Droplet sliding on an inclined substrate with chemical defects

Abstract

We numerically study the dynamics of a droplet sliding on an inclined and inhomogeneous substrate under gravity force using three-dimensional diffuse interface method. On the path of the sliding droplet, there are two transversely located defects with the shape of circle, and their wettability is different from the substrate. Our aim is to identify the regimes of the droplet motion and figure out the critical conditions between the different regimes. By varying the distance between the two defects, the inclination angle of the substrate, and the size of the defects, three regimes are found according to the status of the droplet: capture, breakup and release. By analyzing geometrical relationships, the shape of the contact line and the force balance of the droplet at rest, we derive critical conditions between each two regimes. The theoretical predictions of critical conditions agree well with our numerical simulations, which provide a comprehensive understanding of the underlying mechanisms of a droplet sliding on a chemical defect substrate.