A Multifunctional Flexible Superhydrophobic Film for All-Weather Thermal Regulation, Anti-Icing, and Droplet Energy Harvesting

Conventional passive radiative coolers suffer from two fundamental limitations: overcooling in cold environments and drastically reduced efficiency under cloudy or rainy conditions. Here, we overcome these challenges by developing a multifunctional flexible superhydrophobic film (AFSF) that synergistically integrates radiative cooling, anti‑icing, and droplet‑based energy harvesting within a single, durable platform. Fabricated via template replication and layer-by-layer spin-coating, the film features a hierarchical micro-/nanostructured surface that endows exceptional superhydrophobicity (water contact angle of 158 ± 0.7°, sliding angle of 8 ± 0.3°) without the need for fluorination. By incorporating 5.88 wt % TiO2 nanoparticles into the intermediate layer, the film achieves a visible reflectance of approximately 70% and a substantial cooling of 14.88 °C relative to the control under simulated solar irradiation (1100 W·m-2). Unlike conventional radiative coolers that suffer from overcooling in cold environments, the AFSF markedly delays ice formation, with a freezing time of 242 s at -20 °C (3.97 times longer than that on bare aluminum) and remains ice‑free after 20 min of continuous supercooled droplet impact. Furthermore, the film functions as a triboelectric layer for raindrop energy harvesting, delivering stable electrical output for over 100 s under periodic droplet impingement at 1.8 Hz. The AFSF also exhibits robust mechanical durability (contact angle > 150° after 24 m sandpaper abrasion) and UV aging resistance (180 min at 15 mW·cm-2, equivalent to 6000 UVI). This work successfully reconciles the often conflicting optical, thermal, and mechanical demands in multifunctional systems and offers a versatile platform for all‑weather thermal regulation, self‑cleaning, anti‑icing, and decentralized microenergy harvesting in complex outdoor environments.