Modeling of the dependence of nanodroplet size on the parameters governing the dewetting process on square micropillar

The nanodroplet formation on a micropillar surface during a dewetting process is investigated in this study using a numerical approach. The formation of nanodroplet is governed by the recoiling of captive wet region on the top surface of micropillar after the detachment of two bridge-shaped meniscuses from neighboring droplets. In this study, the correlation among the size of nanodroplet, the geometrical parameters of square micropillars, and the parameters governing the dewetting process. Dimensional analysis is used to determine independent dimensionless groups to characterize the diameter of nanodroplet i.e. the Ohnesorge number (Oh), the Capillary number (Ca), the dimensionless liquid thickness (H) and the dimensionless center-to-center distance between micropillars (l). The numerical simulations showed that the size of nanodroplet on the top surface of micropillar depend on the parameters in the dewetting process. The dimensionless nanodroplet diameter (d) grows with the increase of H. The decrease of Ohnesorge number results in nanodroplets with large diameter. When the value of Capillary number increases, the viscous force on the top surface of micropillar magnifies, and leads to the growth of nanodroplet diameter. The simulation results also reveal that the change of d is almost insensitive to the increase of l at a given Ohnesorge and Capillary numbers.