Implementation of PDMS-based Slanted Edge-type Microelectrode Array for Neural Stimulation

Abstract

PDMS-based multi-electrodes are widely used in acute experiments for neural interfaces, and generally have a vertical-edge electrode structure. Previous studies have shown that when stimulating neural tissue with a vertical-edge electrode, a high current density is produced at the edge of the electrode, which makes uniform stimulation difficult. However, slanted-edge electrodes can induce a relatively uniform current density distribution. PDMS is a very stable material, physically and chemically; thus, it is difficult to produce slanted-edge electrodes because no efficient etching process exists. In order to address this problem, we propose a process to fabricate sloped structures using the under-exposure characteristics of photolithography, and to fabricate sloped holes efficiently in PDMS by using it as a cast structure. The validity of the proposed process was verified by fabricating vertical-edge, slanted-edge, and surface-mounted edge electrodes. We verified the current density distribution according to the electrode structure by simulation, and applied signals to vertical-edge and slanted-edge samples to observe the current leakage. It has been confirmed that the slanted-edge structure improves the stability and reliability of the electrode.