UV‐Cured Dense Double Network Hydrogel via Multiple Dynamic Crosslinking for Stable Amphibious Motion Sensing

Abstract Although conductive hydrogels have emerged as promising materials for developing highly flexible sensors in recent years, traditional hydrogels are prone to swelling, which significantly compromises sensor performance. To address this issue, a non‐swelling hydrogel is prepared through a one‐step radical polymerization of acrylic acid (AA), hydroxyethyl methacrylate (HEMA), tannic acid (TA), and quaternized chitosan (QCS) in aqueous water. The resultant poly(AA‐HEMA)‐QCS‐TA (PAHCT) hydrogel features a highly crosslinked network, attributed to the formation of multiple hydrogen bonds among the abundant hydroxyl and carboxyl groups in AA, TA, and QCS, the electrostatic interactions between poly(AA‐HEMA) and QCS, as well as polymer chain entanglements. This innovative architecture significantly enhances the anti‐swelling ability of the PAHCT conductive hydrogel, achieving an equilibrium swelling ratio of 5.5% in water, along with remarkable tensile properties, reaching an elongation of 990%. Furthermore, the introduction of TA further improves the hydrogel's adhesion, ensuring its durability for long‐term service. Consequently, strain sensors based on the non‐swelling PAHCT hydrogel are capable of effectively monitoring human activities across various strain range and enabling reliable underwater communication. These findings open new avenues for the development of wearable sensors in amphibious environments, broadening the application scope of wearable electronics.