Electrochemical Evaluation of Geometrical Effect and Three-dimensionalized Effect of Iridium Oxide Electrodes Used for Retinal Stimulation

Abstract

The geometry dependence and three-dimensionalized effect of the electrochemical properties of iridium oxide electrodes used in retinal prosthesis are discussed herein. Planar electrodes with various geometries were fabricated. Three-dimensionalized electrodes with microfabricated resin cores were also fabricated. The charge storage capacity (CSC) and charge injection capacity (CIC), both of which are important properties for neural stimulation, were quantitatively evaluated. This evaluation showed the important electrode property that the surface area dominantly affects the CSC. On the other hand, the CIC was not proportionally related to the electrode area, confirming that the edge region of the electrodes is significant in the mechanism of action. Moreover, performance enhancement with a three-dimensionalized electrode was clearly confirmed. The fundamental properties of highly effective stimulus electrodes were successfully evaluated and a detailed discussion is presented.