A laser-induced superhydrophobic surface with multiple microstructures for stable drag reduction

To address the issue of water resistance in ship navigation, we developed a drag-reducing surface based on the microstructure of shark skin and a superhydrophobic coating. First, grooves with various microstructures were fabricated on the substrate surface using laser processing. Then, a mixture of octadecyltrichlorosilane, water, and silica solution was uniformly sprayed onto the grooved substrate surface to achieve superhydrophobicity. To enhance and stabilize the drag reduction effect, we optimized the width and spacing of the grooves by adjusting the laser processing parameters, achieving a high drag reduction rate under various flow conditions. In the Reynolds number range of 2 × 105 to 5 × 105, the drag reduction rate of the superhydrophobic coated surface with grooves reached over 66.57 %, which is an improvement of 7 % to 26.51 % compared to the superhydrophobic coated surface without grooves. Additionally, the oxides accumulated on the ribs after laser ablation can slow down the wear of the superhydrophobic coating, significantly enhancing the surface's mechanical durability. This simple and cost-effective surface provides a new approach for laser preparation of drag-reducing surfaces.