Contact dynamics of nanodroplets in carbon nanotubes: effects of electric field, tube radius, and salt ions

We report contact dynamics of nanodroplets in carbon nanotubes using molecular dynamics simulations. The effects of electric field, nanotube radius, and salt ions included in the nanodroplets are explored in more detail. For the cases without applied electric field, the droplet fills the cross section of carbon nanotubes with small radius completely. When the tube radius becomes larger, the droplet retracts towards the surface of the nanotube to minimize the surface tension of the droplet and shows wider extension along the axial direction. When an electric field perpendicular to the axial direction of the carbon nanotubes is applied, the position and shape of the droplets are changed which is also related to the tube radius and whether the droplet contains salt ions. Unlike a planar surface, the nanotube limits spreading of the droplets along the radial direction. The variation of the center of mass of the droplets indicates a significant confinement to the position of the droplets in the electric field. For the salty water droplets, a strong electric field induces ejection of small water clusters from the droplet in a nanotube with large radius. As a consequence, the droplet and water clusters are separated and moved to two opposite sides of the nanotube by the electric field.