Conductive Hydrogels with a Bilayer Structure to Realize Multifunctions in Extreme Environments

Conductive hydrogels (CHs) have attracted considerable interest for the detection of physiological movements and health conditions. However, traditional CHs cannot meet the increasing demands of soft electronics due to their nonadhesive, brittle, freezable, and vaporizable natures. In this work, bilayer hydrogels were prepared to address this issue, which consisted of a conductive polyacrylamide (PAM) hydrogel as the bottom layer as well as an adhesive side as the top layer from grape seed protein (GSP) and tannic acid (TA), respectively. Due to the synergy of material composition and structure engineering, the obtained gel exhibited high extensibility (an elongation at break of 4000%) and excellent adhesion onto metal, wood, rubber, and skin. Furthermore, the introduction of lithium chloride empowered the resultant hydrogel with high sensitivity (GF = 1.14 within 1000% strain, and GF = 4.36 above 1000% strain), freeze resistance (a strain of 3700% at −20 °C), and antidehydrating capacity (a weight retention ratio of 63.9% after storing it in an open environment for 30 days). Consequently, this multifunctional sensor could detect various human motions quickly and reliably. With remarkable performances in extreme environments, it has great potential in strain sensors, human–machine interfaces, and soft robots.