Live demonstration: Noise-immune current-integration-based CMOS amperometric sensor platform with 1.2 μm × 2.05μm electroless-plated microelectrode array for robust bacteria counting

Amperometric pathogen counting using a microelectrode array has been intensively investigated. The primary difficulty in achieving amperometric pathogen counting is developing a microelectrode with size almost identical to that of the target. The literature reported the development of a on-chip bacteria-sized (1.2 μm × 2.05 μm) microelectrode array using a self-aligned electroless plating technique for bacteria counting. Since the redox current flowing through the microelectrode depends primarily on its size, a bacteria-sized microelectrode can handle low currents on the order of nA. To maintain sufficient signal-to-noise ratio (SNR) with a bacteria-sized microelectrode, a noise reduction scheme must be developed. However, a noise reduction scheme for a bacteria-sized microelectrode has not yet been reported. We have implemented a current integrator (CI) that is known to be highly effective for noise reduction. A test chip with the CI was fabricated in a 0.6-μm CMOS process and on-chip bacteria-sized microelectrode array were formed using electroless plating. In this demonstration, robust 2D direct counting of microbeads used the CI and the bacteria-sized microelectrode array is introduced.