Dynamics of nanoscale droplets on moving surfaces

Langmuir. 2013 Jun 11;29(23):6936-43. doi: 10.1021/la401131x. Epub 2013 May 28.

Abstract

We use molecular dynamics (MD) simulations to investigate the dynamic wetting of nanoscale water droplets on moving surfaces. The density and hydrogen bonding profiles along the direction normal to the surface are reported, and the width of the water depletion layer is evaluated first for droplets on three different static surfaces: silicon, graphite, and a fictitious superhydrophobic surface. The advancing and receding contact angles, and contact angle hysteresis, are then measured as a function of capillary number on smooth moving silicon and graphite surfaces. Our results for the silicon surface show that molecular displacements at the contact line are influenced greatly by interactions with the solid surface and partly by viscous dissipation effects induced through the movement of the surface. For the graphite surface, however, both the advancing and receding contact angles values are close to the static contact angle value and are independent of the capillary number; i.e., viscous dissipation effects are negligible. This finding is in contrast with the wetting dynamics of macroscale water droplets, which show significant dependence on the capillary number.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Graphite / chemistry
  • Hydrophobic and Hydrophilic Interactions
  • Molecular Dynamics Simulation*
  • Nanostructures / chemistry*
  • Particle Size
  • Silicon / chemistry
  • Surface Properties

Substances

  • Graphite
  • Silicon