Eco-Friendly Skin-Wrinkle-Inspired Micro-Nano Structured Cellulose Composite Fibers for Highly Efficient Daytime Radiative Cooling

Passive radiative cooling fabrics offer a sustainable pathway to reduce energy consumption in thermal management, yet their reliance on petroleum-derived materials and complex coating processes compromises both environmental compatibility and wearability. To address these challenges, we propose a bioinspired, coating-free strategy by designing regenerated cellulose/SiO₂ nanoparticle fibers (RCSF) via wet-spinning. Mimicking the micro-nano structure of the human skin surface (protrusion height ≈ 2 μm), the RCSF achieves simultaneous high solar reflectivity (93.7% at 0.4-1 μm) and infrared emissivity (0.98 at 8-13 μm) through intrinsic material properties rather than external coatings. The hierarchical porous structure enhances the specific surface area while maintaining air permeability (75% improvement vs pristine cellulose fabrics) and moisture-wicking performance. Under 800 W m^-2 solar irradiation, RCSF exhibits a net cooling power of 100.1 W m^-2, translating to a 5 °C temperature reduction in summer environments compared with regenerated cellulose fibers (RCF). Crucially, this one-step fabrication method eliminates toxic paints and energy-intensive post-treatments, offering a cost-effective alternative to conventional coated fabrics. By integrating renewable cellulose with skin-wrinkle-inspired structural design, our work establishes a paradigm for eco-efficient radiative cooling materials that balance optical performance, wearer comfort, and scalable manufacturing.