A Silk Nanofiber‐Mediated Controlled Swelling‐Locking Strategy for Tough, Anti‐Swelling Hydrogels Toward Underwater Sensing

ABSTRACT Conductive hydrogels are promising for wearable sensors in human motion detection owing to their skin‐like softness, strain sensitivity, and biocompatibility. However, their practical application in aqueous environments is severely hindered by swelling‐induced mechanical deterioration and electrical instability. Herein, a tough, anti‐swelling conductive hydrogel for underwater sensing is reported, enabled by a “silk nanofiber‐mediated controlled‐swelling‐locking” (SNF‐CSL) strategy. In this approach, silk nanofibers (SNFs) are incorporated into a polyvinyl alcohol (PVA) matrix, followed by controlled swelling in a pyrrole solution to facilitate uniform monomer diffusion and adsorption onto SNFs. Subsequent ammonium persulfate‐initiated oxidative polymerization induces in situ formation and structural locking of a continuous polypyrrole (PPy) network, effectively stabilizing the swollen hydrogel configuration. The resulting PVA/SNF/PPy hydrogel exhibits skin‐matching Young's modulus (130.5 kPa), exceptional toughness (0.46 MJ m − 3 ), and excellent anti‐swelling stability (equilibrium swelling ratio of 3.9%). As a strain sensor, the hydrogel demonstrates high sensitivity (gauge factor of 2.14), fast response (20 ms), and durable performance over 1000 cycles, while enabling Morse code communication under aquatic environments. This work establishes a simple and broadly applicable strategy for designing robust anti‐swelling hydrogel sensors tailored for aquatic applications.