Fabrication of platinum spherical electrodes and their characterisation using a reverse telemetry system

As part of an on-going research effort in the area of vision prosthetics, a 100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application specific integrated circuit (ASIC) and a 10 × 10 electrode array for interfacing with surviving neurons of the retina has been designed. We describe a technique for the consistent and accurate formation of platinum spheres that are used in the electrode array. The technique uses a controlled discharge across an ionized air gap. We also discuss a simple reverse telemetry feature of the ASIC that provides in-situ, end-of-phase voltage across the stimulating electrodes and use this feature to characterize the electrodes in physiological saline.