One-step fabrication of multifunctional fusiform hierarchical micro/nanostructures on copper by femtosecond laser

In this paper, one-step fabrication of fusiform hierarchical micro/nanostructures on copper surface by femtosecond laser is proposed. According to the preferential valley ablation, Marangoni effect based on melt hydrodynamics and the coupling of the incident light and surface plasmon polaritons, the formation mechanism of the fusiform hierarchical micro/nanostructures is explained. And the effect of laser parameters including the defocusing distance, laser power, and scanning speed on the surface morphology is investigated. Also, the quantitative analysis of the fusiform tapers is carried out. It is demonstrated that the three-dimensional size of the fusiform hierarchical micro/nanostructures could be controlled by adjusting laser parameters. In addition, the potential applications of the fusiform hierarchical micro/nanostructures in microliter droplet directional transportation and light absorption are explored.