Evaluation of a Pseudo Zero-Potential Flexible Readout Circuit for Resistive Sensor Matrixes

Abstract

The zero potential technique is an efficient way to selectively condition passive resistive sensor arrays. However, for flexible wearable sensor systems, the currently utilised amplifiers are not desirable as they are normally based on rigid devices. We present a variation of the zero potential approach utilising flexible thin-film transimpedance amplifiers. This integrated amplifier is based on IGZO thin-film transistors (TFTs) and has a measured cut-off frequency of $\approx 4$ kHz, which is sufficient for most sensing applications. To understand the performance when conditioning a grid of sensors, the flexible system was simulated and compared to the results obtained from rigid transimpedance amplifiers. While these rigid devices led to virtually no crosstalk between sensors, the flexible transimpedance amplifier maintained a selectivity factor of nearly 3. At the same time, the fully flexible IGZO amplifier can be seamlessly integrated with a flexible sensor array and has a footprint of only 1.6 mm2. This approach can enable easily manufactureable, fully flexible, and wearable sensor systems with a minimum number of active devices, avoiding active matrix structures and individual sensor conditioning while maintaining a certain level of sensitivity.