Flexible organohydrogel ionic skin with Ultra-Low temperature freezing resistance and Ultra-Durable moisture retention

Hypothesis: One prevailing method to construct excellent temperature tolerance/long-lasting moisture hydrogels is to couple the original hydrogel networks with freezing-tolerant/moisture retaining agents, including ionic liquids, inorganic salts, zwitterionic osmolytes, and polyhydric alcohols. Among them, organohydrogels have shed new light on the development of ionic skins with long-term usability and stable sensing performance at subzero temperatures due to their long-lasting water retention and anti-freezing capability. Experiments: We report a dual network organohydrogel by doping conductive ZnSO₄ into the double network hydrogel of polyvinyl alcohol-polyacrylamide (PVA-PAM) with subsequent immersing in a mixed solvent of ethylene glycol (EG) and H₂O. The anti-freezing and moisture retaining abilities of the PVA/PAM/Zn/EG (PPZE) organohydrogel were studied and the sensing performances of the PPZE organohydrogel-based ionic skin were investigated. Findings: The organohydrogel exhibits a high conductivity (0.44 S m⁻¹), excellent fatigue resistance and exceptional moisture retaining ability with more than 99.3% of the initial weight retention after 31 days storage at ambient temperature. Importantly, the PPZE organohydrogel-based ionic skin shows an ultra-low temperature anti-freezing ability and remains flexibility and sensing capability with a high sensitivity (signal response time ∼ 0.23 s) even at -50 °C. The PPZE organohydrogel demonstrates a tremendous potential in artificial skin and health monitoring.