Broad‐Spectrum Bionic Polydisperse Radiative Cooling Fiber Membrane Integrating High Phase Change and Evaporation Efficiency

Abstract Electrospun membranes have been extensively employed as radiative cooling membranes for thermal management in personal and architectural applications, owing to their facile processability and tunable structural configurations. However, intrinsic limitations such as narrow fiber size distribution, inherent hydrophobicity, and insufficient multifunctionality lead to challenges, including inadequate solar spectral coverage, low reflectivity, constrained moisture transport capacity, and absence of dynamic regulation. In this study, a bifurcated electrospun membrane with a broad fiber size distribution is fabricated via a jet splitting approach, providing a wider coverage of the solar spectrum. Inspired by vascular plant transpiration, bioinspired gradient wettability and porous structures are engineered, significantly enhancing moisture evaporation efficiency. Additionally, phase‐change microcapsules (PCMs) with a loading capacity of up to 70 wt.% are successfully integrated into the fibers through a combined electrospinning‐spraying technique, demonstrating a phase change enthalpy (Δ H m ) of 111.8 J g −1 . The optimized membrane exhibits 94.0% solar reflectance with a 0.2 mm thickness only while delivering 93.6 W m −2 radiative cooling power and 392.5 W m −2 evaporative cooling power, enabling a reduction of 5.7–17.4 °C skin temperature. The material integrates broad‐spectrum coverage, high reflectivity, efficient evaporation, and substantial phase‐change enthalpy in a low thickness, exhibiting great potential for personal thermal management and building energy efficiency applications.