Objective High-speed train skirt panels are prone to contamination and difficult to clean under complex environments such as rain and snow, muddy water, and dust. In response to these problems, it is necessary to construct a biomimetic rice-leaf-inspired superhydrophobic structure on the metal substrate surface to achieve the surface functionalization of high-speed train skirt panels.

Method 6005A aluminum alloy is selected as the substrate, and the rice-leave-inspired strip-shaped groove multilevel composite microstructures is inscribed on its surface using TruMicro 5250 green femtosecond laser processing system. After pretreatment, one-dimensional longitudinal grooves are processed in the preset area according to a predetermined scanning path. SEM (scanning electron microscopy) and LSCM (laser scanning confocal microscopy) are used to characterize the surface morphology and three-dimensional roughness. The surface wettability performance of the coating is evaluated through CA (contact angle) and SA (sliding angle) tests. Based on the Cassie-Baxter model, the effective solid fraction of the surface is calculated, and the amplification mechanism of wettability caused by the stripe-shaped groove multilevel rough structure is analyzed.

Result & Conclusion  After laser treatment, a stripe-shaped groove array with a periodic length of approximately 90–100 μm is formed on the above substrate surface, and the surfaces of the grooves and ridges are covered with a large number of micro-scale protrusions and nanoscale protrusions. The Sa (three-dimensional surface roughness) is approximately 5.18 ± 0.67 μm, and the roughness exhibits obvious anisotropy in the directions parallel and perpendicular to the grooves. After femtosecond laser induction and natural aging of the 6005A aluminum alloy structure, the water CA increased from 106.90 ± 1.80° to 174.00 ± 0.86°, and the SA decreases from an adhesive state (no droplet falling even when inverted by 180°) to 5.80° ± 0.90°, exhibiting extremely superhydrophobic and low adhesion characteristics. Simulation calculations show that the effective solid fraction of the structured surface is approximately 0.8%, and more than 99% of the area at the bottom of the droplet is supported by a stable air cushion. Research results indicate that the femtosecond-laser-fabricated biomimetic rice-leaf-inspired superhydrophobic structure has good application prospects for waterproofing, anti-fouling, and self-cleaning functionalization of the exposed metal component surfaces such as high-speed train skirt panels.