Molecular-dynamics investigation of the simple droplet critical wetting behavior at a stripe pillar edge defect

The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on the pillar sidewall, which makes the droplet highly unstable and undermines the overall hydrophobic performance of the pillar. In this work, molecular dynamics (MD) simulation of the simple liquid at a single stripe pillar edge defect is performed to characterize the droplet's critical wetting properties considering the evaporation-condensation effect. From the simulation results, the droplets slide down from the edge defect with a volume smaller than the critical value, which is attributed to the existence of the wetting layer on the stripe pillar sidewall. Besides, the analytical study of the pillar sidewall and wetting layer potential field distribution manifests the relation between the simulation parameters and the degree of the droplet pre-wetting, which agrees well with the MD simulation results.