Superhydrophobic biomimetic microstructures prepared by laser-ablation for drag reduction

The fluid resistance control of the underwater vehicle is the most important means to increase its navigation speed and improve energy efficiency. The 7075 Al alloy widely used in the shell of the aircraft was selected as the research object. Different laser parameters were used to ablate the bionic shark-skin microstructure on its surface, and further chemical modification was used to reduce its surface-free energy. The surface of the prepared Al alloy exhibited superhydrophobicity with a maximum water contact angle (WCA) of 163°. The change of wettability showed that the realization of the superhydrophobic surface was the combined effect of low surface energy materials and micro-nano composite structures. The prepared superhydrophobic surface showed excellent mechanical durability and chemical stability through the mechanical durability tests. The slip length of the superhydrophobic surface was 17.2 µm with deionized water, and the original smooth surface had no slip, suggesting that the prepared superhydrophobic surfaces had good drag-reduction properties. This simple and inexpensive method allows the fabrication of superhydrophobic surfaces with large slip lengths, which can be applied to underwater vehicle hulls to increase speed and range and save energy consumption.