Large-scale continuous production of cellulose/hollow SiO₂ composite aerogel fibers for outdoor all-day radiation cooling

Passive radiant cooling fabrics (PRCF) can effectively reduce the human body surface temperature and alleviate heat stress without consuming energy. These textiles show tremendous potential for personal thermal management and are widely used in outdoor sports, high-temperature operations and other scenarios. However, the development of fiber products with radiative cooling properties from biomass resources presents a considerable challenge. Herein, the hollow silica/regenerated cellulose composite aerogel fibers with a tree-ring structure (HSiO₂/C@C) were continuously fabricated by a novel strategy combining wet coaxial spinning and atmospheric pressure drying. Regenerated cellulose aerogel mixed with hollow silica as a sheath layer imparts the fibers with strong backscattering properties, higher porosity, and guarantees high solar reflectance (92.6 %), high infrared emissivity (96.1 %), and improved thermal insulation (0.062 W·m⁻¹K⁻¹). The relatively dense cellulose aerogel core layer provides the composite fibers with robust mechanical strength (19.4 MPa). The outdoor all-day test further demonstrated that the HSiO₂/C@C fibers exhibit high-performance cooling with an average sub-ambient temperature drop of ∼1.3°C under 850 W·m⁻² solar irradiation and ∼ 4.2°C for nighttime. The fabric-covered arm showed a temperature reduction of 4°C compared with that covered with cotton fabric. The passive radiation cooling textile can also apply to buildings, vehicles and other fields contributing to energy saving and environmental protection. In addition, the hydrophobic modified aerogel fabric shows good comprehensive outdoor-services performance, including good air permeability, anti-dust and durability, thus broadening its applicability in complex environments. This scalable and renewable composite aerogel fiber holds promise as the next generation of personal thermal management textiles for all-day superior radiant cooling.