High-Performance Hydrogel Skins for Bioinspired Robotic Fish in Extreme Ocean Environments

The ocean's extreme environments demand robust materials for next-generation exploration tools. Here, we report a multifunctional poly(vinyl alcohol) hydrogel (PVA-H) fabricated via universal solvent-induced crystallization for bioinspired robotic fish skins. Alkaline solvent induction triggers intrachain crystallization within concentrated PVA solutions, yielding hydrogels with exceptional mechanical strength (compressive strength up to 2.6 MPa, tensile strain >450%), environmental tolerance (resilience to 1 M acetic acid/NaOH, seawater, 3 M NaCl), and optical transparency (>80%). The material demonstrates efficient recyclability (>90% recovery over 10 cycles) and biocompatibility (hemolysis rate <1.5%). Ionic compounding enables stable underwater conductivity and antifreezing performance at -20 °C. Hydrophilicity-driven interfacial water layers inhibit >70% protein adsorption, which confers antifouling properties. Integration of ice templating and solvent crystallization facilitated scalable fabrication of biomimetic fish skins, validated through sustained underwater operation. This work establishes a versatile platform for durable, eco-adaptive marine robotics operating in chemically, thermally, and biologically hostile environments.