Figure 7.

(a) The prototype of the Alpha-IMS predecessor, including 16 additional electrodes for direct stimulation. The microphotodiode array (MPDA) consists of 1500 photodiodes on a surface area of 3 × 3 mm [7]; (b) SEM of the microfabricated SU-8 pillar arrays, each pillar is about 10 μm in diameter and 40–70 μm in height. Insert: a pillar array attracts retinal cells for achieving intimate electrode-cell proximity [74]; (c) MPDA developed by the Palanker group. Insert: blown-up view of a single stimulating element with 3 photodiodes in series [7]; (d) Boston retinal implant chip, showing some of the 256 electrode current drivers. Insert: retinal implant concept with the secondary coil surrounding the cornea [73]. Reproduced from the mentioned references with permission from the related journals.