Improving impedance of implantable microwire multi-electrode arrays by ultrasonic electroplating of durable platinum black

Sharanya Arcot Desai

doi:10.3389/fneng.2010.00005

Abstract

Implantable microelectrode arrays (MEAs) have been a boon for neural stimulation and recording experiments. Commercially available MEAs have high impedances, due to their low surface area and small tip diameters, which are suitable for recording single unit activity. Lowering the electrode impedance, but preserving the small diameter, would provide a number of advantages, including reduced stimulation voltages, reduced stimulation artifacts and improved signal-to-noise ratio. Impedance reductions can be achieved by electroplating the MEAs with platinum (Pt) black, which increases the surface area but has little effect on the physical extent of the electrodes. However, because of the low durability of Pt black plating, this method has not been popular for chronic use. Sonicoplating (i.e. electroplating under ultrasonic agitation) has been shown to improve the durability of Pt black on the base metals of macro-electrodes used for cyclic voltammetry. This method has not previously been characterized for MEAs used in chronic neural implants. We show here that sonicoplating can lower the impedances of microwire multi-electrode arrays (MMEA) by an order of magnitude or more (depending on the time and voltage of electroplating), with better durability compared to pulsed plating or traditional DC methods. We also show the improved stimulation and recording performance that can be achieved in an in vivo implantation study with the sonicoplated low-impedance MMEAs, compared to high-impedance unplated electrodes.

Highlights

Implantable microelectrode arrays (MEAs) have been used to record and stimulate in a number of studies in different regions of the brain (Branner et al, 2001; Vetter et al, 2004; McCreery et al, 2006; Cogan, 2008)
TEST FOR DURABILITY We tested the durability of the Pt black plating by subjecting an electroplated 16-electrode microwire multi-electrode arrays (MMEA), whose impedances were brought down to the same levels by the three different plating methods on 4-electrodes each to additional sonication in physiological saline solution
Scanning Electron Microscopy (SEM) was carried out before and after the durability test to see if there was a difference in surface morphology of the Pt black plating formed by the three plating techniques

Summary

Introduction

Implantable microelectrode arrays (MEAs) have been used to record and stimulate in a number of studies in different regions of the brain (Branner et al, 2001; Vetter et al, 2004; McCreery et al, 2006; Cogan, 2008). Microwire multi-electrode arrays (MMEAs) have been used widely in studies requiring both chronic and acute (

Methods

Results

Conclusion