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 wa s realized by two on-chip shift registers coupled with array control l ogic. In the electrochemical scanning mode, the 400 electrode signals were read successively. The array was used in supporting electrolyte s olutions for imaging of oxygen distributions detected amperometrically at -0.8 V vs Ag/AgCl. Hydrogen peroxide and glucose distributions wer e imaged amperometrically at +0.8 V vs Ag/AgCl. Prior to imaging gluco se distributions, the enzyme glucose oxidase was entrapped into the co nducting polymer polypyrrole simultaneously on all array electrodes. T wo minutes was needed for a successive readout of all 400 microelectro de signals. Diffusion of the analytes was imaged in a time-resolved ma nner by a sequence of successive scans. Therefore, the array of indivi dually addressable microelectrodes can be regarded as an alternative e lectrochemical imaging device to the scanning electrochemical microsco pe.