Implantable nanostructured MEA with biphasic current stimulator for retinal prostheses

Abstract

BACKGROUND:

In retinal prosthetic systems on multi-channel microelectrodes to effectively stimulate retinal neurons, the electrode-electrolyte interface impedance of a microelectrode should be minimized to drive sufficiently large current at a given supply voltage.

OBJECTIVE:

This paper presents the fabrication of the nanostructured microelectrode array with simplified fabrication and its characteristic evaluation using biphasic current stimulator.

METHODS:

The nanostructured microelectrodes with the base diameter of 25 $\mu$ m, 50 $\mu$ m, 75 $\mu$ m are fabricated, and the maximum allowable current injection limits are measured to verify the estimated injection limit. Also, a biphasic stimulator has been fabricated using the 2-stage amplifier and 4 switches based on a stimulator cell. The adjustable load resistance is adopted to control between 5 k $\mathrm{\Omega }$ to 20 k $\mathrm{\Omega }$ , and the biphasic stimulator can drive the stimulation current between 50 uA and 200 uA.

RESULTS:

The proposed electrode-electrolyte interface impedance of the fabricated nanostructured microelectrode is 3178 $\mathrm{\Omega }$ , 1218 $\mathrm{\Omega }$ and 798.8 $\mathrm{\Omega }$ for electrodes with diameter of 25 $\mu$ m, 50 $\mu$ m, 75 $\mu$ m, respectively.

CONCLUSION:

This paper shows the advantages of the nanostructured microelectrode arrays for high resolution retinal prostheses, which could be a basic experiment for artificial retina research.