Amperometric Electrochemical Sensor Array for On-Chip Simultaneous Imaging: Circuit and Microelectrode Design Considerations

Abstract

We propose a switching circuit and an electrode design for measuring multiple microelectrode currents at high speed. Our goal is to realize two-dimensional (2D) imaging of analyte distributions by amperometry. In the proposed amperometric sensor circuit, each electrode is connected to two switches. During measurement, the potential of all electrodes is fixed, the steady-state current is maintained, and the switching is carried out while maintaining the steady-state current. A current buffer circuit was fabricated, its the characteristics were evaluated. The time course of the electrochemical current of an electrolyte was measured using the current buffer circuit. We have also proposed a microelectrode structure to suppress the expansion of the diffusion layer over the microelectrode array. Each electrode has a steady-state current, which is amplified by a redox cycle, and the time to reach the steady state is reduced to about 1/10 of that required by a single microelectrode. The relation between the characteristic lengths of the electrode geometry and the current gain is presented.