Wearable Water-filled Soft Transparent Pressure Sensor Based on Acoustic Guided Waves

Soft pressure sensors are increasingly crucial in a diverse array of applications including soft robotics, electronic skin, haptics, and wearable human-machine interaction. Current pressure sensors based on piezoresistive, capacitive, piezoelectric, triboelectric, and optical sensing typically require micro/nanoparticles and advanced manufacturing techniques that are complex and expensive to achieve sufficient pressing sensing performance. We thus propose a novel soft pressure sensor based on an acoustic guided wave-based sensing mechanism that is easily assembled with a polydimethylsiloxane (PDMS) hollow tube filled with water, a customized piezoelectric transducer for generating ultrasonic vibration in the tube's one end, and a customized stopper for sealing the water in the tube's other end. Sensor pressure sensing performance was characterized to demonstrate its extensive sensing range (up to 135 kPa), great linearity
$(R^{2} > \boldsymbol{0.987})$
, small hysteresis, and high repeatability. The proposed sensor design offers an acoustic-based approach for developing soft pressure sensing, potentially opening research avenues in soft, wearable pressure sensing.