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

Abstract

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 × 10⁴ 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.