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

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.