A Flexible & Translucent CMOS Retinal Prosthesis and in vitro Characterization

Abstract

 

Purpose:

 

To integrate photo sensors with electronics and fine-pitched micro electrode array onto a biocompatible and flexible chip to achieve the resolution and size needed for forming images of biphasic current distribution for retinal prosthesis.

 

Methods:

 

Integrating fine-pitched photo sensors, micro electrodes and electronics onto the retinal chip using flexible CMOS Image Sensor (CIS) technology. The flexible format allows better proximity between electrodes and retinal neurons for localized stimulation, and the integrated electronics allows supplying individual electrode the adequate and appropriate stimulation waveforms. Images are projected onto the chip and corresponding biphasic currents from each pixel for stimulating mouse retina tissue are mapped. In vitro loose patch and whole-cell patch clamp techniques are used to characterize the retinal ganglion cells responses (of wide type and triple knock-out mice) on these arrays.

 

Results:

 

We successfully implemented a flexible, 4,096-element, 3x3 mm retina chip sandwiched between polymer layers in total 30 µm thick, includes multiplexing electronics. The sensing & stimulation area is 2x2 mm with an array of 10 µm electrodes and photo sensors 30 µm in pitch. Local light intensity is converted into biphasic current at each 10 µm electrode (+-50 µA saturated at 1000 lux). Maps of measured current injection from each pixel reproduced the human facial images projected onto these retinal chips. It’s shown that 10 µm-sized electrodes 4 in a group are capable of exciting RGC spiking, and detailed RGC response on the retinal chip is under characterization.

 

Conclusions:

 

We integrated 180 nm CMOS circuits with 30 µm-pitched image sensors and micro electrode array into a single flexible 4,096-pixel retinal chip capable of forming biphasic current distribution of images. In vitro excitation of retinal tissue over the retina chip is under characterization and will be reported in the meeting.  

 

Keywords: retina • electrophysiology: non-clinical