Comment on "Layering transition in confined molecular thin films: Nucleation and growth"

TL;DR

This paper presents a corrected theoretical model for the flow of confined molecular thin films, showing that their viscosity is vastly higher than in bulk, and provides a method to extract this viscosity from experimental data.

Contribution

It offers a revised solution to the flow of confined fluids, correcting previous models and enabling estimation of extremely high viscosities from experimental observations.

Findings

Confined fluid viscosity is about 7 orders of magnitude higher than bulk viscosity.

The model accurately fits experimental data on layer-by-layer squeeze-out.

Both the fluid's kinematic viscosity and surface drag coefficient can be derived from area change over time.

Abstract

When fluid is confined between two molecularly smooth surfaces to a few molecular diameters, it shows a large enhancement of its viscosity. From experiments it seems clear that the fluid is squeezed out layer by layer. A simple solution of the Stokes equation for quasi-two-dimensional confined flow, with the assmption of layer-by-layer flow is found. The results presented here correct those in Phys. Rev. B, 50, 5590 (1994), and show that both the kinematic viscosity of the confined fluid and the coefficient of surface drag can be obtained from the time dependence of the area squeezed out. Fitting our solution to the available experimental data gives the value of viscosity which is ~7 orders of magnitude higher than that in the bulk.