Fabrication of platinum spherical electrodes in an intra-ocular prosthesis using high-energy electrical discharge

A 100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application specific integrated circuit (ASIC) and a 10 x 10 electrode array for interfacing with surviving neurons of the retina has been designed. We discuss the fabrication of the accompanying electrode array that is to be connected to the implant. Specifically, a technique is described that allows the consistent and accurate formation of platinum spheres. The technique uses a controlled discharge across an ionised air gap. The magnitude of the discharge energy (controlled by pre-selecting different discharge capacitors), allows for the control of sphere diameter. One hundred of the said spheres with attached 100 mum diameter platinum wires are then fabricated into an electrode array formed from a silicone base. We demonstrate that using our technique, it is possible to inexpensively fabricate uniform spheres for use in neuroprosthetic devices and that said spheres are suitable for both recording and stimulation of physiological functions. (C) 2003 Elsevier B.V. All rights reserved.