Fabrication of pyramid shaped three-dimensional 8 × 8 electrodes for artificial retina

This paper presents a pyramid shaped three-dimensional 8 × 8 multi-electrode array for artificial retina application. Each electrode features a pyramid shape composed of one (1 1 1) plane and two vertical planes. The cone angle between the (1 1 1) plane and the vertical plane is 19.5°, which is the sharpest angle, as far as reported [1], [2], [3], [4], [5], [6] and [7]. The sharp pyramid shaped electrode is capable of penetrating the inner limiting membrane with minimal invasiveness, which in turns can stimulate retina cells more effectively than a square shaped two-dimensional electrode. The characteristic measurement of impedance magnitude and the phase shift of a single electrode are 1.19 MΩ and −80.8° at 1 kHz, respectively. Although the single three-dimensional electrode covers only 145 μm2 of the base area, its magnitude of impedance is as low as a 900 μm2 area two-dimensional electrode indicating that the three-dimensional electrode has higher signal-to-noise ratio than the two-dimensional electrode.