Flexible Electrode Array for Retinal Stimulation

In this Work, ITO/PET (Indium Tin Oxide / Polyethylene Terephthalate) electrode structure which provides biocompatibility, mechanical stability and flexibility is fabricated. Flexible ITO/PET implantable electrode array for a retina has been developed. The electrode array is fabricated on a thin PET/ITO substrate and is encapsulated using, SU- 8, an insulating material. PET substrate and SU-8 polymer make electrodes flexible so that they could shape to contoured tissues. A layer of gold on the stimulation sites serves to reduce the electrode/tissue interface impedance. Prototypes of 4×4 and 12×6 electrode arrays are fabricated for primary and dense configuration of retina prosthesis respectively. The exposed electrode diameters are 125μm for primary and 100μm for dense micro electrode array. The stimulation sites of primary configuration were connected via 50μm interconnects with 5 μm spacing. 40μm width traces with 15 μm spacing connect sites to bonding pads in the other design. To verify the functionality of the micro fabricated electrodes, the electrochemical impedance spectroscopy is measured. The electrode/tissue impedance was 19.4KΩ at 1 KHz for 7854μm2 area.