Anti-swelling hydrogels via metal coordination network for underwater motion sensors and wireless electronic devices

Hydrogel-based wearable electronic devices have received growing interest in recent years. However, swelling of hydrogels in an aquatic environment dramatically diminishes their mechanical and electrical properties, thus hampering the practical applications. The construction of underwater strain sensors is a considerable challenge. In this study, we report a strategy to introduce the metal coordination network into the PVA network and successfully prepare an anti-swelling gel material. The anti-swelling property (equilibrium swelling ratio of 0% after 8 d in water) is achieved by the grafting of poly(Cu–arylacetylide) chains and the introduction of the metal–ligand network. Compared with PVA hydrogel, the tensile strength of the s anti-swelling hydrogel increased from 10 kPa to 139 kPa, the elongation at break increased from 133% to 341%, and the Young's modulus increased from 10 kPa to 18 kPa. Notably, the hydrogel can retain 88% of its initial toughness after 20 d of immersion in an aquatic environment. The anti-swelling hydrogel has good reliability in detecting small and large strains. On this basis, a strain sensor is further developed, which has high sensitivity in monitoring movement in air and underwater. Moreover, hydrogel-based wireless electronic devices are also developed, demonstrating their promise for communication in complex water environments. It is believed that the design of our anti-swelling hydrogel will provide the impetus for expanding the application of wearable electronic devices.