Porous PDMS films with multiscale structures for enhanced passive radiative cooling

Passive radiative cooling (PRC) has emerged as a promising zero-energy thermal management strategy for building energy conservation and device temperature regulation. However, conventional fabrication routes for cooling films typically involve complex procedures, and the pore structures are challenging to regulate, which limits spectral tunability and scalable manufacturing. Here, a simple and scalable water-induced phase separation strategy is developed to fabricate multiscale porous polydimethylsiloxane (PDMS) radiative cooling films. Simulations reveal that pores with tunable porosity and diameter perturb the local electric field distribution, thereby enhancing backward scattering of incident light. By adjusting the water content, both the average pore size and porosity can be systematically controlled to optimize scattering behavior. The resulting porous PDMS film achieves an average solar reflectance of 67.5% and an infrared emissivity of 92.6%, exhibiting enhanced radiative cooling property. Xenon-lamp tests further confirm its promising cooling potential, achieving a reduced temperature of 16.3℃ compared to a wooden substrate. This work provides a cost-effective and structurally tunable strategy for fabricating porous PDMS-based radiative cooling materials, advancing the applicability in scalable thermal management system.