Characterization of Electrochemically-Treated Platinum Bulk Electrodes

Abstract

Purpose: : We have previously proposed a method to realize large-surface-area platinum electrodes using bulk micromachining (Terasawa et al. ARVO 2008).The purpose of this study is to improve the charge injection capability of the electrodes by enhancing its surface area and to characterize them.

Methods: : Bullet-shaped electrodes were cut out with a turning machine from a bulk platinum bar. After cable connection and substrate formation, the electrodes were immersed in PBS at room temperature and DC voltage between -5.0V and +5.0V vs. return electrode (large stainless steel foil) was applied periodically for 15.5 hours. The electrodes were characterized by scanning electron microscopy, cross section analysis, cyclic voltammetry and surface-area estimation.

Results: : Highly porous surfaces were obtained after electrochemical etching. Scanning electron microscopy of the cross section of the etched electrodes revealed that positions of crystal grain boundary corresponded with microstructures of the electrodes' surface after etching. An increase of the surface area of the electrode was confirmed both in cyclic voltammogram and voltage waveform. The roughness factor of the electrode increased from 5 to 53 in average after etching.

Conclusions: : We succeeded in enhancing surface area of bullet-shaped electrodes through electrochemical etching. We are planning a study of optimization of the etching condition as well as long-term stimulation study in vitro and in vivo to ensure the durability of the electrodes.

Keywords: retina • sclera