Study of wetting and spontaneous motion of droplets on microstructured surfaces with the lattice Boltzmann method

The influence of arrangement of micro-pillars on wetting and self-motion of droplets is numerically studied via a three-dimensional lattice Boltzmann model for multiphase flow. Substrates textured with identical pillar array density but different arrangements are considered. The results show that the prediction of Cassie-Baxter model can be improved with the modified roughness factors. In addition, transportation of droplets on the stepwise gradient structured substrates is investigated. A simple model, taking account of pillar arrangement, is developed to estimate droplet velocity. The results show that it is critical to restrain droplet spreading in the lateral direction to achieve higher velocity and longer transportation distance.