Large Area, High Aspect Ratio Microelectrode Arrays

Abstract

A method is described for the fabrication of arrays of conducting, high aspect-ratio microwires for use as electrodes. The electrode arrays are fabricated by electrochemical deposition of metals, including Ni, Pt, Ag, Au and Rh, in channel glass templates having parallel, uniform, hollow channels with diameters that range from sub-micrometer to over 100 micrometers. The metals completely fill the hollow channels, yielding highly uniform electrodes with aspect ratios on the order of 1000 or more. The glass template electrically insulates the electrodes from one another. The electrode array wafers are cut and polished to a thickness ranging from about 100 to 2000 micrometers. The overall surface area is as large as 1 square centimeter. Alternatively, the wafers can be partially etched with acid to remove some of the glass matrix surrounding the electrodes, exposing an array of bare, solid wire stubs. The high aspect ratio microelectrode arrays were initially fabricated in order to provide the electrical interface for an intraocular retinal prosthesis, but have additional applications including biological and chemical sensing. Arrays with different channel sizes, different electrode spacing (with pitch from approximately 3R to 20R, where R is the electrode radius), and different geometrical arrangement are presented.