Pulsed electric fields trigger the single droplet jumping departure from hybrid wetting substrates: A molecular dynamics study

Larger droplets have greater thermal resistance and limit the condensation performance if pinned on substrates during dropwise condensation. Millimeter-sized droplets are removable by pulsed electric fields (E-Fields). As the droplet size decreases, surface energy and interfacial adhesion dominate droplet detachment, and whether smaller pinned droplets can also be controllably detached remains unknown. In this work, molecular dynamics simulations are performed to investigate the jumping departure of pinned droplets induced by pulsed E-Fields. Without the E-Field, substrates with deeper nanostructures or lower wettability promote the wetting transition of condensed droplets from the Wenzel state to the Cassie state and facilitate spontaneous departure, but these substrates also suppress droplet formation. When an E-Field is applied, water molecules align with the E-Field direction, the droplet is elongated and obtains an upward kinetic energy. When the E-Field is switched off, the elongated droplet collapses, and the upward inertia overcomes energy dissipation and surface adhesion, resulting in the droplet jumping off the substrate. The droplet jumping is governed by deformation dynamics and is characterized by the electric capillary number (Ca E ). With sufficient E-Field duration, the droplet with a larger Ca E (corresponding to a larger droplet size and a stronger E-Field) jumps more easily. Therefore, a pulsed E-Field can selectively trigger the departure of droplets larger than a critical size. These results demonstrate that pulsed E-Fields provide a potential way to overcome nanodroplet pinning and control droplet departure on highly wetting substrates.