Controllable anisotropic wettability behaviours of droplets by varying profile stripe structures

Anisotropic wettability of bionic structures is often achieved through anisotropic patterns, so the parameters of that are key to managing surface wettability behaviours. In this work, we fabricate three kinds of one-dimensional (1D) stripe structures with distinct profile shapes for studing the method of controlling anisotropic wettability behaviours of water droplets. By controlling their profiles and depths, the anisotropic wettability of stripes can be effectively managed and mitigated. Even with the same stripe periods, we can achieve two opposing wetting effects, namely isotropic hydrophobicity and anisotropic hydrophilicity. The experiments show that the π-shaped stripes possess isotropic superhydrophobicity, and their adhesion force to water droplets in the direction perpendicular to the groove is approximately ten times that in the parallel direction. Meanwhile, the willow-leaf-shaped stripes show anisotropic hydrophilic properties and good ductility to water droplets. Taking advantage of inductively coupled plasma-reactive ion etching (ICP-RIE) with a low undercut, this method provides a novel perspective on the design of interfaces for droplet manipulation, pick-and-place applications, and the localised control of reactions.