Numerical Study on Droplet Sliding across Micropillars

Abstract

Droplet sliding on surfaces is an important phenomenon since it widely happens in microfluidic industry. In this article, we simulate droplets sliding across micropillars on smooth substrates to test how the pillars with different intrinsic wettability influence the movement of droplets. The simulation is performed using a particle-based numerical method, many-body dissipative particle dynamics (MDPD). The simulated results show that the heterogeneous area (built by arranged micropillars) can influence the dynamical contact angles significantly. Both the advancing and receding contact angles increase when the droplet front slides on the heterogeneous area, and their difference is also enlarged, thus the contact line may be pinned. The droplet shows a creeping motion style when its front climbs over each pillar. We also find when the droplet enwraps all pillars, the composite liquid/solid surfaces have no effect on the advancing and receding contact angles. The outcomes support the viewpoint that the wettability is a contact-line-based problem instead of a contact-area-based one