Wrinkling of freely floating smectic films

TL;DR

This paper investigates the spontaneous wrinkling phenomena in thin, freely floating smectic liquid-crystalline films, revealing their transient undulation patterns and developing a model for pattern formation and wavelength selection.

Contribution

It introduces the first detailed study of dynamic wrinkling in smectic films, including experimental observations and a theoretical model for pattern formation.

Findings

Wrinkles have submillimeter wavelengths.

Wrinkling occurs as a transient response to lateral compression.

The pattern formation is dynamic and can be modeled theoretically.

Abstract

We demonstrate spontaneous wrinkling as a transient dynamical pattern in thin freely floating smectic liquid-crystalline films. The peculiarity of such films is that, while flowing liquid-like in the film plane, they cannot quickly expand in the direction perpendicular to that plane. At short time scales they therefore behave in two dimensions like quasi-incompressible membranes. Such films can develop a transient undulation instability or form bulges in response to lateral compression. Optical experiments with freely floating bubbles on parabolic flights and in ground lab experiments are reported. The characteristic wavelengths of the wrinkles are in the submillimeter range. We demonstrate the dynamic nature of the pattern formation mechanism and develop a basic model for the wavelength selection and wrinkle orientation.