Leaf‐Inspired Eutectic Skin With Extreme Fatigue Resistance and Robust Wet Adhesion for Amphibious Epidermal Electronics

Reliable skin‐interfacing electronics require soft materials that simultaneously tolerate repeated mechanical deformation and maintain robust adhesion in moist environments. However, conventional hydrogels are inherently limited by water‐induced swelling and interfacial failure. Inspired by the vein‐reinforced architecture of Acorus calamus leaves, we present a fatigue‐resistant and environmentally stable “eutectic skin” composed of an aligned polyurethane fibrous network embedded within a hydrophobic eutectogel matrix. The intrinsic hydrophobicity suppresses hydration to ensure exceptional dimensional stability with less than 1.1% swelling over 100 days. Crucially, the hierarchical fiber reinforcement imparts a unique “soft‐yet‐strong” mechanical behavior. The composite exhibits a tissue‐like softness (Shore A hardness of 13.6 A) yet achieves a true tensile strength of 106.51 MPa and a fatigue fracture threshold of 5.02 × 10 4 J m − 2 (≈3399‐fold enhancement) via strain‐induced crystallization. This exceptional toughness allows the material to sustain 100,000 cycles of notched stretching without crack propagation. The hydrophobic matrix also enables strong wet adhesion to skin (152.2 J m − 2 ). This stable ionic interface supports high‐fidelity electrophysiological signal acquisition during underwater operation and continuous 7‐day monitoring. This work establishes a generalizable strategy for engineering mechanically resilient soft ionotronic interfaces for next‐generation wearable bioelectronics.