Wettability regulation from superhydrophilic to superhydrophobic via nanosecond laser ablation

Metal surfaces play a crucial role in numerous applications, from self-cleaning and anti-icing to anti-fogging and oil-water separation. The regulation of their wettability is essential to enhance their performance in these areas. This paper proposes a multi-state regulation method for metal surface wettability, leveraging nanosecond laser ablation. By creating non-uniform microstructures on a metal surface, the contact area between the solid and liquid phases can be increased, resulting in the attainment of superhydrophilic properties (contact angle (CA), ranging from 4.6° to 8.5°). Conversely, the construction of uniform microstructures leads to a decreased solid-liquid contact area, thereby rendering the metal surface hydrophilic (CA = 12.2°–53°). Furthermore, through heat treatment on a surface with uniform microstructures, organic matter adsorption can be promoted while simultaneously reducing surface energy. This process results in the metal surface acquiring hydrophobic properties (CA = 92.1°–133.5°), facilitated by the “air cushion effect.” Building on the hydrophobic surface, stearic acid modification can further reduce surface energy, ultimately bestowing the metal surface with superhydrophobic properties (CA = 150.1°–152.7°, and sliding angle = 3.8°). Performance testing has validated the durability and self-cleaning effectiveness of the fabricated superhydrophobic surface while also highlighting the excellent anti-fog performance of the superhydrophilic surface. These findings strongly indicate the immense potential of these surfaces in various engineering applications.