Morphology evolution and dynamics of sliding nanodroplets under external forces: A molecular dynamics study

Abstract

The effects of external forces and surface wetting properties on the directional motion of nanodroplets are studied through molecular dynamics simulations. We find that when droplet motion reaches a steady state, the steady velocity shows an unusual relationship with the external force such that the profile has two nearly linear regimes. This behavior differs from previous experimental and theoretical results. The underlying mechanism of the two linear regimes is explored and is closely related to the two distinct regimes of droplet deformation. The transition between these two regimes can be roughly determined by a value of approximately 1.2 in terms of the ratio of Le*L0* or Se*S0*. In addition, we observe an interesting phenomenon, a “caterpillar-crawling-like motion,” rarely reported in experiments thus far, which involves periodical oscillations in both the droplet shape and the velocity of the center of mass of the droplet. Moreover, we construct a dynamic phase diagram to describe the correlation between the transition of dynamics and the morphological transition among various shapes (nearly round, corner-like, pear-like, zucchini-like, calabash-like, and rivulet-like).