Stomata-Inspired Composite Films for All-Climate Dynamic Thermal Management in High-Humidity Environments

Passive daytime radiative cooling faces two fatal challenges in high-humidity environments: radiative transmission attenuation in the atmospheric window in summer and overcooling caused by static high emissivity in winter. Existing technologies can only solve one of these problems and cannot achieve all-climate adaptation. Inspired by the dynamic transpiration regulation mechanism of plant stomata, we have fabricated a humidity-responsive cellulose-hydrogel composite film, which autonomously adjusts the pore size of the porous structure via moisture adsorption-desorption to selectively modulate near-infrared reflectance. This film achieves a solar reflectance of 92.0% and an infrared emissivity of 96.1%. At high temperatures, it triggers a synergistic evaporative-radiative cooling effect, realizing a 15.6 °C sub-ambient temperature drop and effectively offsetting the cooling performance degradation caused by high humidity; at low temperatures, the material suppresses its radiative cooling power by reducing its solar reflectance. With excellent mechanical properties and weather resistance, it provides a novel design paradigm for all-climate intelligent thermal management in high-humidity regions.