A Universal Mechanism of Nanoscale Transport of Interfacial Liquids Near a Solid Surface

Properties and characteristics of interfacial fluids confined by a solid surface play critical roles in a variety of physical and chemical processes. One of the most intriguing features of a solid-liquid interface is that the reconfiguration of near-surface liquid molecules gives rise to an oscillatory profile of liquid properties. Molecular dynamics (MD) simulations have disclosed an in-plane ordering and a shifted glassy transition of liquid nanofilm confined by a solid surface. Here we report our analysis of the transport of simple liquids adjacent to a solid wall using MD simulations. The oscillatory distribution of interfacial liquids is shown to be governed by self-diffusion, surface-induced convection and shifted glass transition in a combined manner. In particular, we put forward an universal governing equation for the oscillatory density profiles of interfacial liquids, which can be derived either from the free energy analysis of a discrete molecular system, or from the Reynolds transport theorem under the continuum framework. The analytical solution to the governing equations is able to capture all prominent features of the patterned oscillations of interfacial liquids and bridges the gap between molecular dynamics of liquids and their macroscopic continuum behaviors.