Gellan gum-based ionic conductive hydrogel with self-healing capability, piezoionicity and ionic thermoelectricity as flexible sensors

Abstract

Hydrogels are regarded as promising materials for fabrication of flexible wearable devices due to their flexibility, deformability and stretchability. However, it remains challenges, such as inadequate mechanical properties, insufficient conductivity and limited sensing stability and sensitivity. This study developed an ionically conductive hydrogel based on gellan gum cross-linking with manganese ions and phytic acid. The hydrogel displays not only improved mechanical performances with tensile strength (68.7 kPa), elongation at break (132.6%) and tensile modulus (120.9 kPa), but also self-healing capability. In addition, the hydrogel exhibits an ionic conductivity of 1.06 S/m due to the movements of ions, and thereby displayed outstanding piezoresistive sensing performance (GF=1.75) for monitoring human motions. Moreover, the hydrogel exhibits piezoionicity (4.37 mV/kPa) and ionic thermoelectricity (75 μV/K) for generating potential differences due to the differences in migration rates of cations and anions induced by pressure and temperature gradient. The hydrogel sensor facilitates precise sensing under pressure and temperature differentials, offering a new approach to integrating energy harvesting with pressure and temperature sensing. Furthermore, training and recognition of sensing signals using a convolutional neural network achieved a recognition accuracy of 92.8% for input signals, demonstrating the potential for application in human-machine interaction. This study provides a novel strategy for developing new-generation flexible wearable sensors.