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.

I Introduction

Visual prosthesis capable of eliciting visual sense in a blind or visually impaired individual through electrical stimulation is mainly utilized for restoring vision of patients blinded by retinitis pigmentosa (RP) or age-related macular degeneration (AMD) [1], because of the photoreceptors in the retinal of the patients are damaged but the remaining inner retinal circuitry remains largely intact [2]. Implantable microelectrodes are needed for stimulating the remaining inner retinal cells which should be fabricated for meeting strict requirements such as biological compatibility, thin, flexible and low electrochemistry impedance to ensure safe and long-term effective stimulation.