Femtosecond laser machining of the novel superhydrophobic microstructure for the oil-water separation

Bionic micro/nano structures with superhydrophobicity is extensively used in oil-water separation. However, the fabrication of such tiny structures involves intricate processes, often requiring additional steps such as chemical or mechanical post-processing. With the development of the laser machining, it is feasible to fabricate structures in micro/nano scale via the ablation of ultrafast laser beam. Inspired by the function of the funnel, a novel through-hole structure was designed and manufactured by femtosecond laser in high dimensional precision. The copper film with the funnel-like through-hole structure exhibited remarkable hydrophobic properties, with a water contact angle of 160 ± 2° and a sliding angle ≤ 5°, facilitating the high-quality and high-efficiency separation of water-oil/organic liquids, compared with the conventional through-hole structures, such as circular or rectangular structures. Furthermore, the prepared film demonstrated exceptional capabilities of anti-freezing, anti-pollution, environmental stability, and versatility, examined by enduring treatments involving acidic liquids, immersion in hot solutions, freezing, and scratching. In sum, this work offers innovative concepts and valuable insights on the design and fabrication of functional structures with ultrafast laser machining.