Transforming Droplets into Liquid Films in Nanochannels under Rotating Electric Fields Studied by Molecular Dynamics

It is first proposed to use a rotating electric field to stretch a droplet into a liquid film pinned to the insulated channel inner wall as a new type of active liquid valve. The molecular dynamics (MD) simulations are performed to prove that droplets in nanochannels can be stretched and expanded into closed liquid films under the action of rotating electric fields. The variations of the liquid cross-sectional area and droplet surface energy with time are calculated. The liquid film formation occurs mainly through two modes: gradual expansion and liquid column rotation. In most cases, increasing the electric field strength and angular frequency favors liquid film closing. At higher angular frequencies, decreasing the angular interval favors liquid film closing. The opposite is true at lower angular frequencies. The process of closing the hole-containing liquid film, which has formed a dynamic equilibrium, is a surface energy increase process, which requires greater electric field strength and angular frequency.