Numerical study on the influence of the corner curvature of circular micropillar on microdroplet size via a dewetting process

The influence of the corner curvature of circular micropillar on microdroplet formation by a dewetting process was numerically investigated. The diameter of the microdroplets is mainly determined by the capillary effect and viscous force contributed by the wetted surface i.e. on the top surface of micropillar magnifies, which slows down the movement of water front attached to the top surface of micropillar. The numerical simulations showed that the corner curvature of the micropillars play an important role in determining the flow pattern of the dewetting process, especially the evolution and movement of the meniscus across the micropillar before a microdroplet is formed. The water front on the top surface of micropillar with right-angle corner moves much slower than that on the micropillar with round corner. The numerical results also indicate that the curvature radius (r) on circular micropillar is one of the parameters governing the size of the microdroplets formed on the top surface of the micropillars after the dewetting process, while the microdroplet diameter decreases with the increase of the dimensionless of curvature corner.