Wettability and droplet energetics on micro-scale wavy and V-grooved surfaces

The wetting physics and wetting transition on micro-wavy and micro V-grooved surfaces of similar topographic scales are investigated and compared with an emphasis on the droplet stability and anisotropic wetting that promotes liquid drainage. To develop 3D models of liquid droplets and to assess the morphology and spreading of liquid droplets across a wide range of parametric space, Surface Evolver (SE) has been used. The effect of roughness parameters of micro V-grooved surfaces such as groove height, groove width, pillar width, and groove angle on the wetting behavior is analyzed and compared to the same for the corresponding dimensional variation of pitch, amplitude, and depth of the asperities of micro-wavy surfaces. For all the comparable configurations, surfaces with micro-wavy textures exhibit higher wettability and smaller stable droplets than micro V-grooved surfaces. In addition, after specific threshold values of the aforementioned topographic parameters, the Cassie-Wenzel wetting transition is observed. Although wettability on micro-scale wavy and V-grooved surfaces have been widely examined because of their obvious importance, comparison of wetting physics and droplet energetics on them for similar roughness scale has not been conducted before. Therefore, the developed model may be useful in designing micro-structured V-grooved and wavy surfaces with tunable directional wetting properties.