Poly(vinyl alcohol)/Pullulan/NaCl Conductive Hydrogels with High Strength and Sensitivity for Wearable Strain Sensors

Ionic conductive hydrogels have emerged as promising candidates for wearable sensors. However, it is still challenging to fabricate hydrogels simultaneously with a balanced mechanical strength, ionic conductivity, and sensitivity. In this work, Poly(vinyl alcohol) (PVA)/Pullulan/Sodium chloride (NaCl) ionic conductive hydrogels were prepared by soaking frozen–thawed PVA/Pullulan hydrogels in NaCl solution to obtain the balanced properties. Due to the synergy of the semi-interpenetrating network and salting-out effect, the hydrogels exhibited a large tensile strength of 2.72 MPa. Besides, the hydrogels had a high ionic conductivity (up to 10.44 S/m) and good sensitivity (gauge factor up to 5.98). The hydrogel was assembled as a strain sensor for the detection of human joint movement. Besides, hydrogel sensors can provide efficient information transmission through the Morse code. The presented PVA/Pullulan/NaCl hydrogels have suggested promising prospects for wearable sensors.