Multi-Functional and Multi-Stimulus Sensitive Self-Powered Hydrogel for Skin Mimicry and Energy Harvester

Self-powered hydrogel i-skin (ionic skins) with excellent mechanical properties and multi-stimuli responsiveness resembling natural skin is highly desirable but remains a significant challenge. This study introduced a novel multi-stimuli-sensitive self-powered hydrogel, formed by integrating multiple hydrogen bonds and a polyampholyte network, which exhibited excellent mechanical properties, fatigue resistance, high transparency, strong adhesion, and anti-freezing capability. The cations and anions on the polyampholyte, along with their free counterions, enabled the piezoionic behavior with the output voltage and voltage decay time highly sensitive to the applied pressure and contact shape. Following the release of relatively high pressure, the hydrogel exhibited a prolonged voltage decay time of up to 35 s. The presence of multiple hydrogen bonds and the low water content endowed the hydrogel with sensitivity to both humidity and temperature. These functionalities rendered the hydrogel a promising candidate for skin-mimetic applications and energy harvesting in next-generation flexible sensing devices and human–machine interfaces.