A Highly Parallel Capacitive Sensing Circuit for High-Throughput Thin-Film Transistor Digital Microfluidic Chips

This paper presents a capacitive sensing circuit for high-throughput active-matrix (AM) thin-film transistor (TFT) digital microfluidic (DMF) chips, with highly parallel operations to reduce frame time and thereby enhance chip throughput. The proposed circuit integrates a capacitance-to-frequency converter (CFC) into each DMF cell column, enabling simultaneous capacitance sensing and readout of DMF cells in the same row. Furthermore, a pipelined control scheme is devised to parallelize operations across rows, reducing frame time by over 81% compared to conventional DMF chips. Integrated with double-gate (DG) unipolar n-type amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs, the proposed circuit achieves a sensitivity of 13.06 kHz/pF and a resolution of 7.2 fF for a DMF array scale of 150 × 300.