2-DIMENSIONAL IMAGING OF O-2, H2O2, AND GLUCOSE DISTRIBUTIONS BY AN ARRAY OF 400 INDIVIDUALLY ADDRESSABLE MICROELECTRODES

A monolithic array of 400 individually addressable microelectrodes was fabricated in a modified CMOS process. The platinum electrodes, each 36 mu m x 36 mu m in size, were arranged in a square matrix of overall area 1 cm(2). Individual addressing of each electrode in the array was realized by two on-chip shift registers coupled with array control logic. In the electrochemical scanning mode, the 400 electrode signals were read successively. The array was used in supporting electrolyte solutions for imaging of oxygen distributions detected amperometrically at -0.8 V vs Ag/AgCl. Hydrogen peroxide and glucose distributions were imaged amperometrically at +0.8 V vs Ag/AgCl. Prior to imaging glucose distributions, the enzyme glucose oxidase was entrapped into the conducting polymer polypyrrole simultaneously on all array electrodes. Two minutes was needed for a successive readout of all 400 microelectrode signals. Diffusion of the analytes was imaged in a time-resolved manner by a sequence of successive scans. Therefore, the array of individually addressable microelectrodes can be regarded as an alternative electrochemical imaging device to the scanning electrochemical microscope.