Modelling rare rupture of nanoscale liquid thin films #

Jingbang Liu, James Sprittles, Duncan Lockerby, Tobias Grafke

14:10 Tuesday in 4Q08.

Part of the Microfluidics and flow in porous media session.

Abstract #

Controlling the spontaneous rupture of nanoscale liquid thin films plays a crucial role in various applications such as thin-film solar cell manufacturing, insulation layer coating, and in lab-on-a-chip devices. Over the past few decades, theoretical work based on the long-wave theory of thin liquid films has successfully identified a critical film height, below which the surface nanowaves become linearly unstable, leading to spontaneous rupture. This dewetting in the so-called ‘spinodal regime’ has been repeatedly confirmed in experiments using atomic force microscopy on polymer films. However, rupture events are also observed for films thicker than the critical film height, which are considered linearly stable, in a different manner. It is believed that the random (Brownian) movement of particles is the cause of dewetting in this ‘thermal regime’ but the theoretical framework predicting the rupture is missing.

In this talk, we present a theory to account for the rupture of a two dimensional linearly stable thin film by utilizing fluctuating hydrodynamics and rare events theory. By modelling the film dynamics with the stochastic thin-film equation and solving it numerically, we observe rupture in the linearly stable thermal regime and record the average waiting time, which agrees well with the theoretical estimation obtained from Kramer’s Law. Molecular dynamics (MD) simulations are performed and the results are in accordance with the numerics and the theory. We also discuss possible ways to extend the theory and the MD into three dimensions.