Fabrication of Flexible Convex-Shaped Microelectrodes for Epiretinal Prostheses

By means of microfabrication technology,an array of 6×6 flexible convex-shaped microelectrodes was designed and fabricated with Parylene C as the bulk material,in which the diameter of Parylene based flexible convex-shaped microelectrode is 80 μm,the width of metal traces is 40 μm,the spacing of electrode is 280 μm and the pitch between metal traces is 80 μm.The single electrode is about 10 μm in height with an apparent protruding feature.The surface of electrode and trace is smooth and intact with a distinct outline.Impedance measurement results show that the impedance of the flexible convex-shaped microelectrode decreased dramatically with the increase of frequency,indicating a high-pass feature.The impedance of the microelectrode was 10 kΩ at 1 kHz,about 30% lower than that of the planar electrode with the same base surface area,which helps to raise the signal-to-noise ratio so that it can be used in epiretinal prostheses.The fabrication technique of the flexible convex-shaped microelectrode is simple,favorable to realize high-efficiency batch fabrication and to enhance the integration level of microelectrode.