Facile “Synergistic Inner–Outer Activation” Strategy for Nano‐Engineering of Nature‐Skin–Derived Wearable Daytime Radiation Cooling Materials

Abstract Natural skin–derived products, as traditional wearable materials are widely used in people's daily life due to the products’ excellent origins. Herein, a versatile daytime‐radiation cooling wearable natural skin (RC‐skin) consisting of the collagen micro‐nano fibers with the on‐demand double‐layer radiation cooling structure is nano‐engineered through the proposed facile “synergistic inner–outer activation” strategy. The bottom layer (inner strategy) of the RC‐skin is fabricated by filling the skin with the Mg₁₁(HPO₃)₈(OH)₆ nanoparticles by soaking. The superstratum (outer strategy) is constituted by a composite coating with an irregular microporous structure. The RC‐skin harvests the inherent advantages of natural building blocks including sufficient hydrophobicity, excellent mechanical properties, and friction resistance. Owing to the subtle double‐layer structure design, the solar reflectance and the average emissivity in the mid‐infrared band of RC‐skin are ≈92.7% and ≈95%, respectively. Therefore, the RC‐skin's temperature in the sub‐ambient is reduced by ≈7.5 °C. Various outdoor practical application experiments further substantiate that RC‐skin has superior radiation cooling performances. Collectively, RC‐skin has broad‐application prospects for intelligent wearing, low‐carbon travel, building materials, and intelligent thermoelectric power generation, and this study also provides novel strategies for developing natural‐skin–derived functional materials.