Mutual wetting transition between isotropic and anisotropic on directional structures fabricated by femotosecond laser

This paper reports on the mutual wetting transitions between anisotropic and isotropic on directional structures fabricated by femtosecond (fs) laser. The directional structures are composed of flat Si triangular patterns and fs laser induced spikes. After chemical deposition of a layer of fluoroalkylsilane, the triangular areas and periodic spikes exhibited hydrophobicity and superhydrophobicity, respectively. With increasing water volume, the droplet experienced a series of mutual wetting transitions due to the stick-jump behaviors of triple-phase contact line in orthogonal directions. The typical dynamic triple-phase contact line behaviors were quantitatively analyzed, based on which the specific energy barriers exerted by triangular patterns were speculated. A two-strip model was introduced to explain the reason of mutual wetting transitions.