Analysis of depinning behavior of drop on chemically heterogeneous surface

Abstract

Three types of depinning behaviors of a drop on a heterogeneous surface are numerically investigated. Depinning is found to occur due to two processes: slow- and fast-moving. A dynamic equilibrium results from competition between gravity and the capillary force in the whole drop. At the microscopic scale, based on measurement of the real-time contact angle, the local force balance in the contact line region is maintained by the unbalanced Young's force and the substrate resistance in the slow-moving stage, while the unbalanced Young's force provides the driving force for contact line motion in the fast-moving stage.