Viscous Bursting of Suspended Films

Abstract

Soap films break up by an inertial process. We present here the first observations on freely suspended films of long-chain polymers, where viscous effects are dominant and no surfactant is present. A hole is nucleated at time 0 and grows up to a radius $R(t)$ at time $t$. A surprising feature is that the liquid from the hole is not collected into a rim (as it is in soap films): The liquid spreads out without any significant change of the film thickness. The radius $R(t)$ grows exponentially with time, $R\ensuremath{\propto}\mathrm{exp}(\frac{t}{\ensuremath{\tau}})$ [while in soap films $R(t)$ is linear]. The rise time $\ensuremath{\tau}\ensuremath{\propto}\frac{\ensuremath{\eta}e}{2\ensuremath{\gamma}}$ where $\ensuremath{\eta}$ is viscosity, $e$ is thickness (in the micron range), and $\ensuremath{\gamma}$ is surface tension. A simple model is developed to explain this growth law.