Handheld bio-impedance measurement system based on an instrument-on-chip

In this paper we present a compact system for impedance measurement in the kHz-MHz frequency range with attoFarad resolution. It has been designed to address micro- and nano-scale bio-sensing applications, such as impedimetric flow cytometry or molecular affinity bio-sensors. The core of the detection system is an integrated circuit that features a low noise current amplifier, a two-phase square waveform lock-in detector and two ΣΔ analog-to-digital converters. The CMOS chip is complemented by all the blocks needed to perform spectroscopy measurements, including versatile signal generation, digital processing and PC data transmission. The whole stand-alone system is USB powered and can reach sub-fF resolution in capacitive tracking on a sub-millisecond time scale.