Symmetrization of Thin Free-Standing Liquid Films via Capillary-Driven Flow

TL;DR

This paper investigates how thin free-standing liquid films relax and symmetrize their perturbations through capillary-driven flow, combining experiments and a hydrodynamic model to understand the dynamics and influencing factors.

Contribution

It introduces a comprehensive hydrodynamic model for the symmetrization process in thin films and experimentally validates the dependence of symmetrization time on physical parameters.

Findings

Symmetrization time depends on membrane thickness, surface tension, and viscosity.

The model accurately predicts the relaxation dynamics observed in experiments.

Capillary forces drive the film towards symmetric equilibrium shape.

Abstract

We present experiments to study the relaxation of a nano-scale cylindrical perturbation at one of the two interfaces of a thin viscous free-standing polymeric film. Driven by capillarity, the film flows and evolves towards equilibrium by first symmetrizing the perturbation between the two interfaces, and eventually broadening the perturbation. A full-Stokes hydrodynamic model is presented which accounts for both the vertical and lateral flows, and which highlights the symmetry in the system. The symmetrization time is found to depend on the membrane thickness, surface tension, and viscosity.