Scalable eco-friendly fabrication of hierarchical superhydrophobic metal surfaces for atmospheric water harvesting

Abstract The worldwide shortage of freshwater has fueled interest in atmospheric water harvesting (AWH) as a promising option for decentralized water generation. In this study, a scalable method for the fabrication of superhydrophobic (SHP) metal surfaces by sandblasting and hot-water treatment (HWT) followed by fluorination is introduced to improve AWH performance. Aluminum alloy, copper, and zinc substrates were designed to have hierarchical micro-/nanostructures and then fluorinated to render them SHP. Of these, copper showed superior water collection efficiency owing to its high thermal conductivity and optimized surface texture. Under controlled humidity and temperature, water collection on copper was enhanced by 80% compared to aluminum alloy and 34% compared to zinc. To further enhance condensation and droplet drainage, bioinspired groove patterns were fabricated on copper surfaces. When tilted at 45°, the grooved samples exhibited a 21% increase in water collection efficiency compared to flat SHP copper surfaces, owing to improved droplet coalescence and guided drainage. Overall, this study highlights the critical roles of substrate material, hierarchical surface design, and tilt angle in advancing passive atmospheric water-harvesting technologies.