Anti-swelling conductive polyampholyte hydrogels via ionic complexations for underwater motion sensors and dynamic information storage

Swelling of hydrogels in aquatic environment is ubiquitous but unfavorable for underwater applications, which dramatically diminishes their mechanical properties. In this study, we report an anti-swelling conductive hydrogel based on a polyampholyte copolymer of acrylic acid and 1-butyl-3-vinylimidazolium bromide. The hydrogel exhibits high optical transparency, remarkable mechanical property, and good ionic conductivity. The anti-swelling property is achieved by balanced ionic complexation and hydrogen bonding with careful selection of the monomer feeding ratios. The conductive hydrogel is capable of sensing accurate and stable electro-mechanic responses under both small and large strains, making it a good candidate as strain sensors for monitoring human motions both in air and underwater. Furthermore, the unique material is patternable due to asymmetric swelling and shrinking kinetics, thus providing opportunities for the realization of dynamic information storage. It is believed that our design of anti-swelling conductive hydrogel can be a driving force towards broadening applications of hydrogel iontronics.