Highly sensitive, super high stretchable hydrogel strain sensor with underwater repeated adhesion and rapid healing

Traditional hydrogel-based strain sensors do not work well under water due to extreme swelling and poor adhesion to substrates in water-rich conditions. Inspired by the jellyfish tentacles, a super stretchable dual crosslinked hydrogel was prepared as a motion sensor underwater. The hydrogel contained a cationic surfactant, hexadecyl trimethyl ammonium bromide (CTAB), that crosslinked with hydrophobic lauryl methacrylate (LMA) units in an AA-LMA copolymer. Al3+ ions also coordinated with carboxyl groups in PAA chains and amino groups on chitosan (CS) to form ionic crosslink points. The formed hydrogel exhibited excellent anti-swelling characteristics, superior tensile properties (≈3000%), and rapid self-healing performance. Due to the complementary effects of electrostatic interactions and dynamic chemical bond formation, the hydrogel efficiently and repeatably adhered to various biological tissues, such as hogskin and shrimp, in aquatic environments. Moreover, the hydrogel-based strain sensor showed high sensitivity (GF = 2.04) over a wide sensing range from 0 to 1000% strain with high stability in air and water. The prepared materials' unique performance further expands their application prospects in flexible wearable devices, anti-counterfeiting recognition, and other fields in environmental conditions.