The fabrication of unwettable superhydrophobic surfaces by reactive wetting of AgCuTi into an AAO template

Multi-level hierarchical surface roughness is the key to natural superhydrophobic materials. In this work, rough surfaces of a novel superhydrophobic material are achieved by the reactive wetting technique. The molten AgCuTi alloy is applied to infiltrate into the porous anodic aluminum oxide (AAO) membrane, and wetting of molten AgCuTi is promoted by the reaction layer formed at the interface between AAO and AgCuTi. The AgCuTi infiltrates the AAO nanopores and forms the first-level surface roughness based on reactive wetting. To release the nanostructures embedded in the AAO pores, hydrothermal etching with NaOH aqueous solution was used to remove AAO. Meanwhile, TiO₂ nanostructures are synthesized under hydrothermal conditions, resulting in the second-level surface roughness. After modification, the surface is found to exhibit excellent superhydrophobic properties, including a high water contact angle (WCA) and low roll-off angle (RA). The superhydrophobic surface also shows self-cleaning, mechanical durability and long-term stability. The as-prepared surface exhibits excellent repellence for water solutions with different pH values. This method could be applied to fabricate superhydrophobic surfaces on different kinds of materials, showing broad application prospects.