Design and fabrication of a high-density flexible microelectrode array

Retinal prosthesis can be utilized for restoring vision to blind patients caused by retinitis pigmentosa or age-related macular degeneration. We proposed a 1025-channel high-density flexible microelectrode array (fMEA) for retinal prosthesis based on two kinds of substrate materials: polyimide (PI) and parylene-C (PA). We designed the fMEA with 25×41 pixels, and the diameter of each stimulating microelectrode was 60 µm with a center-to-center spacing of 160 µm. The fMEA was microfabricated with dual-metal-layer structure based on a simplified fabrication process. Meanwhile, the as-fabricated samples were electroplated with platinum gray, which significantly reduced the electrochemical impedance from 110 kΩ to 16 kΩ at 1 kHz, and also provided much larger charge storage capacity. We expect these results will promote the engineering of high-density fMEA for neural stimulation and recording.