Bouncing dynamics of nanodroplets impacting superhydrophobic surfaces: The coupling influence of wetting transitions and scale effects

When nanodroplets rebound from nanopillar-arrayed superhydrophobic surfaces, the coupling influence of wetting transitions and scale effects on the bouncing dynamics is for the first time investigated via molecular dynamics (MD) simulations. The simulation results show that two bouncing patterns, the Cassie state bouncing and the Wenzel state bouncing, are always observed on nanopillar-arrayed superhydrophobic surfaces in a wide range of We= 1.5-95 as the coupling influence is changed by various aspect ratios and surface wettability. At same Weber number, the contact time of the Cassie state bouncing is constant, but that of the Wenzel state bouncing being increased with the increased aspect ratio. However, the contact time is always increased with the increased surface wettability regardless of the bouncing pattern. Based on that, scaling laws of contact time are eventually established for these two bouncing patterns, respectively.