Novel two-stage CMOS-MEMS capacitive-type tactile-sensor with ER-fluid fill-in for sensitivity and sensing range enhancement

This study has presented a novel two-stage CMOS-MEMS capacitance-type tactile sensor with ER-fluid fill-in to extend the sensing range. Merits of the sensor are: (1) small tactile force (mN) is detected by first-stage sensing-unit with sensing range modulated by driving-voltage through ER-fluid; (2) larger tactile force (N) is detected by the second-stage sensing-unit. Moreover, sensing range and sensitivity can be further modulated using different ER-fluid. This tactile-sensor is implemented using TSMC 0.18μm 1P6M CMOS process, in-house post-CMOS releasing, ER-fluid filling, and parylene sealing process. Measurement results demonstrate the modulation of sensing ranges are 0~50mN (as the bias-voltage for ER-fluid is 0-1V), and 0~90mN (as the bias-voltage for ER-fluid is 10V); sensitivities are 0.15fF/mN (bias-voltage for ER-fluid is 0-1V) and 0.1fF/mN (bias-voltage for ER-fluid is 10V) for first-stage. Moreover, the second-stage has a larger sensing range (0~2.5N) and the sensitivity can also be modulated by bias voltage (3.55fF/N for 0.5V and 3fF/N for 5V).