Highly\nStretchable and Transparent Thermistor Based\non Self-Healing Double Network Hydrogel

Abstract

An ultrastretchable\nthermistor that combines intrinsic stretchability,\nthermal sensitivity, transparency, and self-healing capability is\nfabricated. It is found the polyacrylamide/carrageenan double network\n(DN) hydrogel is highly sensitive to temperature and therefore can\nbe exploited as a novel channel material for a thermistor. This thermistor\ncan be stretched from 0 to 330% strain with the sensitivity as high\nas 2.6%/°C at extreme 200% strain. Noticeably, the mechanical,\nelectrical, and thermal sensing properties of the DN hydrogel can\nbe self-healed, analogous to the self-healing capability of human\nskin. The large mechanical deformations, such as flexion and twist\nwith large angles, do not affect the thermal sensitivity. Good flexibility\nenables the thermistor to be attached on nonplanar curvilinear surfaces\nfor practical temperature detection. Remarkably, the thermal sensitivity\ncan be improved by introducing mechanical strain, making the sensitivity\nprogrammable. This thermistor with tunable sensitivity is advantageous\nover traditional rigid thermistors that lack flexibility in adjusting\ntheir sensitivity. In addition to superior sensitivity and stretchability\ncompared with traditional thermistors, this DN hydrogel-based thermistor\nprovides additional advantages of good transparency and self-healing\nability, enabling it to be potentially integrated in soft robots to\ngrasp real world information for guiding their actions.