Anti-freezing, resilient and tough hydrogels for sensitive and large-range strain and pressure sensors

Hydrogel sensors are peculiarly attractive in flexible wearable electronics due to the stretchability and strain-responsive ability. However, flexible sensors (e.g. electronic skin) in practice require to perceive both strain and pressure concurrently and repeatedly, which put forward an imperative demand for multi-model and durable hydrogel sensors. Additionally, freezing intolerance is also an urgent problem to be addressed for low-temperature applications of hydrogel sensors. Herein, we constructed a wearable multi-model hydrogel sensor featuring with sensitive and large-range strain and pressure detection capacity, together with long-term stability and wide operating temperature range, based on a resilient, anti-fatigue and freezing-tolerant chitosan-poly(hydroxyethyl acrylamide) double-network (CS-PHEAA DN) hydrogel, which was fabricated via post-crosslinking CS-PHEAA composite hydrogel into NaCit solution. The ions simultaneously furnished the hydrogel with superior mechanics (stretchability, supercompressibility, excellent resilience and remarkable fatigue resistance), prominent ionic conductivity and low temperature tolerance. Impressively, the assembled hydrogel sensor exhibited preeminent sensitivity and cycling stability on detecting multi-type and large-range deformation (elongation, compression and bend), pressure and various human motions even at low temperatures. Remarkably, the fabricated hydrogel/aluminum hybrid combination serving as a flexible sensor maintained mechanical advantages, sensitive sensing capacity and good durability within a wide temperature range. This work provides a feasible method to construct anti-freezing, durable and multi-mode hydrogel sensors with high sensitivity and large-range detection capacity and paves a way for versatile applications in electronic skin, human-motion detection and intelligence device.