The improvement of an electrode array for retinal prosthesis is described. Two elements of fundamental technology required in next-generation retinal prosthesis, the miniaturization of and wiring of a stimulus electrode, were investigated. To miniaturize the stimulus electrode without performance degradation, surface coating by iridium oxide (IrOx), a high performance material, was introduced. The electrochemical properties and durability of an IrOx coated electrode were evaluated through in vitro and in vivo experimentation. Results showed that IrOx coating delivers a higher performance with sufficient durability and contributes to the miniaturization of the electrode without degrading the stimulus capability. Smart-wiring technology using CMOS microchips was also investigated. A prototype electrode array with CMOS microchips was fabricated to clarify the concept. A dedicated CMOS microchip was hybrid-integrated into a stimulus electrode array. Results of in vivo experiments showed that the fabricated array stimulated retinal cells effectively. Miniaturized electrodes with an IrOx coating and smart-wiring technology enable the fabrication of a super-multi-channel (i.e., more than 1000) electrode array, which is required for next-generation retinal prosthesis.
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