Designing the Future of Cooling: Superhydrophobic Passive Daytime Radiative Cooling Systems

Passive daytime radiative cooling (PDRC) is a sustainable technology that reduces temperature by utilizing materials with high solar reflectance and thermal emittance to provide cooling without electricity. However, its performance is often compromised by dust and environmental contamination, with even minimal dust deposition (0.1 mg/cm²) reducing cooling capacity by ∼7.1 W/m². To overcome this, superhydrophobicity has been integrated into PDRC systems through various techniques and materials. This Review explores superhydrophobic PDRC (SH-PDRC) systems, examining their principles, preparation strategies, and material innovations. Advanced fabrication methods, including electrohydrodynamics, phase separation, chemical vapor deposition, and layered patterns, have enabled the development of hierarchical structures that optimize solar reflectance, infrared emissivity, and water repellency. A variety of polymeric, inorganic, and hybrid materials is used to achieve durability, thermal stability, and environmental resilience. These materials are tailored to enhance performance for long-term use in extreme conditions, ensuring a high radiative cooling efficiency. SH-PDRC systems have potential applications in wearable textiles, agricultural greenhouses, and food preservation, demonstrating their versatility. By summarizing recent progress and challenges, this Review aims to provide researchers with clear guidelines for fabricating advanced SH-PDRC systems that achieve enhanced cooling performance, environmental durability, and efficiency, paving the way for designing the future of cooling.