Comparison of the rupture dynamics of smectic bubbles and soap bubbles

Abstract

The rupture of soap films has attracted scientific interest for over a century, but only few qualitative and quantitative experiments of bursting soap bubbles have been reported so far. Thermotropic smectic films behave, in many respects, in a very similar manner to lyotropic (soap) films. We compare the rupture dynamics of smectic A bubbles on a qualitative level with that of soap bubbles. Our attention is focused on the velocity of the progressing rim around the growing hole, the stability of this rim, changes in the thickness of the film during rupture and the propagation of mechanical waves ahead of the rim in the remaining film. Differences in the internal structures of soap films and smectic films manifest themselves in different rupture characteristics. The experiments help us to understand the dynamical properties of quasi-two-dimensional liquid films far from their mechanical equilibrium.

Keywords:

• rupture dynamics
• thin films
• smectic liquid crystal
• soap

Acknowledgements

The authors would like to thank Ulrike Kornek for her collaboration in some of the experiments and Christian Bohley for assistance in FEM calculations of light propagation through undulated films. We acknowledge financial support by the Deutsche Forschungsgemeinschaft under Grant STA 452/20.