When surfactant molecules induce "cracks" in soap films

Pauline Petit, Marie Le Merrer and Anne-Laure Biance (Liquides aux Interfaces team) have just published in the journal JFM rapids an article entitled « Holes and cracks in rigid soap films ». A focus on this work was written by José Bico.

In this article, the authors have revisited the very classical problem of the bursting dynamics of a soap film. A soap film is drawn on a metallic frame, bursting is initiated with a heated needle and the hole opening dynamics is recorded by high speed imaging. A deviation to the classical law for soap film bursting, known for more than 60 years, is observed when the physico-chemistry of surfactants is varied. The deviation is predicted theoretically by taking into account the elasticity of the interfaces. Besides, "crack" patterns, similar to fractures in a solid membrane, are observed during the liquid film opening. Although very simple, this experiment brings a new method to determine the elasticity of complex liquid gas interfaces, at large deformations and large deformation rates. In addition, the influence of surfactants on the bursting film shape (for instance, the ejection of secondary droplets can be inhibited) brings new insights into the effect of physico-chemistry on liquid foam stability.


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