The Molecular Dynamics Simulation of Droplet Spreading

Pieter van Remoortere
Department of Chemical Engineering and Materials Science
University of Minnesota

There is an important unresolved issue about what boundary condition to use around the three-phase contact region at the macroscopic level to describe the spontaneous spreading of a liquid at the solid-vapor interface. In the past decade, continuum descriptions of spreading on both the macroscopic and the supramolecular level have emerged, featuring the role of long-range forces in the thin films that precede the macroscopic contact "line." Ellipsometric studies of the very tip of the spreading liquid reveal, however, the importance of short-range forces. The primary film develops on the initially dry solid as a sequential stacking of distinct molecular layers.

This speaker has made molecular dynamics simulations which provide the time-dependent molecular configurations around the three-pase contact region as it advances. The results shed a light on the molecular mechanism of contact line motion. His results were for a sessile droplet and a drop confined between parallel walls. The liquid-vapor interfaces can be visualized by plotting the time-dependent isosurfaces of density. This makes it possible to measure dynamic and equilibrium contact angles as well as the spreading of the liquid layers adjacent to the wall.