Bio‐Inspired Porous‐Hollow Biomass‐Based Microfiber Prepared by Phase Separation Evolution for Efficient Radiative Cooling

Abstract Inspired by the thermal regulation functions of microstructures of silver ants' hair and white beetle scales, this study systematically investigates the regulation of structure on and within biomass‐based microfibers, while simultaneously revealing the radiative cooling mechanism of the porous‐hollow microfiber. A porous microfiber membrane is efficiently fabricated via microfluidic blow spinning using a spinning emulsion composed of oil and water phases. Polyhydroxyalkanoate dissolved in dichloromethane served as the continuous oil phase in the spinning solution, while konjac glucomannan dissolved in water acted as the discrete water phase. Additionally, potassium titanate nanowhiskers (PT) are incorporated into the oil phase. Incorporating PT is beneficial for radiative cooling due to the high solar reflectance and long‐wave infrared emissivity of PT. The laminar two‐phase flow simulation showed that the static pressure difference influenced the surface pore structure, while the viscosity regulated the internal hollow structure. The porous‐hollow thick demonstrates a reflectivity of 95.11% in sunlight and near‐infrared range, alongside an emissivity of 93.90% in the mid‐infrared range. The porous‐hollow microfiber thick membrane exhibits a temperature reduction of 11 and 11.6 °C compared to the ambient temperature and black cotton clothing, respectively. The finite difference time domain simulation demonstrates that porous‐hollow microfibers induce multiple Mie scattering resonances, enhancing reflectivity. Besides, when used as a food packaging material, the porous‐hollow microfiber thick membrane significantly decreased the incidence of sunburn. This study presents the mechanisms of microstructure regulation and enhanced radiative cooling, promoting the optimization and application of biomass‐based radiative cooling membranes.