Recent studies have shown that the triple-phase contact line has critical effect on the contact angle hysteresis of surfaces.In this study,patterned surfaces with various surface structures of different area fractions were prepared by electron etching on a silicon wafer.The advancing angle,receding angle and hysteresis angle of these surfaces were measured.Our experimental results showed that while the geometry of microstructure and contact line have a minor effect on the advancing angle,they have a significant effect on the receding angle and thus the hysteresis angle.We have shown that the effect of microstructure and the contact line can be described by a quantitative parameter termed the triple-phase line ratio.The theoretical predictions were in good agreement with our experimental results.
In this study,a theoretical model was established for predicting the equilibrium shape of the droplet on flat and spherical surfaces.The theoretical equilibrium shape of heavy droplets could be obtained once contact angle and volume of droplets were given.It showed that the predictions of the theoretical flat model were in good agreement with the shape obtained by Surface Evolver when the contact angle is below 120 and the droplet size is on the order of capillary length.This available range will decrease and increase when the heavy droplet is on convex and concave spherical surface,respectively,in contrast to that on flat surface.The available range will decrease more for higher curvature of convex spherical surfaces.
