The dynamic behavior of microdroplet formation on the top surface of micropillar during a dewetting process

The dynamic behavior of droplet formation on micropillar surface during a dewetting process is investigated in this paper via a numerical approach. The simulation results suggest that the formation of droplet is governed by the recoiling of captive wet region on the top surface of micropillar after two bridge-shaped meniscus detachments from neighboring droplets. The numerical simulations also show that the cross-sectional shape and its orientation of micropillar play an important role in determining the flow pattern of the dewetting process, especially the evolution and movement of meniscus across the micropillar before a microdroplet is formed. The dimensionless group, i.e., the Ohnesorge number (Oh), the Capillary number (Ca) and the dimensionless liquid thickness (H), characterizes the dimensionless diameter (d) and formation time (td ) of droplet. Both can be expressed as the product of polynomial functions of dimensionless group, and approach to an asymptotic solution for H greater than unity.