Flexible silicon structures for a retina implant

Worldwide there are some different approaches toward the development of a retina implant as a visual prosthesis for people suffering from retinitis pigmentosa (RP). In this work we present an epiretinal implant system with the emphasis on the retina stimulator which differs significantly from other approaches by using flexible single-crystal silicon. This substrate provides on the one hand the flexibility required by the implant to adapt the retina shape. On the other hand it enables us to integrate complex circuitry monolithically on the stimulator chip. Especially circuitry for a bus system can be placed in the immediate vicinity of the stimulating microelectrode array ensuring the possibility of increasing the number of microelectrodes. The CMOS-compatible fabrication process consists of a combination of wet chemical anisotropic etching producing an silicon mesa array and plasma etching forming the flexible crosspieces between those 'silicon islands'. The testing results of the fabricated flexible silicon structures are presented and discussed in this paper.