gms | German Medical Science

Objective: Retinitis Pigmentosa (RP) and age-related macular degeneration (AMD) cause degeneration of photoreceptor cells, leading to blindness in affected patients. A retinal prosthesis based on an epiretinal implant can partially restore vision in these patients. The quality of the restored image strongly depends on the number of electrodes and the field of view of the implanted devices. Current implant devices are limited in the number of electrodes due to their passive connectors. The presented work aims to develop an implant device with more than 1,000 electrodes.

Materials and Methods: We designed a chip with more than 1,000 electrodes. To minimize the electronic connectors, each electrode is connected to a selector transistor in a 32x32 array configuration with row and column decoders. Each electrode will be individually addressed by the selector transistor.

Results: A chip with 32x32 electrodes has been fabricated on a silicon-on-insulator (SOI) substrate. This chip consists of p-type transistors as selectors combined with IrOx electrodes. The source and gate of each transistor are connected to the common connection lines of each row and column, reducing the number of electronic connectors to 64. The IrOx electrodes are directly connected to the drains of the transistors, interfacing with ganglion cells to deliver stimulation signals. In the next steps, the chip will be transferred to a flexible polyimide substrate and encapsulated with parylene C to maintain the mechanical flexibility required for integration with the curved shape of the retina.

Acknowledgement: This work was funded by the Deutsche Forschungsgemeinschaft (DFG), GRK2610/1 project number 424556709.