One-step fabrication of superhydrophobic surfaces with different adhesion via laser processing

Abstract

In this study, we developed a simple, low-cost and convenient method to fabricate grid structures of different scales on the surface of 6061 aluminum alloy via laser processing. By changing the line spacing (50, 150, 250, 300 μm) during laser beam irradiation, different sizes of the square-shaped unprocessed surface areas and cross groove structures could be achieved. By adjusting the area ratio between the accumulative microstructure and the unprocessed surface, the adhesion of a water droplet to the surface could be varied from a state of low adhesion (line spacing of 50 or 150 μm) to a state of high adhesion (line spacing of 250 or 300 μm). The results indicated that different surface wettabilities could be obtained on aluminum alloy surfaces through the combination of a crisscross groove structure and unprocessed surface, which together formed a square groove structure. Corrugated protuberances, granular bumps and pit texture were formed on the groove structure. The surface showed excellent superhydrophobic properties. The contact angle was as high as 154.6° and the sliding angle was 6° for a line spacing of 150 μm. In this case, the low adhesion led to a rolling and self-cleaning behavior. For the larger line spacings, the wetting state of the water droplet indicated a high adhesion to the surface and a transition of the Cassie-Baxter state to the Wenzel state. Surfaces with high adhesion are of great significance for water collection and preservation. The approach presented in this study provides a facile, low-cost and efficient method to fabricate superhydrophobic surfaces on all types of metallic materials for commercial applications.