Surface reduction of freely floating smectic bubbles

ABSTRACT

Elongated freely floating smectic bubbles are observed during their relaxation to equilibrium sphere shape. Unlike soap bubbles that perform weakly damped oscillations into equilibrium, this relaxation is overdamped in smectics by internal structure reorganisation processes. The bubble area reduction of centimetre-sized freely floating bubbles with few nanometres film thickness is recorded with high-speed optical imaging in microgravity and analysed quantitatively. We find a nearly linear reduction of the film area with time, driven by capillary forces and inhibited by smectic layer reorganisations. Characteristic times are in the milliseconds range, with little correlation to the film thickness and bubble size. Instead, the homogeneity of the films and the number and sizes of islands of excess layers that spontaneously form on the films appear to have crucial influence on the dynamics. The efficiency of this process sets the time scale of the film area shrinkage. We discuss the limitations of a minimalistic model that captures smectic layer reorganisation processes.

Graphical Abstract

KEYWORDS:

• Freely suspended films
• smectic liquid crystals
• hydrodynamics
• bubble dynamics

Acknowledgements

Thomas John and Ulrike Kornek are acknowledged for developing the prototype of the image analysis software.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft: [STA 425/28-2] and Deutsches Zentrum für Luft- und Raumfahrt: [Grant Numbers 50WM1430 and 50WM1744].