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 (STF) and solving it numerically, we observe rupture in the linearly stable thermal regime and record the average waiting time for rupture. We show that the STF can be rearranged into the form of a gradient flow, which allows us to apply Kramer’s law from the rare events theory to obtain a theoretical prediction of the average waiting time. Molecular dynamics (MD) simulations are also performed and we find good agreements between the numerics, the prediction, and the MD. As the average waiting time increases exponentially with the thickness of the film, adaptive multilevel splitting method is used in the simulations.
Jingbang is a postodoctoral researcher in the Mathematics Department at the UiO. After a Master's Degree at the University of Oxford, Jingbang recently earned his PhD at the University of Warwick.