Molecular Dynamics Simulation of Electrically-Assisted Spreading of an Ionically Conducting Water Droplet

Molecular dynamics simulations are performed to study the spreading behavior of a nanosized water droplet that contains freely moving ions subject to an imposed electric field parallel to a solid surface. Results show that positive and negative ions respond to the applied electric field in a different manner, whereas water molecules are polarized by realigning themselves in the electric field. These localized behaviors of the ions and polarized molecules define the droplet deformation and spreading on a solid substrate. Both the ion concentration and the strength of the applied field play an important role in re-alignment of the polarized water molecules and in the movement of ions. The existence of the freely moving ions causes the droplet to spread differently from the pure liquid. It is observed that an ionically conducting water droplet undergoes the asymmetric-to-symmetric spreading transition at about the field strength of 0.05V/Å, which is considerably smaller than the same sized water droplet without ions. Also, the ionically conducting droplet completely wets the solid surface in the presence of a strong electric field.