Flexible Piezoelectric Sensor With a Sandwich Structure Composed of Ionic Conductive Hydrogel and PVDF Film

Wearable devices impose stringent demands on sensor materials, structural processes, material costs, wearability, and operational performance. This study developed an innovative sandwich-structured flexible piezoelectric sensor fabricated using ionic conductive hydrogel and PVDF film. The fabrication process involved the preparation of ionic conductive PVA/gelatin double-network hydrogel (CPGH) through a freeze-thaw cycle and saltwater immersion process. The sandwich structure was developed using a CPGH and PVDF film, which effectively enhanced the deformation capacity of the PVDF film, stress concentration, and internal polarization intensity. Test results indicated that the proposed sensor can generate linear output and has higher sensitivity, short response times, robust stability, and reliability. The sensor can be used to monitor the bending angle of finger joints, displaying an impressive linear fit with a coefficient of determination (
${R} ^{{2}}$
) of 0.97538 within the range of 30° to 135°. Furthermore, the sensor has potential in other applications, which involve distinguishing different human gait patterns.