Adhesive and Anti-Swelling Cu²⁺-Based Hydrogel by Solution Displacement for Underwater Sensing and Communication

Adhesive hydrogels are widely used for wearable sensors, but their swelling feature can affect adhesion and sensing ability in aqueous environments. To address this limitation, a conductive poly(acrylic acid)-poly(butylacrylate)-Cu²⁺ (PAA-PBA-Cu²⁺) hydrogel was constructed using a solution displacement method, resulting in abundant interactions within the hydrogel matrix. Due to these interactions, the hydrogel exhibited good mechanical strength (293% tensile strain and 103 kPa elastic modulus), anti-swelling property, and adhesion strength (37.6 kPa on Cu-based substrate). The PAA-PBA-0.1 M-based sensor can present well sensing ability in both air and underwater environment, which can sensitively distinguish the different body actions. The anti-swelling performance and adhesion have endowed the sensor with stable and accurate signal output in underwater environment, respectively. Additionally, the sensor can also be used for underwater communication, which can guarantee human safety in underwater operations. In addition, based on the fine photothermal conversion ability of Cu²⁺, the hydrogel can offer temperature compensation potential, thereby ensuring the stability and sensitivity of the signal outputs in various underwater environments.