric long period fiber gratings which have been used for a variety of sensing applications. However fabrication by a CO2 laser beam demands a time consuming laser scanning process which increases the difficulty and cost of fabrication. In this paper a fibre sensor based on a fibre heterostructure with a simple configuration consisting of a series of periodical tapers in a photonic crystal fibre (PCF) sandwiched between two singlemode fibres is proposed and investigated experimentally. The tapers are periodically fabricated along the PCF section using a CO2 laser beam. The proposed fibre heterostructure can be used for strain sensing by measuring the wavelength blueshift of the multimode interference dip of the transmission spectrum as a function of strain. An average stain sensitivity of -68.4 pm/μ ɛ has been experimentally achieved over a microstrain range from 0 to 100 μ ɛ. Assuming in practice that the sensor is interrrogated with a ratiometric power measurement system, then the strain resolution is estimated to be better than 1.18×10-2 microstrain. The mechanisms for refractive index modulation periodically tapered PCF under tensile strain measurements are complex but may be regarded as a combination of stress-relaxation and refractive index perturbations over the length of the tapered PCF induced by strain and by tapering. The proposed fibre strain sensor has the advantage of low temperature sensitivity (average 8.4 pm/°C) and an experimental demonstration of this reduced sensitivity is also presented. The proposed strain sensor benefits from simplicity of fabrication and achieves a competitive sensitivity compared with other existing fibre-optic sensors.
Fabrication of controllable form submicrometer structures on positive photoresist by one-photon absorption direct laser writing technique
NASA Astrophysics Data System (ADS)
Tong, Quang Cong; Do, Minh Thanh; Journet, Bernard; Ledoux-Rak, Isabelle; Lai, Ngoc Diep
We demonstrate a very simple and low-cost method based on one-photon absorption direct laser writing technique to fabricate arbitrary two-dimensional (2D) polymeric submicrometer structures with controllable form. In this technique, a continuous-wave green laser beam (532 nm) with very weak power is tightly focused into a positive photoresist (S1805) by a high numerical aperture (NA) objective lens (OL), depolymerizing the polymer in a local submicrometer region. The focusing spot is then moved in a controllable trajectory by a 3D piezo translation stage, resulting in desired structures. The low absorption effect of the photoresist at the excitation wavelength allows obtaining structures with submicrometer size and great depth. In particular, by controlling the exposure dose, e.g. the scanning speed, and the scanning configuration, the structures have been created in positive (cylindrical material in air) or negative (air holes) form. The 2D square structures with periods in between 0.6 μm and 1 μm and with a feature size of about 150 nm have been demonstrated with an OL of NA = 0.9 (air-immersion). The fabricated results are well consistent with those obtained numerically by using a vectorial diffraction theory for high NA OLs. This investigation should be very useful for fabrication of photonic and plasmonic templates.
Feasibility of measuring density and temperature of laser produced plasmas using spectroscopic techniques.
Edens, Aaron D.
A wide variety of experiments on the Z-Beamlet laser involve the creation of laser produced plasmas. Having a direct measurement of the density and temperature of these plasma would an extremely useful tool, as understanding how these quantities evolve in space and time gives insight into the causes of changes in other physical processes, such as x-ray generation and opacity. We propose to investigate the possibility of diagnosing the density and temperature of laser-produced plasma using temporally and spatially resolved spectroscopic techniques that are similar to ones that have been successfully fielded on other systems. Various researchers have measured the density and temperature of laboratory plasmas by looking at the width and intensity ratio of various characteristic lines in gases such as nitrogen and hydrogen, as well as in plasmas produced off of solid targets such as zinc. The plasma conditions produce two major measurable effects on the characteristic spectral lines of that plasma. The 1st is the Stark broadening of an individual line, which depends on the electron density of the plasma, with higher densities leading to broader lines. The second effect is a change in the ratio of various lines in the plasma corresponding to different ionization states. By looking at the ratio of these lines, we can gain some understanding of the plasma ionization state and consequently its temperature (and ion density when coupled with the broadening measurement). The hotter a plasma is, the higher greater the intensity of lines corresponding to higher ionization states. We would like to investigate fielding a system on the Z-Beamlet laser chamber to spectroscopically study laser produced plasmas from different material targets.
Fluorescence enhancement from nano-gap embedded plasmonic gratings by a novel fabrication technique with HD-DVD
NASA Astrophysics Data System (ADS)
Bhatnagar, K.; Pathak, A.; Menke, D.; Cornish, P. V.; Gangopadhyay, K.; Korampally, V.; Gangopadhyay, S.
We demonstrate strong electromagnetic field enhancement from nano-gaps embedded in silver gratings for visible wavelengths. These structures fabricated using a store-bought HD-DVD worth 10 and conventional micro-contact printing techniques have shown maximum fluorescence enhancement factors of up to 118 times when compared to a glass substrate under epi-fluorescent conditions. The novel fabrication procedure provides for the development of a cost-effective and facile plasmonic substrate for low-level chemical and biological detection. Electromagnetic field simulations were also performed that reveal the strong field confinement in the nano-gap region embedded in the silver grating, which is attributed to the combined effect of localized as well as propagating surface plasmons.
Fluorescence enhancement from nano-gap embedded plasmonic gratings by a novel fabrication technique with HD-DVD.
Bhatnagar, K; Pathak, A; Menke, D; Cornish, P V; Gangopadhyay, K; Korampally, V; Gangopadhyay, S
We demonstrate strong electromagnetic field enhancement from nano-gaps embedded in silver gratings for visible wavelengths. These structures fabricated using a store-bought HD-DVD worth $10 and conventional micro-contact printing techniques have shown maximum fluorescence enhancement factors of up to 118 times when compared to a glass substrate under epi-fluorescent conditions. The novel fabrication procedure provides for the development of a cost-effective and facile plasmonic substrate for low-level chemical and biological detection. Electromagnetic field simulations were also performed that reveal the strong field confinement in the nano-gap region embedded in the silver grating, which is attributed to the combined effect of localized as well as propagating surface plasmons.
An investigation of density measurement method for yarn-dyed woven fabrics based on dual-side fusion technique
NASA Astrophysics Data System (ADS)
Zhang, Rui; Xin, Binjie
Yarn density is always considered as the fundamental structural parameter used for the quality evaluation of woven fabrics. The conventional yarn density measurement method is based on one-side analysis. In this paper, a novel density measurement method is developed for yarn-dyed woven fabrics based on a dual-side fusion technique. Firstly, a lab-used dual-side imaging system is established to acquire both face-side and back-side images of woven fabric and the affine transform is used for the alignment and fusion of the dual-side images. Then, the color images of the woven fabrics are transferred from the RGB to the CIE-Lab color space, and the intensity information of the image extracted from the L component is used for texture fusion and analysis. Subsequently, three image fusion methods are developed and utilized to merge the dual-side images: the weighted average method, wavelet transform method and Laplacian pyramid blending method. The fusion efficacy of each method is evaluated by three evaluation indicators and the best of them is selected to do the reconstruction of the complete fabric texture. Finally, the yarn density of the fused image is measured based on the fast Fourier transform, and the yarn alignment image could be reconstructed using the inverse fast Fourier transform. Our experimental results show that the accuracy of density measurement by using the proposed method is close to 99.44% compared with the traditional method and the robustness of this new proposed method is better than that of conventional analysis methods.
New technique for the fabrication of miniature thin film heat flux gauges
NASA Astrophysics Data System (ADS)
Collins, Matthew; Chana, Kam; Povey, Thomas
This paper details the improvements made to the design and fabrication of thin-film heat flux gauges at Oxford. These improvements have been driven by the desire to improve measurement accuracy and resolution in short duration wind-tunnel experiments. A thin-film heat flux gauge (TFHFG) measures heat flux by recording the temperature history of thin film resistive temperature sensors sputtered onto an insulating substrate. The heat flux can then be calculated using Fourier's law of heat conduction. A new fabrication process utilising technology from the manufacture of flexible printed circuit boards is outlined, which enables the production of significantly smaller and more robust gauges than those previously used.
Fabrication of Electrospun Polymer Fibers with Nonspherical Cross-Sections Using a Nanopressing Technique.
Chen, Jiun-Tai; Kao, Yi-Huei; Kuo, Tyng-Yow; Liu, Chih-Ting; Chiu, Yu-Jing; Chu, Chien-Wei; Chi, Mu-Huan; Tsai, Chia-Chan
The fabrication of electrospun polymer fibers is demonstrated with anisotropic cross-sections by applying a simple pressing method. Electrospun polystyrene or poly(methyl methacrylate) fibers are pressed by flat or patterned substrates while the samples are annealed at elevated temperatures. The shapes and morphologies of the pressed polymer fibers are controlled by the experimental conditions such as the pressing force, the pressing temperature, the pressing time, and the surface pattern of the substrate. At the same pressing force, the shape changes of the polymer fibers can be controlled by the pressing time. For shorter pressing times, the deformation process is dominated by the effect of pressing and fibers with barrel-shaped cross-sections can be generated. For longer pressing times, the effect of wetting becomes more important and fibers with dumbbell-shaped cross-sections can be obtained. Hierarchical polymer fibers with nanorods are fabricated by pressing the fibers with porous anodic aluminum oxide templates.
Techniques for fabrication and construction of three-dimensional scaffolds for tissue engineering
Lu, Tingli; Li, Yuhui; Chen, Tao
Three-dimensional biomimetic scaffolds have widespread applications in biomedical tissue engineering because of their nanoscaled architecture, eg, nanofibers and nanopores, similar to the native extracellular matrix. In the conventional "top-down" approach, cells are seeded onto a biocompatible and biodegradable scaffold, in which cells are expected to populate in the scaffold and create their own extracellular matrix. The top-down approach based on these scaffolds has successfully engineered thin tissues, including skin, bladder, and cartilage in vitro. However, it is still a challenge to fabricate complex and functional tissues (eg, liver and kidney) due to the lack of vascularization systems and limited diffusion properties of these large biomimetic scaffolds. The emerging "bottom-up" method may hold great potential to address these challenges, and focuses on fabricating microscale tissue building blocks with a specific microarchitecture and assembling these units to engineer larger tissue constructs from the bottom up. In this review, state-of-the-art methods for fabrication of three-dimensional biomimetic scaffolds are presented, and their advantages and drawbacks are discussed. The bottom-up methods used to assemble microscale building blocks (eg, microscale hydrogels) for tissue engineering are also reviewed. Finally, perspectives on future development of the bottom-up approach for tissue engineering are addressed. PMID:23345979
Techniques for fabrication and construction of three-dimensional scaffolds for tissue engineering.
Lu, Tingli; Li, Yuhui; Chen, Tao
Three-dimensional biomimetic scaffolds have widespread applications in biomedical tissue engineering because of their nanoscaled architecture, eg, nanofibers and nanopores, similar to the native extracellular matrix. In the conventional "top-down" approach, cells are seeded onto a biocompatible and biodegradable scaffold, in which cells are expected to populate in the scaffold and create their own extracellular matrix. The top-down approach based on these scaffolds has successfully engineered thin tissues, including skin, bladder, and cartilage in vitro. However, it is still a challenge to fabricate complex and functional tissues (eg, liver and kidney) due to the lack of vascularization systems and limited diffusion properties of these large biomimetic scaffolds. The emerging "bottom-up" method may hold great potential to address these challenges, and focuses on fabricating microscale tissue building blocks with a specific microarchitecture and assembling these units to engineer larger tissue constructs from the bottom up. In this review, state-of-the-art methods for fabrication of three-dimensional biomimetic scaffolds are presented, and their advantages and drawbacks are discussed. The bottom-up methods used to assemble microscale building blocks (eg, microscale hydrogels) for tissue engineering are also reviewed. Finally, perspectives on future development of the bottom-up approach for tissue engineering are addressed.
A green salt-leaching technique to produce sericin/PVA/glycerin scaffolds with distinguished characteristics for wound-dressing applications.
Aramwit, Pornanong; Ratanavaraporn, Juthamas; Ekgasit, Sanong; Tongsakul, Duangta; Bang, Nipaporn
Sericin/PVA/glycerin scaffolds could be fabricated using the freeze-drying technique; they showed good physical and biological properties and can be applied as wound dressings. However, freeze-drying is an energy- and time-consuming process with a high associated cost. In this study, an alternative, solvent-free, energy- and time-saving, low-cost salt-leaching technique is introduced as a green technology to produce sericin/PVA/glycerin scaffolds. We found that sericin/PVA/glycerin scaffolds were successfully fabricated without any crosslinking using a salt-leaching technique. The salt-leached sericin/PVA/glycerin scaffolds had a porous structure with pore interconnectivity. The sericin in the salt-leached scaffolds had a crystallinity that was as high as that of the freeze-dried scaffolds. Compared to the freeze-dried scaffolds with the same composition, the salt-leached sericin/PVA/glycerin scaffolds has larger pores, a lower Young's modulus, and faster rates of biodegradation and sericin release. When cultured with L929 mouse fibroblast cells, a higher number of cells were found in the salt-leached scaffolds. Furthermore, the salt-leached scaffolds were less adhesive to the wound, which would reduce pain upon removal. Therefore, salt-leached sericin/PVA/glycerin scaffolds with distinguished characteristics were introduced as another choice of wound dressing, and their production process was simpler, more energy efficient, and saved time and money compared to the freeze-dried scaffolds.
Sonosynthesis of nano TiO2 on wool using titanium isopropoxide or butoxide in acidic media producing multifunctional fabric.
Behzadnia, Amir; Montazer, Majid; Rashidi, Abousaeid; Rad, Mahnaz Mahmoudi
This study presents a novel idea to prepare nanocrystalline structure of TiO2 under ambient pressure at 60-65 °C using in situ sonochemical synthesis by hydrolysis of either titanium isopropoxide or titanium butoxide in an acidic aqueous solution. The nano titanium dioxide coated wool fabrics possess significant antibacterial/antifungal activity and self-cleaning property by discoloring Methylene blue stain under sunlight irradiation. This process has no negative effect on cytotoxicity and tensile strength of the sonotreated fabric even reduces alkaline solubility and photoyellowing and improves hydrophilicity. More titanium isopropoxide or titanium butoxide as a precursor led to higher photocatalytic activities of the treated fabrics. Also introducing more ethanol improved the adsorption of TiO2 on the wool fabric surface leading to enhanced photocatalytic activity. EDS and XRD patterns, SEM images, X-ray mapping confirmed the presence of nano TiO2 particles on the fabric surface. The role of both solvent and precursor concentrations on the various properties of the fabric was investigated and the optimized conditions were obtained using response surface methodology.
A New Technique Producing Double-Sided Spherical Fresnel Lens Segments Assembled to Large Aperture Lenses
NASA Astrophysics Data System (ADS)
Ohmori, H.; Takahashi, Y.; Shimizu, H.; Uehara, Y.; Suzuki, T.; Ueno, Y.; Hillman, L. W.; Zuccaro, A.; EUSO Collaboration
A new technique of molding of lens segments has been developed to produce a large, double-sided, curved Fresnel lenses for refractive telescopes. The molding process involves two steps of spherically curved plate formation and lens gro ove transfer onto the curved plate. These molding process have been carried out with two sides of the diamond-cut dies set in the hydraulic press machine at elevated temperatures to the lens material that is a transparent UV-acrylic of Mitsubishi. Ultra-precision dies were made of oxygen-free copp er, which were cut by diamond to ols to make Fresnel facets. A four-axis ultra-precision cutting machine has been developed first to manufacture ultra-precision mold dies. Double-sided, curved Fresnel lens segments will be used as circumference petals of lenses of 2500mm aperture surrounding a 1500mm diameter central lens.
Fabrication of cryogenic inertial-confinement-fusion targets using target free-fall technique. Report No. 2-82
Kim, K.; Murphy, M.J.
Techniques for fabricating cryogenic inertial confinement fusion targets (i.e., spherical shells containing a uniform layer of DT ice) are investigated using target free-fall concept. Detection and characterization of the moving targets are effected by optoelectronic means, of which the principal is an RF ac-interferometer. This interferometer system demonstrates, for the first time, the speed capabilities of the phase-modulation ac-interferometry. New techiques developed for handling, holding, launching, and transporting targets are also described. Results obtained at both room and cryogenic temperatures are presented.
Fabrication of IrSi(3)/p-Si Schottky diodes by a molecular beam epitaxy technique
NASA Technical Reports Server (NTRS)
Lin, T. L.; Iannelli, J. M.
IrSi(3)/p-Si Schottky diodes have been fabricated by a molecular beam epitaxy technique at 630 C. Good surface morphology was observed for IrSi(3) layers grown at temperatures below 680 C, and an increasing tendency to form islands is observed in samples grown at higher temperatures. Good diode current-voltage characteristics were observed and Schottky barrier heights of 0.14-0.18 eV were determined by activation energy analysis and spectral response measurement.
Electron Beam Lithography Double Step Exposure Technique for Fabrication of Mushroom-Like Profile in Bilayer Resist System
NASA Astrophysics Data System (ADS)
Kornelia, Indykiewicz; Bogdan, Paszkiewicz; Tomasz, Szymański; Regina, Paszkiewicz
The Hi/Lo bilayer resist system exposure in e-beam lithography (EBL) process, intended for mushroom-like profile fabrication, was studied. Different exposure parameters and theirs influence on the resist layers were simulated in CASINO software and the obtained results were compared with the experimental data. The AFM technique was used for the estimation of the e-beam penetration depth in the resist stack. Performed numerical and experimental results allow us to establish the useful ranges of the exposure parameters.
Feasibility study of applying an advanced composite structure technique to the fabrication of helicopter rotor blades
NASA Technical Reports Server (NTRS)
Gleich, D.
The fabrication of helicopter rotary wings from composite materials is discussed. Two composite spar specimens consisting of compressively prestressed stainless steel liner over-wrapped with pretensioned fiberglass were constructed. High liner strength and toughness together with the prescribed prestresses and final sizing of the part are achieved by means of cryogenic stretch forming of the fiber wrapped composite spar at minus 320 F, followed by release of the forming pressure and warm up to room temperature. The prestresses are chosen to provide residual compression in the metal liner under operating loads.
Methods of Fabricating a Layer of Metallic Glass-Based Material Using Immersion and Pouring Techniques
NASA Technical Reports Server (NTRS)
Hofmann, Douglas (Inventor)
Systems and methods in accordance with embodiments of the invention implement layers of metallic glass-based materials. In one embodiment, a method of fabricating a layer of metallic glass includes: applying a coating layer of liquid phase metallic glass to an object, the coating layer being applied in a sufficient quantity such that the surface tension of the liquid phase metallic glass causes the coating layer to have a smooth surface; where the metallic glass has a critical cooling rate less than 1000 K/s; and cooling the coating layer of liquid phase metallic glass to form a layer of solid phase metallic glass.
Immobilization techniques in the fabrication of nanomaterial-based electrochemical biosensors: a review.
Putzbach, William; Ronkainen, Niina J
The evolution of 1st to 3rd generation electrochemical biosensors reflects a simplification and enhancement of the transduction pathway. However, in recent years, modification of the transducer with nanomaterials has become increasingly studied and imparts many advantages. The sensitivity and overall performance of enzymatic biosensors has improved tremendously as a result of incorporating nanomaterials in their fabrication. Given the unique and favorable qualities of gold nanoparticles, graphene and carbon nanotubes as applied to electrochemical biosensors, a consolidated survey of the different methods of nanomaterial immobilization on transducer surfaces and enzyme immobilization on these species is beneficial and timely. This review encompasses modification of enzymatic biosensors with gold nanoparticles, carbon nanotubes, and graphene.
TECHNICAL NOTE: New photosensitive ultrathin films fabricated by the Langmuir Blodgett technique
NASA Astrophysics Data System (ADS)
Hafiz, H. R.
A new hybrid LB film composed of an azobenzene-based photochromic layer (the host) and a p-phenylenediacrylic acid-based photosensitive layer (the guest) has been fabricated. The host was demonstrated to regulate the photoreaction kinetics of the guest during UV illumination. The photoresponses of the relevant guest chromophores were verified to be very sensitive to the intermolecular bonding state during the course of the illumination. Both the conversion factor (and its sensitivity) and the insoluble fraction were determined; they imply that such hybrid LB film has a photoresist fingerprint. The photoreactivity of the LB film was explained in terms of a model structure.
Advances in CIS devices fabricated by a non-vacuum technique
Leidholm, C.R.; Norsworthy, G.A.; Roe, R.; Halani, A.; Basol, B.M.; Kapur, V.K.
A novel, non-vacuum technique based on nano-particle deposition has been developed for the formation of CIS-type solar cell absorbers. Solar cells with {gt}12{percent} efficiency were previously demonstrated using this technique. Improvements in module integration processes have recently yielded 8{percent} minimodules of 75 cm{sup 2} area. {copyright} {ital 1999 American Institute of Physics.}
Formulation of curcumin-loaded solid lipid nanoparticles produced by fatty acids coacervation technique.
Chirio, Daniela; Gallarate, Marina; Peira, Elena; Battaglia, Luigi; Serpe, Loredana; Trotta, Michele
Curcumin (CU) loaded solid lipid nanoparticles (SLNs) of fatty acids (FA) were prepared with a coacervation technique based on FA precipitation from their sodium salt micelles in the presence of polymeric non-ionic surfactants. Myristic, palmitic, stearic, and behenic acids, and different polymers with various molecular weights and hydrolysis grades were employed as lipid matrixes and stabilisers, respectively. Generally, spherical-shaped nanoparticles with mean diameters below 500 nm were obtained, and using only middle-high hydrolysis, grade-polymer SLNs with diameters lower than 300 nm were produced. CU encapsulation efficiency was in the range 28-81% and highly influenced by both FA and polymer type. Chitosan hydrochloride was added to FA SLN formulations to produce bioadhesive, positively charged nanoparticles. A CU-chitosan complex formation could be hypothesised by DSC analysis, UV-vis spectra and chitosan surface tension determination. A preliminary study on HCT-116 colon cancer cells was developed to evaluate the influence of CU-loaded FA SLNs on cell viability.
Methods of discovery and techniques to study endophytic fungi producing fuel-related hydrocarbons.
Strobel, Gary A
One promising area in the search for renewable bio-fuels is the discovery of microorganisms that produce fuel-related hydrocarbons (mycodiesel) that is in stark contrast to yeast fermentation that utilizes expensive sugars or starch to produce ethanol, which is a proven and useful source of fuel, but by no means is it ideal. Recently, a number of endophytic fungi have been isolated and described that make compounds such as mono- terpenoids, alkanes, cyclohexanes, cyclopentanes, and alkyl alcohols/ketones, benzenes and polyaromatic hydrocarbons. Many of these compounds are either identical to or are closely related to those specific classes of molecules that are found in diesel. Most importantly, these organisms make hydrocarbons while utilizing cellulosic polymers found in all plant-based agricultural wastes. Also discussed are some novel methods and techniques to quantitatively and qualitatively study hydrocarbon production by these microbes. Two models are discussed for identifying potential fuel-related compounds, scaling up production of them and advanced engine testing. Finally, it seems possible that endophytic fungi may have an additional attribute of having contributed to the formation of crude oil in the first place and a description of the paleobiosphere, to test this hypothesis, is in this review.
NATALIE: a 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques.
Tarisien, M; Plaisir, C; Gobet, F; Hannachi, F; Aléonard, M M; Rebii, A
We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the β(+) activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons.
NATALIE: A 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques
Tarisien, M.; Plaisir, C.; Gobet, F.; Hannachi, F.; Aleonard, M. M.; Rebii, A.
We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the {beta}{sup +} activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons.
Isolation of palm oil-utilising, polyhydroxyalkanoate (PHA)-producing bacteria by an enrichment technique.
Alias, Zazali; Tan, Irene K P
In early attempts to isolate palm oil-utilising bacteria from palm oil mill effluent (POME), diluted liquid samples of POME were spread on agar containing POME as primary nutrient. 45 purified colonies were screened for intracellular lipids by staining with Sudan Black B. Of these, 10 isolates were positively stained. The latter were grown in a nitrogen-limiting medium with palm olein (a triglyceride) or saponified palm olein (salts of fatty acids) as carbon source. None of the isolates grew in the palm olein medium but all grew well in the saponified palm olein medium. Of the latter however, only one isolate was positively stained with Nile Blue A, indicating the presence of PHA. This method did not successfully generate bacterial isolates which could metabolise palm olein to produce PHA. An enrichment technique was therefore developed whereby a selective medium was designed. The latter comprised minerals and palm olein (1% w/v) as sole carbon source to which POME (2.5% v/v) was added as the source of bacteria. The culture was incubated with shaking at 30 degrees C for 4 weeks. Out of seven isolates obtained from the selective medium, two isolates, FLP1 and FLP2, could utilise palm olein for growth and production of the homopolyester, poly(3-hydroxybutyrate). FLP1 is gram-negative and is identified (BIOLOG) to have 80% similarity to Burkholderia cepacia. When grown with propionate or valerate, FLP1 produced a copolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate).
Application of radiosurgical techniques to produce a primate model of brain lesions
Kunimatsu, Jun; Miyamoto, Naoki; Ishikawa, Masayori; Shirato, Hiroki; Tanaka, Masaki
Behavioral analysis of subjects with discrete brain lesions provides important information about the mechanisms of various brain functions. However, it is generally difficult to experimentally produce discrete lesions in deep brain structures. Here we show that a radiosurgical technique, which is used as an alternative treatment for brain tumors and vascular malformations, is applicable to create non-invasive lesions in experimental animals for the research in systems neuroscience. We delivered highly focused radiation (130–150 Gy at ISO center) to the frontal eye field (FEF) of macaque monkeys using a clinical linear accelerator (LINAC). The effects of irradiation were assessed by analyzing oculomotor performance along with magnetic resonance (MR) images before and up to 8 months following irradiation. In parallel with tissue edema indicated by MR images, deficits in saccadic and smooth pursuit eye movements were observed during several days following irradiation. Although initial signs of oculomotor deficits disappeared within a month, damage to the tissue and impaired eye movements gradually developed during the course of the subsequent 6 months. Postmortem histological examinations showed necrosis and hemorrhages within a large area of the white matter and, to a lesser extent, in the adjacent gray matter, which was centered at the irradiated target. These results indicated that the LINAC system was useful for making brain lesions in experimental animals, while the suitable radiation parameters to generate more focused lesions need to be further explored. We propose the use of a radiosurgical technique for establishing animal models of brain lesions, and discuss the possible uses of this technique for functional neurosurgical treatments in humans. PMID:25964746
Fabricating and controlling PCL electrospun microfibers using filament feeding melt electrospinning technique
NASA Astrophysics Data System (ADS)
Ko, Junghyuk; Ahsani, Vahid; Xiangxiao Yao, Selina; Mohtaram, Nima K.; Lee, Patrick C.; Jun, Martin B. G.
The process of melt electrospinning has received noteworthy attention due to its ability to fabricate micro scaled polymer fibers. Recently, a melt electrospinning process has been attracting attention for biomedical applications, in particular with scaffold fabrication for tissue engineering. In order to enhance cell attachment and proliferation on scaffolds, it is important to control fiber diameters to create an environment to which cells can attach, grow, and proliferate with ease. However, because electrospinning is a process with many parameters, it is particularly difficult to precisely control the diameter of the resulting fibers. Also, polymer powders or pellets melted in nozzles are typically used for melt electrospinning. However, a filament feeding melt electrospinning process has not been yet been implemented. In this study, we developed a melt electrospinning device which can feed PCL (Polycaprolactone, Mw: 80 000 g mol-1) filaments for advanced electrospun fiber diameter control. The PCL filaments were first fabricated by a small scale micro-compounder and then fed into the melting chamber of the electrospinning device. The system was then heated to a desired temperature, and the melt was extruded through a nozzle. The potential difference between the nozzle and counter electrode then drew down the PCL extrudate, creating fine microfibers. Temperature was controlled and monitored via a customized temperature control system. In order to control the dispensing of the PCL filaments, a customized control algorithm using NI (National Instruments) LabVIEW was used. In order to actively cool PCL filaments, a miniature computer fan was attached on the side of the melting chamber so that the filaments would not buckle. This paper reveals the investigation of significant process parameters that influence fiber diameters and their optimization. For instance, applied voltages, distances between the nozzle and a counter electrode, processing temperatures, and
An alternative conversion technique for fabricating an interim fixed implant-supported complete arch prosthesis.
Hashemzadeh, Shervin; Yilmaz, Burak; Zugaro, Fred; McGlumphy, Edwin
The conversion technique enables the immediate loading of implants using an existing or a new complete denture. Acrylic resin is generally used directly intraorally when the conventional conversion technique is used. The technique described suggests picking-up the interim copings and capturing the soft tissue contour with the conversion prosthesis with a polyether impression material when 4 implants are placed with an angled implant protocol. A polyether impression was made to complete an autopolymerized reline jig reline. Acrylic resin was applied on the cast generated from this impression outside the oral cavity. This technique may minimize chair time and maximize the ability of the technician/clinician to adapt the prosthesis to the soft tissue contour.
Introduction on the fabrication technique of phosphor in glass by tape-casting and investigation on the chromaticity property.
Wang, Fangyu; Lin, Yue; Shi, Hongling; Wang, Wenchao; Deng, Zhonghua; Chen, Jian; Yuan, Xuanyi; Cao, Yongge
We introduce a new fabrication technique of phosphor in glass (PiG) for light-emitting diodes (LEDs) employing the tape-casting. Through the detailed process described herein and the measurement results, it is clear that the PiG-on-glass not only share the same characteristic of those obtained from other techniques or the bulk PiG, but with more precisely controlled width from a few to hundreds micrometers. The samples are mounted on blue InGaN LED chips to test the color properties of the white light. Besides, we established an empirical model that could predict the final color properties of LEDs solely by the phosphor concentration of phosphor glass under certain conditions. This model would greatly facilitate the design of PiG-based LEDs.
Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents
NASA Astrophysics Data System (ADS)
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.
In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ˜600 kA with ˜200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.
Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.
In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As a result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.
Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; ...
In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less
Fabrication of a grazing incidence telescope by grinding and polishing techniques on aluminum
NASA Technical Reports Server (NTRS)
Gallagher, Dennis; Cash, Webster; Green, James
The paper describes the fabrication processes, by grinding and polishing, used in making the mirrors for a f/2.8 Wolter type-I grazing incidence telescope at Boulder (Colorado), together with testing procedure used to determine the quality of the images. All grinding and polishing is done on specially designed machine that consists of a horizontal spindle to hold and rotate the mirror and a stroke arm machine to push the various tools back and forth along the mirrors length. The progress is checked by means of the ronchi test during all grinding and polishing stages. Current measurements of the telescope's image quality give a FWHM measurement of 44 arcsec, with the goal set at 5-10 arcsec quality.
A statistical comparison of two carbon fiber/epoxy fabrication techniques
NASA Technical Reports Server (NTRS)
Hodge, A. J.
A statistical comparison of the compression strengths of specimens that were fabricated by either a platen press or an autoclave were performed on IM6/3501-6 carbon/epoxy composites of 16-ply (0,+45,90,-45)(sub S2) lay-up configuration. The samples were cured with the same parameters and processing materials. It was found that the autoclaved panels were thicker than the platen press cured samples. Two hundred samples of each type of cure process were compression tested. The autoclaved samples had an average strength of 450 MPa (65.5 ksi), while the press cured samples had an average strength of 370 MPa (54.0 ksi). A Weibull analysis of the data showed that there is only a 30 pct. probability that the two types of cure systems yield specimens that can be considered from the same family.
Immobilization Techniques in the Fabrication of Nanomaterial-Based Electrochemical Biosensors: A Review
Putzbach, William; Ronkainen, Niina J.
The evolution of 1st to 3rd generation electrochemical biosensors reflects a simplification and enhancement of the transduction pathway. However, in recent years, modification of the transducer with nanomaterials has become increasingly studied and imparts many advantages. The sensitivity and overall performance of enzymatic biosensors has improved tremendously as a result of incorporating nanomaterials in their fabrication. Given the unique and favorable qualities of gold nanoparticles, graphene and carbon nanotubes as applied to electrochemical biosensors, a consolidated survey of the different methods of nanomaterial immobilization on transducer surfaces and enzyme immobilization on these species is beneficial and timely. This review encompasses modification of enzymatic biosensors with gold nanoparticles, carbon nanotubes, and graphene. PMID:23580051
Optimized Shielding and Fabrication Techniques for TiN and Al Microwave Resonators
NASA Astrophysics Data System (ADS)
Kreikebaum, John Mark; Kim, Eunseong; Livingston, William; Dove, Allison; Calusine, Gregory; Hover, David; Rosenberg, Danna; Oliver, William; Siddiqi, Irfan
We present a systematic study of the effects of shielding and packaging on the internal quality factor (Qi) of Al and TiN microwave resonators designed for use in qubit readout. Surprisingly, Qi =1.3x106 TiN samples investigated at 100 mK exhibited no significant changes in linewidth when operated without magnetic shielding and in an open cryo-package. In contrast, Al resonators showed systematic improvement in Qi with each successive shield. Measurements were performed in an adiabatic demagnetization refrigerator, where typical ambient fields of 0.2 mT are present at the sample stage. We discuss the effect of 100 mK and 500 mK Cu radiation shields and cryoperm magnetic shielding on resonator Q as a function of temperature and input power in samples prepared with a variety of surface treatments, fabrication recipes, and embedding circuits. This research was supported by the ARO and IARPA.
One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect
Nguyen, Dam Thuy Trang; Tong, Quang Cong; Ledoux-Rak, Isabelle; Lai, Ngoc Diep
In this work, local thermal effect induced by a continuous-wave laser has been investigated and exploited to optimize the low one-photon absorption (LOPA) direct laser writing (DLW) technique for fabrication of polymer-based microstructures. It was demonstrated that the temperature of excited SU8 photoresist at the focusing area increases to above 100 °C due to high excitation intensity and becomes stable at that temperature thanks to the use of a continuous-wave laser at 532 nm-wavelength. This optically induced thermal effect immediately completes the crosslinking process at the photopolymerized region, allowing obtain desired structures without using the conventional post-exposure bake (PEB) step, which is usually realized after the exposure. Theoretical calculation of the temperature distribution induced by local optical excitation using finite element method confirmed the experimental results. LOPA-based DLW technique combined with optically induced thermal effect (local PEB) shows great advantages over the traditional PEB, such as simple, short fabrication time, high resolution. In particular, it allowed the overcoming of the accumulation effect inherently existed in optical lithography by one-photon absorption process, resulting in small and uniform structures with very short lattice constant.
Multilayered film microreactors fabricated by a one-step thermal bonding technique with high reproducibility and their applications.
Min, Kyoung-Ik; Kim, Jin-Oh; Kim, Heejin; Im, Do Jin; Kim, Dong-Pyo
We report the versatile uses of multilayered polyimide (PI) film microreactors with various functions including pressure tolerance, three-dimensional mixing and multistep membrane emulsification. Such PI film microreactors were fabricated by a simple one-step thermal bonding technique with high reproducibility. Upon bonding at 300 °C for 1 hour, the thin and flexible film microdevices could withstand pressure up to 8.6 MPa and 16.3 MPa with PI adhesive film or fluoropolymer adhesive, respectively, due to differences in wettability. The hydrophilic and hydrophobic microchannel devices were used to generate monodisperse oil-in-water (O/W) and water-in-oil (W/O) droplets, and polymer micro/nanoparticles at a high generation frequency. A monolithic and chemical resistant film microreactor with a three-dimensional serpentine microchannel was used for the selective reduction of ester to aldehyde by efficient mixing and quenching in a flash chemistry manner, within a several 10(1) millisecond time scale. Furthermore, a novel multilayered film microreactor for organic-aqueous biphasic interfacial reactions was devised by embedding a membrane layer to induce chaotic mixing in both the interface and emulsified phase by flowing through multiple numbers of meshed structures along the hydrophobic channel. This simple and economic fabrication technique significantly facilitates mass production of multilayered film devices that could be useful as a platform for various microfluidic applications in chemistry and biology.
Novel nanostructured biodegradable polymer matrices fabricated by phase separation techniques for tissue regeneration.
Hsu, S-H; Huang, S; Wang, Y-C; Kuo, Y-C
Biomimetic nanostructures have a wide range of applications. In particular, biodegradable polymer nanostructures that mimic the subtleties of extracellular matrix may provide favorable cell interactions. In this study, a co-solvent system was developed to configure a thermodynamically metastable biodegradable polymer solution, from which novel nanostructured matrices subsequently formed via wet phase separation (quaternary) or a combination with thermally induced phase separation. Three-dimensional (3D) nanostructured porous matrices were further fabricated by combination with particle-leaching (100-300μm glucose). The new co-solvent system may generate matrices with reproducible nanostructures from a variety of biodegradable polymers such as poly(d,l-lactide) (PLA), poly(ε-caprolactone) (PCL) and PCL-based polyurethane. In vitro cell culture experiments were performed with mouse pre-osteoblasts (MC3T3-E1) and human bone marrow-derived mesenchymal stem cells (hBM-MSC) to evaluate the osteoinductive potential of PLA nanostructures. The results showed that nanofibrous (<100nm) membranes promoted the bone-related marker gene expression and matrix mineralization of MC3T3-E1 at 14days. Nanofibrous 3D matrices seeded with hBM-MSC without osteogenic induction supplements demonstrated a 2.5-fold increase in bone matrix deposition vs. the conventional microporous matrices after 14 and 21days. Antimicrobial nanofibers were further obtained by plasma-assisted coating of chitosan on PLA nanofibers. This study reveals a platform for fabricating novel biodegradable nanofibrous architecture, with potential in tissue regeneration.
Vitamin E TPGS used as emulsifier in the solvent evaporation/extraction technique for fabrication of polymeric nanospheres for controlled release of paclitaxel (Taxol).
Mu, L; Feng, S S
The D-alpha-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) was applied in the present investigation as surfactant stabiliser to fabricate paclitaxel-loaded PLGA nanospheres in the solvent evaporation/extraction technique with successful achievement. Laser light scattering system (LLS), scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), Fourier transform infra-red spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were employed to characterise the nanopsheres fabricated in various recipes under various preparation conditions for size and size distribution, surface morphology, thermogram property and surface chemistry. Encapsulation efficiency and in vitro release was measured by the high-performance liquid chromatography (HPLC). The outcomes were discussed with respect to the development of polymeric nanospheres delivery system of the anticancer drug, paclitaxel (Taxol((R))). The produced nanospheres were found in fine spherical shape with smooth surfaces and without aggregation or adhesion. There was no significant difference in morphology between the vitamin E TPGS emulsified and PVA emulsified PLGA nanospheres. However, it was found that, in comparison with the traditional chemical emulsifier PVA, the TPGS could significantly improve the encapsulation efficiency of the drug in the PLGA nanospheres, which could be as high as 100%. The size of the vitamin E TPGS emulsified nanospheres ranged from 300 to 800 nm and the size distribution was narrow with polydispersity of 0.005-0.045. XPS investigation demonstrated that there were residual surfactant molecules remained on the surface although the TPGS could be washed out relatively thoroughly in the process of nanospheres formation. This finding was also confirmed by FTIR-PAS investigation of the nanospheres. The in vitro release indicated that the release property of paclitaxel from the nanospheres strongly depends on the emulsifier
Effect of cryopreservation technique and season on the survival of in vitro produced cattle embryos.
Gupta, Alisha; Singh, Jaswant; Anzar, Muhammad
Embryo cryopreservation is a major tool for conservation and propagation of genetically superior animals. However, it adversely affects the survival of embryos. The objective of this study was to determine the effects of cryopreservation technique (vitrification compared with slow freezing) and different seasons in which oocytes were obtained on the post-warming survival of in vitro produced (IVP) cattle morulae. In experiment 1, morulae (Day 6 post-IVF), obtained from abattoir-sourced oocytes during spring, summer, fall and winter over a period of 3.5 years, were subjected to either vitrification (n=271 morulae), slow freezing (n=281 morulae) or no freezing (control; n=249 morulae). After warming, the morulae were cultured to the expanded blastocyst stage (Day 8 post-IVF). Data were compared using Glimmix procedure in SAS(®). Blastocyst rate differed (P<0.05) among the treatments: unfrozen control (78±3.6%), vitrification (52±4.6%) and slow freezing (35±4.2%). The re-expansion of vitrified morulae upon warming was not correlated with subsequent blastocyst rate (r=-0.048; P>0.05). The morulae produced during fall season had lesser (P<0.05) cleavage and morula rates (67±1.6%; Day 2 post-IVF and 22±1.4%; Day 6 post-IVF, respectively) than all other seasons (74±1.1 and 30±1.2%, respectively). Blastocyst rate was the least (P<0.05) when oocytes were collected during the summer season in both control and slowly frozen groups. Blastocyst development rate did not change due to season in vitrification group (P>0.05). In conclusion, vitrification is a more desirable technique than slow freezing for cryopreservation of IVP cattle morulae. If the slow freezing method is employed, greater success can be achieved using oocytes collected in the winter and spring with a primary contributing factor being lesser morulae development if oocytes are collected in the fall and also the lesser blastocyst formation of cryopreserved morulae when oocytes are collected in the summer.
Fabrication of Thermoelectric Devices Using Additive-Subtractive Manufacturing Techniques: Application to Waste-Heat Energy Harvesting
NASA Astrophysics Data System (ADS)
Tewolde, Mahder
Thermoelectric generators (TEGs) are solid-state devices that convert heat directly into electricity. They are well suited for waste-heat energy harvesting applications as opposed to primary energy generation. Commercially available thermoelectric modules are flat, inflexible and have limited sizes available. State-of-art manufacturing of TEG devices relies on assembling prefabricated parts with soldering, epoxy bonding, and mechanical clamping. Furthermore, efforts to incorporate them onto curved surfaces such as exhaust pipes, pump housings, steam lines, mixing containers, reaction chambers, etc. require custom-built heat exchangers. This is costly and labor-intensive, in addition to presenting challenges in terms of space, thermal coupling, added weight and long-term reliability. Additive manufacturing technologies are beginning to address many of these issues by reducing part count in complex designs and the elimination of sub-assembly requirements. This work investigates the feasibility of utilizing such novel manufacturing routes for improving the manufacturing process of thermoelectric devices. Much of the research in thermoelectricity is primarily focused on improving thermoelectric material properties by developing of novel materials or finding ways to improve existing ones. Secondary to material development is improving the manufacturing process of TEGs to provide significant cost benefits. To improve the device fabrication process, this work explores additive manufacturing technologies to provide an integrated and scalable approach for TE device manufacturing directly onto engineering component surfaces. Additive manufacturing techniques like thermal spray and ink-dispenser printing are developed with the aim of improving the manufacturing process of TEGs. Subtractive manufacturing techniques like laser micromachining are also studied in detail. This includes the laser processing parameters for cutting the thermal spray materials efficiently by
Large-area fabrication and characterisation of ultraviolet regime metamaterials manufactured using self-assembly techniques (Conference Presentation)
NASA Astrophysics Data System (ADS)
Wardley, William P.; Nasir, Mazhar E.; Rodríguez Fortuño, Francisco J.; Vilain, Sébastien; Skov Campbell, Serena; Wurtz, Gregory A.; Zayats, Anatoly; Dickson, Wayne
Metamaterials have a number of interesting and potentially useful applications in a variety of fields, such as chemical and biological sensing, enhancement of spontaneous emission, nonlinear optics and as substrates for use in surface enhanced Raman spectroscopy (SERS). However, to date the low-wavelength cutoff for the majority of work at the higher frequency end of the spectrum has been determined by use of the coinage metals, which intrinsically prohibit their implementation below a vacuum wavelength of approximately 500nm for gold and 350nm for silver. Producing nanostructured plasmonic media that exhibit metamaterial functionalities in the ultraviolet will have a number of benefits. Not only will working in a new range of the electromagnetic spectrum allow for higher energy photons to be controlled, but a number of other benefits arise from the behaviour of different materials in the ultraviolet. For instance, many biological molecules, including DNA, exhibit fluorescence in the UV range, allowing for label-free detection and analysis of biological material; the intrinsic electronic absorption can be used to increase this label-free bio-sensitivity as well as enable the possibility of SE(R)RS, a process further enhanced by the frequency dependence on the efficiency of this scattering process. Here, we demonstrate the fabrication and characterisation of metamaterials operating in the deep-near UV. By using alternatives to the coinage metals, including aluminium and gallium, we have measured optical responses in the system down to approximately 200 nm. Sample preparation utilises a self-assembly method, allowing for the production of macroscopic-sized assemblies (> 1 cm2) of nanometric elements (radius ~ 25 nm, separation ~ 100 nm). Careful control of the fabrication conditions allows fine control of the structural parameters, which in turn allows tunability of the optical properties over a wide range of wavelengths (> 200 nm). The structures produced include
Broadband terahertz anti-reflective structure fabricated by femtosecond laser drilling technique
NASA Astrophysics Data System (ADS)
Zhang, Yibin; Yuan, Minghui; Chen, Lin; Cai, Bin; Yang, Rui; Zhu, Yiming
We fabricated several reverse conical holes on high-resistivity silicon substrate with different power and pulse number of femtosecond laser, and investigated their patterns and features by using scanning electron microscope (SEM). Then, we chose one of the experimental parameters prepared a reverse conical anti-reflection structure sample with period of 90 μm. Terahertz Time-domain Spectroscopy (THz-TDS) was used to test its properties. Compared with the nonstructural high-resistivity silicon, the transmission of structural high-resistivity silicon increases by the maximum of 14% in the range 0.32-1.30 THz. Furthermore, we simulated the sample by finite integral method (FIM). The simulated results show good consistency with experimental results. The transmission effect of the reverse conical holes were optimized via simulation. Results show that the related transmission effect can be improved by increasing the pulse numbers and decreasing the spot size of the femtosecond laser. The different transmission window can also be tuned by changing the reverse conical structure of different periods.
Fabrication technique of large-scale lightweight SiC space mirror
NASA Astrophysics Data System (ADS)
Zhang, Ge; Zhao, Rucheng; Zhao, Wenxing
Silicon carbide (SiC) is a new type candidate material for large-scale lightweight space mirror. Its low thermal distortion, high stiffness, high optical quality, and its dimensional stability are better than other traditional optical substrate materials such as ULE, Zerodure, Beryllium (Be) and so on. In this paper, the lightweight silicon carbide space mirror blank was fabricated by reaction sintering. As a space born mirror material, silicon carbide must be an optical grade ceramic. So we prepared the silicon carbide green body with gel-casting method. Then some carbon materials were supplemented into the green body which will bring reaction-sintering with silicon in a vacuum furnace during 1500-1600°C, ultimately the reaction bonded silicon carbide was made. The diameter of SiC space mirror blank we have made is 680mm. If expanding the size of the vacuum furnace, bigger mirror blank can be obtained. The test results show that the mechanical and thermal properties of RB-SiC are excellent with bending strength of 350MPa, fracture toughness of 4.1 MPaÂ.m1/2 and coefficient of thermal expansion(CET) of 2.67×10-6/K. The surface roughness(RMS) could be better than 3nm.
Fabrication techniques and applications of flexible graphene-based electronic devices
NASA Astrophysics Data System (ADS)
Luqi, Tao; Danyang, Wang; Song, Jiang; Ying, Liu; Qianyi, Xie; He, Tian; Ningqin, Deng; Xuefeng, Wang; Yi, Yang; Tian-Ling, Ren
In recent years, flexible electronic devices have become a hot topic of scientific research. These flexible devices are the basis of flexible circuits, flexible batteries, flexible displays and electronic skins. Graphene-based materials are very promising for flexible electronic devices, due to their high mobility, high elasticity, a tunable band gap, quantum electronic transport and high mechanical strength. In this article, we review the recent progress of the fabrication process and the applications of graphene-based electronic devices, including thermal acoustic devices, thermal rectifiers, graphene-based nanogenerators, pressure sensors and graphene-based light-emitting diodes. In summary, although there are still a lot of challenges needing to be solved, graphene-based materials are very promising for various flexible device applications in the future. Project supported by the National Natural Science Foundation of China (Nos. 60936002, 61025021, 61434001, 61574083), the State Key Development Program for Basic Research of China (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002) and the Special Fund for Agroscientific Research in the Public Interest of China (No. 201303107). M.A.M is additionally supported by the Postdoctoral Fellowship (PDF) Program of the Natural Sciences and Engineering Research Council (NSERC) of Canada and China's Postdoctoral Science Foundation (CPSF).
Fabrication of dense (Th,U)O 2 pellets through microspheres impregnation technique
NASA Astrophysics Data System (ADS)
Pai, Rajesh V.; Dehadraya, J. V.; Bhattacharya, Shovit; Gupta, S. K.; Mukerjee, S. K.
ThO 2 microspheres were prepared by internal gelation process using a pre-boiled hexamethylenetetramine (HMTA), urea solution. The microspheres were characterized with respect to tap density, specific surface area and pore size distribution. An indigenously designed and fabricated apparatus was used for the impregnation of uranium in thoria microspheres. The loading of uranium was found to vary with the concentration of uranyl nitrate solution, operational vacuum and the time of impregnation. These process conditions were optimized to obtain soft (Th,U)O 2 microspheres containing 3-4 mol% of uranium, which are readily amenable for pelletization. The green pellets could be sintered to ˜96% of T.D. by heating in air up to 1350 °C for a period of 2-4 h. The polished surface of the fractured pellets showed a smooth surface without any berry structure. The shrinkage behaviour of the pellets was also studied in air using a dilatometer. The SEM studies of the pellets indicated a uniform microstructure with average grain size of 1 μm. The elemental scanning by the EDX method showed the uniform distribution of uranium in the microspheres and pellets.
Experimental Technique for Producing and Recording Precise Particle Impacts on Transparent Window Materials
NASA Technical Reports Server (NTRS)
Gray, Perry; Guven, Ibrahim
A new facility for making small particle impacts is being developed at NASA. Current sand/particle impact facilities are an erosion test and do not precisely measure and document the size and velocity of each of the impacting particles. In addition, evidence of individual impacts is often obscured by subsequent impacts. This facility will allow the number, size, and velocity of each particle to be measured and adjusted. It will also be possible to determine which particle produced damage at a given location on the target. The particle size and velocity will be measured by high speed imaging techniques. Information as to the extent of damage and debris from impacts will also be recorded. It will be possible to track these secondary particles, measuring size and velocity. It is anticipated that this additional degree of detail will provide input for erosion models and also help determine the impact physics of the erosion process. Particle impacts will be recorded at 90 degrees to the particle flight path and also from the top looking through the target window material.
Characterization of a laser-produced plasma using the technique of point-projection absorption spectroscopy
O'Neill, D.M.; Lewis, C.L.S.; Neely, D.; Davidson, S.J. ); Rose, S.J. ); Lee, R.W. )
The technique of point-projection spectroscopy has been shown to be applicable to the study of expanding aluminum plasmas generated by {similar to}80 ps laser pulses incident on massive, aluminum stripe targets of {similar to}125 {mu}m width. Targets were irradiated at an intensity of 2.5{plus minus}0.5{times}10{sup 13} W/cm{sup 2} in a line focus geometry and under conditions similar to those of interest in x-ray laser schemes. Hydrogenic and heliumlike aluminum resonance lines were observed in absorption using a quasicontinuous uranium backlighter plasma. Using a pentaerythrital Bragg crystal as the dispersive element, a resolving power of {similar to}3500 was achieved with spatial resolution at the 5-{mu}m level in frame times of the order of 100 ps. Reduction of the data for times up to 150 ps after the peak of the incident laser pulse produced estimates of the temperature and ion densities present, as a function of space and time. The one-dimensional Lagrangian hydrodynamic code MEDUSA coupled to the atomic physics non-local-thermodynamic-equilibrium ionized material package was used to simulate the experiment in planar geometry and has been shown to be consistent with the measurements.
Spontaneous high piezoelectricity in poly(vinylidene fluoride) nanoribbons produced by iterative thermal size reduction technique.
Kanik, Mehmet; Aktas, Ozan; Sen, Huseyin Sener; Durgun, Engin; Bayindir, Mehmet
We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar γ phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar γ phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 μA peak short-circuit current output.
Comparison of Y2O3:Bi3+ phosphor thin films fabricated by the spin coating and radio frequency magnetron techniques
NASA Astrophysics Data System (ADS)
Jafer, R. M.; Yousif, A.; Kumar, Vinod; Pathak, Trilok Kumar; Purohit, L. P.; Swart, H. C.; Coetsee, E.
The reactive radio-frequency (RF) magnetron sputtering and spin coating fabrication techniques were used to fabricate Y2-xO3:Bix=0.5% phosphor thin films. The two techniques were analysed and compared as part of investigations being done on the application of down-conversion materials for a Si solar cell. The morphology, structural and optical properties of these thin films were investigated. The X-ray diffraction results of the thin films fabricated by both techniques showed cubic structures with different space groups. The optical properties showed different results because the Bi3+ ion is very sensitive towards its environment. The luminescence results for the thin film fabricated by the spin coating technique is very similar to the luminescence observed in the powder form. It showed three obvious emission bands in the blue and green regions centered at about 360, 410 and 495 nm. These emissions were related to the 3P1-1S0 transition of the Bi3+ ion situated in the two different sites of the Y2O3 matrix with I a-3(206) space group. Whereas the thin film fabricated by the radio frequency magnetron technique showed a broad single emission band in the blue region centered at about 416 nm. This was assigned to the 3P1-1S0 transition of the Bi3+ ion situated in one of the Y2O3 matrix's sites with a Fm-3 (225) space group. The spin coating fabrication technique is suggested to be the best technique to fabricate the Y2O3:Bi3+ phosphor thin films.
A simplified technique for fabricating esthetic cast metal occlusal surfaces for dentures.
Krantz, W A; Ivanhoe, J R; Adrian, E D
This article describes a simplified method for making esthetic cast metal occlusal surfaces. Monoplane posterior acrylic resin block teeth, cast in a nickel-chrome alloy, are coated with silane and an esthetic composite resin veneer is applied to the buccal surface. These veneered posterior metal teeth are incorporated in the wax setup and the dentures are processed and finished. The dentist's routine technique for delivering dentures to the patient can be followed.
Herbal Extract Incorporated Nanofiber Fabricated by an Electrospinning Technique and its Application to Antimicrobial Air Filtration.
Choi, Jeongan; Yang, Byeong Joon; Bae, Gwi-Nam; Jung, Jae Hee
Recently, with the increased attention to indoor air quality, antimicrobial air filtration techniques have been studied widely to inactivate hazardous airborne microorganisms effectively. In this study, we demonstrate herbal extract incorporated (HEI) nanofibers synthesized by an electrospinning technique and their application to antimicrobial air filtration. As an antimicrobial herbal material, an ethanolic extract of Sophora flavescens, which exhibits great antibacterial activity against pathogens, was mixed with the polymer solution for the electrospinning process. We measured various characteristics of the synthesized HEI nanofibers, such as fiber morphology, fiber size distribution, and thermal stability. For application of the electrospun HEI nanofibers, we made highly effective air filters with 99.99% filtration efficiency and 99.98% antimicrobial activity against Staphylococcus epidermidis. The pressure drop across the HEI nanofiber air filter was 4.75 mmH2O at a face air velocity of 1.79 cm/s. These results will facilitate the implementation of electrospun HEI nanofiber techniques to control air quality and protect against hazardous airborne microorganisms.
Design and fabrication of high performance wafer-level vacuum packaging based on glass-silicon-glass bonding techniques
NASA Astrophysics Data System (ADS)
Zhang, Jinwen; Jiang, Wei; Wang, Xin; Zhou, Jilong; Yang, Huabing
In this paper, a high performance wafer-level vacuum packaging technology based on GSG triple-layer sealing structure for encapsulating large mass inertial MEMS devices fabricated by silicon-on-glass bulk micromachining technology is presented. Roughness controlling strategy of bonding surfaces was proposed and described in detail. Silicon substrate was thinned and polished by CMP after the first bonding with the glass substrate and was then bonded with the glass micro-cap. Zr thin film was embedded into the concave of the micro-cap by a shadow-mask technique. The glass substrate was thinned to about 100 µm, wet etched through and metalized for realizing vertical feedthrough. During the fabrication, all patterning processes were operated carefully so as to reduce extrusive fragments to as little as possible. In addition, a high-performance micro-Pirani vacuum gauge was integrated into the package for monitoring the pressure and the leak rate further. The result shows that the pressure in the package is about 120 Pa and has no obvious change for more than one year indicating 10-13 stdcc s-1 leak rate.
Fabrication of narrow-striped InAs/GaAs quantum dot laser with wet etching technique
NASA Astrophysics Data System (ADS)
Li, S. G.; Gong, Q.; Cao, C. F.; Wang, X. Z.; Xia, L. Z.; Yan, J. Y.; Wang, Y.
An InAs/GaAs quantum dot laser, fabricated with a narrow-striped width of 6 μm by a wet etching technique, is reported. The etching solutions are composed of three components, i.e. phosphoric acid, hydrogen peroxide, and deionized water. We observed that the unavoidable undercutting was changed with the ratio of etching solution in the GaAs materials. By taking a suitable ratio of etching solution, good performance of quantum dot laser with a size of 6 μm × 700 μm was achieved for fabrication at room temperature. Under continuous wave mode, the lasing wavelength exhibited a single mode, which is located in the region of 1051 nm. In contrast, multimode lasing with a series of non-lasing gaps appeared and the spectra were gradually broadened to the high energy side by increasing the injection current. The laser has one facet power more than 22 mW, with a slope efficiency of 140 mW/A, just a little above threshold current.
Fast fabrication of copper nanowire transparent electrodes by a high intensity pulsed light sintering technique in air.
Ding, Su; Jiu, Jinting; Tian, Yanhong; Sugahara, Tohru; Nagao, Shijo; Suganuma, Katsuaki
Copper nanowire transparent electrodes have received increasing interest due to the low price and nearly equal electrical conductivity compared with other TEs based on silver nanowires and indium tin oxide (ITO). However, a post-treatment at high temperature in an inert atmosphere or a vacuum environment was necessary to improve the conductivity of Cu NW TEs due to the easy oxidation of copper in air atmosphere, which greatly cancelled out the low price advantage of Cu NWs. Here, a high intensity pulsed light technique was introduced to sinter and simultaneously deoxygenate these Cu NWs into a highly conductive network at room temperature in air. The strong light absorption capacity of Cu NWs enabled the welding of the nanowires at contact spots, as well as the removal of the thin layer of residual organic compounds, oxides and hydroxide of copper even in air. The Cu NW TE with a sheet resistance of 22.9 Ohm sq(-1) and a transparency of 81.8% at 550 nm has been successfully fabricated within only 6 milliseconds exposure treatment, which is superior to other films treated at high temperature in a hydrogen atmosphere. The HIPL process was simple, convenient and fast to fabricate easily oxidized Cu NW TEs in large scale in an air atmosphere, which will largely extend the application of cheap Cu NW TEs.
Osmogen-Mediated One-Step Technique of Fabricating Hollow Microparticles for Encapsulation and Delivery of Bioactive Molecules.
Kharel, Sharad; Lee, Wei Li; Lee, Xuan Yi; Loo, Say Chye Joachim
Microparticulate systems composed of biodegradable polymers, such as poly(d,l-lactic-co-glycolic acid) (PLGA), are widely used for controlled release of bioactive molecules. However, the acidic microenvironment within these microparticles, as they degrade, has been reported to perturb the configuration of most encapsulated proteins. In addition, these polymer particles are also reported to suffer from unrealistically slow and incomplete release of proteins. To address these drawbacks, hollow PLGA microparticles are fabricated through a novel one-step oil-in-water emulsion solvent evaporation technique, by capitalizing on the osmotic property of an osmogen. The effects of fabrication para-meters on particle size and morphology, i.e., volume space of hollow cavity and shell thickness, are also studied. These hollow microparticles are subsequently loaded with bovine insulin microcrystals. It is shown that insulin release profiles can be tuned by simply changing the amount of osmogen in the formulation. At the same time, these hollow microparticles are shown to be effective in maintaining the bioactivity of the encapsulated protein.
Evaluation of shear bond strength between zirconia core and ceramic veneers fabricated by pressing and layering techniques: In vitro study
Subash, M.; Vijitha, D.; Deb, Saikat; Satish, A.; Mahendirakumar, N.
Statement of Problem: Although ceramic veneered on to zirconia core have been in use for quite some time, information regarding the comparative evaluation of the Shear bond strength of Pressable & Layered ceramic veneered on to zirconia core is limited. Purpose of study: To evaluate the shear bond strength of zirconia core and ceramic veneer fabricated by two different techniques, Layering (Noritake CZR) and Pressing (Noritake, CZR Press). Materials and Method: 20 samples of zirconia blocks were fabricated and the samples were divided into group A & B. Group A - Ceramic Veneered over zirconia core by pressing using Noritake CZR Press. Group B - Ceramic Veneered over zirconia core by layering using Noritake CZR. The veneered specimens were mounted on to the center of a PVC tube using self-cure acrylic resin leaving 3 mm of the veneered surface exposed as cantilever. Using a Universal testing machine the blocks were loaded up to failure. Result: The results were tabulated by using independent samples t-test. The mean shear bond strength for Pressed specimens was 12.458 ± 1.63(S.D) MPa and for layered specimens was 8.458 ± 0.845(S.D) MPa. Conclusion: Pressed specimens performed significantly better than the layered specimen with a P value 0.001. Clinicians and dental laboratory technicians should consider the use of pressed ceramics as an alternative to traditional layering procedures to reduce the chances of chipping or de-lamination of ceramics PMID:26538929
Vesicles Cytoplasmic Injection: An Efficient Technique to Produce Porcine Transgene-Expressing Embryos.
Luchetti, C G; Bevacqua, R J; Lorenzo, M S; Tello, M F; Willis, M; Buemo, C P; Lombardo, D M; Salamone, D F
The use of vesicles co-incubated with plasmids showed to improve the efficiency of cytoplasmic injection of transgenes in cattle. Here, this technique was tested as a simplified alternative for transgenes delivery in porcine zygotes. To this aim, cytoplasmic injection of the plasmid alone was compared to the injection with plasmids co-incubated with vesicles both in diploid parthenogenic and IVF zygotes. The plasmid pcx-egfp was injected circular (CP) at 3, 30 and 300 ng/μl and linear (LP) at 30 ng/μl. The experimental groups using parthenogenetic zygotes were as follows: CP naked at 3 ng/μl (N = 105), 30 ng/μl (N = 95) and 300 ng/μl (N = 65); Sham (N = 105); control not injected (N = 223); LP naked at 30 ng/μl (N = 78); LP vesicles (N = 115) and Sham vesicles (N = 59). For IVF zygotes: LP naked (N = 44) LP vesicles (N = 94), Sham (N = 59) and control (N = 79). Cleavage, blastocyst and GFP+ rates were analysed by Fisher's test (p < 0.05). The parthenogenic CP naked group showed lower cleavage respect to control (p < 0.05). The highest concentration of plasmids to allow development to blastocyst stage was 30 ng/μl. There were no differences in DNA fragmentation between groups. The parthenogenic LP naked group resulted in high GFP rates (46%) and also allowed the production of GFP blastocysts (33%). The cytoplasmic injection with LP vesicles into parthenogenic zygotes allowed 100% GFP blastocysts. Injected IVF showed higher cleavage rates than control (p < 0.05). In IVF zygotes, only the use of vesicles produced GFP blastocysts. The use of vesicles co-incubated with plasmids improves the transgene expression efficiency for cytoplasmic injection in porcine zygotes and constitutes a simple technique for easy delivery of plasmids.
Variation in the volatile oil composition of Eucalyptus citriodora produced by hydrodistillation and supercritical fluid extraction techniques.
Mann, Tavleen S; Babu, G D Kiran; Guleria, Shailja; Singh, Bikram
This work reports variations in the yields and quality of volatiles produced from Eucalyptus citriodora leaves by different hydrodistillation (HD) and supercritical carbon dioxide extraction (SCE) techniques. HD techniques (1.5%) produced higher yields compared to SCE (0.7%). Citronellal, the major component, was maximum in the extract produced by SCE (79%) followed by oil produced by water-steam distillation (WSD) (72.6%) and water distillation (WD) (62.4%) techniques. Chemical composition of glycoside-bound volatiles produced by acid hydrolysis during HD was found to be very different from free volatiles, although in a minor quantity. The extent of artefact formation and release of aglycones was more profound in the bound volatile oil produced by WD than WSD. Highest oxygenated monoterpenes were found in SCE and WSD (93% each) followed by WD (91.4%). Although the SCE produced lower yields than the HD techniques, its extract is superior in quality in terms of higher concentration of citronellal.
Fabrication of novel silicone capsules with tunable mechanical properties by microfluidic techniques.
Vilanova, Neus; Rodríguez-Abreu, Carlos; Fernández-Nieves, Alberto; Solans, Conxita
A novel approach for the synthesis of silicone capsules using double W/O/W emulsions as templates is introduced. The low viscosity of the silicone precursors enables the use of microfluidic techniques to accurately control the size and morphology of the double emulsion droplets, which after cross-linking result in the desired monodisperse silicone capsules. Their shell thickness can be finely tuned, which in turn allows control over their permeability and mechanical properties; the latter are particularly important in a variety of practical applications where the capsules are subjected to large external forces. The potential of these capsules for controlled release is also demonstrated using a model hydrophilic substance.
Theoretical modeling and experiments on a DBR waveguide laser fabricated by the femtosecond laser direct-write technique.
Duan, Yuwen; McKay, Aaron; Jovanovic, Nemanja; Ams, Martin; Marshall, Graham D; Steel, M J; Withford, Michael J
We present a model for a Yb-doped distributed Bragg reflector (DBR) waveguide laser fabricated in phosphate glass using the femtosecond laser direct-write technique. The model gives emphasis to transverse integrals to investigate the energy distribution in a homogenously doped glass, which is an important feature of femtosecond laser inscribed waveguide lasers (WGLs). The model was validated with experiments comparing a DBR WGL and a fiber laser, and then used to study the influence of distributed rare earth dopants on the performance of such lasers. Approximately 15% of the pump power was absorbed by the doped "cladding" in the femtosecond laser inscribed Yb doped WGL case with the length of 9.8 mm. Finally, we used the model to determine the parameters that optimize the laser output such as the waveguide length, output coupler reflectivity and refractive index contrast.
Top gate ZnO-Al2O3 thin film transistors fabricated using a chemical bath deposition technique
NASA Astrophysics Data System (ADS)
Gogoi, Paragjyoti; Saikia, Rajib; Changmai, Sanjib
ZnO thin films were prepared by a simple chemical bath deposition technique using an inorganic solution mixture of ZnCl2 and NH3 on glass substrates and then were used as the active material in thin film transistors (TFTs). The TFTs were fabricated in a top gate coplanar electrode structure with high-k Al2O3 as the gate insulator and Al as the source, drain and gate electrodes. The TFTs were annealed in air at 500 °C for 1 h. The TFTs with a 50 μm channel length exhibited a high field-effect mobility of 0.45 cm2/(V·s) and a low threshold voltage of 1.8 V. The sub-threshold swing and drain current ON-OFF ratio were found to be 0.6 V/dec and 106, respectively.
CAFM investigations of filamentary conduction in Cu2O ReRAM devices fabricated using stencil lithography technique.
Singh, Bharti; Mehta, B R; Varandani, Deepak; Savu, Andreea Veronica; Brugger, Juergen
With the objective of understanding the role of size and current level of filamentary regions on the resistive switching parameters, detailed conductive atomic force microscope investigations of resistive memory cells having different dimensions have been carried out in this study. Cu-Cu(2)O-Ti memory cells having dimensions of 150, 50 and 25 μm have been fabricated on the same substrate using a stencil lithography technique. The dependence of resistive switching parameters on the device dimensions can be directly related to the average size, current level of the filaments and difference in these parameters between the low resistance state (LRS) and high resistance state (HRS). It is observed that the large increase in the ratio of current in the two states in cells having lower dimensions is mainly due to the smaller number of conducting regions in the HRS, indicating efficient switching from the LRS to the HRS at lower dimensions.
Fabrication and photoelectric response of poly(allylamine hydrochloride)/PM thin films by layer-by-layer deposition technique.
Chu, Jinfang; Li, Xingchang; Zhang, Jianping; Tang, Ji'an
Thin films of poly(allylamine hydrochloride) (PAH) and bacteriorhodopsin (bR) embedded in purple membrane (PM) have been prepared by layer-by-layer (LBL) self-assembly technique. The results obtained by UV-Vis spectroscopy and atomic force microscopy (AFM) analysis showed that the biological activity of bR was preserved and PM fragments could be well oriented onto the ITO substrate. A photo-electrochemical cell with the structure of ITO/(PAH/PM)(n)/electrolyte (0.5M KCl)/Pt was fabricated and studied. The photocurrent peaks of (PAH/PM)(6) corresponding to light-on and light-off were about 200 and 100 nA/cm(2), respectively, with the former enhanced 30% higher than that of the reference films made of (PDAC/PM)(6).
III-V compound semiconductor multi-junction solar cells fabricated by room-temperature wafer-bonding technique
NASA Astrophysics Data System (ADS)
Arimochi, Masayuki; Watanabe, Tomomasa; Yoshida, Hiroshi; Tange, Takashi; Nomachi, Ichiro; Ikeda, Masao; Dai, Pan; He, Wei; Ji, Lian; Lu, Shulong; Yang, Hui; Uchida, Shiro
We have developed III-V compound semiconductor multi-junction solar cells by a room-temperature wafer-bonding technique to avoid the formation of dislocations and voids due to lattice mismatch and thermal damage during a conventional high-temperature wafer-bonding process. First, we separately grew an (Al)GaAs top cell on a GaAs substrate and an InGaAs bottom cell on an InP substrate by metal solid source molecular beam epitaxy. Thereafter, we successfully bonded these sub-cells by the room-temperature wafer-bonding technique and fabricated (Al)GaAs ∥ InGaAs wafer-bonded solar cells. To the best of our knowledge, the obtained GaAs ∥ InGaAs and AlGaAs ∥ InGaAs wafer-bonded solar cells exhibited the lowest electrical and optical losses ever reported. The AlGaAs ∥ InGaAs solar cells reached the maximum efficiency of 27.7% at 120 suns. These results suggest that the room-temperature wafer-bonding technique has high potential for achieving higher conversion efficiencies.
An innovative technique to simply fabricate ZrO₂-HA-TiO₂ nanostructured layers.
Samanipour, F; Bayati, M R; Golestani-Fard, F; Zargar, H R; Troczynski, T; Mirhabibi, A R
For the first time, ZrO₂-HA-TiO₂ layers were synthesized through EPD-Enhanced MAO (EEMAO) technique in only one step where no supplementary treatment was required. SEM, XRD, EDX, and XPS techniques were employed to propose a correlation between the growth parameters and the physical and chemical properties of the layers. The layers revealed a porous structure where applying higher voltages and/or utilizing higher concentrated electrolytes resulted in formation of wider pores and increasing the zirconium concentration in the layers; meanwhile, prolonging the growth time had the same effects. The layers mainly consisted of anatase, hydroxyapatite, monoclinic ZrO₂, and tetragonal ZrO₂ phases. Increasing the voltage, electrolyte concentration, and time, hydroxyapatite as well as tetragonal ZrO₂ was decomposed to α-TCP, monoclinic ZrO₂, and ZrO. The nanosized zirconia particles (d = 20-60 nm) were further accumulated on the vicinity of the layers when thicker electrolytes were utilized or higher voltages were applied. Emphasizing on the chemical and electrochemical foundations, a probable formation mechanism was finally put forward.
Microfluidic channel fabrication method
Arnold, Don W.; Schoeniger, Joseph S.; Cardinale, Gregory F.
A new channel structure for microfluidic systems and process for fabricating this structure. In contrast to the conventional practice of fabricating fluid channels as trenches or grooves in a substrate, fluid channels are fabricated as thin walled raised structures on a substrate. Microfluidic devices produced in accordance with the invention are a hybrid assembly generally consisting of three layers: 1) a substrate that can or cannot be an electrical insulator; 2) a middle layer, that is an electrically conducting material and preferably silicon, forms the channel walls whose height defines the channel height, joined to and extending from the substrate; and 3) a top layer, joined to the top of the channels, that forms a cover for the channels. The channels can be defined by photolithographic techniques and are produced by etching away the material around the channel walls.
Research and Development on Advanced Silicon Carbide Thin Film Growth Techniques and Fabrication of High Power and Microwave Frequency Silicon Carbide-Based Device Structures
0W " -Annual Letter Report- N,4 Research and Developmen. on Advanced Silicon Carbide Thin Film Growth Techniques and Fabrication of High Power and...Microwave Frequency Silicon Carbide -Based Device Structures Supported under Grant #N00014-88-K-0341/P00002 Office of the Chief of Naval Research Report...SUBTITLE Research and Development on Advanced S. FUNDING NUMBERS Silicon Carbide Thin Filn.Growth Technl.ques and R&T:212k003---03 Fabrication of High
Fabrication and Characterization of a Micro Methanol Sensor Using the CMOS-MEMS Technique.
Fong, Chien-Fu; Dai, Ching-Liang; Wu, Chyan-Chyi
A methanol microsensor integrated with a micro heater manufactured using the complementary metal oxide semiconductor (CMOS)-microelectromechanical system (MEMS) technique was presented. The sensor has a capability of detecting low concentration methanol gas. Structure of the sensor is composed of interdigitated electrodes, a sensitive film and a heater. The heater located under the interdigitated electrodes is utilized to provide a working temperature to the sensitive film. The sensitive film prepared by the sol-gel method is tin dioxide doped cadmium sulfide, which is deposited on the interdigitated electrodes. To obtain the suspended structure and deposit the sensitive film, the sensor needs a post-CMOS process to etch the sacrificial silicon dioxide layer and silicon substrate. The methanol senor is a resistive type. A readout circuit converts the resistance variation of the sensor into the output voltage. The experimental results show that the methanol sensor has a sensitivity of 0.18 V/ppm.
Fabrication and Characterization of a Micro Methanol Sensor Using the CMOS-MEMS Technique
Fong, Chien-Fu; Dai, Ching-Liang; Wu, Chyan-Chyi
A methanol microsensor integrated with a micro heater manufactured using the complementary metal oxide semiconductor (CMOS)-microelectromechanical system (MEMS) technique was presented. The sensor has a capability of detecting low concentration methanol gas. Structure of the sensor is composed of interdigitated electrodes, a sensitive film and a heater. The heater located under the interdigitated electrodes is utilized to provide a working temperature to the sensitive film. The sensitive film prepared by the sol-gel method is tin dioxide doped cadmium sulfide, which is deposited on the interdigitated electrodes. To obtain the suspended structure and deposit the sensitive film, the sensor needs a post-CMOS process to etch the sacrificial silicon dioxide layer and silicon substrate. The methanol senor is a resistive type. A readout circuit converts the resistance variation of the sensor into the output voltage. The experimental results show that the methanol sensor has a sensitivity of 0.18 V/ppm. PMID:26512671
Lithographically fabricated silicon microreactor for in situ characterization of heterogeneous catalysts—Enabling correlative characterization techniques
Baier, S.; Rochet, A.; Hofmann, G.; Kraut, M.; Grunwaldt, J.-D.
We report on a new modular setup on a silicon-based microreactor designed for correlative spectroscopic, scattering, and analytic on-line gas investigations for in situ studies of heterogeneous catalysts. The silicon microreactor allows a combination of synchrotron radiation based techniques (e.g., X-ray diffraction and X-ray absorption spectroscopy) as well as infrared thermography and Raman spectroscopy. Catalytic performance can be determined simultaneously by on-line product analysis using mass spectrometry. We present the design of the reactor, the experimental setup, and as a first example for an in situ study, the catalytic partial oxidation of methane showing the applicability of this reactor for in situ studies.
A sol-powder coating technique for fabrication of yttria stabilised zirconia
Wattanasiriwech, Darunee . E-mail: email@example.com; Wattanasiriwech, Suthee; Stevens, Ron
Yttria stabilised zirconia has been prepared using a simple sol-powder coating technique. The polymeric yttria sol, which was prepared using 1,3 propanediol as a network modifier, was homogeneously mixed with nanocrystalline zirconia powder and it showed a dual function: as a binder which promoted densification and a phase modifier which stabilised zirconia in the tetragonal and cubic phases. Thermal analysis and X-ray diffraction revealed that the polymeric yttria sol which decomposed at low temperature into yttrium oxide could change the m {sup {yields}} t phase transformation behaviour of the zirconia, possibly due to the small particle size and very high surface area of both yttria and zirconia particles allowing rapid alloying. The sintered samples exhibited three crystalline phases: monoclinic, tetragonal and cubic, in which cubic and tetragonal are the major phases. The weight fractions of the individual phases present in the selected specimens were determined using quantitative Rietveld analysis.
Advances in superconducting quantum electronic microcircuit fabrication
NASA Technical Reports Server (NTRS)
Kirschman, R. K.; Notarys, H. A.; Mercereau, J. E.
Standard microelectronic fabrication techniques have been utilized to produce batch quantities of superconducting quantum electronic devices and circuits. The overall goal is a fabrication technology yielding circuits that are rugged and stable and capable of being fabricated controllably and reproducibly in sizeable quantities. Our progress toward this goal is presented, with primary emphasis on the most recent work, which includes the use of electron-beam lithography and techniques of hybrid microelectronics. Several prototype microcircuits have been successfully fabricated. These microcircuits are formed in a thin-film parent material consisting of layers of superconducting and normal metals, and use proximity-effect structures as the active circuit elements.
Novel materials, fabrication techniques and algorithms for microwave and THz components, systems and applications
NASA Astrophysics Data System (ADS)
Liang, Min
This dissertation presents the investigation of several additive manufactured components in RF and THz frequency, as well as the applications of gradient index lens based direction of arrival (DOA) estimation system and broadband electronically beam scanning system. Also, a polymer matrix composite method to achieve artificially controlled effective dielectric properties for 3D printing material is studied. Moreover, the characterization of carbon based nano-materials at microwave and THz frequency, photoconductive antenna array based Terahertz time-domain spectroscopy (THz-TDS) near field imaging system, and a compressive sensing based microwave imaging system is discussed in this dissertation. First, the design, fabrication and characterization of several 3D printed components in microwave and THz frequency are presented. These components include 3D printed broadband Luneburg lens, 3D printed patch antenna, 3D printed multilayer microstrip line structure with vertical transition, THz all-dielectric EMXT waveguide to planar microstrip transition structure and 3D printed dielectric reflectarrays. Second, the additive manufactured 3D Luneburg Lens is employed for DOA estimation application. Using the special property of a Luneburg lens that every point on the surface of the Lens is the focal point of a plane wave incident from the opposite side, 36 detectors are mounted around the surface of the lens to estimate the direction of arrival (DOA) of a microwave signal. The direction finding results using a correlation algorithm show that the averaged error is smaller than 1º for all 360 degree incident angles. Third, a novel broadband electronic scanning system based on Luneburg lens phased array structure is reported. The radiation elements of the phased array are mounted around the surface of a Luneburg lens. By controlling the phase and amplitude of only a few adjacent elements, electronic beam scanning with various radiation patterns can be easily achieved
An electrochemical and structural study of highly uniform tin oxide nanowires fabricated by a novel, scalable solvoplasma technique as anode material for sodium ion batteries
NASA Astrophysics Data System (ADS)
Mukherjee, Santanu; Schuppert, Nicholas; Bates, Alex; Jasinski, Jacek; Hong, Jong-Eun; Choi, Moon Jong; Park, Sam
A novel solvoplasma based technique was used to fabricate highly uniform SnO2 nanowires (NWs) for application as an anode in sodium-ion batteries (SIBs). This technique is scalable, rapid, and utilizes a rigorous cleaning process to produce very pure SnO2 NWs with enhanced porosity; which improves sodium-ion hosting and reaction kinetics. The batch of NWs obtained from the plasma process were named the ;as-made; sample and after cleaning the ;pure; sample. Structural characterization showed that the as-made sample has a K+ ion impurity which is absent in the pure samples. The pure samples have a higher maximum specific capacity, 400.71 mAhg-1, and Coulombic efficiency, 85%, compared to the as-made samples which have a maximum specific capacity of 174.69 mAhg-1 and Coulombic efficiency of 74% upon cycling. A study of the electrochemical impedance spectra showed that the as-made samples have a higher interfacial and diffusion resistance than the pure samples and resistances increased after 50 cycles of cell operation for both samples due to progressive electrode degradation. Specific energy vs specific power plots were employed to analyze the performance of the system with respect to the working conditions.
A MEMS-based tunable coplanar patch antenna fabricated using PCB processing techniques
NASA Astrophysics Data System (ADS)
Maddela, M.; Ramadoss, R.; Lempkowski, R.
In this paper, a tunable coplanar rectangular patch antenna (CPA) designed using a MEMS varactor is reported. The MEMS varactor is monolithically integrated with the antenna on Duroid substrate using printed circuit processing techniques. Specifically, the MEMS varactor located at one of the radiating edges capacitively loads the CPA. The resonant frequency of the antenna is tuned electrostatically by applying a DC bias voltage between the MEMS varactor and the actuation pad on the antenna. The movable MEMS varactor membrane deflects downward toward the actuation pad due to an electrostatic force of attraction caused by the applied DC bias voltage. The deflection of the varactor membrane decreases the air gap, thereby increasing the loading capacitance. The increase in the loading capacitance results in a downward shift in the resonant frequency of the CPA. The CPA is center fed at the second radiating edge using a 50 Ω CPW feed line. The CPA operates in the frequency range from 5.185 to 5.545 GHz corresponding to the down and up states of the varactor. The tunable frequency range is about 360 MHz and the return loss is better than 40 dB in the entire tuning range. In this tuning range, the required DC voltage is in the range of 0-116 V.
Ultrasensitive Impedimetric Biosensor Fabricated by a New Immobilisation Technique for Parathyroid Hormone.
Özcan, Hakkı Mevlüt; Yildiz, Kübra; Çakar, Cansu; Aydin, Tuba; Asav, Engin; Sağiroğlu, Ayten; Sezgintürk, Mustafa Kemal
This paper presents a novel ultrasensitive and rapid impedimetric biosensor with new immobilisation materials for parathyroid hormone (PTH) with the aim to determine the PTH level in serum for the diagnosis and monitoring of parathyroid diseases such as hyperparathyroidism, adenoma, and thyroid cancer. The interaction between PTH and the biosensor was investigated with an electrochemical method. The biosensor was based on the gold electrode modified by mercaptohexanol (6-MHL). Anti-parathyroid hormone (anti-PTH) was covalently immobilised onto a self-assembled monolayer (SAM) by using epiclorhidrina (EPI) with ethanolamine (EA). The EPI-EA interaction represents the first use of these for the construction of biosensors in published reports. The immobilisation of the anti-PTH was monitored by electrochemical impedance spectroscopy, cyclic voltammetry and scanning electron microscopy (SEM) techniques. After the optimisation studies of immobilisation materials such as 6-MHL, EPI, EA and glutaraldehyde, linearity, repeatability and sensitivity of biosensor were evaluated as the performance of biosensor. PTH was detected within a linear range of 0.1-0.6 pg/ml, and the detection limit was 0.1 fg/ml. The specificity of the biosensor was also investigated. Finally, the described biosensor was used to detect the PTH levels in artificial serum samples.
Fabrication of a dual-planar-coil dynamic microphone by MEMS techniques
NASA Astrophysics Data System (ADS)
Horng, Ray-Hua; Chen, Kuo-Feng; Tsai, Yao-Cheng; Suen, Cheng-You; Chang, Chao-Chih
A dual-planar-coil miniature dynamic microphone, one of the electro-acoustic transducers working with the principle of the electromagnetic induction, has been realized by semiconductor micro-processing and micro-electro-mechanical system (MEMS) techniques. This MEMS microphone mainly consists of a 1 µm thick diaphragm sandwiched by two spiral coils and vibrating in the region with the highest magnetic flux density generated by a double magnetic system. In comparison with the traditional dynamic microphone, besides the miniaturized dimension, the MEMS microphone also provides 325 times the vibration velocity of the diaphragm faster than the traditional microphone. Measured by an audio analyzer, the frequency response of the MEMS microphone is only 4.5 dBV Pa-1 lower than that of the traditional microphone in the range between 50 Hz and 20 kHz. The responsivity of -54.8 dB Pa-1 (at 1 kHz) of the MEMS device is competitive to that of a traditional commercial dynamic microphone which typically ranges from -50 to -60 dBV Pa-1 (at 1 kHz).
Fabrication of hydroxyapatite thin films on zirconia using a sputtering technique.
Ozeki, K; Goto, T; Aoki, H; Masuzawa, T
Hydroxyapatite (HA) thin films were prepared on a zirconia (ZrO2) substrate using a sputtering technique, and the film was also coated on a titanium (Ti) substrate for comparison. The coated films were recrystallised using a hydrothermal treatment to reduce film dissolution. The films were then characterised by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The osteocompatiblity of the films was evaluated by investigating the alkaline phosphatase (ALP) activity and the size of the bone formation area of osteoblast cells. In the XRD patterns of the as-sputtered films on the ZrO2 substrate, there are no peaks except for those from the ZrO2 substrate. After the hydrothermal treatment, HA peaks appeared in the patterns. Nanoparticles (less than 20 nm) were observed on the ZrO2 substrates in the SEM images of the as-sputtered films. After the hydrothermal treatment, particles of 20-40 nm were observed on the film, whereas the HA film on the Ti substrate was covered by a larger number of globular particles (20-60 nm). In the osteoblast cell cultures, the ALP activity and bone formation area on the HA films on both the ZrO2 and Ti substrates increased after the hydrothermal treatment of the films, and the values for the ZrO2 substrate were higher than those for the Ti substrate.
A simple and low-cost technique to fabricate and experience interference birefringent filters
NASA Astrophysics Data System (ADS)
Velasquez, Pablo; Moreno, Ignacio S.; Sanchez-Lopez, M. d. M.; Puerto, D.
In this work we propose and demonstrate a very simple method to produce interference birefringent filters. We use the birefringence properties of usual commercial scotch, which acts as a uniaxial material. By superimposing several scotch layers with parallel orientation, and placing them between two crossed polarizers oriented at 45 degrees, we can measure the birefringence of the material. We use a portable fiber spectrophotometer to characterize the layers birefringence in the visible range. We developed a software to calculate the transmission properties of different types of birefringent filters, including folded and fan Solc filters. In the simulations we include the information of the material birefringence that we obtain experimentally, thus leading to a precise description of the transmission properties in the entire visible range. A very simple system permits to align the scotch layers with the proper angles and create a birefringent filter. We have designed several filters with different spectral properties. The measurement of the transmission obtained with the portable spectrophotometer confirms experimentally the prediction given by the simulation software.
Ultrasound-Induced Organogel Formation Followed by Thin Film Fabrication via Simple Doctor Blading Technique for Field-Effect Transistor Applications.
Xu, Jiaju; Wang, Yulong; Shan, Haiquan; Lin, Yiwei; Chen, Qian; Roy, V A L; Xu, Zongxiang
We demonstrate doctor blading technique to fabricate high performance transistors made up of printed small molecular materials. In this regard, we synthesize a new soluble phthalocyanine, tetra-n-butyl peripheral substituted copper(II) phthalocaynine (CuBuPc), that can easily undergo gel formation upon ultrasonic irradiation, leading to the formation of three-dimensional (3D) network composed of one-dimensional (1D) nanofibers structure. Finally, taking the advantage of thixotropic nature of the CuBuPc organogel, we use the doctor blade processing technique that limits the material wastage for the fabrication of transistor devices. Due to the ultrasound induced stronger π-π interaction, the transistor fabricated by doctor blading based on CuBuPc organogel exhibits significant increase in charge carrier mobility in comparison with other solution process techniques, thus paving a way for a simple and economically viable preparation of electronic circuits.
Fabrication of hydroxyapatite thin films on polyetheretherketone substrates using a sputtering technique.
Ozeki, K; Masuzawa, T; Aoki, H
Hydroxyapatite (HA) thin films were coated on a polyetheretherketone (PEEK) substrate using a sputtering technique. A thin titanium (Ti) intermediate layer was formed between the HA and the PEEK surface to improve adhesion of the HA film to the PEEK substrate. The coated films were recrystallized using a hydrothermal treatment to reduce the dissolution of the HA film. The films were then characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and a UV-Vis spectrophotometer. A pull-out test was performed to measure the film-to-substrate adhesion strength, and an immersion test was performed in ultra-pure water. In the XRD patterns of the sputtered film with the Ti intermediate layer on the PEEK substrate, small HA peaks and large Ti peaks were observed. After the hydrothermal treatment, the intensity of the HA peaks increased. The transmittance of the HA films with 5 and 10nm Ti intermediate layers was >79% and 68%, respectively, in the visible light wavelength region (400-700nm) after the hydrothermal treatment. The adhesion strength of the hydrothermally treated HA films increased with decreasing thickness of the Ti intermediate layer, and the strength reached 2.7MPa with the 5-nm-thick Ti intermediate layer. In the immersion test, the HA film with a 5-nm-thick Ti intermediate layer without hydrothermal treatment exhibited a released Ti concentration of 42.0±2.4ppb. After hydrothermal treatment, the released Ti concentration decreased to 17.3±1.1ppb.
New technique for fabrication of low loss high temperature stable high reflectivity FBG sensor arrays
NASA Astrophysics Data System (ADS)
Mihailov, Stephen J.; Grobnic, Dan; Walker, Robert B.; Hnatovsky, Cyril A.; Ding, Huimin; Coulas, David; Lu, Ping
Fiber Bragg gratings (FBG) arrays in silica based optical fibers are increasingly used in applications involving system monitoring in extreme high temperature environments. Where operational temperatures are < 600 °C, traditional UVlaser inscribed FBGs are not appropriate since the induced Type I index change is erased. Instead two competing FBG technologies exist: 1) regenerative FBGs resulting from high temperature annealing of a UV-laser written grating in a hydrogen loaded fiber and 2) FBGs written with femtosecond infrared pulse duration radiation (fs-IR), either using the point-by-point method or using the phase mask approach. Regenerative gratings possess low reflectivity and are cumbersome to produce, requiring high temperature processing in an oxygen free environment. Multiple pulse Type II femtosecond IR laser induced gratings made with a phase mask, while having very good thermal stability, also tend to have high insertion loss (~ 1dB/grating) limiting the number of gratings that can be concatenated in a sensor array. Recently it has been shown that during multiple pulse type II thermally stable fs-IR FBG production, two competing process occur: an initial induced fs-IR type I FBG followed by a thermally stable high insertion loss type II FBG. In this paper, we show that if only a type I FBG is written using type II intensity conditions but limited numbers of pulses and then annealed above 600 °C, the process results in a type II grating that is stable up to 1000 °C with very low insertion loss ideal for an FBG sensor array.
Emulsion-cryogelation technique for fabricating a versatile toolbox of hierarchical polymeric monolith and its application in chromatography.
Li, Yaping; Qi, Li; Li, Nan; Ma, Huimin
A novel poly (glycidyl methacrylate-co-ethylene dimethacrylate) monolith has been fabricated via the environmental friendly cryogelation-emulsion technique. The polymerization process is assisted by self-assembly of typical tri-block copolymer Pluronic F127 at sub-zero temperature using ice crystal as template, which can avoid consumption of organic porogenic solvents and thermal unstability of emulsion system. The developed monolith possesses hierarchical networks, which is confirmed by nitrogen adsorption measurement, mercury intrusion porosimetry, scanning electron microscopy and permeability testing. Further, the effect of the amounts of Pluronic F127 on the microstructure has been investigated. Moreover, the prepared polymer monolith undergoes acidic hydrolysis of epoxy groups into hydroxyl groups on the surface and its liquid chromatographic performance is explored by separating model analytes. The results indicate that the unique porous polymer monolith with hierarchical networks could be prepared via an organic porogen-free approach and used for analysis of polar and nonpolar molecules, extending the application of cryogelation-emulsion technique and methacrylate-based monolith.
Low-cost, high-throughput fabrication of cloth-based microfluidic devices using a photolithographical patterning technique.
Wu, Peijing; Zhang, Chunsun
In this work, we first report a facile, low-cost and high-throughput method for photolithographical fabrication of microfluidic cloth-based analytical devices (μCADs) by simply using a cotton cloth as a substrate material and employing an inexpensive hydrophobic photoresist laboratory-formulated from commercially available reagents, which allows patterning of reproducible hydrophilic-hydrophobic features in the cloth with well-defined and uniform boundaries. Firstly, we evaluated the wicking properties of cotton cloths by testing the wicking rate in the cloth channel, in combination with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses. It is demonstrated that the wicking properties of the cloth microfluidic channel can be improved by soaking the cloth substrate in 20 wt% NaOH solution and by washing the cloth-based microfluidic patterns with 3 wt% SDS solution. Next, we studied the minimum dimensions achievable for the width of the hydrophobic barriers and hydrophilic channels. The results indicate that the smallest width for a desired hydrophobic barrier is designed to be 100 μm and that for a desired hydrophilic channel is designed to be 500 μm. Finally, the high-throughput μCADs prepared using the developed fabrication technique were demonstrated for colorimetric assays of glucose and protein in artificial urine samples. It has been shown that the photolithographically patterned μCADs have potential for a simple, quantitative colorimetric urine test. The combination of cheap cloth and inexpensive high-throughput photolithography enables the development of new types of low-cost cloth-based microfluidic devices, such as "microzone plates" and "gate arrays", which provide new methods to perform biochemical assays or control fluid flow.
A comparison of 3D poly(ε-caprolactone) tissue engineering scaffolds produced with conventional and additive manufacturing techniques by means of quantitative analysis of SR μ-CT images
NASA Astrophysics Data System (ADS)
Brun, F.; Intranuovo, F.; Mohammadi, S.; Domingos, M.; Favia, P.; Tromba, G.
The technique used to produce a 3D tissue engineering (TE) scaffold is of fundamental importance in order to guarantee its proper morphological characteristics. An accurate assessment of the resulting structural properties is therefore crucial in order to evaluate the effectiveness of the produced scaffold. Synchrotron radiation (SR) computed microtomography (μ-CT) combined with further image analysis seems to be one of the most effective techniques to this aim. However, a quantitative assessment of the morphological parameters directly from the reconstructed images is a non trivial task. This study considers two different poly(ε-caprolactone) (PCL) scaffolds fabricated with a conventional technique (Solvent Casting Particulate Leaching, SCPL) and an additive manufacturing (AM) technique (BioCell Printing), respectively. With the first technique it is possible to produce scaffolds with random, non-regular, rounded pore geometry. The AM technique instead is able to produce scaffolds with square-shaped interconnected pores of regular dimension. Therefore, the final morphology of the AM scaffolds can be predicted and the resulting model can be used for the validation of the applied imaging and image analysis protocols. It is here reported a SR μ-CT image analysis approach that is able to effectively and accurately reveal the differences in the pore- and throat-size distributions as well as connectivity of both AM and SCPL scaffolds.
Ion and X-ray techniques used for study of laser-produced plasmas
NASA Astrophysics Data System (ADS)
Wolowski, J.; Parys, P.; Rosinski, M.; Ryć, L.; Woryna, E.
This review article describes apparatus for ion and X-ray diagnostics, which were used in experimental studies of laser-produced plasmas performed by the IPPLM's team in collaboration with other researchers at IPPLM and PALS Research Centre in Prague (the Czech Republic). The investigations of expanding laser-produced plasma properties in dependence on laser beam parameters were done by means of ion diagnostics devices: ion collectors (ICs), cylindrical ion energy analyzer (IEA) and the mass spectrograph of the Thomson type. At IPPLM, different types of detectors have been developed for measurement of X-ray emission. Properties of laser-produced beams of ions and X-ray radiation were analysed in the cooperative experiments performed with the use of a high-energy iodine laser PALS at the PALS Research Centre ASCR in the Czech Republic and the low-energy repetitive laser at IPPLM.
Fabrication of regular TiO2 nanoporous films derived by combining nanoimprint technique with sol-gel method.
Zhong, Peng; Que, Wenxiu; Zhang, Jin
In this paper, honeycomb-like regular TiO2 nanoporous films deposited on different substrates including ITO glass and silicon wafer are fabricated by combining a nanoimprint technique with a sol-gel method. A novel soft polymer mold containing a thin layer of polymethylmethacrylate and a thicker layer of polydimethylsiloxane, which is obtained from an anodic aluminum oxide template, is carried out for the nanoimprint process. TiO2 precursor solution prepared by the sol-gel processing is used as the nanoimprinted material. After imprinting, the polydimethylsiloxane back layer is easily peeled off before the polymethylmethacrylate mold is chemically removed to avoid any demolding problem. The SEM images show that the honeycomb-like regular nanostructure of the initial anodic aluminum oxide template can be preserved completely on TiO2 via this method, and the XRD results indicate that there is a crystalline transition from amorphous to anatase of TiO2 after 450 degrees C heat treatment.
Air cavity-based Fabry-Perot interferometer sensor fabricated using a sawing technique for refractive index measurement
NASA Astrophysics Data System (ADS)
Jung, Eun Joo; Lee, Woo-Jin; Kim, Myoung Jin; Hwang, Sung Hwan; Rho, Byung Sup
We have demonstrated a refractive index sensor based on a fiber optic Fabry-Perot (FP) interferometer with an open air cavity fabricated using a one-step mechanical sawing technique. The sensor head consists of a short FP cavity near the fiber patch cord tip, which was assembled by joining a ceramic ferrule and a single-mode fiber together. Owing to the open air cavity in the sensor head, various liquid samples with different refractive index can fill in-line air cavity, which makes the device usable as a refractometer. Moreover, due to the sensor head encircled with the robust ceramic ferrule, the device is attractive for sensing measurement in harsh environments. The sensor was tested in different refractive index solutions. The experimental result shows that the attenuation peak wavelength of the sensor is shifted toward a shorter wavelength with increasing refractive index, and the refractive index sensitivity is ˜92.5 nm/refractive index unit (RIU) and 73.75 dB/RIU. The proposed sensor can be used as an in-line refractometer for many potential applications in the sensing field.
Fabrication of an inexpensive and high efficiency microphotoreactor using CO2 laser technique for photocatalytic water treatment applications.
Eskandarloo, Hamed; Badiei, Alireza
In this study, a micro-photoreactor with catalyst-immobilized micro-channels was designed and fabricated using CO2 laser as a simple and inexpensive technique. The micro-photoreactor is composed of an array of micro-channels, a quartz plate, and an array of UV-LEDs. The micro-channels with the dimension of 400 µm width, 50 µm depth, and 80 cm length were inscribed on a flat plate of poly(methyl methacrylate) (PMMA). The illuminated specific surface area for the designed micro-reactor was calculated to be 25000 m(-1). To examine the performance of miniaturized photoreactor, the photocatalytic degradation of 4-Nitrophenol as a refractory pollutant was investigated. The effects of operational variables on the performance of micro-photoreactor were studied. Higher photocatalytic degradation is obtained for low flow rates, high light intensities, long micro-channels lengths, and low inlet concentrations. Also, the performance of micro-photoreactor was examined in the presence of different types of TiO2 catalysts with an average particle size between 5 and 27 nm (such as P25, PC500, Merck, and UV100) and textile dyes with different chemical structures (such as Acid Orange 7, Acid Violet 19, Basic Red 46, Methyl Orange, and Malachite Green). Finally, the reusability of miniaturized photoreactor was evaluated and the results showed satisfactory stability and reusability for the designed micro-reactor in the photocatalytic degradation of organic pollutants.
Femtosecond laser fabricated multimode fiber sensors interrogated by optical-carrier-based microwave interferometry technique for distributed strain sensing
NASA Astrophysics Data System (ADS)
Hua, Liwei; Song, Yang; Huang, Jie; Cheng, Baokai; Zhu, Wenge; Xiao, Hai
A multimode fiber (MMF) based cascaded intrinsic Fabry-Perot interferometers (IFPIs) system is presented and the distributed strain sensing has been experimentally demonstrated by using such system. The proposed 13 cascaded IFPIs have been formed by 14 cascaded reflectors that have been fabricated on a grade index MMF. Each reflector has been made by drawing a line on the center of the cross-section of the MMF through a femtosecond laser. The distance between any two adjacent reflectors is around 100 cm. The optical carrier based microwave interferometry (OCMI) technique has been used to interrogate the MMF based cascaded FPIs system by reading the optical interference information in the microwave domain. The location along with the shift of the interference fringe pattern for each FPI can be resolved though signal processing based on the microwave domain information. The multimode interference showed very little influence to the microwave domain signals. By using such system the strain of 10-4 for each FPI sensor and the spatial resolution of less than 5 cm for the system can be easily achieved.
Highly conducting and crystalline doubly doped tin oxide films fabricated using a low-cost and simplified spray technique
NASA Astrophysics Data System (ADS)
Ravichandran, K.; Muruganantham, G.; Sakthivel, B.
Doubly doped (simultaneous doping of antimony and fluorine) tin oxide films (SnO 2:Sb:F) have been fabricated by employing an inexpensive and simplified spray technique using perfume atomizer from aqueous solution of SnCl 2 precursor. The structural studies revealed that the films are highly crystalline in nature with preferential orientation along the (2 0 0) plane. It is found that the size of the crystallites of the doubly doped tin oxide films is larger (69 nm) than that (27 nm) of their undoped counterparts. The dislocation density of the doubly doped film is lesser (2.08×10 14 lines/m 2) when compared with that of the undoped film (13.2×10 14 lines/m 2), indicating the higher degree of crystallinity of the doubly doped films. The SEM images depict that the films are homogeneous and uniform. The optical transmittance in the visible range and the optical band gap of the doubly doped films are 71% and 3.56 eV respectively. The sheet resistance (4.13 Ω/□) attained for the doubly doped film in this study is lower than the values reported for spray deposited fluorine or antimony doped tin oxide films prepared from aqueous solution of SnCl 2 precursor (without using methanol or ethanol).
Effect of titanium addition on the thermal properties of diamond/cu-ti composites fabricated by pressureless liquid-phase sintering technique.
Chung, Chih-Yu; Chu, Chao-Hung; Lee, Mu-Tse; Lin, Chun-Ming; Lin, Su-Jien
In this study, minor-addition elements such as Si, Co, Cr, W, Mo, and Ti were added to matrix to improve the wettability between the diamonds and Cu matrix. The pressureless liquid-phase sintering technique adopted in this study provides a low-cost method for producing diamond/Cu composites with high potential for industrial mass production. Thermal properties of the diamond/Cu-Ti composites fabricated by pressureless liquid-phase sintering at 1373 K with variation in Ti contents were thoroughly investigated. XRD and TEM analysis show that TiC layer formed in the interface between Cu and diamond. The composites exhibited thermal conductivity as high as 620 W/m · K for 50 vol% diamond/Cu-0.6 at % Ti composite with diamond particle size of 300 µm. This value comes up to 85% of the thermal conductivity calculated by the Hasselman and Johnson (H-J) theoretical analysis. Under these conditions, a suitable coefficient of thermal expansion of 6.9 ppm/K was obtained.
Effect of Titanium Addition on the Thermal Properties of Diamond/Cu-Ti Composites Fabricated by Pressureless Liquid-Phase Sintering Technique
Chung, Chih-Yu; Chu, Chao-Hung; Lee, Mu-Tse; Lin, Chun-Ming; Lin, Su-Jien
In this study, minor-addition elements such as Si, Co, Cr, W, Mo, and Ti were added to matrix to improve the wettability between the diamonds and Cu matrix. The pressureless liquid-phase sintering technique adopted in this study provides a low-cost method for producing diamond/Cu composites with high potential for industrial mass production. Thermal properties of the diamond/Cu-Ti composites fabricated by pressureless liquid-phase sintering at 1373 K with variation in Ti contents were thoroughly investigated. XRD and TEM analysis show that TiC layer formed in the interface between Cu and diamond. The composites exhibited thermal conductivity as high as 620 W/m·K for 50 vol% diamond/Cu-0.6 at % Ti composite with diamond particle size of 300 µm. This value comes up to 85% of the thermal conductivity calculated by the Hasselman and Johnson (H-J) theoretical analysis. Under these conditions, a suitable coefficient of thermal expansion of 6.9 ppm/K was obtained. PMID:24715816
HA/nylon 6,6 porous scaffolds fabricated by salt-leaching/solvent casting technique: effect of nano-sized filler content on scaffold properties.
Mehrabanian, Mehran; Nasr-Esfahani, Mojtaba
Nanohydroxyapatite (n-HA)/nylon 6,6 composite scaffolds were produced by means of the salt-leaching/solvent casting technique. NaCl with a distinct range size was used with the aim of optimizing the pore network. Composite powders with different n-HA contents (40%, 60%) for scaffold fabrication were synthesized and tested. The composite scaffolds thus obtained were characterized for their microstructure, mechanical stability and strength, and bioactivity. The microstructure of the composite scaffolds possessed a well-developed interconnected porosity with approximate optimal pore size ranging from 200 to 500 μm, ideal for bone regeneration and vascularization. The mechanical properties of the composite scaffolds were evaluated by compressive strength and modulus tests, and the results confirmed their similarity to cortical bone. To characterize bioactivity, the composite scaffolds were immersed in simulated body fluid for different lengths of time and results monitored by scanning electron microscopy and energy dispersive X-ray microanalysis to determine formation of an apatite layer on the scaffold surface.
Design, Fabrication, and Operation of Innovative Microalgae Culture Experiments for the Purpose of Producing Fuels: Final Report, Phase I
Not Available
A conceptual design was developed for a 1000-acre (water surface) algae culture facility for the production of fuels. The system is modeled after the shallow raceway system with mixing foils that is now being operated at the University of Hawaii. A computer economic model was created to calculate the discounted breakeven price of algae or fuels produced by the culture facility. A sensitivity analysis was done to estimate the impact of changes in important biological, engineering, and financial parameters on product price.
Electro-Optical Sensor Fabricated Using a Bulk Cleavage Technique and Its Characteristics for Near-Field Intra-Body Communication
NASA Astrophysics Data System (ADS)
Furuya, Akinori; Sasaki, Ai-ichiro; Morimura, Hiroki; Aihara, Kimihisa; Shinagawa, Mitsuru
This paper describes how to obtain a low cost electro-optical (EO) sensor module for the mass production of near-field intra-body communication devices. In this study, we used a bulk cleavage technique to fabricate EO modulators without the need for any optical polishing or washing processes, and clarified the feasibility of assembling optical components using only a passive alignment technique with a compact housing.
Fabrication of a LiNbO3 optical waveguide lens by titanium-indiffused proton-exchanged technique
NASA Astrophysics Data System (ADS)
Chung, Suk M.; Kim, Jae-Chang; Yoon, Tae-Hoon
In this paper we report the fabrication of a planar optical waveguide lens on a Y-cut LiNbO3 substrate by Ti-indiffusion and Ti-indiffused proton-exchange (TIPE). LiNbO3 planar waveguides are fabricated and refractive indices of the waveguides are measured. Based on the measured indices, planar waveguide lenses are designed and fabricated. The measured focal point and spot size of the fabricated lens are in good agreement with those of the designed lens.
Marginal accuracy of nickel chromium copings fabricated by conventional and accelerated casting procedures, produced with ringless and metal ring investment procedures: A comparative in vitro study
Alex, Deepa; Shetty, Y. Bharath; Miranda, Glynis Anita; Prabhu, M. Bharath; Karkera, Reshma
Background: Conventional investing and casting techniques are time-consuming and usually requires 2–4 h for completion. Accelerated nonstandard, casting techniques have been reported to achieve similar quality results in significantly less time, namely, in 30–40 min. During casting, it is essential to achieve compensation for the shrinkage of solidifying alloy by investment expansion. The metal casting ring restricts the thermal expansion of investment because the thermal expansion of the ring is lesser than that of the investment. The use of casting ring was challenged with the introduction of the ringless technique. Materials and Methods: A total of 40 test samples of nickel chromium (Ni-Cr) cast copings were obtained from the patterns fabricated using inlay casting wax. The 20 wax patterns were invested using metal ring and 20 wax patterns were invested using the ringless investment system. Of both the groups, 10 samples underwent conventional casting, and the other 10 underwent accelerated casting. The patterns were casted using the induction casting technique. All the test samples of cast copings were evaluated for vertical marginal gaps at four points on the die employing a stereo optical microscope. Results: The vertical marginal discrepancy data obtained were tabulated. Mean and standard deviations were obtained. Vertical discrepancies were analyzed using analysis of variance and Tukey honestly significantly different. The data obtained were found to be very highly significant (P < 0.001). Mean vertical gap was the maximum for Group II (53.64 μm) followed by Group IV (47.62 μm), Group I (44.83 μm) and Group III (35.35 μm). Conclusion: The Ni-Cr cast copings fabricated with the conventional casting using ringless investment system showed significantly better marginal fit than that of cast copings fabricated from conventional and accelerated casting with metal ring investment and accelerated casting using ringless investment since those copings had
Multi-MeV laser-produced particle sources: Characterization by activation techniques
NASA Astrophysics Data System (ADS)
Gerbaux, M.; Aléonard, M. M.; Claverie, G.; Gobet, F.; Hannachi, F.; Malka, G.; Scheurer, J. N.; Tarisien, M.; Méot, V.; Morel, P.; Faure, J.; Glinec, Y.; Guemnie-Tafo, A.; Malka, V.; Manclossi, M.; Santos, J.
We present here results obtained in an experiment carried out using the CPA beam of the "Salle Jaune" laser system at Laboratoire d'Optique Appliquée (LOA). The generation of high energy electrons and protons escaping from the plasma has been investigated in the interaction of a 2 J, 30 fs laser with CH or metallic foils. The energy and angular distributions of the supra-thermal electrons produced with different targets are characterized by using both an electron spectrometer and bremsstrahlung induced (γ ,n) reactions. We measured simultaneously the number of energetic protons produced using (p,n) reactions. A correlation between the electrons and the protons production is observed together with a dependence of the number of supra-thermal electrons on the atomic number of the target element.
Structural properties of ZnO:Al films produced by the sol–gel technique
Zaretskaya, E. P. Gremenok, V. F.; Semchenko, A. V.; Sidsky, V. V.; Juskenas, R. L.
ZnO:Al films are produced by sol–gel deposition at temperatures of 350–550°C, using different types of reagents. Atomic-force microscopy, X-ray diffraction analysis, Raman spectroscopy, and optical transmittance measurements are used to study the dependence of the structural, morphological, and optical properties of the ZnO:Al coatings on the conditions of deposition. The optical conditions for the production of ZnO:Al layers with preferred orientation in the [001] direction and distinguished by small surface roughness are established. The layers produced in the study possess optical transmittance at a level of up to 95% in a wide spectral range and can be used in optoelectronic devices.
Physical-Chemical Characterization of Nanodispersed Powders Produced by a Plasma-Chemical Technique
NASA Astrophysics Data System (ADS)
Georgieva, M.; Vissokov, Grancharov G., IV
This article presents a review on the physical-chemical properties and characteristics of plasma-chemically produced nanodispersed powders (NDP), such as metals, oxides, nitrides, carbides, and catalysts. The plasma-chemical preparation of the powders was carried out in thermal plasma (TP) created by means of high-current electric arcs, plasma jets, high-frequency (HF) discharges, etc. We also discuss certain properties and characteristics of the NDPs, which are determined largely by the conditions of preparation.
Characterization of composites fabricated from discontinuous random carbon fiber thermoplastic matrix sheets produced by a paper making process
NASA Astrophysics Data System (ADS)
Ducote, Martin Paul, Jr.
In this thesis, a papermaking process was used to create two randomly oriented, high performance composite material systems. The primary objective of this was to discover the flexural properties of both composite systems and compare those to reported results from other studies. In addition, the process was evaluated for producing quality, randomly oriented composite panels. Thermoplastic polymers have the toughness and necessary strength to be alternatives to thermosets, but with the promise of lower cycle times and increased recyclability. The wet-lay papermaking process used in this study produces a quality, randomly oriented thermoplastic composite at low cycle times and simple production. The materials chosen represent high performance thermoplastics and carbon fibers. Short chopped carbon fiber filled Nylon 6,6 and PEEK composites were created at varying fiber volume fractions. Ten nylon based panels and five PEEK based panels were subjected to 4-point flexural testing. In several of the nylon-based panels, flexural testing was done in multiple direction to verify the in-plane isotropy of the final composite. The flexural strength performance of both systems showed promise when compared to equivalent products currently available. The flexural modulus results were less than expected and further research should be done into possibly causes. Overall, this research gives good insight into two high performance engineering composites and should aid in continued work.
Overview of results from PVRC programs on half-bead/temper-bead/controlled deposition techniques for improvement of fabrication and service performance of Cr-Mo steels
Lundin, C.D.
The PVRC, Materials and Fabrication Division, Committee on Welds has sponsored several programs on the optimization of welding procedures and techniques to be used for the fabrication and repair of Cr-Mo and low-alloy steels. Recently, a dedicated 3-year effort on the understanding of the effects of various controlled deposition techniques on the HAZ properties of welds in low-alloy pressure vessel steels was accomplished. The understanding of these techniques, which can favorably affect the ease of fabrication and enhance service performance by prolonging trouble-free pressure vessel life, is considered essential for extending the normally anticipated life of vessels and associated components. The recent PVRC Committee on Welds program was conducted concurrently with the National Board of Pressure Vessel Inspectors considerations on rule modifications for repair of pressure vessels, and the information generated was readily available to NBIC for consideration. Furthermore, the successful culmination of the repair weld testing efforts led to additional work on improving the utility of low carbon 1{1/4}Cr-{1/2}Mo weld metal by introduction of elements designed to improve elevated temperature properties without impairing weldability (fabrication) potential. This program is currently being conducted at The University of Tennessee (UT). It is discussed in this paper.
Comparison of manually produced and automated cross country movement maps using digital image processing techniques
NASA Technical Reports Server (NTRS)
Wynn, L. K.
The Image-Based Information System (IBIS) was used to automate the cross country movement (CCM) mapping model developed by the Defense Mapping Agency (DMA). Existing terrain factor overlays and a CCM map, produced by DMA for the Fort Lewis, Washington area, were digitized and reformatted into geometrically registered images. Terrain factor data from Slope, Soils, and Vegetation overlays were entered into IBIS, and were then combined utilizing IBIS-programmed equations to implement the DMA CCM model. The resulting IBIS-generated CCM map was then compared with the digitized manually produced map to test similarity. The numbers of pixels comprising each CCM region were compared between the two map images, and percent agreement between each two regional counts was computed. The mean percent agreement equalled 86.21%, with an areally weighted standard deviation of 11.11%. Calculation of Pearson's correlation coefficient yielded +9.997. In some cases, the IBIS-calculated map code differed from the DMA codes: analysis revealed that IBIS had calculated the codes correctly. These highly positive results demonstrate the power and accuracy of IBIS in automating models which synthesize a variety of thematic geographic data.
Fluorescence technique for on-line monitoring of state of hydrogen-producing microorganisms
Seibert, Michael; Makarova, Valeriya; Tsygankov, Anatoly A.; Rubin, Andrew B.
In situ fluorescence method to monitor state of sulfur-deprived algal culture's ability to produce H.sub.2 under sulfur depletion, comprising: a) providing sulfur-deprived algal culture; b) illuminating culture; c) measuring onset of H.sub.2 percentage in produced gas phase at multiple times to ascertain point immediately after anerobiosis to obtain H.sub.2 data as function of time; and d) determining any abrupt change in three in situ fluorescence parameters; i) increase in F.sub.t (steady-state level of chlorophyll fluorescence in light adapted cells); ii) decrease in F.sub.m', (maximal saturating light induced fluorescence level in light adapted cells); and iii) decrease in .DELTA.F/F.sub.m'=(F.sub.m'-F.sub.t)/F.sub.m' (calculated photochemical activity of photosystem II (PSII) signaling full reduction of plastoquinone pool between PSII and PSI, which indicates start of anaerobic conditions that induces synthesis of hydrogenase enzyme for subsequent H.sub.2 production that signal oxidation of plastoquinone pool asmain factor to regulate H.sub.2 under sulfur depletion.
Treatment of real wastewater produced from Mobil car wash station using electrocoagulation technique.
El-Ashtoukhy, E-S Z; Amin, N K; Fouad, Y O
This paper deals with the electrocoagulation of real wastewater produced from a car wash station using a new cell design featuring a horizontal spiral anode placed above a horizontal disc cathode. The study dealt with the chemical oxygen demand (COD) reduction and turbidity removal using electrodes in a batch mode. Various operating parameters such as current density, initial pH, NaCl concentration, temperature, and electrode material were examined to optimize the performance of the process. Also, characterization of sludge formed during electrocoagulation was carried out. The results indicated that the COD reduction and turbidity removal increase with increasing the current density and NaCl concentration; pH from 7 to 8 was found to be optimum for treating the wastewater. Temperature was found to have an insignificant effect on the process. Aluminum was superior to iron as a sacrificial electrode material in treating car wash wastewater. Energy consumption based on COD reduction ranged from 2.32 to 15.1 kWh/kg COD removed depending on the operating conditions. Finally, the sludge produced during electrocoagulation using aluminum electrodes was characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analysis.
Homogeneous metal matrix composites produced by a modified stir-casting technique
Kennedy, A.R.; McCartney, D.G.; Wood, J.V.
Al-based metal matrix composites have been made by a novel liquid processing route which is not only cheap and versatile but produces composites with extremely uniform distributions of the reinforcing phase. Particles of TiB{sub 2}, TiC and B{sub 4}C have been spontaneously incorporated, that is without the use of external mechanical agitation, into Al and Al-alloy melts in volume fractions as high as 0.3. This has been achieved through the use of wetting agents which produce K-Al-F based slags on the melt surface. Spontaneous particle entry and the chemistry of the slag facilitate the generation of good distributions of the reinforcing phase in the solidified composite castings. Non-clustered, near homogeneous distributions have been achieved irrespective of the casting conditions and the volume fraction, type or size of the reinforcement. The majority of the reinforcement becomes engulfed into the solid metal grains during solidification rather than, what is more commonly the case, being pushed to the inter-granular regions. This intra-granular distribution of the reinforcement is likely to improve the mechanical properties of the material.
A combined powder melt and infiltration growth technique for fabricating nano-composited Y-Ba-Cu-O single-grain superconductor
NASA Astrophysics Data System (ADS)
Li, Guo-Zheng; Li, Jia-Wei; Yang, Wan-Min
The top-seeded melt growth (MG) and infiltration growth (IG) techniques are the two most popular methods of fabricating single-grain Y-Ba-Cu-O (YBCO) bulk superconductors, which are also considered as two distinctly different processes. In this study, we report a combined powder melt and infiltration growth (PM-IG) technique for fabricating nano-composited YBCO single-grain superconductors using raw metallic oxides. In this new technique, a solid source pellet (SSP) of composition nano-Y2O3 + BaO + CuO + 1 wt.%CeO2 and a liquid source pellet (LSP) of composition nano-Y2O3 + 10BaO + 16CuO are employed, thus during heat treatment process the powder melt in SSP (corresponding to the final YBCO bulk) and liquid infiltration from LSP to SSP coexist. Because the process of precursor powder synthesis is avoided, the fabrication flow is much simplified and the experimental efficiency is increased significantly. Microstructural observation indicates that a large number of Y2BaCuO5 nano-inclusions (around 100 nm) are trapped in the YBa2Cu3O7-δ superconducting matrix. Measurements of levitation force and trapped field prove the superior performance of the nano-composited YBCO sample. The calculated zero-field J c at 77 K reaches 6.98 × 104 A cm-2, nearly 23% higher than the sample fabricated by the conventional IG technique. Thus, this study supplies a practical method for fabricating nano-composited YBCO bulk superconductors with high performance.
Task force: a management technique that produces quality decisions and employee commitment.
Moore, C H; Kovach, K M
A task force is a technique that can be used by the dietitian-manager to develop solutions for specific, identified problems. Because employees are directly involved in the decision-making process, better solutions--ones that are also more acceptable to the work group--result. To implement a task force, management must plan the strategy: Select a facilitator, explain the concept and problem to the work group, select task force participants, and make meeting arrangements. The task force meetings should be structured to maximize efficiency and productivity. The plan of action is developed by the task force members; all decisions are based upon input from the work group. Successful implementation of the solutions is the responsibility of the task force. Applications for task forces in both the clinical and food management areas are numerous and result in both tangible and intangible benefits.
SEM studies on BSCCO superconducting ceramic produced by spray frozen, freeze drying technique
NASA Astrophysics Data System (ADS)
Bunescu, M.-C.; Aldica, G.; Badica, P.; Vasiliu, F.; Nita, P.; Mandache, S.
Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) have been used to evidence the occurrence, morphology and microcomposition of the superconducting phases (Bi,Pb) 2Sr 2Ca 2Cu 3O 10 + δ (2223) and (Bi,Pb) 2Sr 2CaCu 2O 8 + δ (2212), and of other non-superconducting phases, in the sintered pellets obtained from nitrate solution by spray frozen, freeze drying technique. For decomposition of the nitrate powder four different heat treatments were used. Superconducting and structure properties of the pellets have been tested by AC susceptibility measurments (610 Hz, 0.5 Oe) and X-ray diffraction analysis, respectively. A correlation between the SEM and EDS observations and the superconducting properties has been established.
Investigation of Ni-Cr-Si-Fe-B coatings produced by the electron beam cladding technique
NASA Astrophysics Data System (ADS)
Zimogliadova, T. A.; Drobyaz, E. A.; Golkovskii, M. G.; Bataev, V. A.; Durakov, V. G.; Cherkasova, N. Yu
This paper presents the results of structural investigations and results of tribological and microhardness tests of the coating obtained by electron beam cladding of a Ni-Cr-Si-Fe-B self-fluxing alloy on low-carbon steel. After electron beam treatment high-quality dense layer with a thickness of 1.2-1.8 mm was obtained. The structure of the coating consisted of dendrite crystals based on y-Ni-solid solution and eutectic with complex composition. Microhardness of the coating achieves 370 HV. Wear-resistance of the coating obtained by electron-beam cladding technique was 1.6-fold higher than that of low-carbon carburized steel.
Fabrication and Characterization of Functionally Graded Al/SiCp Composites Produced by Remelting and Sedimentation Process
NASA Astrophysics Data System (ADS)
Pourmajidian, Maedeh; Akhlaghi, Farshad
A new process termed here as remelting and sedimentation (RAS) was developed to produce functionally graded Al/SiC composites with a smooth concentration gradient of SiC particles along the height of samples, as opposed to a step change. For this purpose, first settling velocities of different-sized SiC particles in aluminum A356 melt were measured, and the results exhibited a reasonably good agreement with those predicted via the modified Stokes law. Then slices of particulate Al/SiC composites with different SiC contents of 5, 10, 15, and 20 vol.% were stacked in a cast iron mold and heated at 650 °C resulting in remelting and unification of the different composite parts. Considering the preliminary settling experiments, the composite slurry was held at this temperature for three different times to investigate the optimum holding time for obtaining a smooth gradient of SiC concentration along the height of the sample. After quenching, the samples were sectioned and subjected to metallographic studies and hardness measurements. The results confirmed that holding the melt for 60 s provides sufficient settling and redistribution of SiC particles and results in successful production of a functionally graded material.
Spectral fluorescence signature techniques and absorption measurements for continuous monitoring of biofuel-producing microalgae cultures
NASA Astrophysics Data System (ADS)
Martín de la Cruz, M. C.; Gonzalez Vilas, L.; Yarovenko, N.; Spyrakos, E.; Torres Palenzuela, J. M.
Biofuel production from microalgae can be both sustainable and economically viable. Particularly in the case of algal growth in wastewater an extra benefit is the removal or biotransformation of pollutants from these types of waters. A continuous monitoring system of the microalgae status and the concentration of different wastewater contaminants could be of great help in the biomass production and the water characterisation. In this study we present a system where spectral fluorescence signature (SFS) techniques are used along with absorption measurements to monitor microalgae cultures in wastewater and other mediums. This system aims to optimise the microalgae production for biofuel applications or other uses and was developed and tested in prototype indoor photo-bioreactors at the University of Vigo. SFS techniques were applied using the fluorescence analyser INSTAND-SCREENER developed by Laser Diagnostic Instruments AS. INSTAND-SCREENER permits wavelength scanning in two modes, one in UV and another in VIS. In parallel, it permits the on-line monitoring and rapid analysis of both water quality and phytoplankton status without prior treatment of the sample. Considering that different contaminants and microalgae features (density, status etc.) have different spectral signatures of fluorescence and absorption properties, it is possible to characterise them developing classification libraries. Several algorithms were used for the classification. The implementation of this system in an outdoor raceway reactor in a Spanish wastewater treatment plant is also discussed. This study was part of the Project EnerBioAlgae (http://www.enerbioalgae.com/), which was funded by the Interreg SUDOE and led by the University of Vigo.
Microbiological techniques for paraffin reduction in producing oil wells: Final report
Oppenheimer, C.H.; Hiebert, F.K.
Alpha Environmental has completed an eighteen month field oriented, cooperative research program with the US Department of Energy to demonstrate a new economically viable process using petroleum degrading microorganisms, a biocatalyst, formation water and inorganic nutrients to recover residual oil from reservoirs. Alpha's mixed community of microorganisms decomposes crude oil to produce detergents, CO/sub 2/, and new cells, thus mechanically and chemically releasing oil from reservoir pores. The naturally-occurring bacteria utilized in this project were previously selected by screening and isolating microorganisms from soils contaminated with crude oil and petroleum products. The activity and level of salt tolerance (to 20% salinity) of the bacteria is enhanced by a biocatalyst, previously developed by Alpha Environmental. Field evidence suggests that the biocatalyst provides catalytic oxygen to the microorganisms in the reservoir, which augments low levels of in-situ molecular oxygen. 25 refs., 10 figs., 6 tabs.
Techniques used to identify tornado producing thunderstorms using geosynchronous satellite data
NASA Technical Reports Server (NTRS)
Schrab, Kevin J.; Anderson, Charles E.; Monahan, John F.
Satellite imagery in the outbreak region in the time prior to and during tornado occurrence was examined in detail to obtain descriptive characteristics of the anvil plume. These characteristics include outflow strength (UMAX), departure of anvil centerline from the storm relative ambient wind (MDA), storm relative ambient wind (SRAW), and maximum surface vorticity (SFCVOR). It is shown that by using satellite derived parameters which characterize the flow field in the anvil region, the occurrence and intensity of tornadoes, which the parent thunderstorm produces, can be identified. Analysis of the censored regression models revealed that the five explanatory variables (UMAX, MDA, SRAW, UMAX-2, and SFCVOR) were all significant predictors in the identification of tornadic intensity of a particular thunderstorm.
Design of Solid Form Xenon-124 Target for Producing I-123 Radioisotope Using Computer Simulation Techniques
Kamali Moghaddam, K.; Sadeghi, M.; Kakavand, T.; Shokri Bonab, S.
Recently in Cyclotron and Nuclear Medicine Department of NRCAM, at Atomic Energy organization of Iran (AEOI), a system for producing 1-123 via Xe-124 gas target technology, has been constructed and installed. One of the major problems in this system is the highly expensive cost of the enriched Xenon-124 gas. Therefore, saving this gas inside the system is very important. Unfortunately, by accidental rupture of the window foil or bad function of O-rings, the whole Xenon gas will escape from the system immediately. In this paper, by using computer codes; ALICE91, SRIM and doing some calculations we are going to demonstrate our latest effort for feasibility study of producing I-123 with the above mentioned reactions, but using Xe-124 solid target instead. According to our suggested design, a conical shaped irradiation vessel made of copper with 1 mm thickness, 1 cm outlet diameter, 5 cm length and 12 deg. angle at summit can be fixed inside a liquid nitrogen housing chamber. The Xenon-124 gas will be sent to the inside of this very cold conical trap and eventually deposited on its surface in solid form. Our calculation shows that during bombardment with 17-28 MeV proton energy, the thickness of solidified Xenon layer will remain around .28 mm. Likewise; thermo-dynamical calculation shows that in order to prevent the evaporation of solidified Xenon, the maximum permissible proton beam current for this system should be less than 1.4 {mu}A. According to these working conditions, the production yield of I-123 can be predicted to be around 150 mCi/{mu}Ah. (authors)
Developing Techniques for the Utilization of Planctomycetes As Producers of Bioactive Molecules
Jeske, Olga; Surup, Frank; Ketteniß, Marcel; Rast, Patrick; Förster, Birthe; Jogler, Mareike; Wink, Joachim; Jogler, Christian
Planctomycetes are conspicuous, ubiquitous, environmentally important bacteria. They can attach to various surfaces in aquatic habitats and form biofilms. Their unique FtsZ-independent budding cell division mechanism is associated with slow growth and doubling times from 6 h up to 1 month. Despite this putative disadvantage in the struggle to colonize surfaces, Planctomycetes are frequently associated with aquatic phototrophic organisms such as diatoms, cyanobacteria or kelp, whereby Planctomycetes can account for up to 50% of the biofilm-forming bacterial population. Consequently, Planctomycetes were postulated to play an important role in carbon utilization, for example as scavengers after phototrophic blooms. However, given their observed slow growth, such findings are surprising since other faster- growing heterotrophs tend to colonize similar ecological niches. Accordingly, Planctomycetes were suspected to produce antibiotics for habitat protection in response to the attachment on phototrophs. Recently, we demonstrated their genomic potential to produce non-ribosomal peptides, polyketides, bacteriocins, and terpenoids that might have antibiotic activities. In this study, we describe the development of a pipeline that consists of tools and procedures to cultivate Planctomycetes for the production of antimicrobial compounds in a chemically defined medium and a procedure to chemically mimic their interaction with other organisms such as for example cyanobacteria. We evaluated and adjusted screening assays to enable the hunt for planctomycetal antibiotics. As proof of principle, we demonstrate antimicrobial activities of planctomycetal extracts from Planctopirus limnophila DSM 3776, Rhodopirellula baltica DSM 10527, and the recently isolated strain Pan216. By combining UV/Vis and high resolution mass spectrometry data from high-performance liquid chromatography fractionations with growth inhibition of indicator strains, we were able to assign the antibiotic
Metal halogen battery construction with improved technique for producing halogen hydrate
Fong, Walter L.; Catherino, Henry A.; Kotch, Richard J.
An improved electrical energy storage system comprising, at least one cell having a positive electrode and a negative electrode separated by aqueous electrolyte, a store means wherein halogen hydrate is formed and stored as part of an aqueous material having a liquid level near the upper part of the store, means for circulating electrolyte through the cell, conduit means for transmitting halogen gas formed in the cell to a hydrate forming apparatus associated with the store, said hydrate forming apparatus including, a pump to which there is introduced quantities of the halogen gas and chilled water, said pump being located in the store and an outlet conduit leading from the pump and being substantially straight and generally vertically disposed and having an exit discharge into the gas space above the liquid level in the store, and wherein said hydrate forming apparatus is highly efficient and very resistant to plugging or jamming. The disclosure also relates to an improved method for producing chlorine hydrate in zinc chlorine batteries.
Fabrication of microlens arrays on soda-lime glass using a laser direct-write technique and a thermal treatment assisted by a CO2 laser
NASA Astrophysics Data System (ADS)
Delgado, Tamara; Nieto, Daniel; Flores-Arias, María Teresa
A low-cost method for fabricating microlens arrays on commercial soda-lime glass is presented. The hybrid technique is composed by a laser direct writing technique and a laser assisted post-thermal treatment. In particular we use a nanosecond Q-Switch Nd:YVO4 laser for fabricating the initial structure of microposts on soda-lime glass substrates and a CO2 laser combined with a furnace for reshaping and improving its morphological and optical qualities. This new fabrication approach lets us obtain a high quality microlenses array with a diameter of 50 μm, sag 1.5 μm, focal length 1 mm and a spot size of 7.8 μm. Furthermore, the proposed technique preserves the advantages of the laser direct-write technique in terms of design flexibility, simplicity, fast prototyping, low cost and so on; while the alternative laser assisted thermal treatment lets us overcome the bounding problems presented in other conventional thermal treatments.
Structural characterization of nickel oxide/hydroxide nanosheets produced by CBD technique
Taşköprü, T.; Zor, M.; Turan, E.
Graphical abstract: SEM images of (a) as deposited β-Ni(OH)2 and (b) NiO samples deposited with pH 10 solution. The inset figures shows the absorbance spectra of (a) β-Ni(OH)2 and (b) NiO samples. - Highlights: • The formation of β-Ni(OH){sub 2} and NiO were confirmed with XRD, SEM, FT-IR and Raman. • Porous nickel oxide was synthesized after heat treatment of nickel hydroxide. • The increase in pH value changes the nanoflake structure to hexagonal nanosheet. • On increasing the pH from 8 to 11, the band gap decreases from 3.52 to 3.37 eV. - Abstract: Nickel hydroxide samples were deposited onto glass substrates using Ni(NO{sub 3}){sub 2}·6H{sub 2}O and aqueous ammonia by chemical bath deposition technique. The influence of pH of solution was investigated by means of X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, optical absorption and BET analysis. The as-deposited samples were identified as β-Ni(OH){sub 2}, were transformed into NiO after heat treatment in air at 500 °C for 2 h. Porous nickel oxide nanosheets are obtained by heating nickel hydroxide nanosheets. The optical transitions observed in the absorbance spectra below optical band gap is due to defects or Ni{sup 2+} vacancies in NiO samples. The band gap energy of NiO samples changes between 3.37 and 3.52 eV depending on the pH values.
Alternative techniques for producing a quality surimi and kamaboko from common carp (Cyprinus carpio).
Jafarpour, A; Gorczyca, E M
The demand for surimi and kamaboko is increasing in the world at the same time as the supply of the fish traditionally used has declined. In an effort to increase the range and hence supply of fish used, factors increasing the quality of surimi and kamaboko from common carp were investigated. The best surimi and kamaboko characteristics were produced by a modified conventional method (MCM) rather than traditional method (TM), alkaline-aided method (AAM), and pH modified method (PMM). MCM processing used centrifugation instead of decanting and filtering to optimize dewatering and remove the sarcoplasmic proteins (Sp-P). The temperature sweep test, at the end of sol-gel transition stage (at 75 degrees C), showed significantly (P < 0.05) greater G' for the kamaboko from MCM than that from other methods tested. Furthermore, the greatest and the least gel strengths were obtained with MCM and TM kamaboko, respectively. The protein recovery was about 67%, 74%, 87%, and 92% for TM, AAM, MCM, and PMM, respectively. TM and MCM resulted in the removal of Sp-P as determined by SDS-PAGE. The superiority of MCM kamaboko gel characteristics was supported by scanning electron micrographs (SEM) of the gel, which showed a significantly (P < 0.05) greater number of polygonal structures than for the TM kamaboko, which had the fewest and largest polygonal structures. The pH-shifting methods improved the textural quality of the resultant kamaboko compared with TM. However, a simple modification (centrifugation compared with decanting) by MCM in the surimi process can further improve the quality of the surimi and kamaboko gels. Furthermore, because it removed Sp-P and still preserved gel strength, it suggests that Sp-P are not required for gel strength.
Estimation of VOC emissions from produced-water treatment ponds in Uintah Basin oil and gas field using modeling techniques
NASA Astrophysics Data System (ADS)
Tran, H.; Mansfield, M. L.; Lyman, S. N.; O'Neil, T.; Jones, C. P.
Emissions from produced-water treatment ponds are poorly characterized sources in oil and gas emission inventories that play a critical role in studying elevated winter ozone events in the Uintah Basin, Utah, U.S. Information gaps include un-quantified amounts and compositions of gases emitted from these facilities. The emitted gases are often known as volatile organic compounds (VOCs) which, beside nitrogen oxides (NOX), are major precursors for ozone formation in the near-surface layer. Field measurement campaigns using the flux-chamber technique have been performed to measure VOC emissions from a limited number of produced water ponds in the Uintah Basin of eastern Utah. Although the flux chamber provides accurate measurements at the point of sampling, it covers just a limited area of the ponds and is prone to altering environmental conditions (e.g., temperature, pressure). This fact raises the need to validate flux chamber measurements. In this study, we apply an inverse-dispersion modeling technique with evacuated canister sampling to validate the flux-chamber measurements. This modeling technique applies an initial and arbitrary emission rate to estimate pollutant concentrations at pre-defined receptors, and adjusts the emission rate until the estimated pollutant concentrations approximates measured concentrations at the receptors. The derived emission rates are then compared with flux-chamber measurements and differences are analyzed. Additionally, we investigate the applicability of the WATER9 wastewater emission model for the estimation of VOC emissions from produced-water ponds in the Uintah Basin. WATER9 estimates the emission of each gas based on properties of the gas, its concentration in the waste water, and the characteristics of the influent and treatment units. Results of VOC emission estimations using inverse-dispersion and WATER9 modeling techniques will be reported.
Whole-tree agarwood-inducing technique: an efficient novel technique for producing high-quality agarwood in cultivated Aquilaria sinensis trees.
Liu, Yangyang; Chen, Huaiqiong; Yang, Yun; Zhang, Zheng; Wei, Jianhe; Meng, Hui; Chen, Weiping; Feng, Jindong; Gan, Bingchun; Chen, Xuyu; Gao, Zhihui; Huang, Junqin; Chen, Bo; Chen, Hongjiang
Agarwood is the fragrant resin-infused wood derived from the wounded trees of Aquilaria species. It is a valuable non-timber forest product used in fragrances and as medicine. Reforestation for Aquilaria trees in combination with artificial agarwood-inducing methods serves as a way to supply agarwood and conserve of wild Aquilaria stock. However, the existing agarwood-inducing methods produce poor-quality agarwood at low yield. Our study evaluated a novel technique for producing agarwood in cultivated Aquilaria trees, called the whole-tree agarwood-inducing technique (Agar-Wit). Ten different agarwood inducers were used for comparison of Agar-Wit with three existing agarwood-inducing methods. For Aquilaria trees treated with these ten inducers, agarwood formed and spread throughout the entire tree from the transfusion point in the trunk to the roots and branches of the whole tree. Agarwood yield per tree reached 2,444.83 to 5,860.74 g, which is 4 to 28 times higher than that by the existing agarwood-inducing methods. Furthermore, this agarwood derived from Agar-Wit induction was found to have a higher quality compared with the existing methods, and similar to that of wild agarwood. This indicates Agar-Wit may have commercial potential. Induction of cultivated agarwood using this method could satisfy the significant demand for agarwood, while conserving and protecting the remaining wild Aquilaria trees.
Advanced Fabrication Techniques for Precisely Controlled Micro and Nano Scale Environments for Complex Tissue Regeneration and Biomedical Applications
NASA Astrophysics Data System (ADS)
Holmes, Benjamin
As modern medicine advances, it is still very challenging to cure joint defects due to their poor inherent regenerative capacity, complex stratified architecture, and disparate biomechanical properties. The current clinical standard for catastrophic or late stage joint degradation is a total joint implant, where the damaged joint is completely excised and replaced with a metallic or artificial joint. However, these procedures still only lasts for 10-15 years, and there are hosts of recovery complications which can occur. Thus, these studies have sought to employ advanced biomaterials and scaffold fabricated techniques to effectively regrow joint tissue, instead of merely replacing it with artificial materials. We can hypothesize here that the inclusion of biomimetic and bioactive nanomaterials with highly functional electrospun and 3D printed scaffold can improve physical characteristics (mechanical strength, surface interactions and nanotexture) enhance cellular growth and direct stem cell differentiation for bone, cartilage and vascular growth as well as cancer metastasis modeling. Nanomaterial inclusion and controlled 3D printed features effectively increased nano surface roughness, Young's Modulus and provided effective flow paths for simulated arterial blood. All of the approaches explored proved highly effective for increasing cell growth, as a result of increasing micro-complexity and nanomaterial incorporation. Additionally, chondrogenic and osteogenic differentiation, cell migration, cell to cell interaction and vascular formation were enhanced. Finally, growth-factor(gf)-loaded polymer nanospheres greatly improved vascular cell behavior, and provided a highly bioactive scaffold for mesenchymal stem cell (MSC) and human umbilical vein endothelial cell (HUVEC) co-culture and bone formation. In conclusion, electrospinning and 3D printing when combined effectively with biomimetic and bioactive nanomaterials (i.e. carbon nanomaterials, collagen, nHA, polymer
Progress in fabrication of large magnetic sheilds by using extended YBCO thick films sprayed on stainless steel with the HVOF technique
Pavese, F.; Bergadano, E.; Ferri, D.
Fabricating a full box-type magnetic shield, by spraying a thick film of commercial YBCO powder on stainless steel with the oxygen-fuel high-velocity technique (HVOF, also referred to as {open_quotes}continuous detonation spray{close_quotes} (CDS)), requires the solution of several specific problems since the design stage of the project. The design problems of this type of shield are examined and the results obtained in the early stages of the realization are discussed.
Effect of CeO{sub 2} addition on the properties of FeAl based alloy produced by mechanical alloying technique
Khaerudini, Deni S.; Muljadi,; Sardjono, P.; Tetuko, Anggito P.; Sebayang, P.; Ginting, M.
Iron aluminides based on FeAl is notable for their low materials cost, ease of fabrication and good corrosion, suffixation and oxidation resistance. However, the application based on these unique properties still require the development of Fe-Al based alloy since it shows some drawbacks such as a lack of high temperature strength and low ductility. To improve the mechanical properties of FeAl based alloy, ceria (CeO{sub 2}) will be added to this compound. FeAl based alloy produced by the mechanical alloying (MA) technique. The developed specimens then assessed with respect to oxidation behaviour in high temperature, scale microstructure and hardness. The surface morphologies of the alloy evaluated and observed using scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscopy (EDX). The phase structures of oxide scale formed on them were identified by X-ray diffraction (XRD). The results found that the FeAl intermetallic compound containing CeO{sub 2} 0.5 wt.% is less pores and CeO{sub 2} 1.0 wt.% is more homogen in powder and solid form, higher hardness and increase in their resistance to oxidation behaviour in high temperature compared with another percentage of CeO{sub 2}.
PHBV/PLLA-based composite scaffolds fabricated using an emulsion freezing/freeze-drying technique for bone tissue engineering: surface modification and in vitro biological evaluation.
Sultana, Naznin; Wang, Min
Tissue engineering combines living cells with biodegradable materials and/or bioactive components. Composite scaffolds containing biodegradable polymers and nanosized osteoconductive bioceramic with suitable properties are promising for bone tissue regeneration. In this paper, based on blending two biodegradable and biocompatible polymers, namely poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(L-lactic acid) (PLLA) with incorporated nano hydroxyapatite (HA), three-dimensional composite scaffolds with controlled microstructures and an interconnected porous structure, together with high porosity, were fabricated using an emulsion freezing/freeze-drying technique. The influence of various parameters involved in the emulsion freezing/freeze-drying technique was studied for the fabrication of good-quality polymer scaffolds based on PHBV polymers. The morphology, mechanical properties and crystallinity of PHBV/PLLA and HA in PHBV/PLLA composite scaffolds and PHBV polymer scaffolds were studied. The scaffolds were coated with collagen in order to improve wettability. During in vitro biological evaluation study, it was observed that SaOS-2 cells had high attachment on collagen-coated scaffolds. Significant improvement in cell proliferation and alkaline phosphatase activity for HA-incorporated composite scaffolds was observed due to the incorporation of HA. After 3 and 7 days of culture on all scaffolds, SaOS-2 cells also had normal morphology and growth. These results indicated that PHBV/PLLA-based scaffolds fabricated via an emulsion freezing/freeze-drying technique were favorable sites for osteoblastic cells and are promising for the applications of bone tissue engineering.
One-Step Fabrication of Stretchable Copper Nanowire Conductors by a Fast Photonic Sintering Technique and Its Application in Wearable Devices.
Ding, Su; Jiu, Jinting; Gao, Yue; Tian, Yanhong; Araki, Teppei; Sugahara, Tohru; Nagao, Shijo; Nogi, Masaya; Koga, Hirotaka; Suganuma, Katsuaki; Uchida, Hiroshi
Copper nanowire (CuNW) conductors have been considered to have a promising perspective in the area of stretchable electronics due to the low price and high conductivity. However, the fabrication of CuNW conductors suffers from harsh conditions, such as high temperature, reducing atmosphere, and time-consuming transfer step. Here, a simple and rapid one-step photonic sintering technique was developed to fabricate stretchable CuNW conductors on polyurethane (PU) at room temperature in air environment. It was observed that CuNWs were instantaneously deoxidized, welded and simultaneously embedded into the soft surface of PU through the one-step photonic sintering technique, after which highly conductive network and strong adhesion between CuNWs and PU substrates were achieved. The CuNW/PU conductor with sheet resistance of 22.1 Ohm/sq and transmittance of 78% was achieved by the one-step photonic sintering technique within only 20 μs in air. Besides, the CuNW/PU conductor could remain a low sheet resistance even after 1000 cycles of stretching/releasing under 10% strain. Two flexible electronic devices, wearable sensor and glove-shaped heater, were fabricated using the stretchable CuNW/PU conductor, demonstrating that our CuNW/PU conductor could be integrated into various wearable electronic devices for applications in food, clothes, and medical supplies fields.
Microstructure Characterization and Corrosion Resistance Behavior of New Cobalt-Free Maraging Steel Produced Through ESR Techniques
NASA Astrophysics Data System (ADS)
Seikh, Asiful H.; Halfa, Hossam; Baig, Muneer; Khan, Sohail M. A.
In this study, two different grades (M23 and M29) of cobalt-free low nickel maraging steel have been produced through electroslag remelting (ESR) process. The corrosion resistance of these ESR steels was investigated in 1 M H2SO4 solution using linear potentiodynamic polarization (LPP) and electrochemical impedance spectroscopy (EIS) techniques. The experiments were performed for different immersion time and solution temperature. To evaluate the corrosion resistance of the ESR steels, some significant characterization parameters from LPP and EIS curves were analyzed and compared with that of conventional C250 maraging steel. Irrespective of measurement techniques used, the results show that the corrosion resistance of the ESR steels was higher than the C250 steel. The microstructure of ESR steels was composed of uniform and well-distributed martensite accompanied with little amount of retained austenite in comparison with C250 steel.
Surface plasmon resonances, optical properties, and electrical conductivity thermal hystersis of silver nanofibers produced by the electrospinning technique.
Barakat, Nasser A M; Woo, Kee-Do; Kanjwal, Muzafar A; Choi, Kyung Eun; Khil, Myung Seob; Kim, Hak Yong
In the present study, silver metal nanofibers have been successfully prepared by using the electrospinning technique. Silver nanofibers have been produced by electrospinning a sol-gel consisting of poly(vinyl alcohol) and silver nitrate. The dried nanofiber mats have been calcined at 850 degrees C in an argon atmosphere. The produced nanofibers do have distinct plasmon resonance compared with the reported silver nanoparticles. Contrary to the introduced shapes of silver nanoparticles, the nanofibers have a blue-shifted plasmon resonance at 330 nm. Moreover, the optical properties study indicated that the synthesized nanofibers have two band gap energies of 0.75 and 2.34 eV. An investigation of the electrical conductivity behavior of the obtained nanofibers shows thermal hystersis. These privileged physical features greatly widen the applications of the prepared nanofibers in various fields.
Research and Development on Advanced Silicon Carbide Thin Film Growth Techniques and Fabrication of High Power and Microwave Frequency Silicon Carbide-Based Device Structures
AD-A243 531IIII!IIHUHllAlll| DTIC Annual Letter Report EL Vr DECA S C Research and Development on Advanced Silicon Carbide Thin Film Growth...Techniques and Fabrication of High Power and Microwave Frequency Silicon Carbide -Based Device Structures Supported under Grant #N00014-88-K-0341/P00002 Office...Letter l/,1- 2 3 lj9 l 4. TITLE AND SUBTITLE Research and Develp~nt on Advanced S. FUNDING NUMBERS Silicon Carbide Thin Film .Growth Techniques and R&T
Microstructure and Mechanical Properties of Aluminum-Alumina Bulk Nanocomposite Produced by a Novel Two-Step Ultrasonic Casting Technique
NASA Astrophysics Data System (ADS)
Vishwanatha, H. M.; Eravelly, Jayakumar; Kumar, Cheruvu Siva; Ghosh, Sudipto
An unprecedented uniform distribution of nano-dispersoids in aluminum-alumina bulk nanocomposite and enhancement in mechanical properties were achieved through a novel ultrasonic casting technique involving two-step ultrasonication. Ultrasonic casting can be classified into two types: (a) contact type, in which the sonicating probe is in direct contact with the liquid melt during ultrasonication and (b) non-contact type, in which the ultrasonic waves reach the liquid melt through the mold wall. Each of the processes has certain disadvantages, and the present study aims at eliminating the primary disadvantages of both the processes, through a novel two-step ultrasonic casting technique. The significant improvement in distribution was possibly due to the cavitation in the mold, leading to the elimination of non-uniformity in the cooling rate at the mesoscopic scale. The improvement in mechanical properties is explained through microstructure analysis in correlation with EBSD analysis, TEM analysis, hardness test, and tensile test. The yield strength of the nanocomposite produced by the two-step process was ~38 pct higher than that produced by non-contact and contact methods.
In-situ sonosynthesis of nano N-doped ZnO on wool producing fabric with photo and bio activities, cell viability and enhanced mechanical properties.
Behzadnia, Amir; Montazer, Majid; Rad, Mahnaz Mahmoudi
Here, a simple processing route is introduced for preparation of N-doped nano structure ZnO at 75-80°C using in-situ sonosynthesis method through hydrolysis of zinc acetate at pH≈9-10 adjusting with ammonia. Synthesis and fabrication of nano N-doped ZnO were carried out on the wool fabric through impregnation of the fabric in ultrasound bath using different concentrations of zinc acetate followed by curing. The antibacterial and antifungal activities of the treated fabrics were assessed against two common pathogenic bacteria including Escherichia coli, Staphylococcus aureus and the diploid fungus namely Candida albicans. The photo-catalytic activity of nano N-doped ZnO particles on the wool fabric was determined by degradation of Methylene Blue under daylight irradiation. Increasing zinc acetate and prolonged sonication time led to higher photo-catalytic activity as more dye stain degraded from the stained treated fabric under daylight. Higher photo-catalytic activity was observed on the nano N-doped ZnO sonotreated wool fabric having more hydrophilicity. Finally, the treatment indicated no negative effect on the fabric safety while reduced alkaline solubility and yellowness even enhanced the fabric tensile strength. The response surface methodology was also utilized to optimize the wool fabric treatment conditions.
Fast fabrication of nano-structured anti-reflection layers for enhancement of solar cells performance using plasma sputtering and infrared assisted roller embossing techniques.
Liu, Shih-Jung; Liao, Che-Ting
This paper reports the continuous fabrication of dual-side nano-structured anti-reflection protective layer for performance enhancement of solar cells using plasma sputtering and infrared assisted roller embossing techniques. Nano-structures were first deposited onto the surface of glass substrates using the plasma sputtering technique. After electroforming, a nickel master mold containing nano-array of 30 nm was obtained. The mold was then attached to the surfaces of the two metallic rollers in an infrared assisted roll-to-roll embossing facility. The embossing facility was used to replicate the nano-structures onto 60 μm thick polyethylene terephthalate (PET) films in the experiments. The embossed films were characterized using UV-vis spectrophotometer, atomic force microscope (AFM), and scanning electron microscope (SEM); its total conversion efficiency for solar cells was also measured by a solar simulator. The experimental results showed that the fabricated films could effectively reduce the reflectance and increase the conversion efficiency of solar cells. The proposed method shows great potential for fast fabrication of the anti-reflection protective layer of solar cells due to its simplicity and versatility.
Chemical assembly of TiO2 and TiO2@Ag nanoparticles on silk fiber to produce multifunctional fabrics.
Li, Guohong; Liu, Hong; Zhao, Hongshi; Gao, Yuqiang; Wang, Jiyang; Jiang, Huaidong; Boughton, R I
A carefully designed surface modification technique for the manufacture of multifunctional silk textile nanocomposite materials is successfully developed by the functionalization of silk with TiO(2) and TiO(2)@Ag nanoparticles (NPs). The NPs are assembled onto a silk substrate through covalent linkages, including enediol ligand-metal oxide bonding, resin dehydration and the acylation of silk. Owing to the strong chemical bonding, silk fibroin fabric (SFF) and the NPs form a stable composite system. The functionalized SFF, especially TiO(2)@Ag NP-functionalized SFF are endowed with remarkable UV protection properties, and an efficient anti-bacterial capability toward Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Furthermore, the nearly total photodegradation of methylene orange (MO) under UV illumination illustrates that functionalized SFF possesses high photocatalytic and self-cleaning capability. This multifunctional silk material satisfies the market demand for natural "smart" products, and is a promising practical material for use in the textile industry, hospital sterilization and environmental cleanup.
High Electron Mobility Ge n-Channel Metal-Insulator-Semiconductor Field-Effect Transistors Fabricated by the Gate-Last Process with the Solid Source Diffusion Technique
NASA Astrophysics Data System (ADS)
Maeda, Tatsuro; Morita, Yukinori; Takagi, Shinichi
We fabricate high-k/Ge n-channel metal-insulator-semiconductor field-effect transistors (MISFETs) by the gate-last process with the thermal solid source diffusion to achieve both of high quality source/drain (S/D) and gate stack. The n+/p junction formed by solid source diffusion technique of Sb dopant shows the excellent diode characteristics of ˜1.5×105 on/off ratio between +1 and -1 V and the quite low reverse current density of ˜4.1×10-4 A/cm2 at +1 V after the fabrication of high-k/Ge n-channel MISFETs that enable us to observe well-behaved transistor performances. The extracted electron mobility with the peak of 891 cm2/(V.s) is high enough to be superior to the Si universal electron mobility especially in low Eeff.
MR-compatible antibiotic interlocked nail fabrication for the management of long bone infections: first case report of a new technique
Successful management of intramedullary long bone osteomyelitis remains a challenge for both surgeons and patients. Patients are often immune-compromised and have endured multiple surgeries. Treatment principles include antibiotic administration (systemically +/- locally), surgical debridement of the infection site and stabilization. Since their description in 2002, antibiotic coated nails have become part of the armamentarium for the treatment of osteomyelitis allowing both local elution of antibiotics and stabilization of a debrided long bone. Limitations to their utilization have remained, in part from the technical difficulty of fabrication and MRI artifacts. We describe a new surgical technique of fabrication that has the advantages of being simple, reproducible, with an end product free of MRI artifacts. PMID:24636020
Investigation on pretreatment of centrifugal mother liquid produced in the production of polyvinyl chloride by air-Fenton technique.
Sun, Yingying; Hua, Xiuyi; Ge, Rui; Guo, Aitong; Guo, Zhiyong; Dong, Deming; Sun, Wentian
Centrifugal mother liquid (CML) is one of the main sources of wastewater produced during the production of polyvinyl chloride in chlor-alkali industry. CML is a typical poorly biodegradable organic wastewater, containing many kinds of refractory pollutants. Specifically, it contains dissolved refractory polymers, especially polyvinyl alcohol (PVA), which can pass though the biotreatment processes and clog the membranes used for further treatment. In this study, to ensure the CML applicable to biotreatment and membrane treatment, a novel efficient and mild technique, air-Fenton treatment, was employed as a pretreatment technique to improve biodegradability of the CML and to break down the polymers in the CML. Firstly, the technique was optimized for the CML treatment by optimizing the main parameters, including the dosage of ferrous sulfate, initial pH of the wastewater, [H2O2]/[Fe(2+)], aeration rate, reaction time, and temperature, based on removal efficiency of COD and PVA from the CML. Then, the optimized technique was tested and evaluated. The results indicated that under the optimized conditions, the air-Fenton treatment could remove 66, 98, and 55 % of the COD, PVA, and TOC, respectively, from the CML. After the treatment, biodegradability of the wastewater increased significantly (BOD/COD increased from 0.31 to 0.68), and almost all of the PVA polymers were removed or broken down. Meanwhile, concentration of the remaining iron ions, which were added during the treatment, was also quite low (only 2.9 mg/L). Furthermore, most of the suspended materials and ammonia nitrogen, and some of the phosphorus in the wastewater were removed simultaneously.
Techniques for Estimating Emissions Factors from Forest Burning: ARCTAS and SEAC4RS Airborne Measurements Indicate Which Fires Produce Ozone
NASA Technical Reports Server (NTRS)
Chatfield, Robert B.; Andreae, Meinrat O.
Previous studies of emission factors from biomass burning are prone to large errors since they ignore the interplay of mixing and varying pre-fire background CO2 levels. Such complications severely affected our studies of 446 forest fire plume samples measured in the Western US by the science teams of NASA's SEAC4RS and ARCTAS airborne missions. Consequently we propose a Mixed Effects Regression Emission Technique (MERET) to check techniques like the Normalized Emission Ratio Method (NERM), where use of sequential observations cannot disentangle emissions and mixing. We also evaluate a simpler "consensus" technique. All techniques relate emissions to fuel burned using C(sub burn) = delta C(sub tot) added to the fire plume, where C(sub tot) approximately equals (CO2 + CO). Mixed-effects regression can estimate pre-fire background values of Ctot (indexed by observation j) simultaneously with emissions factors indexed by individual species i, delta epsilon lambda tau alpha-x(sub i)/(C(sub burn))i,j., MERET and "consensus" require more than two emissions indicators. Our studies excluded samples where exogenous CO or CH4 might have been fed into a fire plume, mimicking emission. We sought to let the data on 13 gases and particulate properties suggest clusters of variables and plume types, using non-negative matrix factorization (NMF). While samples were mixtures, the NMF unmixing suggested purer burn types. Particulate properties (bscat, babs, SSA, AAE) and gas-phase emissions were interrelated. Finally, we sought a simple categorization useful for modeling ozone production in plumes. Two kinds of fires produced high ozone: those with large fuel nitrogen as evidenced by remnant CH3CN in the plumes, and also those from very intense large burns. Fire types with optimal ratios of delta-NOy/delta- HCHO associate with the highest additional ozone per unit Cburn, Perhaps these plumes exhibit limited NOx binding to reactive organics. Perhaps these plumes exhibit limited NOx
Techniques for Estimating Emissions Factors from Forest Burning: ARCTAS and SEAC4RS Airborne Measurements Indicate which Fires Produce Ozone
NASA Technical Reports Server (NTRS)
Chatfield, Robert B.; Andreae, Meinrat O.
Previous studies of emission factors from biomass burning are prone to large errors since they ignore the interplay of mixing and varying pre-fire background CO2 levels. Such complications severely affected our studies of 446 forest fire plume samples measured in the Western US by the science teams of NASA's SEAC4RS and ARCTAS airborne missions. Consequently we propose a Mixed Effects Regression Emission Technique (MERET) to check techniques like the Normalized Emission Ratio Method (NERM), where use of sequential observations cannot disentangle emissions and mixing. We also evaluate a simpler "consensus" technique. All techniques relate emissions to fuel burned using C(burn) = delta C(tot) added to the fire plume, where C(tot) approximately equals (CO2 = CO). Mixed-effects regression can estimate pre-fire background values of C(tot) (indexed by observation j) simultaneously with emissions factors indexed by individual species i, delta, epsilon lambda tau alpha-x(sub I)/C(sub burn))I,j. MERET and "consensus" require more than emissions indicators. Our studies excluded samples where exogenous CO or CH4 might have been fed into a fire plume, mimicking emission. We sought to let the data on 13 gases and particulate properties suggest clusters of variables and plume types, using non-negative matrix factorization (NMF). While samples were mixtures, the NMF unmixing suggested purer burn types. Particulate properties (b scant, b abs, SSA, AAE) and gas-phase emissions were interrelated. Finally, we sought a simple categorization useful for modeling ozone production in plumes. Two kinds of fires produced high ozone: those with large fuel nitrogen as evidenced by remnant CH3CN in the plumes, and also those from very intense large burns. Fire types with optimal ratios of delta-NOy/delta- HCHO associate with the highest additional ozone per unit Cburn, Perhaps these plumes exhibit limited NOx binding to reactive organics. Perhaps these plumes exhibit limited NOx binding to
Identification of gunshot residues in fabric targets using sector field inductively coupled plasma mass spectrometry technique and ternary graphs.
Freitas, João Carlos D; Sarkis, Jorge E Souza; Negrini Neto, Osvaldo; Viebig, Sônia Bocamino
During criminal investigations involving firearms, the detection of gunshot residues (GSRs) is one of the most important evidences. In the present study, a new method to identify trace evidences of GSRs, deposited around the bullet entrance hole, in different types of fabrics used as targets, is described. The experiments were carried out using a 0.38-inch caliber revolver, and 9-mm and 0.40-inch caliber pistols. Testimonies of 2.25 cm(2) of the fabrics were cut around the bullet entrance and digested with 10% nitric acid. Antimony, barium, and lead were analyzed in the remaining solution using a sector field inductively coupled plasma mass spectrometer. The concentrations of the elements were detected at levels up to few microgram per square centimeter. The use of ternary graphics allowed us to identify specific patterns of distribution for blank samples and the clear distinction between the revolver and pistols used.
Trace detection of herbicides by SERS technique, using SERS-active substrates fabricated from different silver nanostructures deposited on silicon
NASA Astrophysics Data System (ADS)
Cao Dao, Tran; Quynh Ngan Luong, Truc; Cao, Tuan Anh; Hai Nguyen, Ngoc; Kieu, Ngoc Minh; Thuy Luong, Thi; Le, Van Vu
In this report we present the initial results of the use of different silver nanostructures deposited on silicon for trace detection of paraquat (a commonly used herbicide) using the surface-enhanced Raman scattering (SERS) effect. More specifically, the SERS-active substrates were fabricated from silver nanoparticles (AgNPs) deposited onto the flat surface of a silicon wafer (AgNPs@Si substrate), as well as on the surface of an obliquely aligned silicon nanowire (SiNW) array (AgNPs@SiNWs substrate), and from silver nanodendrites (AgNDs) deposited onto the flat surface of a silicon wafer (AgNDs@Si substrate). Results showed that with the change of the structure of the SERS-active substrate, higher levels of SERS enhancement have been achieved. Specifically, with the fabricated AgNDs@Si substrate, paraquat concentration as low as 1 ppm can be detected.
Improved wax mold technique forms complex passages in solid structures
NASA Technical Reports Server (NTRS)
Hellbaum, R. F.; Page, A. D.; Phillips, A. R.
Low-cost fabricating technique produces minute, complex air passages in fluidic devices. Air jet interactions in these function as electronic and electromechanical control systems. Wax cores are fabricated without distortion by two-wax process using nonsoluble pattern-wax and water-soluble wax. Significant steps in fabrication process are discussed.
A high aspect ratio SU-8 fabrication technique for hollow microneedles for transdermal drug delivery and blood extraction
NASA Astrophysics Data System (ADS)
Chaudhri, Buddhadev Paul; Ceyssens, Frederik; De Moor, Piet; Van Hoof, Chris; Puers, Robert
Protein drugs, e.g. hormonal drugs, cannot be delivered orally to a patient as they get digested in the gastro-intestinal (GI) tract. Thus, it is imperative that these kinds of drugs are delivered transdermally through the skin. To provide for real-time feedback as well as to test independently for various substances in the blood, we also need a blood sampling system. Microneedles can perform both these functions. Further, microneedles made of silicon or metal have the risk of breaking inside the skin thereby leading to complications. SU-8, being approved of as being biocompatible by the Food and Drug Agency (FDA) of the United States, is an attractive alternative because firstly it is a polymer material, thereby reducing the chances of breakages inside the skin, and secondly it is a negative photoresist, thereby leading to ease of fabrication. Thus, here we present very tall (around 1600 µm) SU-8 polymer-based hollow microneedles fabricated by a simple and repeatable process, which are a very good candidate for transdermal drug delivery as well as blood extraction. The paper elaborates on the details that allow the fabrication of such extreme aspect ratios (>100).
A study on ultra-precision machining technique for Al6061-T6 to fabricate space infrared optics
NASA Astrophysics Data System (ADS)
Ryu, Geun-man; Lee, Gil-jae; Hyun, Sang-won; Sung, Ha-yeong; Chung, Euisik; Kim, Geon-hee
In this paper, analysis of variance on designed experiments with full factorial design was applied to determine the optimized machining parameters for ultra-precision fabrication of the secondary aspheric mirror, which is one of the key elements of the space cryogenic infrared optics. A single point diamond turning machine (SPDTM, Nanotech 4μpL Moore) was adopted to fabricate the material, AL6061-T6, and the three machining parameters of cutting speed, feed rate and depth of cut were selected. With several randomly assigned experimental conditions, surface roughness of each condition was measured by a non-contact optical profiler (NT2000; Vecco). As a result of analysis using Minitab, the optimum cutting condition was determined as following; cutting speed: 122 m/min, feed rate: 3 mm/min and depth of cut: 1 μm. Finally, a 120 mm diameter aspheric secondary mirror was attached to a particularly designed jig by using mixture of paraffin and wax and successfully fabricated under the optimum machining parameters. The profile of machined surface was measured by a high-accuracy 3-D profilometer(UA3P; Panasonic) and we obtained the geometrical errors of 30.6 nm(RMS) and 262.4 nm(PV), which satisfy the requirements of the space cryogenic infrared optics.
Comparison of the Effect of Dentin Bonding, Dentin Sealing Agents on the Microleakage of Provisional Crowns Fabricated with Direct and Indirect Technique-An Invitro Study
Muthukumar, B; Kumar, M Vasantha
Background Postoperative sensitivity after temporization is a common complaint in Fixed Partial Denture patients. It is caused by weak and ill fitting temporary restorations which results in microleakage. This can be controlled by providing good temporary restorations and by coating the exposed dentinal tubules of the prepared tooth with dentin bonding agent or dental varnish. Aim The purpose of the study was to determine the effect of dentin-bonding, dentin sealing agents on the microleakage of temporary crowns made by tooth colored auto polymerizing resin fabricated with direct and indirect technique. Materials and Methods Thirty premolar and molar human teeth were collected which were extracted recently was used for the study. The teeth were marked and divided into 3 groups each containing 10 nos. They were individually mounted with self-cure acrylic resin. It was then mounted on a milling machine and crown preparations done. Temporary crowns were fabricated by direct and indirect method with two types of materials. In group A (Control group), the temporary crowns fabricated with both direct and indirect method were cemented directly with temporary luting cement. In group B dentine-bonding agent (solobond M) was applied once to the prepared surface of each tooth specimen before the cementation of temporary crowns where as in case of group C a single layer of dental varnish is applied prior to crown cementation. The entire specimens were immersed in 1% methylene blue and allowed to undergo thermal treatment. It was then sectioned in a hard tissue microtome. Each section was evaluated for dye penetration into the dentin tubules by comparing it with a visual scale. Statistical Analysis SPSS Version 13 software was used for non-parametric data analysis by a qualified statistician. P-values less than 0.05 (p-value<0.05) were considered to be statistically significant. Results Group B (Dentin Bonding Agent) specimens cemented with crowns fabricated in direct technique
Modified use of methylene blue in the tissue compression technique to detect sarcocysts in meat-producing animals.
Ng, Yit Han; Subramaniam, Vellayan; Lau, Yee Ling
Sarcocystosis in meat-producing animals is a major cause of reduced productivity in many countries, especially those that rely on agriculture. Although several diagnostic methods are available to detect sarcocystosis, many are too time-consuming for routine use in abattoirs and meat inspection centers, where large numbers of samples need to be tested. This study aimed to compare the sensitivity of the methylene blue tissue preparation, unstained tissue preparation and nested PCR in the detection of sarcocysts in tissue samples. Approximately three-fold more sarcocysts were detected in methylene blue-stained tissue compared to unstained controls (McNemar's test: P<0.01). Test sensitivity was comparable to that of the gold standard for sarcocyst detection, nested polymerase chain reaction. These results suggest that methylene blue can be used in tissue compression as a rapid, safe, and inexpensive technique for the detection of ruminant sarcocystosis in abattoirs.
On the Use of the Electrospinning Coating Technique to Produce Antimicrobial Polyhydroxyalkanoate Materials Containing In Situ-Stabilized Silver Nanoparticles
Castro-Mayorga, Jinneth Lorena; Fabra, Maria Jose; Cabedo, Luis; Lagaron, Jose Maria
Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver nanoparticles (AgNPs) was successfully developed and characterized in terms of morphology, thermal, mechanical, and barrier properties. The obtained materials reduced the bacterial population of Salmonella enterica below the detection limits at very low silver loading of 0.002 ± 0.0005 wt %. As a result, this study provides an innovative route to generate fully renewable and biodegradable materials that could prevent microbial outbreaks in food packages and food contact surfaces. PMID:28336838
High flux of relativistic electrons produced in femtosecond laser-thin foil target interactions: characterization with nuclear techniques.
Gerbaux, M; Gobet, F; Aléonard, M M; Hannachi, F; Malka, G; Scheurer, J N; Tarisien, M; Claverie, G; Méot, V; Morel, P; Faure, J; Glinec, Y; Guemnie-Tafo, A; Malka, V; Manclossi, M; Santos, J J
We present a protocol to characterize the high energy electron beam emitted in the interaction of an ultraintense laser with matter at intensities higher than 10(19) W cm(-2). The electron energies and angular distributions are determined as well as the total number of electrons produced above a 10 MeV threshold. This protocol is based on measurements with an electron spectrometer and nuclear activation techniques, combined with Monte Carlo simulations based on the GEANT3 code. The method is detailed and exemplified with data obtained with polypropylene and copper thin solid targets at a laser intensity of 2x10(19) W cm(-2). Special care is taken of the different sources of uncertainties. In particular, the reproducibility of the laser shots is considered.
High flux of relativistic electrons produced in femtosecond laser-thin foil target interactions: Characterization with nuclear techniques
Gerbaux, M.; Gobet, F.; Aleonard, M. M.; Hannachi, F.; Malka, G.; Scheurer, J. N.; Tarisien, M.; Claverie, G.; Meot, V.; Morel, P.
We present a protocol to characterize the high energy electron beam emitted in the interaction of an ultraintense laser with matter at intensities higher than 10{sup 19} W cm{sup -2}. The electron energies and angular distributions are determined as well as the total number of electrons produced above a 10 MeV threshold. This protocol is based on measurements with an electron spectrometer and nuclear activation techniques, combined with Monte Carlo simulations based on the GEANT3 code. The method is detailed and exemplified with data obtained with polypropylene and copper thin solid targets at a laser intensity of 2x10{sup 19} W cm{sup -2}. Special care is taken of the different sources of uncertainties. In particular, the reproducibility of the laser shots is considered.
On the Use of the Electrospinning Coating Technique to Produce Antimicrobial Polyhydroxyalkanoate Materials Containing In Situ-Stabilized Silver Nanoparticles.
Castro-Mayorga, Jinneth Lorena; Fabra, Maria Jose; Cabedo, Luis; Lagaron, Jose Maria
Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver nanoparticles (AgNPs) was successfully developed and characterized in terms of morphology, thermal, mechanical, and barrier properties. The obtained materials reduced the bacterial population of Salmonella enterica below the detection limits at very low silver loading of 0.002 ± 0.0005 wt %. As a result, this study provides an innovative route to generate fully renewable and biodegradable materials that could prevent microbial outbreaks in food packages and food contact surfaces.
Application of the Ta liner technique to produce Ca beams at INFN-Legnaro National Laboratories (INFN-LNL)
Galatà, A. Sattin, M.; Manzolaro, M.; Martini, D.; Facco, A.; Tinschert, K.; Spaedtke, P.; Lang, R.; Kulevoy, T.
The ECR ion sources are able to produce a wide variety of highly charged metallic ion beams thanks to the development of different techniques (ovens, sputtering, direct insertion, metal ions from volatile compounds (MIVOC)). In the case of the ovens, the sticking of the hot vapors on the surface of the plasma chamber leads to high material consumption rates. For elements like Ca, a tantalum liner inserted inside the chamber can be used to limit this phenomenon. The modeling of temperature distribution inside the chamber with and without the liner was carried out with COMSOL-multiphysics code. Results of simulation and the comparison with experiments performed at INFN-Legnaro National Laboratories with Ca beams are discussed.
Application of the Ta liner technique to produce Ca beams at INFN-Legnaro National Laboratories (INFN-LNL).
Galatà, A; Sattin, M; Manzolaro, M; Martini, D; Facco, A; Tinschert, K; Spaedtke, P; Lang, R; Kulevoy, T
The ECR ion sources are able to produce a wide variety of highly charged metallic ion beams thanks to the development of different techniques (ovens, sputtering, direct insertion, metal ions from volatile compounds (MIVOC)). In the case of the ovens, the sticking of the hot vapors on the surface of the plasma chamber leads to high material consumption rates. For elements like Ca, a tantalum liner inserted inside the chamber can be used to limit this phenomenon. The modeling of temperature distribution inside the chamber with and without the liner was carried out with COMSOL-multiphysics code. Results of simulation and the comparison with experiments performed at INFN-Legnaro National Laboratories with Ca beams are discussed.
A comparative analysis of the accuracy of implant master casts fabricated from two different transfer impression techniques
Patil, Rupali; Kadam, Pankaj; Oswal, Chetan; Patil, Seema; Jajoo, Shweta; Gachake, Arati
Aim: This study evaluated and compared two impression techniques in terms of their dimensional accuracies to reproduce implant positions on working casts. Materials and Methods: A master model was designed to simulate a clinical situation. Impressions were made using four techniques: (1) Stock open tray (SOT) technique; (2) stock closed tray (SCT) technique; (3) custom open tray (COT) technique; and (3) custom closed tray (CCT) technique. Reference points on the hexagonal silhouette of the implant on master model and onto the analogs of the obtained master casts were compared after using the four impression techniques. Measurements were made using an optical microscope, capable of recording under 50x magnifications. The means and standard deviations of all the groups and subgroups were calculated and statically analyzed using analysis of variance (ANOVA) and Tukey's test. Results: The open tray impressions showed significantly less variation from the master model and all the techniques studied were comparable. Conclusion: All the techniques studied shown some distortion. COT showed the most accurate results of all the techniques. PMID:27114954
Design and fabrication of microstrip antenna arrays
NASA Technical Reports Server (NTRS)
A microstrip array project was conducted to demonstrate the feasibility of designing and fabricating simple, low cost, low sidelobe phased arrays with circular disk microstrip radiating elements. Design data were presented for microstrip elements and arrays including the effects of the protective covers, the mutual interaction between elements, and stripline feed network design. Low cost multilayer laminate fabrication techniques were also investigated. Utilizing this design data two C-band low sidelobe arrays were fabricated and tested: an eight-element linear and a sixty-four element planar array. These arrays incorporated stripline Butler matrix feed networks to produce a low sidelobe broadside beam.
Method and apparatus for fabricating a thin-film solar cell utilizing a hot wire chemical vapor deposition technique
Wang, Qi; Iwaniczko, Eugene
A thin-film solar cell is provided. The thin-film solar cell comprises an a-SiGe:H (1.6 eV) n-i-p solar cell having a deposition rate of at least ten (10) .ANG./second for the a-SiGe:H intrinsic layer by hot wire chemical vapor deposition. A method for fabricating a thin film solar cell is also provided. The method comprises depositing a n-i-p layer at a deposition rate of at least ten (10) .ANG./second for the a-SiGe:H intrinsic layer.
New nano-sized Al2O3-BN coating 3Y-TZP ceramic composites for CAD/CAM-produced all-ceramic dental restorations. Part I. Fabrication of powders.
Yang, Se Fei; Yang, Li Qiang; Jin, Zhi Hao; Guo, Tian Wen; Wang, Lei; Liu, Hong Chen
Partially sintered 3 mol % yttria-stabilized tetragonal zirconium dioxide (ZrO(2), zirconia) polycrystal (3Y-TZP) ceramics are used in dental posterior restorations with computer-aided design-computer-aided manufacturing (CAD/CAM) techniques. High strength is acquired after sintering, but shape distortion of preshaped compacts during their sintering is inevitable. The aim of this study is to fabricate new machinable ceramic composites with strong mechanical properties that are fit for all-ceramic dental restorations. Aluminum oxide (Al(2)O(3))-coated 3Y-TZP powders were first prepared by the heterogeneous precipitation method starting with 3Y-TZP, Al(NO(3))(3) . 9H(2)O, and ammonia, then amorphous boron nitride (BN) was produced and the as-received composite powders were coated via in situ reaction with boric acid and urea. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to analyze the status of Al(2)O(3)-BN on the surface of the 3Y-TZP particles. TEM micrographs show an abundance of Al(2)O(3) particles and amorphous BN appearing uniformly on the surface of the 3Y-TZP particles after the coating process. The size of the Al(2)O(3) particles is about 20 nm. The XRD pattern shows clearly the peak of amorphous BN among the peaks of ZrO(2).
Liquid crystal modified photonic crystal fiber (LC-PCF) fabricated with an un-cured SU-8 photoresist sealing technique for electrical flux measurement.
Kuo, Shu-Ming; Huang, Yu-Wen; Yeh, Szu-Ming; Cheng, Wood-Hi; Lin, Che-Hsin
The optical transmission properties of photonic crystal fibers (PCFs) can be manipulated by modifying the pattern arrangement of the air channels within them. This paper presents a novel MEMS-based technique for modifying the optical transmission properties of commercial photonic-crystal fiber (PCF) by selectively filling the voids within the fiber structure with liquid crystals. In the proposed approach, an un-cured SU-8 ring pattern with a thickness of 5 μm is fabricated using a novel stamping method. The PCF is then brought into contact with the SU-8 pattern and an infra-red (IR) laser beam is passed through the fiber in order to soften the SU-8 surface; thereby selectively sealing some of the air channels with molten SU-8. Liquid crystals (LCs) are then infiltrated into the un-sealed holes in the PCF via capillary effects in order to modify the transmission properties of the PCF. Two selectively-filled PCFs are fabricated, namely an inner-ring LC-PCF and a single-line LC-PCF, respectively. It is shown that the two LC-PCFs exhibit significantly different optical behaviors. The practical applicability of the proposed selective-filling approach is demonstrated by fabricating an electric field sensor. The experimental results show that the sensor has the ability to measure electric fields with an intensity of up to 40 kV/cm.
Crustal Seismic Anisotropy Produced by Rock Fabric Terranes in the Taiwan Central Range Deformational Orogen: Integrative Study Combining Rock Physics, Structural Geology, and Passive/Active-Source Seismology
NASA Astrophysics Data System (ADS)
Okaya, D. A.; Ross, Z.; Christensen, N. I.; Wu, F. T.; Byrne, T. B.
The island of Taiwan is currently under construction due to the collision of the northwestern corner of the Philippine Sea plate and the embedded Luzon island arc with the larger continental Eurasian plate. This collision is responsible for the current growth of the Central Range that dominates the eastern half of the island. An international collaboration involving several USA and Taiwan universities and academic institutions was formed to study how the orogen evolves through time and to understand the role of a colliding island arc in mountain building. The project, Taiwan Integrated Geodynamics Research (TAIGER), was funded by NSF-Continental Dynamics and Taiwan National Science Council. The Central Range grows at one of the most rapid rates of uplift in the world, exposing metamorphic rocks that were once at least 10 km deep. The range offers unique opportunities for studies of crustal seismic anisotropy for two major reasons: (1) its geological makeup is conducive for producing crustal seismic anisotropy; that is, the rocks are highly foliated; and (2) a seismological data volume of significant breadth offers extensive coverage of sources and recording stations throughout the region. We carried out a crustal shear wave splitting study by data mining 3300 local earthquakes collected in the TAIGER 2009 sea-land experiment. We used an automated P and S wave arrival time picking method (Ross and Ben-Zion, 2014) applied to over 100,000 event-station pairs. These data were analyzed for shear-wave splitting using the MFAST automated package (Savage et al., 2010), producing 3300 quality shear wave split measurements. The splitting results were then station-averaged. The results show NNE to NE orientation trends that are consistent with regional cleavage strikes. Average crustal shear wave split time is 0.244 sec. These measurements are consistent with rock physics measurements of Central Range slate and metamorphic acoustic velocities. The splits exhibit orientations
Free form fabrication of thermoplastic composites
Kaufman, S.G.; Spletzer, B.L.; Guess, T.R.
This report describes the results of composites fabrication research sponsored by the Laboratory Directed Research and Development (LDRD) program at Sandia National Laboratories. They have developed, prototyped, and demonstrated the feasibility of a novel robotic technique for rapid fabrication of composite structures. Its chief innovation is that, unlike all other available fabrication methods, it does not require a mold. Instead, the structure is built patch by patch, using a rapidly reconfigurable forming surface, and a robot to position the evolving part. Both of these components are programmable, so only the control software needs to be changed to produce a new shape. Hence it should be possible to automatically program the system to produce a shape directly from an electronic model of it. It is therefore likely that the method will enable faster and less expensive fabrication of composites.
High performance indium-zinc-oxide thin-film transistors fabricated with a back-channel-etch-technique
NASA Astrophysics Data System (ADS)
Xu, Hua; Lan, Linfeng; Xu, Miao; Zou, Jianhua; Wang, Lei; Wang, Dan; Peng, Junbiao
Indium-zinc-oxide thin-film transistors (TFTs) with back-channel-etch (BCE) structure were demonstrated. A stacked structure of Mo/Al/Mo was used as the source/drain electrodes and patterned by a wet-etch-method. Good etching profile with few residues on the channel was obtained. The TFT showed a field effect mobility of 11.3 cm2 V-1 s-1 and a sub-threshold swing of 0.24 V/decade. The performance of this kind of TFT was better than that of the TFT with etch-stopper-layer structure, which was proved to be due to the lower contact resistance. The BCE-TFTs fabricated with this method have good prospect due to the advantage of low cost.
Meniscus-force-mediated layer transfer technique using single-crystalline silicon films with midair cavity: Application to fabrication of CMOS transistors on plastic substrates
NASA Astrophysics Data System (ADS)
Sakaike, Kohei; Akazawa, Muneki; Nakagawa, Akitoshi; Higashi, Seiichiro
A novel low-temperature technique for transferring a silicon-on-insulator (SOI) layer with a midair cavity (supported by narrow SiO2 columns) by meniscus force has been proposed, and a single-crystalline Si (c-Si) film with a midair cavity formed in dog-bone shape was successfully transferred to a poly(ethylene terephthalate) (PET) substrate at its heatproof temperature or lower. By applying this proposed transfer technique, high-performance c-Si-based complementary metal-oxide-semiconductor (CMOS) transistors were successfully fabricated on the PET substrate. The key processes are the thermal oxidation and subsequent hydrogen annealing of the SOI layer on the midair cavity. These processes ensure a good MOS interface, and the SiO2 layer works as a "blocking" layer that blocks contamination from PET. The fabricated n- and p-channel c-Si thin-film transistors (TFTs) on the PET substrate showed field-effect mobilities of 568 and 103 cm2 V-1 s-1, respectively.
Fabrication process of superconducting integrated circuits with submicron Nb/AlOx/Nb junctions using electron-beam direct writing technique
NASA Astrophysics Data System (ADS)
Aoyagi, Masahiro; Nakagawa, Hiroshi
For enhancing operating speed of a superconducting integrated circuit (IC), the device size must be reduced into the submicron level. For this purpose, we have introduced electron beam (EB) direct writing technique into the fabrication process of a Nb/AlOx/Nb Josephson IC. A two-layer (PMMA/(alpha) M-CMS) resist method called the portable conformable mask (PCM) method was utilized for having a high aspect ratio. The electron cyclotron resonance (ECR) plasma etching technique was utilized. We have fabricated micron or submicron-size Nb/AlOx/Nb Josephson junctions, where the size of the junction was varied from 2 micrometer to 0.5 micrometer at 0.1 micrometer intervals. These junctions were designed for evaluating the spread of the junction critical current. We achieved minimum-to-maximum Ic spread of plus or minus 13% for 0.81-micrometer-square (plus or minus 16% for 0.67-micrometer-square) 100 junctions spreading in 130- micrometer-square area. The size deviation of 0.05 micrometer was estimated from the spread values. We have successfully demonstrated a small-scale logic IC with 0.9-micrometer-square junctions having a 50 4JL OR-gate chain, where 4JL means four junctions logic family. The circuit was designed for measuring the gate delay. We obtained a preliminary result of the OR- gate logic delay, where the minimum delay was 8.6 ps/gate.
Correction of facial asymmetry associated with vertical maxillary excess and mandibular prognathism by combined orthognathic surgery and guiding templates and splints fabricated by rapid prototyping technique.
Ying, B; Ye, N; Jiang, Y; Liu, Y; Hu, J; Zhu, S
The facial asymmetry associated with vertical maxillary excess and mandibular prognathism is one of the more complicated types in the field of oral and maxillofacial surgery. The purpose of this study was to investigate the efficacy of combined orthognathic surgeries, together with guiding templates and splints fabricated by rapid prototyping technique, for the correction of facial asymmetry. Fourteen patients with facial asymmetry associated with vertical maxillary excess and mandibular prognathism were included. A maxillary Le Fort I osteotomy, a sagittal split ramus osteotomy on the shorter side of the face, and an intraoral vertical ramus osteotomy on the longer side of the face were performed with the aid of guiding templates and splints fabricated by rapid prototyping technique. Parameters reflecting maxillary canting, ramal inclination, mandibular deviation, and chin inclination were measured before surgery, 7 days after surgery, and 1 year after surgery, and compared. Significant differences in these parameters were found between the two sides preoperatively, whereas no differences were observed postoperatively. Facial asymmetry was corrected in all patients with satisfactory outcomes. In conclusion, combined orthognathic surgery and guiding templates and splints can offer improvements in accuracy, complexity, and duration over traditional procedures for the correction of facial asymmetry associated with vertical maxillary excess and mandibular prognathism.
Fabric analysis and ICP: Under-used geoanalytical techniques of value for plant biostratigraphy, provenance and palaeoecology
Bateman, R.M. )
Inductively-coupled plasma-arc spectrometry (ICP) is a rapid, automated method of quantifying the bulk geochemistry of artificially vitrified rocks. Measurable elements (cations of atomic No > 10) are partitioned into three categories (major, minor, trace) of decreasing abundance and increasing potential error. Even a basic analysis of the ten major elements plus loss-on-ignition is sufficient to finger-print a sample, yielding a data-set that can be fed directly into a multivariate analysis to compare and classify rocks. Thus, ex situ plant-bearing blocks can be correlated with their source horizons. ICP data also aid indirect correlation of plant-bearing horizons per se. Extensive ICP sampling reveals spatial trends that can be interpreted palaeoenvironmentally (e.g. indicating the direction of a nearby volcano, or distinguishing between biogenic and non-biogenic limestones enclosing permineralized plants). In contrast variables recorded during fabric analysis are physical rather than chemical, particulate rather than bulk, and few rather than many. Two orientations, relative to magnetic north and to the bedding plane, are taken from clast populations; these are summarized as three values (mean dip, resultant vector, vector magnitude) that can be tested against randomness. Although data are traditionally obtained from large (> 2 cm) abiotic clasts, transported fossil plant fragments are equally suitable. Adpressions are oriented by exposing bedding planes, permineralizations by reconstructing beds in the laboratory and then repeatedly transversely cutting blocks to trace the fossils. Singly, fabrics reflect the hydraulic conditions prevailing in the depositional environment immediately prior to burial; in aggregate, they indicate the direction of the source community relative to the depositional sink.
Using GIS techniques to detect the impact of territorial evolution on producing natural hazard in Northern Romania, commune Vorniceni
NASA Astrophysics Data System (ADS)
Gălbău, Ionela
Using techniques of information, such as Geographic Information Systems (GIS), on spatial analysis, offers numerous possibilities in terms of spatial emphasizing the study area and marking hazard risk areas (especially landslides). Although the means ultra modern techniques have advanced, using GIS in spatial planning remains the most important technique used. Also, GIS maps obtained are more objective than paper made by hand, using the same data and the same conceptual model. The study area, commune Vorniceni is situated in the north of Romania, Ibaneasa River basin, a tributary of Jijiei and occupies an area of 63 km2. The area has experienced over the past 50 years, a trend not only territorial but also morphological and morphometric. This study involves a relation between the evolution of territorial distribution of the population of the commune Vorniceni and influence on the environment. The construction of the dam reservoir Ibaneasa River using poor borrow pits, meant a starting point for the development of landslides. Brutal antropic intervention on the environment by building a dam or lake clogging the two reservoirs (ponds) increased possibility of negative phenomena in the area. These phenomena directly affect the village population as territorial evolution involved the construction of settlements in areas with potential risk of landslides. The analysis of the factors that have influenced the evolution of territorial and producing negative phenomena and making GIS database will be followed by the realization of a hypsometric map of slopes, slope inclination and land use. All this, highlights the relationship anthropic environment - natural environment, and not turning both low population provides another opportunity to use the land in a beneficial way by harnessing the risk map obtained. Although not without shortcomings, the method proved to be a feasible and cost-effective approach for assessing landslide susceptibility and mapping. "ACKNOWLEDGMENT This
A rapid culture technique produces functional dendritic-like cells from human acute myeloid leukemia cell lines.
Ning, Jian; Morgan, David; Pamphilon, Derwood
Most anti-cancer immunotherapeutic strategies involving dendritic cells (DC) as vaccines rely upon the adoptive transfer of DC loaded with exogenous tumour-peptides. This study utilized human acute myeloid leukemia (AML) cells as progenitors from which functional dendritic-like antigen presenting cells (DLC) were generated, that constitutively express tumour antigens for recognition by CD8(+) T cells. DLC were generated from AML cell lines KG-1 and MUTZ-3 using rapid culture techniques and appropriate cytokines. DLC were evaluated for their cell-surface phenotype, antigen uptake and ability to stimulate allogeneic responder cell proliferation, and production of IFN-γ; compared with DC derived from normal human PBMC donors. KG-1 and MUTZ-3 DLC increased expression of CD80, CD83, CD86, and HLA-DR, and MUTZ-3 DLC downregulated CD14 and expressed CD1a. Importantly, both KG-1 and MUTZ-3-derived DLC promoted proliferation of allogeneic responder cells more efficiently than unmodified cells; neither cells incorporated FITC-labeled dextran, but both stimulated IFN-γ production from responding allogeneic CD8(+) T cells. Control DC produced from PBMC using the FastDC culture also expressed high levels of critical cell surface ligands and demonstrated good APC function. This paper indicates that functional DLC can be cultured from the AML cell lines KG-1 and MUTZ-3, and FastDC culture generates functional KG-1 DLC.
Low-Cost Gas Sensors Produced by the Graphite Line-Patterning Technique Applied to Monitoring Banana Ripeness
Manzoli, Alexandra; Steffens, Clarice; Paschoalin, Rafaella T.; Correa, Alessandra A.; Alves, William F.; Leite, Fábio L.; Herrmann, Paulo S. P.
A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness. PMID:22163963
Identification of acetic acid bacteria in traditionally produced vinegar and mother of vinegar by using different molecular techniques.
Yetiman, Ahmet E; Kesmen, Zülal
Culture-dependent and culture-independent methods were combined for the investigation of acetic acid bacteria (AAB) populations in traditionally produced vinegars and mother of vinegar samples obtained from apple and grape. The culture-independent denaturing gradient gel electrophoresis (DGGE) analysis, which targeted the V7-V8 regions of the 16S rRNA gene, showed that Komagataeibacter hansenii and Komagataeibacter europaeus/Komagataeibacter xylinus were the most dominant species in almost all of the samples analyzed directly. The culture-independent GTG5-rep PCR fingerprinting was used in the preliminary characterization of AAB isolates and species-level identification was carried out by sequencing of the 16S rRNA gene, 16S-23S rDNA internally transcribed to the spacer (ITS) region and tuf gene. Acetobacter okinawensis was frequently isolated from samples obtained from apple while K. europaeus was identified as the dominant species, followed by Acetobacter indonesiensis in the samples originating from grape. In addition to common molecular techniques, real-time PCR intercalating dye assays, including DNA melting temperature (Tm) and high resolution melting analysis (HRM), were applied to acetic acid bacterial isolates for the first time. The target sequence of ITS region generated species-specific HRM profiles and Tm values allowed discrimination at species level.
Focused ion beam preparation techniques dedicated for the fabrication of TEM lamellae of fibre-reinforced composites.
Mucha, Herbert; Kato, Takeharu; Arai, Shigeo; Saka, Hiroyasu; Kuroda, Kotaro; Wielage, Bernhard
Two Focused Ion Beam based transmission electron microscopy (TEM) thin film preparation techniques are introduced. One is dedicated to the preparation of single fibres, the other to fibre/matrix interfaces of fibre reinforced composites. Due to their thin film quality, reliability and predictable processing times both techniques are suited for routine applications in material science like TEM studies of fibre microtextures and fibre/matrix interfaces. Exemplarily they are applied to Carbon Fibres and Carbon Fibre reinforced Carbon Matrix Composites (C/C). The achieved preparation standard in both cases is substantiated by TEM investigations.
Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures.
Chen, Ruei-San; Tang, Chih-Che; Shen, Wei-Chu; Huang, Ying-Sheng
Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe2) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal-semiconductor contact of the FIB-fabricated MoSe2 devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe2-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 Ω(-) (1) cm(-) (1), with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe2 multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe2 are proposed
Characterization of REBa2Cu3O7-X (RE = Gd, Ho) nanostructures, fabricated by a simple technique
NASA Astrophysics Data System (ADS)
Kargar, Mahboubeh; Alikhanzadeh-Arani, Sima; Salavati-Niasari, Masoud; Bagheri, Samira
Simple citrate sol-gel method assisted by ultrasonic irradiation has been employed to fabricate REBa2Cu3O7-X (RE123) (RE = Gd, Ho) nanostructures. The elevated temperature and pressure due to the sudden collapsing the bubbles with a high stability and energy in the ultrasonic procedure gave rise to a clear variation in the morphology, however compared with the bulk samples, the ultrasound waves had no significant effect on the onset critical temperature of the prepared nanoparticles (about 91.4 K). Changes of the magnetic susceptibility with temperature were found to be independent of the applied field strength, probably due to the elimination of the weak links in the products. The influence of various solvents with different vapor pressures and so different destruction powers, including methanol, toluene, 1-butanol, and 1-hexanol, was also studied on the morphology and particle size of the products. The crystalline size of the Ho123 was calculated 32.38 nm, according to the Williamson-Hall plot, in agreement with the TEM images. Using the Rietveld method, the lattice parameters of Ho123 nanoparticles were obtained to be slightly smaller than that of Gd123.
Piezoelectric Micro- and Nanostructured Fibers Fabricated from Thermoplastic Nanocomposites Using a Fiber Drawing Technique: Comparative Study and Potential Applications.
Lu, Xin; Qu, Hang; Skorobogatiy, Maksim
We report an all-polymer flexible piezoelectric fiber that uses both judiciously chosen geometry and advanced materials in order to enhance fiber piezoelectric response. The microstructured/nanostructured fiber features a soft hollow polycarbonate core surrounded by a spiral multilayer cladding consisting of alternating layers of piezoelectric nanocomposites (polyvinylidene enhanced with BaTiO3, PZT, or CNT) and conductive polymer (carbon-filled polyethylene). The conductive polymer layers serve as two electrodes, and they also form two spatially offset electric connectors on the fiber surface designed for the ease of connectorization. Kilometer-long piezoelectric fibers of sub-millimeter diameters are thermally drawn from a macroscopic preform. The fibers exhibit high output voltage of up to 6 V under moderate bending, and they show excellent mechanical and electrical durability in a cyclic bend-release test. The micron/nanosize multilayer structure enhances in-fiber poling efficiency due to the small distance between the conducting electrodes sandwiching the piezoelectric composite layers. Additionally, the spiral structure greatly increases the active area of the piezoelectric composite, thus promoting higher voltage generation and resulting in 10-100 higher power generation efficiency over the existing piezoelectric cables. Finally, we weave the fabricated piezoelectric fibers into technical textiles and demonstrate their potential applications in power generation when used as a sound detector, smart car seat upholstery, or wearable materials.
Microstructure and Mechanical Properties of Al356/SiCp Cast Composites Fabricated by a Novel Technique
NASA Astrophysics Data System (ADS)
Amirkhanlou, Sajjad; Niroumand, Behzad
In this study, SiCp containing composite powders were used as the reinforcement carrier media for manufacturing cast Al356/5 vol.% SiCp composites. Untreated SiCp, milled particulate Al-SiCp composite powder, and milled particulate Al-SiCp-Mg composite powder were injected into Al356 melt. The resultant composite slurries were then cast from either a fully liquid state (stir casting) or semisolid state (compocasting). The results revealed that by injection of composite powders, the uniformity of the SiCp in the Al356 matrix was greatly improved, the particle-free zones in the matrix were disappeared, the SiC particles became smaller, the porosity was decreased, and the matrix microstructure became finer. Compocasting changed the matrix dendritic microstructure to a finer non-dendritic one and also slightly improved the distribution of the SiCp. Simultaneous utilization of Al-SiCp-Mg composite powder and compocasting method increased the macro- and micro-hardness, impact energy, bending strength, and bending strain of Al356/SiCp composite by 35, 63, 20, 20, and 40%, respectively, as compared with those of the composite fabricated by injection of untreated SiCp and stir casting process.
Transplantation of three-dimensional artificial human vascular tissues fabricated using an extracellular matrix nanofilm-based cell-accumulation technique.
Asano, Yoshiya; Shimoda, Hiroshi; Okano, Daisuke; Matsusaki, Michiya; Akashi, Mitsuru
We have established a novel three-dimensional (3D) tissue-constructing technique, referred to as the 'cell-accumulation method', which is based on the self-assembly of cultured human cells. In this technique, cells are coated with fibronectin and gelatin to construct extracellular matrix (ECM) nanofilms and cultured to form multi-layers in vitro. By using this method, we have successfully fabricated artificial tissues with vascular networks constructed by co-cultivation of human umbilical vein-derived vascular endothelial cells between multi-layers of normal human dermal fibroblasts. In this study, to assess these engineered vascular tissues as therapeutic implants, we transplanted the 3D human tissues with microvascular networks, fabricated based on the cell-accumulation method, onto the back skin of nude mice. After the transplantation, we found vascular networks with perfusion of blood in the transplanted graft. At the boundary between host and implanted tissue, connectivity between murine and human vessels was found. Transmission electron microscopy of the implanted artificial vascular tubules demonstrated the ultrastructural features of blood capillaries. Moreover, maturation of the vascular tissues after transplantation was shown by the presence of pericyte-like cells and abundant collagen fibrils in the ECM surrounding the vasculature. These results demonstrated that artificial human vascular tissues constructed by our method were engrafted and matured in animal skin. In addition, the implanted artificial human vascular networks were connected with the host circulatory system by anastomosis. This method is an attractive technique for engineering prevascularized artificial tissues for transplantation. Copyright © 2015 John Wiley & Sons, Ltd.
A new seeding technique for the reliable fabrication of large, SmBCO single grains containing silver using top seeded melt growth
NASA Astrophysics Data System (ADS)
Shi, Y.-H.; Dennis, A. R.; Cardwell, D. A.
Silver (Ag) is an established additive for improving the mechanical properties of single grain, (RE)Ba2Cu3O7-δ [(RE)BCO, RE = Sm, Gd and Y] bulk superconductors. The presence of Ag in the (RE)BCO bulk composition, however, typically reduces the melting temperature of the single crystal seed in the top seeded melt growth (TSMG) process, which complicates significantly the controlled nucleation and subsequent epitaxial growth of a single grain, which is essential for high field engineering applications. The reduced reliability of the seeding process in the presence of Ag is particularly acute for the SmBCO system, since the melting temperature of SmBCO is very close to that of the generic NdBCO(MgO) seed. SmBCO has a high superconducting transition temperature, Tc, and exhibits the most pronounced 'peak' effect at higher magnetic field of all materials in the family of (RE)BCO bulk superconductors and, therefore, has the greatest potential for use in practical applications (compared to GdBCO and YBCO, in particular). Development of an effective seeding process, therefore, is one of the major challenges of the TSMG process for the growth of large, high quantity single grain superconductors. In this paper, we report a novel technique that involves introducing a buffer layer between the seed crystal and the precursor pellet, primarily to inhibit the diffusion of Ag from the green body to the seed during melt processing in order to prevent the melting of the seed. The success rate of the seeding process using this technique is 100% for relatively small batches of samples. The superconducting properties, critical temperature, Tc, critical current density, Jc and trapped fields, of the single grains fabricated using the buffers are reported and the microstructures in the vicinity of the buffer of single grains fabricated by the modified technique are analysed to understand further the effects of buffers on the growth process of these technologically important
Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps
NASA Astrophysics Data System (ADS)
Hippensteele, Steven A.; Poinsatte, Philip E.
In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence
Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps
NASA Technical Reports Server (NTRS)
Hippensteele, Steven A.; Poinsatte, Philip E.
In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence
Fabrication of fracture-free nanoglassified substrates by layer-by-layer deposition with a paint gun technique for real-time monitoring of protein-lipid interactions.
Linman, Matthew J; Culver, Sean P; Cheng, Quan
New sensing materials that are robust, biocompatible, and amenable to array fabrication are vital to the development of novel bioassays. Herein we report the fabrication of ultrathin (ca. 5-8 nm) glass (silicate) layers on top of a gold surface for surface plasmon resonance (SPR) biosensing applications. The nanoglass layers are fabricated by layer-by-layer (LbL) deposition of poly(allylamine) hydrochloride (PAH) and sodium silicate (SiO(x)), followed by calcination at high temperature. To deposit these layers in a uniform and reproducible manner, we employed a high-volume, low-pressure (HVLP) paint gun technique that offers high precision and better control through pressurized nitrogen gas. The new substrates are stable in solution for a long period of time, and scanning electron microscopy (SEM) images confirm that these films are nearly fracture-free. In addition, atomic force microscopy (AFM) indicates that the surface roughness of the silicate layers is low (rms = 2 to 3 nm), similar to that of bare glass slides. By tuning the experimental parameters such as HVLP gun pressure and layers deposited, different surface morphology could be obtained as revealed by fluorescence microscopy and SEM images. To demonstrate the utility of these ultrathin, fracture-free substrates, lipid bilayer membranes composed of phosphorylated derivatives of phosphoinositides (PIs) were deposited on the new substrates for biosensing applications. Fluorescence recovery after photobleaching (FRAP) data indicated that these lipid components in the membranes were highly mobile. Furthermore, interactions of PtdIns(4,5)P2 and PtdIns(4)P lipids with their respective binding proteins were detected with high sensitivity by using SPR spectroscopy. This method of glass deposition can be combined with already well-developed surface chemistry for a range of planar glass assay applications, and the process is amenable to automation for mass production of nanometer thick silicate chips in a highly
A simple method using two-step hot embossing technique with shrinking for fabrication of cross microchannels on PMMA substrate and its application to electrophoretic separation of amino acids in functional drinks.
Wiriyakun, Natta; Nacapricha, Duangjai; Chantiwas, Rattikan
This work presents a simple hot embossing method with a shrinking procedure to produce cross-shape microchannels on poly(methyl methacrylate) (PMMA) substrate for the fabrication of an electrophoresis chip. The proposed method employed a simple two-step hot embossing technique, carried out consecutively on the same piece of substrate to make the crossing channels. Studies of embossing conditions, i.e. temperature, pressure and time, were carried out to investigate their effects on the dimension of the microchannels. Applying a simple shrinking procedure reduced the size of the channels from 700±20µm wide×150±5µm deep to 250±10µm wide×30±2µm deep, i.e. 80% and 64% reduction in the depth and width, respectively. Thermal fusion was employed to bond the PMMA substrate with a PMMA cover plate to produce the microfluidic device. Replication of microchip was achieved by precise control of conditions in the fabrication process (pressure, temperature and time), resulting in lower than 7% RSD of channel dimension, width and depth (n =10 devices). The method was simple and robust without the use of expensive equipment to construct the microstructure on a thermoplastic substrate. The PMMA microchip was used for demonstration of amine functionalization on the PMMA surface, measurement of electroosmotic flow and for electrophoretic separation of amino acids in functional drink samples. The precision of migration time and peak area of the amino acids, Lys, Ile and Phe at 125μM to 500μM, were in the range 3.2-4.2% RSD (n=9 devices) and 4.5-5.3% RSD (n=9 devices), respectively.
Photochemical cutting of fabrics
Piltch, Martin S.
Apparatus for the cutting of garment patterns from one or more layers of fabric. A laser capable of producing laser light at an ultraviolet wavelength is utilized to shine light through a pattern, such as a holographic phase filter, and through a lens onto the one or more layers of fabric. The ultraviolet laser light causes rapid photochemical decomposition of the one or more layers of fabric, but only along the pattern. The balance of the fabric of the one or more layers of fabric is undamaged.
Fabrication of p-type CuO thin films using chemical bath deposition technique and their solar cell applications with Si nanowires
NASA Astrophysics Data System (ADS)
Akgul, Funda Aksoy; Akgul, Guvenc
Recently, CuO has attracted much interest owing to its suitable material properties, inexpensive fabrication cost and potential applications for optoelectronic devices. In this study, CuO thin films were deposited on glass substrates using chemical bath deposition technique and post-deposition annealing effect on the properties of the prepared samples were investigated. p-n heterojunction solar cells were then constructed by coating of p-type CuO films onto the vertically well-aligned n-type Si nanowires synthesized through MACE method. Photovoltaic performance of the fabricated devices were determined with current-voltage (I-V) measurements under AM 1.5 G illumination. The optimal short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency were found to be 3.2 mA/cm-2, 337 mV, 37.9 and 0.45%, respectively. The observed performance clearly indicates that the investigated device structure could be a promising candidate for high-performance low-cost new-generation photovoltaic diodes.
Direct electrochemistry of Shewanella loihica PV-4 on gold nanoparticles-modified boron-doped diamond electrodes fabricated by layer-by-layer technique.
Wu, Wenguo; Xie, Ronggang; Bai, Linling; Tang, Zuming; Gu, Zhongze
Microbial Fuel Cells (MFCs) are robust devices capable of taping biological energy, converting pollutants into electricity through renewable biomass. The fabrication of nanostructured electrodes with good bio- and electrochemical activity, play a profound role in promoting power generation of MFCs. Au nanoparticles (AuNPs)-modified Boron-Doped Diamond (BDD) electrodes are fabricated by layer-by-layer (LBL) self-assembly technique and used for the direct electrochemistry of Shewanella loihica PV-4 in an electrochemical cell. Experimental results show that the peak current densities generated on the Au/PAH multilayer-modified BDD electrodes increased from 1.25 to 2.93 microA/cm(-2) as the layer increased from 0 to 6. Different cell morphologies of S. loihica PV-4 were also observed on the electrodes and the highest density of cells was attached on the (Au/PAH)6/BDD electrode with well-formed three-dimensional nanostructure. The electrochemistry of S. loihica PV-4 was enhanced on the (Au/PAH)4/BDD electrode due to the appropriate amount of AuNPsand thickness of PAH layer.
Fabrication of polyurethane and polyurethane based composite fibres by the electrospinning technique for soft tissue engineering of cardiovascular system.
Kucinska-Lipka, J; Gubanska, I; Janik, H; Sienkiewicz, M
Electrospinning is a unique technique, which provides forming of polymeric scaffolds for soft tissue engineering, which include tissue scaffolds for soft tissues of the cardiovascular system. Such artificial soft tissues of the cardiovascular system may possess mechanical properties comparable to native vascular tissues. Electrospinning technique gives the opportunity to form fibres with nm- to μm-scale in diameter. The arrangement of obtained fibres and their surface determine the biocompatibility of the scaffolds. Polyurethanes (PUs) are being commonly used as a prosthesis of cardiovascular soft tissues due to their excellent biocompatibility, non-toxicity, elasticity and mechanical properties. PUs also possess fine spinning properties. The combination of a variety of PU properties with an electrospinning technique, conducted at the well tailored conditions, gives unlimited possibilities of forming novel polyurethane materials suitable for soft tissue scaffolds applied in cardiovascular tissue engineering. This paper can help researches to gain more widespread and deeper understanding of designing electrospinable PU materials, which may be used as cardiovascular soft tissue scaffolds. In this paper we focus on reagents used in PU synthesis designed to increase PU biocompatibility (polyols) and biodegradability (isocyanates). We also describe suggested surface modifications of electrospun PUs, and the direct influence of surface wettability on providing enhanced biocompatibility of scaffolds. We indicate a great influence of electrospinning parameters (voltage, flow rate, working distance) and used solvents (mostly DMF, THF and HFIP) on fibre alignment and diameter - what impacts the biocompatibility and hemocompatibility of such electrospun PU scaffolds. Moreover, we present PU modifications with natural polymers with novel approach applied in electrospinning of PU scaffolds. This work may contribute with further developing of novel electrospun PUs, which may be
Technique for fabrication of the mandibular denture over the staple bone implant using a permanent heat-cured base.
Goll, G E; Smith, D E
A technique that uses processed bases to which the semiprecision attachments are attached intraorally has been described. The teeth are cured in heat-cured resin directly to the base. Advantages of using heat-cured processed bases are that (1) the base is accurately related to the attachments; (2) there is direct access to the attachments for joining them to the base; (3) extension, retention, and stability can be evaluated prior to completion of the dentures; and (4) accurate jaw relation recordings can be made due to the accuracy of the fit of the bases.
Preliminary Evaluation of Techniques to Fabricate Beryllium, Polyimide, and Ge-doped CH/CD Ablator Materials
Cook, B; Letts, S; Nikroo, A; Nobile, A; McElfresh, M; Cooley, J; Alexander, D
This report including appendices provides information to complete this deliverable. It summarizes the important features of each ablator material, with particular focus to its usefulness for ignition capsules. More detailed discussions of each ablator type are in the Appendix. Included at the end of each separate discussion in the Appendix is a list of all published work with an ICF focus on that ablator type. This report is organized into Be based and polymer (C) based ablators. We summarize status, outstanding issues, and how we plan to address them. Details are in the Appendix. For Be there are two fabrication routes, one by machining bulk pieces into hemi-shells which are then bonded together, and the other by sputtering Be with Cu dopant onto spherical plastic mandrels to build up a wall. This method allows for radial variation in the Cu dopant concentration, while the machining approach is best suited to a uniform doping level. For plastic, we have already made a down select, eliminating polyimide because its performance as an ablator has been seen to be significantly different from that predicted by simulations. The other polymer, GDP (glow discharge polymer or sometimes called plasma polymer) comes in both a normal (hydrogenated) and deuterated form. There are differences between them (besides the H or D) and these will be detailed. The choice between them will be determined in part by cryogenic measurement of the IR absorption spectrum of DT scheduled to occur in the next few months. An initial list of specifications for ignition targets exists. However these specifications are continuing to evolve. This is due to evolving plans for NIF's deliverable energy and to more refined design simulations. Many requirements are not well specified due to lack of knowledge of the effect on the implosion. These requirements include: grain size and texture, fill hole size, fill tube size, bond joint thickness, allowable porosity (size and number), diameter and wall
Fabrication of electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan-copper complex by self-assembly technique.
Mao, Airong; Li, Hongbo; Jin, Dangqin; Yu, Liangyun; Hu, Xiaoya
An electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan-copper complex (MWCNTs/CTS-Cu) was fabricated by self-assembly technique. The MWCNTs/CTS-Cu modified GCE showed an excellent electrocatalytic activity for the oxidation of paracetamol, and accelerated electron transfer between the electrode and paracetamol. Under optimal experimental conditions, the differential pulse peak current was linear with the concentration of paracetamol in the range of 0.1-200 μmol L(-1) with a detection limit of 0.024 μmol L(-1). The sensitivity was found to be 0.603 A/mol L(-1). The proposed sensor also showed a high selectivity for paracetamol in the presence of ascorbic acid and dopamine. Moreover, the proposed electrode revealed good reproducibility and stability. The proposed method was successfully applied for the determination of paracetamol in tablet and human serum samples.
Quantum size effects in GaAs nanodisks fabricated using a combination of the bio-template technique and neutral beam etching.
Tamura, Yosuke; Kaizu, Toshiyuki; Kiba, Takayuki; Igarashi, Makoto; Tsukamoto, Rikako; Higo, Akio; Hu, Weiguo; Thomas, Cedric; Fauzi, Mohd Erman; Hoshii, Takuya; Yamashita, Ichiro; Okada, Yoshitaka; Murayama, Akihiro; Samukawa, Seiji
We successfully fabricated defect-free, distributed and sub-20-nm GaAs quantum dots (named GaAs nanodisks (NDs)) by using a novel top-down technique that combines a new bio-template (PEGylated ferritin) and defect-free neutral beam etching (NBE). Greater flexibility was achieved when engineering the quantum levels of ND structures resulted in greater flexibility than that for a conventional quantum dot structure because structures enabled independent control of thickness and diameter parameters. The ND height was controlled by adjusting the deposition thickness, while the ND diameter was controlled by adjusting the hydrogen-radical treatment conditions prior to NBE. Photoluminescence emission due to carrier recombination between the ground states of GaAs NDs was observed, which showed that the emission energy shift depended on the ND diameters. Quantum level engineering due to both diameter and thickness was verified from the good agreement between the PL emission energy and the calculated quantum confinement energy.
Tailoring liquid/solid interfacial energy transfer: fabrication and application of multiscale metallic surfaces with engineered heat transfer and electrolysis properties via femtosecond laser surface processing techniques
NASA Astrophysics Data System (ADS)
Anderson, Troy P.; Wilson, Chris; Zuhlke, Craig A.; Kruse, Corey; Hassebrook, Anton; Somanas, Isra; Ndao, Sidy; Gogos, George; Alexander, Dennis
Femtosecond Laser Surface Processing (FLSP) is a powerful technique for the fabrication of self-organized multiscale surface structures on metals that are critical for advanced control over energy transfer at a liquid/solid interface in applications such as electrolysis. The efficiency of the hydrogen evolution reaction on stainless steel 316 electrodes in a 1 molar potassium hydroxide solution is used to analyze the role of surface geometry to facilitate the phase conversion of the liquid to a gaseous state in the vicinity of the interface. It is found that the efficiency of the electrolysis process is directly related to the separation of micro-scale features on an electrode surface. The enhancement is attributed to the size of the valleys between microstructures controlling the contact between an evolving vapor bubble and the electrode surface. The results suggest an alternative pathway for the tailoring of interfacial energy transfer on structured surfaces separate from traditional benchmarks such as surface area and contact angle.
Biocompatible cephalosporin-hydroxyapatite-poly(lactic-co-glycolic acid)-coatings fabricated by MAPLE technique for the prevention of bone implant associated infections
NASA Astrophysics Data System (ADS)
Rădulescu, Dragoş; Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Grumezescu, Alexandru Mihai; Socol, Gabriel; Oprea, Alexandra Elena; Rădulescu, Marius; Surdu, Adrian; Trusca, Roxana; Rădulescu, Radu; Chifiriuc, Mariana Carmen; Stan, Miruna S.; Constanda, Sabrina; Dinischiotu, Anca
In this study we aimed to obtain functionalized thin films based on hydroxyapatite/poly(lactic-co-glycolic acid) (HAp/PLGA) containing ceftriaxone/cefuroxime antibiotics (ATBs) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The prepared thin films were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), selected area electron diffraction (SAED), and infra red (IR) analysis. HAp/PLGA/ATBs thin films sustained the growth of human osteoblasts, proving their good biocompatibility. The microscopic evaluation and the culture-based quantitative assay of the E. coli biofilm development showed that the thin films inhibited the initial step of microbial attachment as well as the subsequent colonization and biofilm development on the respective surfaces. This study demonstrates that MAPLE technique could represent an appealing technique for the fabrication of antibiotics-containing polymeric implant coatings. The bioevaluation results recommend this type of surfaces for the prevention of bone implant microbial contamination and for the enhanced stimulation of the implant osseointegration process.
Performances of ZnO-Based Dye Sensitized Solar Cells Fabricated by Hydrothermal Synthesis and Sol-Gel Technique
NASA Astrophysics Data System (ADS)
Zhu, Li; Fan, Yu-Qing; Zhao, Mao-Cong; Wu, Min; Zhang, Jia-Yu; Xu, Chun-Xiang; Cui, Yi-Ping
ZnO is introduced as an alternative to TiO2 in dye sensitized solar cells (DSSCs) due to its band gap similar to TiO2, higher electron mobility, and flexible procedures of preparations. Several samples of ZnO films are prepared with the hydrothermal synthesis method and the sol-gel technique, respectively. These ZnO films were assembled as photoanodes in DSSCs using N3 dye as the sensitizer. The ZnO-based cells prepared by the hydrothermal synthesis show typical current source characteristics, whose fill factor (FF) is 0.44 and photo-to-electric power conversion efficiency is 0.34%. On the other hand, all the samples prepared with the sol-gel technique show accompanied source characteristics with relatively higher power conversion efficiencies (1%) but a lower FF (0.26). X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements indicate that the sol-gel samples have small particles sizes. Therefore, sol-gel samples could adsorb more dye molecules to generate high conversion efficiencies. At the same time, more grain boundaries make it more possible for injected electrons to recombine with the oxidized electrolyte. Hydrothermal samples have bigger grains, so they show poor conversion efficiency and relatively high FF.
Single and Dual Drug Release Patterns from Shellac Wax-Lutrol Matrix Tablets Fabricated with Fusion and Molding Techniques
Phaechamud, T.; Choncheewa, C.
The objective of this investigation was to prepare the shellac wax matrix tablets by fusion and molding technique incorporated with Lutrol in different ratios to modify the hydrophobicity of matrix tablet. The matrix tablets with single drug were loaded either with propranolol hydrochloride or hydrochlorothiazide as hydrophilic and hydrophobic model drugs, and a dual drug formula was also prepared. The single and dual drug release patterns were studied in a dissolution apparatus using distilled water as medium. Propranolol hydrochloride released from matrix was easier than hydrochlorothiazide. Drug release from shellac wax matrix could be enhanced by incorporation of Lutrol. However retardation of drug release from some matrix tablets was evident for the systems that could form dispersion in the dissolution medium. The gel network from high content of Lutrol was hexagonal which was a dense and more compact structure than the other structures found when low amounts of Lutrol were present in the formula. Therefore, the formulae with high content of Lutrol could prolong drug release more efficiently than those containing low content of Lutrol. Hence shellac wax matrix could modulate the drug release with the addition of Lutrol. Sustainable dual drug release was also obtained from these developed matrix tablets. Thus shellac wax-Lutrol component could be used as a potential matrix tablet prepared with fusion and molding technique with excellent controlled drug release. PMID:25767320
Band Gap Variation of CdInSe and CdZnS Fabricated by High Throughput Combinatorial Growth Technique
NASA Astrophysics Data System (ADS)
Ma, Z. X.; Hao, H. Y.; Xiao, P.; Oehlerking, L. J.; Liu, D. F.; Zhang, X. J.; Yu, K.-M.; Walukiewicz, W.; Mao, S. S.; Yu, P. Y.; Liu, Lei; Yu, Peter Y.
High energy radiation detector operating at room temperature requires the semiconductors having band-gap energies in the range of 1.35 ˜ 2.5 eV, high Z and high carrier mobility-lifetime (μτ) product. We report here the screening of the band-gap energies of compound semiconductor CdIn2Se4 and ZnCdS doped with Sn and In, prepared by high throughput combinatorial growth technique. It is found that the band-gap energies decrease as [Cd] decreases in Cd1-xIn2+2xSe4+2x, and as In or Sn elements are incorporated in ZnxCd1-xS. For both libraries, the μτ can reach a value on the order of 10-4 cm2/V. These results have demonstrated the strong capability of the combinatorial growth technique in rapid material discovery for room temperature radiation detector applications.
Laser Frequency Stabilization for Coherent Lidar Applications using Novel All-Fiber Gas Reference Cell Fabrication Technique
NASA Technical Reports Server (NTRS)
Meras, Patrick, Jr.; Poberezhskiy, Ilya Y.; Chang, Daniel H.; Levin, Jason; Spiers, Gary D.
Compact hollow-core photonic crystal fiber (HC-PCF)gas frequency reference cell was constructed using a novel packaging technique that relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers. The use of this gas cell for laser frequency stabilization was demonstrated by locking a tunable diode laser to the center of the P9 line from the (nu)1+(nu)3 band of acetylene with RMS frequency error of 2.06 MHz over 2 hours. This effort was performed in support of a task to miniaturize the laser frequency stabilization subsystem of JPL/LMCT Laser Absorption Spectrometer (LAS) instrument.
Fabrication of Gd2O3 nanofibers by electrospinning technique using PVA as a structure directing template
NASA Astrophysics Data System (ADS)
Thangappan, R.; Kalaiselvam, S.; Elayaperumal, A.; Jayavel, R.
Gd2O3 fibers from nano to submicron diameter were prepared by electrospinning technique. The polyvinyl alcohol (PVA) was used as a structure directing template for the synthesis of Gd2O3 fibers. The crystal structure and morphology of Gd2O3 fiber were studied by XRD and SEM analyses. The presence of functional groups was confirmed by FTIR spectroscopy. Thermal behavior of PVA/Gd2(NO3)2 hybrid fibers were investigated by thermo-gravimetric analysis. Gd2O3 nanofibers exhibit bright down and upconversion luminescence under ultraviolet light excitation, with potential applications as of light-emitting phosphors, advanced flat panel displays and biological labeling.
Investigation of structural and electrical properties of flat a-Si/c-Si heterostructure fabricated by EBPVD technique
Demiroğlu, D.; Tatar, B.; Kazmanli, K.; Urgen, M.
Flat amorphous silicon - crystal silicon (a-Si/c-Si) heterostructure were prepared by ultra-high vacuum electron beam evaporation technique on p-Si (111) and n-Si (100) single crystal substrates. Structural analyses were investigated by XRD, Raman and FEG-SEM analysis. With these analyses we determined that at the least amorphous structure shows modification but amorphous structure just protected. The electrical and photovoltaic properties of flat a-Si/c-Si heterojunction devices were investigated with current-voltage characteristics under dark and illumination conditions. Electrical properties of flat a-Si/c-Si heterorojunction; such as barrier height Φ{sub B}, diode ideality factor η were determined from current-voltage characteristics in dark conditions. These a-Si/c-Si heterostructure have good rectification behavior as a diode and exhibit high photovoltaic sensitivity.
Cation exchange on the nanoscale: an emerging technique for new material synthesis, device fabrication, and chemical sensing.
Rivest, Jessy B; Jain, Prashant K
Cation exchange is an age-old technique for the chemical conversion of liquids or extended solids by place-exchanging the cations in an ionic material with a different set of cations. The technique is undergoing a major revival with the advent of high-quality nanocrystals: researchers are now able to overcome the limitations in bulk systems and fully exploit cation exchange for materials synthesis and discovery via rapid, low-temperature transformations in the solid state. In this tutorial review, we discuss cation exchange as a promising materials synthesis and discovery tool. Exchange on the nanoscale exhibits some unique attributes: rapid kinetics at room temperature (orders of magnitude faster than in the bulk) and the tuning of reactivity via control of nanocrystal size, shape, and surface faceting. These features make cation exchange a convenient tool for accessing nanocrystal compositions and morphologies for which conventional synthesis may not be established. A simple exchange reaction allows extension of nanochemistry to a larger part of the periodic table, beyond the typical gamut of II-VI, IV-VI, and III-V materials. Cation exchange transformations in nanocrystals can be topotactic and size- and shape-conserving, allowing nanocrystals synthesized by conventional methods to be used as templates for production of compositionally novel, multicomponent, or doped nanocrystals. Since phases and compositions resulting from an exchange reaction can be kinetically controlled, rather than governed by the phase diagram, nanocrystals of metastable and hitherto inaccessible compositions are attainable. Outside of materials synthesis, applications for cation exchange exist in water purification, chemical staining, and sensing. Since nanoscale cation exchange occurs rapidly at room temperature, it can be integrated with sensitive environments such as those in biological systems. Cation exchange is already allowing access to a variety of new materials and processes
Fabrication of Ni-Ti Alloy by Self-Propagating High-Temperature Synthesis and Spark Plasma Sintering Technique
NASA Astrophysics Data System (ADS)
Salvetr, Pavel; Kubatík, Tomáš František; Pignol, Damien; Novák, Pavel
This work is focused on the possibilities of preparing Ni-Ti46 wt pct alloy by powder metallurgy methods. The self-propagating high-temperature synthesis (SHS) and combination of SHS reaction, milling, and spark plasma sintering consolidation (SPS) are explored. The aim of this work is the development of preparation method with the lowest amount of undesirable phases (mainly Ti2Ni phase). The SHS with high heating rate (approx. 200 and 300 K min-1) was applied. Because the SHS product is very porous, it was milled in vibratory disk milling and consolidated by SPS technique at temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C). The microstructures of samples prepared by SHS reaction and combination of SHS reaction, milling, and SPS consolidation are compared. The changes in microstructure with increasing temperature of SPS consolidation are observed. Mechanical properties are tested by hardness measurement. The way to reduce the amount of Ti2Ni phase in structure is leaching of powder in 35 pct hydrochloric acid before SPS consolidation.
Surface-enhanced Raman scattering by colloidal CdSe nanocrystal submonolayers fabricated by the Langmuir–Blodgett technique
Sveshnikova, Larisa L; Duda, Tatyana A; Rodyakina, Ekaterina E; Dzhagan, Volodymyr M; Gordan, Ovidiu D; Veber, Sergey L; Himcinschi, Cameliu; Latyshev, Alexander V; Zahn, Dietrich R T
Summary We present the results of an investigation of surface-enhanced Raman scattering (SERS) by optical phonons in colloidal CdSe nanocrystals (NCs) homogeneously deposited on both arrays of Au nanoclusters and Au dimers using the Langmuir–Blodgett technique. The coverage of the deposited NCs was less than one monolayer, as determined by transmission and scanning electron microscopy. SERS by optical phonons in CdSe nanocrystals showed a significant enhancement that depends resonantly on the Au nanocluster and dimer size, and thus on the localized surface plasmon resonance (LSPR) energy. The deposition of CdSe nanocrystals on the Au dimer nanocluster arrays enabled us to study the polarization dependence of SERS. The maximal SERS signal was observed for light polarization parallel to the dimer axis. The polarization ratio of the SERS signal parallel and perpendicular to the dimer axis was 20. The SERS signal intensity was also investigated as a function of the distance between nanoclusters in a dimer. Here the maximal SERS enhancement was observed for the minimal distance studied (about 10 nm), confirming the formation of SERS "hot spots". PMID:26734529
Fabrication of (Ba1-xSrx)(ZrxTi1-x)O3 ceramics prepared using the combustion technique
NASA Astrophysics Data System (ADS)
Thongtha, A.; Angsukased, K.; Bongkarn, T.
Barium strontium zirconate titanate ((Ba1-xSrx)(ZrxTi1-x)O3 BSZT, x = 0.25 and 0.75) ceramics with a highly crystalline structure were successfully synthesized using the combustion technique, in which urea performed an important role. The effect of calcination (1000-1300 °C) and sintering temperatures (1300-1550 °C) on the phase formation and microstructure of BSZT ceramics were investigated. The pure perovskite phase of BSZT (x = 0.25 and 0.75) powders with a uniform cubic morphology were detected at the calcination temperature of 1300 °C. At the same calcination and sintering temperature, the lattice parameter a of BSZT powder and ceramics with x = 0.75 is higher than x = 0.25. The microstructure of BSZT powders exhibited an almost-spherical morphology and had a porous agglomerated form. The average particle size and the average grain size of all ceramics increased with the increase of calcination and sintering temperatures, but decreased when the content of x increased. The maximum densities of x = 0.25 and 0.75 ceramics were around 5.85 and 5.62 g cm-3 obtained from the samples sintered at 1500 and 1450 °C, respectively.
Fabrication of Ni-Ti Alloy by Self-Propagating High-Temperature Synthesis and Spark Plasma Sintering Technique
NASA Astrophysics Data System (ADS)
Salvetr, Pavel; Kubatík, Tomáš František; Pignol, Damien; Novák, Pavel
This work is focused on the possibilities of preparing Ni-Ti46 wt pct alloy by powder metallurgy methods. The self-propagating high-temperature synthesis (SHS) and combination of SHS reaction, milling, and spark plasma sintering consolidation (SPS) are explored. The aim of this work is the development of preparation method with the lowest amount of undesirable phases (mainly Ti2Ni phase). The SHS with high heating rate (approx. 200 and 300 K min-1) was applied. Because the SHS product is very porous, it was milled in vibratory disk milling and consolidated by SPS technique at temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C). The microstructures of samples prepared by SHS reaction and combination of SHS reaction, milling, and SPS consolidation are compared. The changes in microstructure with increasing temperature of SPS consolidation are observed. Mechanical properties are tested by hardness measurement. The way to reduce the amount of Ti2Ni phase in structure is leaching of powder in 35 pct hydrochloric acid before SPS consolidation.
Identification of a keratinase-producing bacterial strain and enzymatic study for its improvement on shrink resistance and tensile strength of wool- and polyester-blended fabric.
Cai, Shao-Bo; Huang, Zheng-Hua; Zhang, Xing-Qun; Cao, Zhang-Jun; Zhou, Mei-Hua; Hong, Feng
A wool-degrading bacterium was isolated from decomposition wool fabrics in China. The strain, named 3096-4, showed excellent capability of removing cuticle layer of wool fibers, as demonstrated by removing cuticle layer completely within 48 h. According to the phenotypic characteristics and 16S rRNA profile, the isolate was classified as Pseudomonas. Bacteria growth and keratinase activity of the isolate were determined during cultivation on raw wool at different temperatures, initial pH, and rotation speed using orthogonal matrix method. Maximum growth and keratinase activity of the bacterium were observed under the condition including 30 °C, initial pH 7.6, and rotational speeds 160 rpm. The keratinase-containing crude enzyme prepared from 3096-4 was evaluated in the treatment of wool fabrics. The optimal condition of our enzymatic improvement of shrink resistance was the combination of 30 °C, initial pH 7.6, and rotation speeds 160 rpm. After the optimized treatment, the wool fabrics felting shrink was 4.1% at 6 h, and textile strength was not lost.
Fabrication of zirconia composite membrane by in-situ hydrothermal technique and its application in separation of methyl orange.
Kumar, R Vinoth; Ghoshal, Aloke Kumar; Pugazhenthi, G
The main objective of the work was preparation of zirconia membrane on a low cost ceramic support through an in-situ hydrothermal crystallization technique for the separation of methyl orange dye. To formulate the zirconia film on the ceramic support, hydrothermal reaction mixture was prepared using zirconium oxychloride as a zirconia source and ammonia as a precursor. The synthesized zirconia powder was characterized by X-ray diffractometer (XRD), N2 adsorption/desorption isotherms, Thermogravimetric analysis (TGA), Fourier transform infrared analysis (FTIR), Energy-dispersive X-ray (EDX) analysis and particle size distribution (PSD) to identify the phases and crystallinity, specific surface area, pore volume and pore size distribution, thermal behavior, chemical composition and size of the particles. The porosity, morphological structure and pure water permeability of the prepared zirconia membrane, as well as ceramic support were investigated using the Archimedes' method, Field emission scanning electron microscopy (FESEM) and permeability. The specific surface area, pore volume, pore size distribution of the zirconia powder was found to be 126.58m(2)/g, 3.54nm and 0.3-10µm, respectively. The porosity, average pore size and pure water permeability of the zirconia membrane was estimated to be 42%, 0.66µm and 1.44×10(-6)m(3)/m(2)skPa, respectively. Lastly, the potential of the membrane was investigated with separation of methyl orange by means of flux and rejection as a function of operating pressure and feed concentration. The rejection was found to decrease with increasing the operating pressure and increases with increasing feed concentrations. Moreover, it showed a high ability to reject methyl orange from aqueous solution with a rejection of 61% and a high permeation flux of 2.28×10(-5)m(3)/m(2)s at operating pressure of 68kPa.
Evaluation of the marginal and internal gap of metal-ceramic crown fabricated with a selective laser sintering technology: two- and three-dimensional replica techniques
Kim, Ki-Baek; Kim, Jae-Hong; Kim, Woong-Chul; Kim, Hae-Young
PURPOSE One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. MATERIALS AND METHODS The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (α=.05). RESULTS In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). CONCLUSION Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range. PMID:23755345
Experimental study of PLLA/INH slow release implant fabricated by three dimensional printing technique and drug release characteristics in vitro
Background Local slow release implant provided long term and stable drug release in the lesion. The objective of this study was to fabricate biodegradable slow release INH/PLLA tablet via 3 dimensional printing technique (3DP) and to compare the drug release characteristics of three different structured tablets in vitro. Methods Three different drug delivery systems (columnar-shaped tablet (CST), doughnut-shaped tablet (DST) and multilayer doughnut-shaped tablet (MDST)) were manufactured by the three dimensional printing machine and isoniazid was loaded into the implant. Dynamic soaking method was used to study the drug release characteristics of the three implants. MTT cytotoxicity test and direct contact test were utilized to study the biocompatibility of the implant. The microstructures of the implants' surfaces were observed with electron microscope. Results The PLLA powder in the tablet could be excellently combined through 3DP without disintegration. Electron microscope observations showed that INH distributed evenly on the surface of the tablet in a "nest-shaped" way, while the surface of the barrier layer in the multilayer doughnut shaped tablet was compact and did not contain INH. The concentration of INH in all of the three tablets were still higher than the effective bacteriostasis concentration (Isoniazid: 0.025 ~ 0.05 μg/ml) after 30 day's release in vitro. All of the tablets showed initial burst release of the INH in the early period. Drug concentration of MDST became stable and had little fluctuation starting from the 6th day of the release. Drug concentration of DST and CST decreased gradually and the rate of decrease in concentration was faster in DST than CST. MTT cytotoxicity test and direct contact test indicated that the INH-PLLA tablet had low cytotoxicity and favorable biocompatibility. Conclusions Three dimensional printing technique was a reliable technique to fabricate complicated implants. Drug release pattern in MDST was
Film fabrication of Fe or Fe3O4 nanoparticles mixed with palmitic acid for vertically aligned carbon nanotube growth using Langmuir-Blodgett technique
NASA Astrophysics Data System (ADS)
Nakamura, Kentaro; Kuriyama, Naoki; Takagiwa, Shota; Sato, Taiga; Kushida, Masahito
Vertically aligned carbon nanotubes (VA-CNTs) were studied as a new catalyst support for polymer electrolyte fuel cells (PEFCs). Controlling the number density and the diameter of VA-CNTs may be necessary to optimize PEFC performance. As the catalyst for CNT growth, we fabricated Fe or Fe3O4 nanoparticle (NP) films by the Langmuir-Blodgett (LB) technique. The catalyst Fe or Fe3O4 NPs were widely separated by mixing with filler molecules [palmitic acid (C16)]. The number density of VA-CNTs was controlled by varying the ratio of catalyst NPs to C16 filler molecules. The VA-CNTs were synthesized from the catalyst NP-C16 LB films by thermal chemical vapor deposition (CVD) using acetylene gas as the carbon source. The developing solvents used in the LB technique and the hydrogen reduction conditions of CVD were optimized to improve the VA-CNT growth rate. We demonstrate that the proposed method can independently control both the density and the diameter of VA-CNTs.
Post annealing effects on structural, optical and electrical properties of CuSbS2 thin films fabricated by combinatorial thermal evaporation technique
NASA Astrophysics Data System (ADS)
Hussain, Arshad; Ahmed, R.; Ali, N.; Butt, Faheem K.; Shaari, A.; Shamsuri, W. N. Wan; Khenata, R.; Prakash, Deo; Verma, K. D.
Copper antimony sulfide (CuSbS2) thin films were fabricated by combinatorial thermal evaporation technique on well cleaned glass substrates. The deposited thin films were annealed in argon gas atmosphere for 1 h at temperature range of 150-350 °C. The effect of annealing temperature on structural, morphological, optical and electrical properties was studied using the different characterization techniques. The XRD analysis confirmed the crystallinity of the obtained samples with CuSbS2 phase in chalcostibite structure. Optical properties of the deposited samples showed good response in the visible and NIR region, envisaging the potential of CuSbS2 as an efficient solar cell material. The optical band gap of CuSbS2 thin films was measured to be 1.5 eV. A decrease (12.5-1.43 KΩ-cm) was observed for the resistivity of samples with the increase in annealing temperature. The plot of sheet resistance with annealing temperature confirmed the uniformity of samples. These thin films were found as a sustainable substitute material for the absorber layer in conventional thin film solar cell system, because of the abundance and low cost of its constituent elements. This study opens new avenue of research for scalable synthesis of CuSbS2 thin films for solar cell and photovoltaic applications.
An optical amplifier having 5 cm long silica-clad erbium doped phosphate glass fiber fabricated by "core-suction" technique
NASA Astrophysics Data System (ADS)
Goel, Nitin K.; Pickrell, Gary; Stolen, Roger
We have fabricated an erbium-doped phosphate glass fiber with a silica cladding and used 5 cm length of it to form an optical amplifier. A bulk erbium phosphate glass called MM2 was used as a core glass in a silica cladding tube to prepare a preform using "core-suction" technique. This MM2 glass preform was drawn to a fiber and the resultant fiber was of good optical quality, free from air bubbles and major defects. The fiber was mechanically strong enough to allow for ease of handling and could be spliced to conventional silica fiber using commercial fusion splicer. This fiber was then used to setup an EDFA. Our work demonstrates the potential to form silica clad optical fibers with phosphate cores doped with very high levels of rare-earth ions. It is demonstrated that the core suction technique can be used to make a high-gain erbium phosphate fiber amplifier that is compatible with conventional silica fibers.
Fabrication of organic FETs based on printing techniques and the improvement of FET properties by the insertion of solution-processable buffer layers
NASA Astrophysics Data System (ADS)
Itoh, Eiji; Kanamori, Akira
In this study, we developed multilayer deposition and patterning processes that can be used to fabricate all-printed, organic field-effect transistors (OFETs) on the basis of vacuum-free, solution-processable soft-lithography techniques. We have used regioregular poly(3-hexylthiophene) (P3HT) as a soluble p-type polymer semiconductor and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as a soluble n-type semiconductor, and cross-linked poly(vinyl phenol) (CL-PVP) as a low-temperature (<150 °C)-curable soluble polymer gate insulator. We have compared the electrical properties of OFETs with multiwalled carbon nanotubes (MWCNTs), silver nanoparticles (NPs), and their composites (or multilayers) as printed source-drain (S-D) electrodes in order to fabricate vacuum-free, all-printed OFETs. The P3HT-OFETs with MWCNT S-D electrodes exhibited higher hole mobility and on/off ratios than the devices with Ag NP S-D electrodes owing to better contact at the MWCNT/P3HT interface. On the other hand, Ag/molybdenum oxide (MoO3) S-D electrodes considerably enhanced the hole injection and caused the reduction in the on/off ratio and the difficulty in turning off the devices. The PCBM-OFETs with MWCNT S-D electrodes also exhibited higher electron mobility that is almost comparable to that of P3HT-OFETs and lower threshold voltage, which was considered to be due to the enhanced electron injection at the electrode interface.
In vitro and in vivo performance of bioactive Ti6Al4V/TiC/HA implants fabricated by a rapid microwave sintering technique.
Choy, Man Tik; Tang, Chak Yin; Chen, Ling; Wong, Chi Tak; Tsui, Chi Pong
Failure of the bone-implant interface in a joint prosthesis is a main cause of implant loosening. The introduction of a bioactive substance, hydroxyapatite (HA), to a metallic bone-implant may enhance its fixation on human bone by encouraging direct bone bonding. Ti6Al4V/TiC/HA composites with a reproducible porous structure (porosity of 27% and pore size of 6-89 μm) were successfully fabricated by a rapid microwave sintering technique. This method allows the biocomposites to be fabricated in a short period of time under ambient conditions. Ti6Al4V/TiC/HA composites exhibited a compressive strength of 93 MPa, compressive modulus of 2.9 GPa and microhardness of 556 HV which are close to those of the human cortical bone. The in vitro preosteoblast MC3T3-E1 cells cultured on the Ti6Al4V/TiC/HA composite showed that the composite surface could provide a biocompatible environment for cell adhesion, proliferation and differentiation without any cytotoxic effects. This is among the first attempts to study the in vivo performance of load-bearing Ti6Al4V/TiC and Ti6Al4V/TiC/HA composites in a live rabbit. The results indicated that the Ti6Al4V/TiC/HA composite had a better bone-implant interface compared with the Ti6Al4V/TiC implant. Based on the microstructural features, the mechanical properties, and the in vitro and in vivo test results from this study, the Ti6Al4V/TiC/HA composites have the potential to be employed in load-bearing orthopedic applications.
14 CFR 23.605 - Fabrication methods.
Code of Federal Regulations, 2010 CFR
... Fabrication methods. (a) The methods of fabrication used must produce consistently sound structures. If a fabrication process (such as gluing, spot welding, or heat-treating) requires close control to reach...
Au/Cr-ZnO-Ni structured metal-insulator-metal diode fabrication using Langmuir-Blodgett technique for infrared sensing
NASA Astrophysics Data System (ADS)
Azad, Ibrahim; Ram, Manoj K.; Goswami, D. Yogi; Stefanakos, Elias
The thin nanolayer film of ZnO was synthesized through Langmuir-Blodgett (LB) organic precursor film. The zinc stearate monolayer was formed at air-water interface using zinc acetate as a subphase. The zinc stearate monolayers were deposited on silicon (Si), glass, and gold (Au)/chromium (Cr) plated Silicon (Si) substrates using LB technique. Later, the zinc stearate multilayers LB films on various substrates were annealed at two different temperatures (300oC and 550oC) for the fabrication of zinc oxide (ZnO) nanolayer film. The zinc stearate monolayers as well zinc oxide (ZnO) nanolayer films were characterized using atomic force microscopy (AFM) and X-ray diffraction techniques. The X-ray diffraction measurement has shown the hexagonal wurtzite structure of the ZnO nanolayer on the substrate. The average surface roughness was estimated to be 1.076 nm using AFM technique. The metal-insulator-metal (MIM) diode structure was realized by sandwiching ZnO nanolayer film between thin layer of Gold (Au)/Chromium (Cr) and Nickel (Ni) on silicon substrates. The electron tunneling conduction mechanism is understood through the current-voltage (I-V) characteristics of MIM diode. The highest measured sensitivity magnitude of 20 in inverse of voltage (V-1) with rectification ratio of nearly 10 at +/-400 mV in MIM diode is an indicative of its potential application in infrared sensing applications. However, the thin film of ZnO synthesized using LB film as an insulating layer in metal-insulator-metal diode structure was studied for the first time.
Effects of Process Parameters on Fabrication of 2D- C f/Al Composite Parts by Liquid-Solid Extrusion Following the Vacuum Infiltration Technique
NASA Astrophysics Data System (ADS)
Ma, Y. Q.; Qi, L. H.; Zhou, J. M.; Zhang, T.; Li, H. J.
Two-dimensional, carbon-fiber-reinforced aluminum matrix composites (2D- C f/Al composites) were prepared using liquid-solid extrusion by following the vacuum infiltration technique (LSEVI), which was an integrated and comprehensive process that resulted in as composite special-shaped part with ideal infiltration and a satisfied forming effect. According to the current research, we found preheating temperature, squeeze temperature, squeeze pressure, and melting temperature were the key parameters of the LSEVI technique, and it was very important to optimize these process parameters to obtain the ideal composite part. Through the research of orthogonal experimental design of these process parameters, results showed that squeeze pressure was the most significant influence parameter, and optimized parameters of aforementioned parameters were 888 K, 893 K, and 1053 K (615 °C, 620 °C, and 780 °C), 70 MPa, respectively. An infiltration effect of the C f/Al composite was full and uniform, and preparation defects could be avoided effectively under the above process parameters. Two-dimensional (2D) T300 carbon fiber preform was prepared by the method of carbon fiber laminates, and the 2D- C f/Al composite special-shaped part was fabricated successfully using the former optimized parameters of LSEVI. Results indicated a forming effect of the special-shaped part was obtained and that its sizes were reasonable. Through the analyses of microstructure and tensile property test, its infiltration effect and fracture morphology were satisfied. Carbon fibers in the composite played the reinforced effect effectively, so the ultimate tensile strength of the composite part was improved by 115.8 pct than that of the matrix, which proved that the optimized process parameters of the LSEVI technique were reasonable.
Method for Fabricating Composite Structures Using Continuous Press Forming
NASA Technical Reports Server (NTRS)
Farley, Gary L. (Inventor)
A method for fabricating composite structures at a low-cost. moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a net-shape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates. resulting in lower cost and high structural performance.
Method for Fabricating Composite Structures Using Pultrusion Processing
NASA Technical Reports Server (NTRS)
Farley, Gary L. (Inventor)
A method for fabricating composite structures at a low-cost, moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a net-shape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.
Method for Fabricating Composite Structures Using Pultrusion Processing
NASA Technical Reports Server (NTRS)
Farley, Gary L. (Inventor)
A method for fabricating composite structures at a low-cost, moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a netshape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electronbeam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.
Fabrication of mullite-bonded porous SiC ceramics from multilayer-coated SiC particles through sol-gel and in-situ polymerization techniques
NASA Astrophysics Data System (ADS)
Ebrahimpour, Omid
second part of the project. Alumina sol was synthesized by the hydrolysis of Aluminum isopropoxide using the Yoldas method. Alumina sol was homogenous and had a needle-like shape with a thickness of 2--3 nm. Crystalline changes during the heating process of alumina sol were studied using XRD. In addition, Fourier transform infrared (FTIR) spectroscopy was performed to identify the functional groups on the alumina sol surface as a function of temperature. In the third part of the project, the feasibility of the in-situ polymerization technique was investigated to fabricate porous SiC ceramics. In this part, the mixture of SiC and calcined alumina powders were coated by polyethylene via in-situ polymerizing referred to as the polymerization compounding process in a slurry phase. The polymerization was conducted under very moderate operational conditions using the Ziegler-Natta catalyst system. Differential scanning calorimetry (DSC) and TGA analysis and morphological studies (SEM and TEM) revealed the presence of a high density of polyethylene on the surface of SiC and alumina powders. The amount of polymer was controlled by the polymerization reaction time. Most parts of particles were coated by a thin layer of polyethylene and polymer. The porous SiC ceramics, which were fabricated by these treated particles showed higher mechanical and physical properties compared to the samples made without any treatment. The relative intensity of mullite was higher compared to the samples prepared by the traditional process. The effects of the sintering temperature, forming pressure and polymer content were also studied on the physical and mechanical properties of the final product. In the last phase of this research work, the focus of the investigation was to take advantage of both the sol-gel processing and in-situ polymerization method to develop a new process to manufacture mullite-bonded porous SiC ceramic with enhanced mechanical and physical properties. Therefore, first the Si
Development of techniques for producing static strata maps and development of photointerpretive methods based on multitemporal LANDSAT data
NASA Technical Reports Server (NTRS)
Colwell, R. N. (Principal Investigator); Hay, C. M.; Thomas, R. W.; Benson, A. S.
Progress in the evaluation of the static stratification procedure and the development of alternative photointerpretive techniques to the present LACIE procedure for the identification of training fields is reported. Statistically significant signature controlling variables were defined for use in refining the stratification procedure. A subset of the 1973-74 Kansas LACIE segments for wheat was analyzed.
Development of techniques for producing static strata maps and development of photointerpretation methods based on multitemporal LANDSAT data
NASA Technical Reports Server (NTRS)
Colwell, R. N. (Principal Investigator); Hay, C. M.; Thomas, R. W.; Benson, A. S.
The progress of research conducted in support of the Large Area Crop Inventory Experiment (LACIE) is documented. Specific tasks include (1) evaluation of the static stratification procedure and modification of that procedure if warranted, and (2) the development of alternative photointerpretative techniques to the present LACIE procedures for the identification and selection of training fields (areas).
Fabrication of nanostructures using MBE and MOVPE
NASA Astrophysics Data System (ADS)
Ahopelto, J.; Lipsanen, H. K.; Sopanen, M.; Koljonen, T.; Tuomi, T.; Airaksinen, V. M.; Sinkkonen, J.; Sirén, E.
Two different fabrication techniques to obtain nanometer scale structures without the use of lithography are demonstrated. Quantum dots are made on GaAs by growing strained InP islands by metal-organic vapour phase epitaxy. Quantum confinement of carriers is achieved by the growth of quantum wells on the InP islands. Molecular beam epitaxy is used for the fabrication of a gold island mask on GaAs. Reactive ion etching through the gold mask produces a high density of GaAs columns with diameters down to 20 nm.
Short communication: Genetic correlations between number of embryos produced using in vivo and in vitro techniques in heifer and cow donors.
Jaton, C; Koeck, A; Sargolzaei, M; Price, C A; Baes, C; Schenkel, F S; Miglior, F
Multiple embryos can be produced from a heifer or cow donors using an in vivo or an in vitro technique. Comparisons of the number of embryos produced by the same donors as heifers and cows and using different techniques are limited. The main objectives of this study were to assess the genetic correlation between the number of embryos produced by Holstein donors using an in vivo and in vitro technique as a heifer and as a cow. The data set used was recorded by Holstein Canada and included all successful superovulations or ovum pickup and in vitro fertilization procedures performed on Holstein donors for more than 20yr. The type of technique used was known for all records and the status of the donor at recovery was retrieved from calving records. Bivariate repeatability animal model analyses were performed for both the total number of embryos (NE) and the number of viable embryos (VE) recovered per procedure. Logarithmic transformation was performed on the traits to normalize the data. Heritability estimates for the donor varied between 0.14 (0.02) and 0.19 (0.03) over all analyses, indicating that the number of embryos produced by a donor is influenced by the genetic potential of the donor. Genetic correlations between records produced in vivo and in vitro were moderately high and positive (NE=0.85±0.07; VE=0.63±0.09), suggesting that donors with high genetic potential for in vivo superovulation tend also to have high potential to produce multiple embryos in vitro. Similarly, the moderately high genetic correlations (NE=0.79±0.05; VE=0.72±0.05) found between heifer and cow records indicate that a donor tends to produce a comparable number of embryos as a heifer or as a cow. The estimated repeatabilities (0.23 to 0.35) indicated that the number of embryos recovered should be somewhat repeatable in the same donor over time. On the other hand, the service sires seem not to play an important role on the total number of embryos produced by a donor no matter the
Sharp high-aspect-ratio AFM tips fabricated by a combination of deep reactive ion etching and focused ion beam techniques.
Caballero, David; Villanueva, Guillermo; Plaza, Jose Antonio; Mills, Christopher A; Samitier, Josep; Errachid, Abdelhamid
The shape and dimensions of an atomic force microscope tip are crucial factors to obtain high resolution images at the nanoscale. When measuring samples with narrow trenches, inclined sidewalls near 90 degrees or nanoscaled structures, standard silicon atomic force microscopy (AFM) tips do not provide satisfactory results. We have combined deep reactive ion etching (DRIE) and focused ion beam (FIB) lithography techniques in order to produce probes with sharp rocket-shaped silicon AFM tips for high resolution imaging. The cantilevers were shaped and the bulk micromachining was performed using the same DRIE equipment. To improve the tip aspect ratio we used FIB nanolithography technique. The tips were tested on narrow silicon trenches and over biological samples showing a better resolution when compared with standard AFM tips, which enables nanocharacterization and nanometrology of high-aspect-ratio structures and nanoscaled biological elements to be completed, and provides an alternative to commercial high aspect ratio AFM tips.
Morphological appearances and photo-controllable coloration of dye-doped cholesteric liquid crystal/polymer coaxial microfibers fabricated by coaxial electrospinning technique.
Lin, Jia-De; Chen, Che-Pei; Chen, Lin-Jer; Chuang, Yu-Chou; Huang, Shuan-Yu; Lee, Chia-Rong
This study systematically investigates the morphological appearance of azo-chiral dye-doped cholesteric liquid crystal (DDCLC)/polymer coaxial microfibers obtained through the coaxial electrospinning technique and examines, for the first time, their photocontrollable reflection characteristics. Experimental results show that the quasi-continuous electrospun microfibers can be successfully fabricated at a high polymer concentration of 17.5 wt% and an optimum ratio of 2 for the feeding rates of sheath to core materials at 25 °C and a high humidity of 50% ± 2% in the spinning chamber. Furthermore, the optical controllability of the reflective features for the electrospun fibers is studied in detail by changing the concentration of the azo-chiral dopant in the core material, the UV irradiation intensity, and the core diameter of the fibers. Relevant mechanisms are addressed to explain the optical-control behaviors of the DDCLC coaxial fibers. Considering the results, optically controllable DDCLC coaxial microfibers present potential applications in UV microsensors and wearable smart textiles or swabs.
Studies on the fabrication of Ag/Hg1Ba2Ca1Cu2O6+dgr/CdSe heterostructures using the pulse electrodeposition technique
NASA Astrophysics Data System (ADS)
Shivagan, D. D.; Shirage, P. M.; Pawar, S. H.
Metal/superconductor/semiconductor (Ag/Hg1Ba2Ca1Cu2O6+dgr (Hg-1212)/CdSe) heterostructures have been successfully fabricated using the pulse electrodeposition technique. The electrochemical parameters are optimized and diffusion free growth of CdSe on to Ag/Hg-1212 was obtained by employing underpotential deposition and by studying nucleation and growth mechanism during deposition. The heterostructures are characterized by x-ray diffraction, scanning electron microscopy studies and low-temperature four-probe electrical resistivity measurements. After the deposition of CdSe, the critical transition temperature of Hg-1212 films was found to be increased from 115 K with Jc (77 K) = 1.7 × 103 A cm-2 to 117.2 K with Jc (77 K) = 1.91 × 103 A cm-2. Tc and Jc (77 K) values were 120.3 K and 3.7 × 103 A cm-2, respectively, when the heterostructure was irradiated with red He-Ne laser. The improvements in superconducting properties of Hg-1212 in Ag/Hg-1212/CdSe heterostructures have been explained at length in this paper.
Development of techniques for producing static strata maps and development of photointerpretive methods based on multitemporal LANDSAT data
NASA Technical Reports Server (NTRS)
Colwell, R. N. (Principal Investigator)
The results and progress of work conducted in support of the Large Area Crop Inventory Experiment (LACIE) are documented. Research was conducted for two tasks. These tasks include: (1) evaluation of the UCB static stratification procedure and modification of that procedure if warranted; and (2) the development of alternative photointerpretive techniques to the present LACIE procedure for the identification and selection of training areas for machine-processing of LACIE segments.
Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique
Kim, Jae-Hong; Kim, Ki-Baek; Kim, Woong-Chul; Kim, Ji-Hwan
Objective This study aimed to evaluate the accuracy and precision of polyurethane (PUT) dental arch models fabricated using a three-dimensional (3D) subtractive rapid prototyping (RP) method with an intraoral scanning technique by comparing linear measurements obtained from PUT models and conventional plaster models. Methods Ten plaster models were duplicated using a selected standard master model and conventional impression, and 10 PUT models were duplicated using the 3D subtractive RP technique with an oral scanner. Six linear measurements were evaluated in terms of x, y, and z-axes using a non-contact white light scanner. Accuracy was assessed using mean differences between two measurements, and precision was examined using four quantitative methods and the Bland-Altman graphical method. Repeatability was evaluated in terms of intra-examiner variability, and reproducibility was assessed in terms of inter-examiner and inter-method variability. Results The mean difference between plaster models and PUT models ranged from 0.07 mm to 0.33 mm. Relative measurement errors ranged from 2.2% to 7.6% and intraclass correlation coefficients ranged from 0.93 to 0.96, when comparing plaster models and PUT models. The Bland-Altman plot showed good agreement. Conclusions The accuracy and precision of PUT dental models for evaluating the performance of oral scanner and subtractive RP technology was acceptable. Because of the recent improvements in block material and computerized numeric control milling machines, the subtractive RP method may be a good choice for dental arch models. PMID:24696823
An in vitro study to compare the accuracy of the master cast fabricated by four different transfer impression techniques for single-tooth implant replacement.
Lahori, Manesh; Nagrath, Rahul; Agrawal, Prateek
Single tooth implant retained crowns have become a recognized technique for the replacement of the missing teeth. With the predictable integration of implants, the emphasis is shifted towards precise prosthesis. Minor movement of the impression coping retained inside the impression material can occur during all the procedures, leading to the three-dimensional spatial inaccuracies in the master casts. Therefore, the present study was undertaken with the purpose to evaluate the accuracy of single-tooth implant impression techniques using four different impression copings, so as to obtain a precise definitive cast for a single-unit implant restoration. A maxillary acrylic resin model with a standard single implant in the first molar region was used to simulate a clinical situation. A total of 60 impressions were made with polyvinylsiloxane impression material, which were divided into four groups of 15 impressions each. Group I used non-modified square impression coping, while in group II, III and IV square impression coping were modified differently. Master casts fabricated for all the groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. The master casts obtained with the roughened and adhesive-coated impression copings showed a lower amount of rotational movement than the masters casts achieved with the non-modified impression copings. Hence, the clinician should use sandblasted and adhesive coated impression copings to achieve a more accurate and precise orientation of the implant replicas in the laboratory master casts in single-tooth implant restorations.
Effects of apple cider vinegars produced with different techniques on blood lipids in high-cholesterol-fed rats.
Budak, Nilgun H; Kumbul Doguc, Duygu; Savas, Cagri M; Seydim, Atif C; Kok Tas, Tugba; Ciris, Metin I; Guzel-Seydim, Zeynep B
Red delicious apples were used to produce natural apple cider with and without inclusion of maceration. Traditional surface and industrial submersion methods were then applied to make vinegar from apple ciders. Apple cider vinegar samples produced with inclusion of maceration in the surface method had the highest total phenolic content, chlorogenic acid, ORAC, and TEAC levels. Cholesterol and apple vinegar samples were administered using oral gavage to all groups of rats except the control group. Apple cider vinegars, regardless of the production method, decreased triglyceride and VLDL levels in all groups when compared to animals on high-cholesterol diets without vinegar supplementation. Apple cider vinegars increased total cholesterol and HDL and LDL cholesterol levels and decreased liver function tests when compared to animals on a high-cholesterol diet without vinegar supplementation. A high-cholesterol diet resulted in hepatic steatosis. VSBM and VSB groups significantly decreased steatosis.