An easy-to-use and low-cost method was used to clad an alumina coating onto the surface of a flexible copper mesh in one-step laser treatment, fabricating a modified layer of nanostructures with different roughness on the surface of the mesh to regulate the surface wettability. Transient thermal analysis was introduced to investigate the change of temperature distribution field caused by the reduction of the scan path spacing. It is found that the cladded aluminum coating on the surface of the copper mesh fabricated by the laser scanning path spacing at 10 μm exhibits an α-Al₂O₃ crystalline form with good durability and separation efficiency exceeding 95% after cyclic testing, delivering water contact angle close to 0° in the air and oil contact angle larger than 160° underwater. To address the oil/water separation needs in microfluidic channel applications, oil-water separation tests and simulations of fluid mechanics were carried out for the pipeline formed by curling the flexible substrate of the separation membrane. Computational fluid dynamics was used to analyze how to regulate the distribution of surface nanoparticles, leading to the redistribution of pressure and velocity fields inside the pipeline, thereby promoting the smooth flow of fluid inside the pipeline and enhancing the oil-water separation performance.