Hydrophobic Radiative Cooling using Zein‐Functionalized Polyvinyl Alcohol Nanofibers with Dielectric Nanoparticles

Abstract Polyvinyl alcohol (PVA) is a promising material for radiative cooling owing to its high infrared emissivity and mechanical flexibility; however, its inherent hydrophilicity limits its practical applications, particularly in humid environments. In this study, a scalable and environmentally friendly approach is introduced to overcome this limitation by incorporating Zein—a hydrophobic protein derived from corn—into a PVA matrix in conjunction with aluminum oxide and silicon dioxide nanoparticles. The resulting composite nanofiber membrane, PZAS, exhibits significantly enhanced hydrophobicity, achieving an average water contact angle of 118.5° over 60 s, compared with ≈40° for pure PVA nanofibers. A high solar reflectance of 91.7% and strong infrared emissivity of 96.9% within the atmospheric transparency window are demonstrated. In outdoor measurements, a temperature reduction of up to 6.9 °C is achieved below ambient temperature. These findings underscore the potential of PZAS as a viable and sustainable radiative cooling material for applications in thermal regulation, particularly in textiles and wearable cooling technologies. The initial hydrophobicity followed by gradual water absorption of PZAS highlights its suitability for advanced biomedical applications, including moisture‐managing textiles, sweat‐based biosensors, and controlled drug delivery systems.