Deformation of water nano-droplets on graphene under the influence of constant and alternative electric fields†
The dynamics of a water nano-droplet on a flexible graphene sheet, in the presence of constant and alternative electric fields with various amplitudes and frequencies, was considered using a molecular dynamics method. It was found that because the water molecules respond to electric field, the nano-droplet elongates in the field direction for a field amplitude larger than 0.08 V Å−1, which is stronger than the predicted value from the Young–Laplace equation. This difference can be described by considering the van der Waals attractions between the droplet molecules and the substrate, which can be calculated by modifying the Young–Laplace equation. Furthermore, under the influence of an alternating field over the GHz frequency range, it was shown that the droplet shape will not change above a threshold frequency, which depends on the relaxation time of the water dipole.