Porous Platinum Electrodes for Retinal Prostheses

Abstract

 

Purpose:

 

We have proposed a bullet-shaped electrode formed by mechanical machining for retinal prostheses (Terasawa et. al., ARVO 2008). The purpose of this study is to enhance the surface area of the electrode by forming a large number of holes onto its surface.

 

Methods:

 

Femtosecond laser pulses were applied onto the surface of a bullet-shaped electrode to make holes. A porous surface was obtained by repeating laser irradiation all over the upper hemisphere of the electrode. Scanning electron microscopy, cyclic voltammetry and impedance spectroscopy was performed to confirm the effect of laser irradiation. We also analyzed the cross section of holes to examine their shape and depth.

 

Results:

 

The impedance of the electrode, measured by applying 1kHz sine wave, decreased from 1264 Ohm by 443 Ohm by laser irradiation. The electrode could inject 1.65 uC/phase current pulses without exceeding the water window in phosphate buffered saline. We succeeded in controlling the depth of holes over the range from 12um to 117 um by adjusting the strength of laser irradiation.

 

Conclusions:

 

We succeeded in enhancing the surface area of bullet-shaped electrodes with femtosecond laser irradiation. We will confirm the reliability of this electrode by long term pulsing in vitro and in vivo in the next step.  

 

 

Keywords: retina