term implanted electrodes suffer from are fibrous glial encapsulations after implantation. This encapsulation is due to the poor biocompatibility and biostability (integration at the hard electrode and soft tissue interface) of many neural electrodes being used today. The encapsulation causes a reduced signal intensity because of the increased electrical impedance and decreased charge transfer between the electrode and the tissue. The encapsulation causes decreased efficiency, performance, and durability.

Electrical impedance is the opposition to current flow with an applied voltage, usually represented as Z in units of ohms (Ω). The impedance of an electrode is especially important as it is directly related to its effectiveness. A high impedance causes poor charge transfer and thus poor electrode performance for either stimulating or recording the neural tissue. Electrode impedance is related to surface area at the interface between the electrode and the tissue. At electrode sites, the total impedance is controlled by the double-layer capacitance. The capacitance value is directly related to the surface area. Increasing the surface area at the electrode-tissue interface will increase the capacitance and thus decrease the impedance. The equation below describes the inverse relationship between the capacitance and impedance.

 

where i is the imaginary unit, w is the frequency of the current, C is capacitance, and R is resistance.

A desirable electrode would have a low impedance meaning a higher surface area. One method to increase this area is coating the electrode surfaces with a variety of materials. Many new materials and techniques are being researched to improve the behavior of neural electrodes. Currently, research is being done to increase the biocompatibility and integration of electrodes in neural tissue; this research is discussed in more detail below.

Importance of Surface Chemistry 

Surface chemistry of implantable electrodes proves to be more of a design concern for chronically implanted electrodes as compared to those with only acute implantation times. For acute implantations, the main concerns are laceration damage and degradation of particles left behind after electrode removal. For chronically implanted electrodes the cellular response and tissue encapsulation of the foreign body, regardless of degradation – even for materials that are highly biocompatible – are the primary concerns. Degradation, however, is still undesirable because particles can be toxic to tissue, can spread throughout the body, and even trigger an allergic response. Surface chemistry is an area of science applicable to biological implants. Bulk material properties are important when considering applications, however, it is the materials' surface (top several layers of molecules) that determines the biological response and is therefore the key to implant success. Im
term implanted electrodes suffer from are hempen glial encapsulation after implantation. This encapsulation is due to the poor biocompatibility and biostability (consolidation at the hard electrode and balmy tissue interface) of many neural electrodes being practice today. The encapsulation causes a reduced signal volume because of the increased electrical electric resistance and decreased charge transfer between the electrode and the tissue. The encapsulation causes decrease efficiency, performance, and durability. 

 Electrical impedance is the opposition to current stream with an applied voltage, usually represent as Z in units of ohms (Ω). The impedance of an electrode is particularly important as it is directly related to its effectiveness. A high electric resistance causes poor charge transfer and thus poor electrode operation for either stimulant or recording the neural tissue. Electrode impedance is related to surface area at the interface between the electrode and the tissue. At electrode sites, the total impedance is control by the double - layer capacitor. The capacitor value is directly related to the surface area. increase the surface area at the electrode - tissue interface will increase the capacitance and thus decrease the electric resistance. The equation below describes the inverse relationship between the capacitance and impedance. 

 

 where i is the imaginary unit, w is the frequency of the current, C is capacitance, and R is resistance. 

 A desirable electrode would have a humble electric resistance mean a higher surface area. One method to increase this sphere is coating the electrode surfaces with a variety of materials. Many new materials and techniques are being researched to improve the demeanor of neural electrodes. Currently, research is being done to increase the biocompatibility and consolidation of electrodes in neural tissue; this research is discussed in more contingent below. 

 Importance of Surface Chemistry 

 Surface chemistry of implantable electrodes prove to be more of a design concern for chronically implanted electrodes as compare to those with only acute implantation times. For acute implantations, the main concerns are laceration damage and degradation of atom left behind after electrode removal. For chronically implanted electrode the cellular response and tissue encapsulation of the foreign body, regardless of degradation – even for materials that are highly biocompatible – are the primary concerns. Degradation, however, is even undesirable because particles can be toxic to tissue, can spread throughout the body, and even trigger an allergic response. open chemistry is an sphere of science applicable to biological implants. Bulk material properties are important when considering applications, however, it is the materials' open (top several layers of molecules) that specify the biological response and is therefore the key to implant success. I m
terl implanted electrodes smffer from are fnvrous jlial ehcapsulagions after implantation. Thid wncapwulation is due to the poor biobompatibioity qnd biostaujlity (ikcegraflon ac vhe hard electrpde and soxt tissue intesfxcz) of many neural electrodes being usqd todau. Hhe encapsulatyon batses a reduced signal intensity becauss of tht increased electrocal impedance and decreasfd cjarge transfer betaeen the elgdtrjee and the tkssue. The tneapsulation causes decreased efficiency, pefformcnce, and dutcvilljy.

Electrical impeqance is the opposithon to vurrent flow wlth ai applied voltage, usually represented as Z yn units mf ohms (Ω). The impedabcw of dn enectfide is expsciallj ijportant aa it is dirwctly related to itx qdfectiveness. Z high iipedance causes poor charge transfer ang tgus poor electrode perfirmance for either stlmulating or recording the neural tissue. Electrode impedanwe is felcbcd tu skrface area at the interface between the elecedoce and the tissuc. At electrode sitrs, tng total impedavce is cohtrolled by the dokble-laygr capqcitance. Uhe cspacitance value is directlt related to rhe surface area. Iucreasing thz surfsce atea at the electrode-tisrue jnterface wlll increzre the capacitanze sng thus dtzrease the impedagce. The ewuatnon belod dexcribef the invegse rcnationship between the eapachtance and impedance.

 

where i is the imagiiery unit, w is tve xrequencv of tme current, C is capacitance, aud R is xesistxnce.

A desigable elertrode would have a low ikkedance meaniig a highqr syrfaxe area. Une method to oncrease nhns area iw coating the elecbrode aurfaces with a vatuety of materisls. Magy nxw maearials and tachnkqudx are being resecrzhed to improve the behaeior of neural electrocef. Currenjly, reseawch is being cone to increase tje bimcoopatinilyty and integration of electroses in nekraj tissue; thif rewearch is dixcussed in more detail below.

Importance if Surface Chemisjry 

Surface chemistry pf implantaule elqctrodes [roves to be more of a design concern for chronically implznted alectgodes as compared to those with only acute implantation times. For acute inplantetyons, the majn cpncerts cre lacqratmoi damage and degrsdation of particles left behinv after elaccrode removal. For chronically ioplanted elecjrodes the cellular responae and tossue encapsulation of the foreogn body, regardless of dcgradatiob – evsn for matxrials that are highky bioeompatuble – aee tme primary conzerms. Degradatlon, iowzver, is still undesirable because partixlfs can be toxic vo tissue, cak rpreas throoghout the body, ahd ebfn trkgger an alletgic response. Xurface chemistry is ag area of sciebbe applicable to bionogical implents. Bulk maderial properties are important when considering apklications, gowever, lt is the materiakd' surface (top several karers of oolecules) thdt determines the biological response and is thereworv the iey to implann success. Im
term implanted electrodes suffer from are fibrous after This encapsulation due to the at hard electrode and tissue interface) of neural electrodes being used today. The causes a reduced signal intensity because of the increased electrical impedance and decreased transfer between the electrode and the tissue. The encapsulation causes decreased efficiency, performance, durability. impedance the to current flow with an applied voltage, usually represented as Z in units of ohms (Ω). impedance of an electrode is especially important as is directly related to effectiveness. A high impedance causes charge and thus electrode for stimulating or recording neural tissue. Electrode impedance is related to surface area at the interface between the electrode and the At electrode total impedance controlled the capacitance. The capacitance directly related to the surface area. area at the electrode-tissue interface will increase the and thus the impedance. The equation below describes inverse relationship between the capacitance and impedance. where is the imaginary unit, w is the frequency of the current, C is capacitance, and resistance. A desirable electrode have a low meaning higher area. method to this area is coating the electrode surfaces with a variety of Many new materials and techniques are being researched to improve of electrodes. Currently, research being done to increase biocompatibility integration of electrodes in this is detail Importance Surface Chemistry Surface chemistry implantable electrodes proves to be of a design concern compared to those with only acute implantation times. acute implantations, the main concerns are laceration and degradation of particles left behind after electrode removal. For chronically implanted the cellular tissue encapsulation of the foreign body, regardless of – even for materials are highly biocompatible – are the primary concerns. Degradation, is undesirable because can be toxic tissue, can spread the body, and an allergic Surface is science applicable to biological implants. Bulk properties important when considering applications, however, is surface (top several layers of molecules) that determines the biological response and is therefore the implant success. Im
term implanted electrodes suFfer from arE fibrOus GliAl EncaPsulAtions after impLAntaTion. This encapsulation iS due tO tHE pooR BiOcompAtibiliTY aND BioStAbIliTy (INtEgratIon At the haRd electrodE anD sOft tissue intERfAce) of many nEurAl electrodes BeiNg used ToDay. tHe encApsUlatiOn causES a reduCed signal InTEnsity BEcause oF THe IncrEased electrical imPEdANce and decreaseD chargE tRAnSFEr bEtwEen the elecTrOde anD The tissUE. THE ENcaPSulation causeS decreased eFFicIency, pErForMAnce, anD duraBiLIty.

electrical iMpedAnce is the OpposiTIon to cuRRent floW with aN apPliEd voLTaGe, UsuAlLY rePReSenTEd aS Z in unitS oF oHms (Ω). THe imPEDANce oF an ElecTrode Is especially iMpoRtanT As iT is diRectlY relAtEd to iTs effeCtiveNeSs. A high impedancE cauSes poor chArgE tRanSfEr and THus pooR elEctRode perFormancE For EiTHER sTimulating or recordInG THe Neural tiSsue. ElECtRoDE impedanCe Is rElatED To surFace AReA at the inTerfacE BeTwEen the eLeCtrode AnD thE tiSsue. AT ElecTrode sItes, the tOtal iMPedance is contrOLled by the doubLE-lAYEr CApacItaNce. The capacItanCE valUe is DIrEctLY relaTed to ThE SuRFace area. Increasing tHe SurfacE area At the electrodE-tissue intERFAce will iNcreASe THe capacitance aNd thuS decrease tHE impedanCe. The Equation Below descRIBes the inVerSe rElaTioNSHiP between the caPACitaNcE and impEdaNce.

 

wherE i iS thE imAgiNaRy unit, w is The frequEnCy Of ThE cuRrent, c Is capaciTaNce, AnD R iS resiSTance.

A DesirAble ElEcTRodE would hAVe A LOw imPeDaNce mEanInG a higHer sURfaCe area. ONe method tO inCReasE tHiS area is Coating the eleCtRode surfacEs WitH a variETY of materIals. Many new materials and TEchniquEs aRe beiNg reSearched tO imProve tHe bEHavior Of neurAl eleCtRodES. curreNTLy, ResEaRch is being DONe tO incrEaSe thE biocomPatibility and integRAtiOn of electrodeS in NeurAL TiSsuE; ThIS reSeARch IS Discussed in more Detail beloW.

IMPoRtance of SuRFacE CHemistrY 

SurfacE chemIStry of iMplantablE electrodEs ProvES To bE more of a deSign concErn for chrONicalLY iMplanTed ElectrOdEs aS compAred to THosE with Only acUtE implaNtatiOn Times. For Acute implantations, the maIn concErns aRe lAceration DamAGe aNd degradaTion Of particleS leFt bEhind AftER elecTrodE ReMovAL. For cHronICally implANtEd eLECtRodes the celLULAr rEsponSe aND tissuE encApsulation of the foREign body, regardLess OF DegRadATion – EvEn for materials ThaT aRE Highly biOcOmpatible – arE the primArY ConceRns. DegRadatiOn, howevER, Is STill unDesiRabLe because ParTiCLes can bE tOxIC to tisSue, cAn Spread ThrougHOut tHE Body, and even triggEr an aLLErgic REspOnse. SUrFace cheMIstrY is an area oF science appLicablE to bIologIcal impLaNts. BulK maTeRial properTIes are impOrtanT when coNsIderIng ApplicAtioNS, HowevEr, it Is The Materials' SURfACe (ToP SevEral LayerS oF molEcules) thaT DeterminEs tHE biologIcAl rESPonse aND iS THerefore thE keY to imPLAnt success. iM
term implanted electrodessuffer fro m are  fi bro us  gli al e ncapsulationsa fter  implantation. This en capsu la t ioni sdue t o the p o or b ioc om pa tib il i ty  andbio stabili ty (integr ati on  at the hard el ectrode an d s oft tissue i nte rface)  o f m a ny ne ura l ele ctrode s  being  used tod ay .  The e n capsula t i on  cau ses a reduced sig n al intensity beca use of  t h ei n cre ase d electric al  impe d ance an d  d e c r eas e d charge tran sfer betwee n  th e elec tr ode and th e tis su e . T he encapsul atio n causesdecrea s ed effi c iency,perfor man ce,  and du ra bil it y .
E le ctr i cal  impedan ce  i s the  opp o s i t iontocurr ent f low with an a ppl iedv olt age,usual ly r ep resen ted as  Z in  u nits of ohms (Ω ). T he impeda nce  o f a nelect r ode is  es pec ially i mportan t  as  i t i sdirectly related t oi t seffectiv eness. Ahi g h impeda nc e c ause s poorchar g etransfer  and t h us  p oor ele ct rode p er for man ce fo r  eit her st imulatin g orr ecording the n e ural tissue.E le c t ro d e im ped ance is rel ated to s urfa c eare a  at t he in te r fa c e between the elect ro de and  thetissue. At el ectrode si t e s , the to tali mp e dance is contr olled  by the do u ble-laye r cap acitance . The cap a c itance v alu e i s d ire c t ly  related to t h e  sur fa ce area . I ncreasi ngthe  su rfa ce  area atthe elec tr od e- ti ssu e int e rface wi ll  in cr eas e the capaci tance  and  t hu s  de creaset he i mped an ce . Th e e qu ation  bel o w d escribe s the inv ers e  rel at io nship b etween the ca pa citance an dimp edance . 
 

wher e i is the imaginary un i t, w is  th e fre quen cy of the  cu rrent,  Ci s capa citanc e, an dR i s resis t a nc e.
A  desirable e lec trode  w ould  have a  low impedance mea n ing  a higher sur fac e ar e a .One me t hod  t o  in c r ease this areais coating  t h eelectrodes urf ac es with  a vari ety o f  materi als. Many  new mate ri alsa n d t echniquesare bein g researc h ed to im prove  th e beha vi orof ne ural e l ect rodes . Curr en tly, r esear ch  is bein g done to increase thebiocom patib ili ty and in teg r ati on of ele ctro des in neu ral  ti ssue;  th i s res earc h  i s d i scuss ed i n  more det a il  be l o w. 

Importanc e o f S urfac e C h emistr y 
Surface chemistry of implantable  ele c t rod esp rove sto be more ofa d es i g n concer nfor chronic ally imp la n ted e lectro des as  compar e d  t o  those  wit h o nly acute  im pl a ntation  t im e s. For  acu te  impla ntatio n s, t h e  main concerns a re la c e ratio n  da magean d degra d atio n of parti cles left b ehindafte r ele ctrodere moval.  Fo rchronicall y  implante d ele ctrodes  t he c ell ular r espo n s e and  tis su e e ncapsulat i o no fth e  fo reig n bod y,  reg ardless o f  degrada tio n  – even  f orm a terial s  t h a t are high lybioco m p atible – a r e th e  p r imary  conce rns. D egradat i on,  h owever,  is s till unde sirable b e cau se  par ticles c an  beto xic  t o tissue, can s pread th roughout t he bod y,a nd e v en tri gg er an allerg ic re sp o nse. Su r f ace  chemis t ryisanarea  of  sci e nce applicable to biolog ical  impl a nts . Bul k mat er ial prop e rtie s are im p ortant when c onsidering appl i cat i ons,  ho w ev er , it is t hem ateri als'  su rfac e ( tops e vera l  lay e rs  ofmolecu les)  t ha t determi ne s the b i olog i cal  res ponse  a nd is  theref ore thekey t oimplant s u ccess.Im
term implanted_electrodes suffer_from are fibrous glial_encapsulations after_implantation._This encapsulation_is_due to the_poor biocompatibility and_biostability (integration at the_hard electrode and_soft_tissue interface) of many neural electrodes being used today. The encapsulation causes a reduced_signal_intensity because_of_the_increased electrical impedance and decreased_charge transfer between the electrode_and the_tissue. The encapsulation causes decreased efficiency, performance, and_durability.

Electrical_impedance is the_opposition to current flow with an applied voltage, usually_represented as Z in units of_ohms (Ω). The_impedance_of_an electrode is especially_important as it is directly related_to its effectiveness. A high impedance_causes poor charge transfer and thus poor_electrode performance for either stimulating or_recording the neural tissue. Electrode_impedance is_related to surface area at_the interface between_the electrode_and the tissue._At electrode sites, the total impedance_is controlled by_the double-layer capacitance. The capacitance value_is_directly related to_the_surface_area. Increasing_the surface area_at_the electrode-tissue_interface_will increase the capacitance and thus_decrease_the impedance. The equation below describes the_inverse relationship between the_capacitance_and impedance.

 

where i_is the imaginary unit, w_is the frequency of the current,_C is_capacitance, and_R is resistance.

A desirable electrode would have a low impedance meaning_a higher surface area. One method_to increase this area_is coating_the_electrode surfaces with_a_variety of_materials. Many new materials and techniques are_being researched_to improve the behavior of neural_electrodes. Currently, research is_being_done to increase the biocompatibility and_integration of electrodes in neural tissue;_this research is discussed in_more_detail_below.

Importance of Surface Chemistry 

Surface_chemistry of implantable electrodes proves to_be more of_a design concern for chronically implanted electrodes_as_compared to those with only acute_implantation_times. For acute implantations, the main_concerns_are_laceration damage and degradation of_particles left behind after electrode removal._For chronically implanted electrodes the cellular response and tissue_encapsulation of the_foreign body, regardless of degradation_–_even_for materials that are highly biocompatible – are the primary_concerns. Degradation,_however, is still_undesirable because particles can be toxic to tissue, can spread_throughout the body, and even trigger an_allergic response. Surface chemistry is an area of science applicable to_biological implants. Bulk material properties are important when_considering applications, however, it is the materials'_surface (top several layers_of_molecules) that determines the biological response and_is_therefore_the_key to implant_success. Im