Nanobubble-induced flow of immersed glassy polymer films

TL;DR

This study investigates how nanobubbles induce flow and deformation in immersed glassy polymer films, combining analytical and numerical methods to predict film rupture and dewetting behavior.

Contribution

It introduces a combined analytical and numerical framework to model nanobubble-induced deformation in glassy polymer films, predicting rupture times and dependencies on physical parameters.

Findings

Surface perturbation follows a viscocapillary power-law in time.

Central film height decays logarithmically before rupture.

Analytical predictions match numerical simulations for rupture conditions.

Abstract

We study the free-surface deformation dynamics of an immersed glassy thin polymer film supported on a substrate, induced by an air nanobubble at the free surface.We combine analytical and numerical treatments of the glassy thin film equation, resulting from the lubrication approximation applied to the surface mobile layer of the glassy film, under the driving of an axisymmetric step function in the pressure term accounting for the nanobubble's Laplace pressure. Using the method of Green's functions, we derive a general solution for the film profile. We show that the lateral extent of the surface perturbation follows an asymptotic viscocapillary power-law behaviour in time, and that the film's central height decays logarithmically in time in this regime. This process eventually leads to film rupture and dewetting at finite time, for which we provide an analytical prediction exhibiting explicitly the dependencies in surface mobility, film thickness and bubble size, among others. Finally, using finite-element numerical integration, we discuss how non-linear effects induced by the curvature and film profile can affect the evolution.