An environment-stable hydrogel with skin-matchable performance for human-machine interface

Ionic hydrogel-based sensors have shined a spotlight on wearable electronics. However, the sensitivity and reliability of hydrogel devices are significantly hampered by the weak adhesion of skin-sensor interface as well as inferior temperature tolerance. Here, inspired by the structure and composition of dermis, a novel skin-attachable and environment-stable hydrogel was designed by integrating collagen into the LiCl-containing chemically cross-linked polyacrylamide hydrogel. The hydrogel exhibited skin-like mechanical properties of low modulus, superior stretchability as well as excellent elasticity. Furthermore, the introduction of collagen endowed the hydrogel with robust and seamless interfaces with diverse materials, including the curved skin. As a result, the hydrogel is capable of serving as a human-machine interface for collecting reliable electrocardiography (ECG) signals and discerning various human motions, with high sensitivity (gauge factor = 10.7), fast response, negligible hysteresis as well as extensive monitoring range. Notably, the hydrogel that can mimick the temperature-tolerant mechanism of most organisms possesses persistent stabilization of adhesive, conductive, sensory and mechanical performances at subzero or ambient conditions. The skin-inspired strategy paves an effective way for the design of multifunctional materials with potential applications in next-generation electronics.