A durable, fluorine-free, and repairable superhydrophobic aluminum surface with hierarchical micro/nanostructures and its application for continuous oil-water separation

Artificial superhydrophobic surfaces have drawn a lot of attention owing to their multifunctional properties. However, the durability and environmental concerns of such surfaces are critical issues that have limited their widespread utilization in real-life applications. In this study, fluorine-free superhydrophobic aluminum surface was fabricated through a simple and cost-effective method. Its dual-scale micro-/nanostructures (MNS) was fabricated by combining chemical etching and hydrothermal processes. After modification with poly-dimethylsiloxane coating using a simple vapor deposition method, surface showed excellent super-hydrophobicity, with a water contact angle of similar to 161 degrees and sliding angle of 4 degrees, and sustained its non-wetting properties against various food liquids. The effect of morphological change on the surface's wettability and the durability of the coating materials were investigated in sandpaper abrasion, tape-peeling, and blade-scratching tests. Compared with micro- or nanostructure surfaces, the MNS surface showed better robustness because of its dual-scale roughness. Furthermore, the abraded surface could effectively restore its superhydrophobicity after being recoated with PDMS. The surface also showed long-term superhydrophobic stability in an ambient environment for over 10 months. Finally, the method was applied to Al mesh with superhydrophobic/superoleophilic properties to separate various oil-water mixtures, yielding a high separation efficiency of up to 94% and outstanding reusability.

Automated summary

Artificial superhydrophobic aluminum surface was successfully fabricated through a simple and cost-effective method, showing excellent durability and non-wetting properties in various environments. The dual-scale micro-/nanostructure surface demonstrated better robustness and restorability compared to micro- or nanostructure surfaces, effectively separating different oil-water mixtures.