Bouncing dynamics of a nanodroplet impacting a superhydrophobic surface under perpendicular electric fields

Abstract

The bouncing dynamics of a nanodroplet impacting a superhydrophobic surface under a perpendicular electric field is studied through molecular dynamics (MD) simulations. Using the electric field strength as a parameter, two bouncing regimes are identified: an inertial force rebounding (IFR) regime ( E < 0.08 V Å −1 ) and an electric field force rebounding (EFFR) regime ( E > 0.08 V Å −1 ). In the IFR regime, the restitution coefficient, ε b , is the same as but the contact time, τ c , is shorter than that without an electric field. In the EFFR regime, ε b is proportional to the electric field strength, whereas τ c decreases with an increase in the electric field strength. On the boundary separating the two regimes (around 0.08 V Å −1 ), both ε b and τ c increase sharply due to the droplet deformation. The droplet bounces off the surface in the shape of a sphere in the IFR regime and as a long strip in the EFFR regime. A new criterion for the bouncing of nanodroplets subjected to a perpendicular electric field is proposed based on the restitution coefficient, Weber number, characteristic length, and factor Φ. The criterion demonstrates that imposing an electric field can help the bouncing of nanodroplets. • The bouncing of nanodroplets subjected to perpendicular electric fields is studied. • Two bouncing regimes are discovered based on the field strength. • Restitution coefficient and contact time are measured in the two regimes. • A criterion is developed to predict bouncing in the presence of the electric field.