Multiple Sampling and Pixel-Wise Accumulation in CMOS Capacitive Sensor Array System for Real-Time Droplet Analysis

Capacitive sensor array (CSA) is vital in precise monitoring for lab-on-chip (LOC) systems. However, shrinking electrode sizes to increase spatial resolution bring challenges like noise interference and large data volumes. This paper presents an FPGA-based system that addresses these problems with multiple sampling (MS) and pixel-wise accumulation (PWA). MS reduces Gaussian noise by sampling multiple frames and retaining only representative data points, while PWA compresses data using Block RAM and minimal combinational logic, reducing size from 118 Mb to 0.46 Mb and boosting SNR to 25.30 dB. The system enables real-time monitoring every 5 seconds instead of 17 minutes, with pipeline sensing and transmission further optimizing sensing time. Experiments demonstrate its effectiveness in distinguish between droplets and monitor evaporation in real time. MS and PWA can be easily integrated into future chip designs, offering scalable solutions for fast and precise monitoring in LOC environments.