Wetting characteristics on hierarchical structures patterned by a femtosecond laser

Micro-scale hierarchical structures consisting of parallel grooves decorated by embossed triangle patterns are prepared by femtosecond laser irradiation on silicon (Si) wafers. The effects of surface morphology on wetting properties are investigated, and the results show that increasing the vertex angle of the triangle and groove spacing will lead to the enhancement of wettability and anisotropy, respectively. The structured surfaces also exhibit high adhesive force with droplets remaining attached to the surface even when the sample is turned upside down. Furthermore, the evaporation process of a water droplet on such an anisotropic surface is characterized to study its dynamic wetting behavior.