Ultra-high stretchable hydrogels with wet adhesion properties as wearable electronic devices for underwater environments

Wearable strain sensors based on conductive hydrogels have garnered significant attention due to their tremendous potential in applications such as human motion and health monitoring. Recently, multifunctional conductive hydrogels have been created for a wide range of applications. However, water molecules can affect the hydrogel performance, making it important to develop conductive hydrogel-based flexible sensors that can maintain stable performance in underwater environments. In this study, acrylic acid (AA) was selected as the hydrogel matrix, and hydrophobic monomer stearyl methylacrylate (SMA) and polydopamine-coated polypyrrole (PPy@PDA) composites were introduced to improve the anti-swelling performance and mechanical properties of the hydrogel. A composite conductive hydrogel was successfully prepared via free radical polymerization. The multiple interactions within the hydrogel increased the crosslinking density of its internal network, resulting in an exceptionally high tensile strain (with a fracture elongation of 2396.59%), excellent wet adhesion properties, and strong anti-swelling characteristics. By leveraging the superior performance of the hydrogel, the developed hydrogel-based flexible sensor demonstrated stable and repeatable signal responses across a wide strain range (0–1000%) and effectively monitored human motion in underwater environments. Notably, the hydrogel sensor could accurately output “SOS” and “UP” signals in underwater settings, opening new possibilities for sensing applications in underwater training, detection, and rescue operations.