Poly(vinyl alcohol)/phosphoric acid gel electrolyte@polydimethylsiloxane sponge for piezoresistive pressure sensors

Piezoresistive pressure sensors based on flexible, ultrasensitive, and squeezable conductive sponges have recently attracted significant attention. However, the preparation of cost-effective conductive sponges with good stability and wide strain range for pressure sensing remains a challenge. Herein, a conductive poly(vinyl alcohol)/phosphoric acid gel electrolyte@polydimethylsiloxane (PVA/H₃PO₄@PDMS) composite was fabricated by impregnating a PDMS sponge into a PVA/H₃PO₄ gel electrolyte. The conductivity of the as-prepared sponges was determined using a gel electrolyte polymer film. The sponge exhibited good sensitivity of 0.1145 kPa^-1 in the low-pressure range (0-6.5 kPa), short response time (70 ms), and durability for over 2700 s (6000 cycles). The gauge factor of the PVA/H₃PO₄@PDMS sponge was 5.51, 1.49, and 0.33 at the strain range of 0-10%, 10-30%, and 30-80%, respectively. Based on these outstanding sensing performances, the sponges were applied for the detection of various human motions, such as vocal cord vibration, joint bending, respiratory rate, and pulse signal detection. Further, the sponge demonstrated their great potential in the fabrication of electronic skin and high-performance flexible wearable electronics. Therefore, the obtained PVA/H₃PO₄ gel electrolyte used as a sponge conductive coating material is a readily available and inexpensive material that can reduce the cost of composite materials for pressure sensing.