Coordination hydrogel enables an extremely stable, highly sensitive, self-healable and robust underwater sensor

Gel-based electronic sensors have wide applications in wearable sensors and soft devices, but serious swelling issues and performance degradation over time greatly hinder their functions in underwater environments. Herein, a coordination-driven strategy for preparing a conductive hydrogel via aqueous solution radical polymerization of methyl acrylamide (MAm) and L-serinyl acrylate copper complex (LSA) was proposed to address this issue. Owing to the dual hydrophobic/hydrophilic network of PMAm as well as the strong interaction between L-serinyl acrylate and Cu 2+ , the PMAm-L hydrogel maintained its robustness (with a swelling ratio of approximately 3 %, a tensile stress of 113 kPa, and a tensile strain of 183 %) and sensing performance (electric conductivity of 0.5 S/m, and gauge factor of 2.1) even after immersion in water for one month, indicating excellent stability. Reversible rupture/reformation of coordinate bonds under deformation confers self-healing properties to the material. Furthermore, a highly sensitive underwater mechanical sensor based on this gel was developed for precise monitoring of subtle human movements, and underwater communication using Morse code was achieved, thereby significantly expanding the functional applications in water environments.