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 the fabrication of flexible wearable devices due to their flexibility, deformability and stretchability. However, challenges such as their inadequate mechanical properties, insufficient conductivity and limited sensing stability and sensitivity remain. An ionically conductive hydrogel based on gellan gum cross-linked with manganese ions and phytic acid was developed in this study. The hydrogel displayed not only improved mechanical performances with a tensile strength of 68.7 kPa, an elongation at break of 132.6% and a tensile modulus of 120.9 kPa but also self-healing capability. In addition, the hydrogel exhibited an ionic conductivity of 1.06 S m⁻¹ due to the movement of ions and thereby displayed an outstanding piezoresistive sensing performance (GF = 1.75) for monitoring human motions. Moreover, the hydrogel exhibited a piezoionicity of 4.37 mV kPa⁻¹ and an ionic thermoelectricity of 75 µV K⁻¹ due to the differences in the migration rates of cations and anions induced by pressure and temperature gradients. The hydrogel sensor facilitated precise sensing under pressure and temperature differentials, offering a new approach to integrating energy harvesting with pressure and temperature sensing. Furthermore, the training and detection of sensing signals using a convolutional neural network achieved a recognition accuracy of 92.8% for input signals, demonstrating the potential for its application in human–machine interactions. This study provides a novel strategy for developing new-generation flexible wearable sensors.