Thermosensitive hydrogel-based, high performance flexible sensors for multi-functional e-skins

Electronic skins (e-skins) have shown great potential in “bionic-machine” technologies. The development of bio-compatible e-skins that mimic the functions of the human skin, which is sensitive to multiple external stimuli, remains a challenge and a highly pursued goal. In this work, we report the synthesis, characterization, and performance-optimization of a thermo-sensitive and conductive hydrogel that displays multimodal sensing capacity. The optimal composition of a hydrogel with a volume phase transition temperature (VPTT) of 38 °C and a transition width of 15 °C was developed. This gel has an elastic modulus similar to that of the human skin, a large stretchability of 1900%, and a high gauge factor of 9.8. The gel is also puncture-resistant, self-healable, and self-adhesive. The as-fabricated hydrogel can sense multimodal stimuli, including force and temperature, with high sensitivity. We demonstrate that the gel possesses important attributes as a candidate for e-skin to monitor physiological signals including temperature, bending, and pressure in real time.