Kaewmanee T.Sakata P.Gridtayawong P.Rueangsawang W.Ponghiransmith C.Chattham N.Pecharapa W.Noinonmueng T.Benchaphanthawee W.Kaewkhao J.Suttiruengwong S.Kanjanaboos P.Mahidol University2026-05-072026-05-072026-07-01Applied Thermal Engineering Vol.299 (2026)13594311https://repository.li.mahidol.ac.th/handle/123456789/116555Radiative cooling via micro-patterned surfaces provides energy-efficient solution for thermal regulation by enhancing selective thermal emission within the atmospheric transparency window (8–13 μm). This study investigates the effects of microstructural patterning through a low-cost and scalable stamping technique. The patterning templates were uniquely produced by the removal of randomly-distributed CaCO<inf>3</inf> polymorphs—calcite and vaterite with specific sizes. The novel calcite-imprinted structures exhibit superior mid-infrared emissivity (>0.96) and maintain consistent temperature reduction across varying weather conditions, outperforming vaterite-based films. However, the cooling performance of unmodified patterns is limited by solar absorption. To address this, TiO<inf>2</inf> (rutile phase) is incorporated into a polymer matrix before being stamped to enhance solar reflectivity. Moreover, hydrophobic aerogels could be inserted between micropattern gaps to facilitate self-cleaning functionality. A composite film containing 3 wt% TiO<inf>2</inf> with the calcite micro-patterning and hydrophobic aerogel achieves a temperature drop of 4.8 °C, compared to 1.2 °C of pristine patterns relative to that of a clear film. For real-world applicability, the optimized patterning strategies were further validated on fiber cement rooftile surfaces, yielding best temperature reductions of 2.5 °C compared to pattern-free coating under a tropical climate. The calculated net cooling power of 3 wt% TiO<inf>2</inf> patterned film with aerogel is 26.9 W/m². This novel passive-cooling stamping strategy is low-cost, scalable, and suitable for large-area deployment, reducing the energy burden of active cooling technologies.Chemical EngineeringEnergyEngineeringArticleSCOPUS10.1016/j.applthermaleng.2026.1310832-s2.0-105037313372