Stretchable, self-healing, anti-freezing PDES ionic gels for rapid temperature-change sensing and health monitoring

Abstract

Ionic gels have emerged as versatile materials for electronic applications such as thermal sensors, motion sensors, and health monitoring. However, their broader application remains limited by challenges such as inadequate thermal stability, susceptibility to freezing, and the absence of self-healing capabilities. In this study, a solvent-free poly(deep eutectic solvent) (PDES) gel was developed with enhanced thermal stability, freeze resistance, mechanical stretchability, and autonomous self-healing ability. The PDES gel demonstrated excellent ionic thermoelectric properties, with an ionic conductivity of 0.463 mS cm-1 and a Seebeck coefficient of 1.73 mV K-1 at room temperature. Consequently, it reliably detected temperature variations from both artificial and biological heat sources when used as an ionic thermoelectric-based thermal sensor module. Furthermore, its performance remained stable after self-healing and under extreme temperature conditions, including sub-0 degrees C and 70 degrees C. Beyond thermal sensing applications, the PDES gel also functioned effectively as a motion sensor, showing consistent resistance changes under mechanical deformation. Additionally, the gel reliably detected electrophysiological signals, such as electromyography (EMG) and electrocardiography (ECG), and maintained consistent performance after self-healing and across various temperature conditions. This study provides a foundation for developing multifunctional ionic gels with applications in energy harvesting devices, wearable electronics, and health monitoring.