Analysis of impact phenomenon on superhydrophobic surfaces based on molecular dynamics simulation

The dynamic behavior of hydrophobic material directly effects its application. The impact phenomenon of droplets on hydrophobic materials is an important indicator to characterize the dynamic properties of hydrophobic materials. At present, the study on impact phenomenon mainly focuses on macroscopic experiments and theoretical analysis. This paper adopts molecular dynamics simulation to systematically investigate the impact phenomenon of a nano-sized water droplets on pillared graphite surface on the nano-scale. The effects of impact speed and angles of nanodroplets on impact phenomenon of droplets was quantitatively analyzed by a variety of impact simulations. Results showed that the droplets experience Cassie, Cassie-Jumping, Wenzel-Jumping, Wenzel-Cassie and Wenzel state successively with the increase of the collision angle and velocity. A rebounce occurs easily at an intermediate collision angle and bigger velocity. By changing the gap, height and area of the pillars on substrate, the influence of the hydrophobic property on impact phenomenon is analyzed. Studies illustrates that the dimensions of the gaps and height of pillars on graphite substrate have a more significant effect on the impact phenomenon when compared with the area of pillars. This research can provide a theoretical reference for the study of dynamic wetting behavior of hydrophobic material.