Underwater Self-Healing and Recyclable Ionogel Sensor for Physiological Signal Monitoring

Ionogels with self-healing properties have become more and more desirable because they can improve the reliability, safety, and fatigue-resistant performance of flexible devices. However, the self-healing property of ionogels is usually susceptible to water molecules, and the application of ionogel sensors is limited to the atmospheric environment. Inspired by gelatinous jellyfish, herein, an underwater self-healing ionogel was prepared via one-step photoinitiated polymerization of acrylic acid 2,2,2-trifluoroethyl ester and N-isopropylacrylamide (NIPAm) in a hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][TFSI]). The dynamic physical interactions (hydrogen bonding and ion-dipole interactions) endowed the ionogel with remarkable transparency, underwater self-healing (up to 96%), toughness (3.93 MJ m^-3), and underwater adhesion. And the cross-linking ionogel could be green recycled by ethanol for further application. Especially, the ionogel-based sensor presented excellent strain and pressure sensing sensitivity, rapid responsiveness (140 ms), and ultrastability. The ionogel could be further assembled into an optical camouflage sensor to detect and distinguish different human motions in real time with high sensitivity, stability, and repeatability, as well as for underwater electrocardiography monitoring wirelessly. This ionogel provides a promising strategy for the development of underwater self-healing sensors.