Amperometric electrochemical sensor array for on-chip simultaneous imaging

Abstract

We propose an amperometric electrochemical sensor array for high-speed measurement of microelectrode currents. The biosensor was fabricated using CMOS technology and a contact photolithographic process to incorporate gold microelectrodes (256 electrodes) on a chip. The sensor circuit employed a current buffer circuit and dual switch. During measurement, all electrodes were kept at a constant potential, currents were at steady-state levels, and rapid switching was performed while maintaining the steady-state current. The measured current range of the current buffer circuit was approximately 1 pA to 1 µA. A microelectrode array (MEA) with auxiliary electrode (AE) was used to suppress expansion of the diffusion layer over the MEA. Steady-state current was obtained and amplified by redox cycling, greatly reducing the time for reaching the steady-state level. The sensor successfully simultaneously measured multipoint cyclic voltammetry and amperometry, and will be useful for measuring local concentration and analyzing the diffusion processes of target molecules.