Double differential MEMS piezoresistive sub-N force sensor with pentacene TFT readout circuit: multidomain design and analysis

This paper presents the design, modeling, and simulation of a double differential microelectromechanical system (MEMS) sub-micronewton (N) force sensor integrated with a Pentacene Thin-Film Transistor (PTFT) readout circuit. The proposed sensor offers low-cost fabrication, low-voltage operation, high sensitivity, and effective cross-axis signal rejection. The sensing structure comprises a central silicon proof mass supported by four beams, each embedded with indium tin oxide (ITO) piezoresistors positioned at regions of maximum tensile and compressive stress. The PTFT was modeled and simulated using TCAD and implemented in Cadence Virtuoso through a Verilog-A model. Differential outputs are processed through a negative-feedback operational amplifier with a gain of 20. An identical setup is implemented on an adjacent flexure of the MEMS structure, and both outputs are compared using a differential comparator. A non-zero comparator output indicates a sensing error. Finite element simulations in COMSOL Multiphysics indicate a nominal resistance () variation of 0.095, with the PTFT operating at – 3 V (threshold voltage – 1.2 V). The sensor achieves an output change of 10 mV, corresponding to a sensitivity of 10 V/nN. The proposed double differential architecture, combined with a PTFT-based readout circuit, ensures accurate nano-force sensing with immunity to cross-axis interference, which further enhances the capability of future MEMS force sensors.