A 32-by-32 CMOS Microelectrode Array for Capacitive Biosensing and Impedance Spectroscopy

This paper presents the design of a 1024-channel dual-modality CMOS biosensor suitable for both capacitive sensing and impedance spectroscopy. The chip serves as a platform for detection, localization and monitoring of bacteria and can be adopted for affinity-based assays. The chip features a 32 x 32 array of unpassivated metal electrodes formed on the top metal of a 0.18 mu m CMOS process, with an overall sensing area of 2.06 mm(2). The system design is based on a shared in-pixel integrator that can be used as a charge amplifier for capacitive sensing (CS) or as part of a transimpedance amplifier for electrical impedance spectroscopy (EIS). The CS mode is capable of a operation bandwidth of 50 MHz at a current consumption of 82 mu A per pixel. The EIS channel operates over a bandwidth between 100 Hz and 1 MHz with a total input-referred current noise of 48 pA(RMS) and a current consumption of 210 mu A per channel.