of conversion electrodes is its large voltage hysteresis. Mapping Balke et al. is aiming to understand the intercalation mechanism for lithium-ion batteries at the nanoscale. This mechanism is understood at the microscale, but behavior of matter changes depending on the size of the material. Zhu et al. are also mapping the intercalation of lithium ions at the nanoscale using scanning probe microscopy. Mathematical models for lithium battery intercalation have been calculated and are still under investigation. Whittingham suggested that there was no single mechanism by which lithium ions move through the electrolyte of the battery. The movement depended on a variety of factors including, but not limited to, particle size, the thermodynamic state or metastable state of the battery and whether the reaction operated continuously. Their experimental data for LiFePO4 – FePO4 suggested the movement of Li-ions in a curved path rather than a linear straight jump within the electrolyte. Intercalation mechanisms have been studied for polyvalent cations as well. Lee et al. has studied and determined the proper intercalation mechanism for rechargeable zinc batteries. Stretchable electronics Research has also been done to use carbon nanotube fiber springs as electrodes. LiMn2O4 and Li4Ti5O12 are the nanoparticles that have been used as the cathode and anode respectively, and have demonstrated the ability to stretch 300% of their original length. Applications for stretchable electronics include energy storage devices and solar cells. Printable batteries Researchers at the University of California, Los Angeles have successfully developed a "nanotube ink" for manufacturing flexible batteries using printed electronics techniques. A network of carbon nanotubes has been used as a form of electronically conducting nanowires in the cathode of a zinc-carbon battery. Using nanotube ink, the carbon cathode tube and manganese oxide electrolyte components of the zinc-carbon battery can be printed as different layers on a surface, over which an anode layer of zinc foil can be printed. This technology replaces charge collectors like metal sheets or films with a random array of carbon nanotubes. The carbon nanotubes add conductance. Thin and flexible batteries can be manufactured that are less than a millimeter thick. Although discharge currents of the batteries are at present below the level of practical use, the nanotubes in the ink allow the charge to conduct more efficiently than in a conventional battery, such that the nanotube technology could lead to improvements in battery performance. Technology like this is applicable to solar cells, supercapacitors,