Shape instabilities of islands in smectic films under lateral compression

Smectic liquid crystals are fluids, and in most rheological situations they behave as such. Nevertheless, when thin freely floating films of smectic A or smectic C materials are compressed quickly in-plane, they resist such stress by buckling similar to solid membranes under lateral stress. We report experimental observations of wrinkling and bulging of finite domains within the films, so-called islands, and give a qualitative explanation of different observed patterns. Depending on the external stress and their dimensions, the islands can expel a specifically shaped bulge in their center, form radial wrinkles or develop target-like wrinkle structures. When the external stress is relaxed, these patterns disappear reversibly.

Automated summary

This study reports the wrinkling and bulging phenomenon of thin freely floating films of smectic liquid crystals under rapid compression in-plane. Different patterns, including specifically shaped bulges, radial wrinkles, and target-like wrinkle structures, were observed depending on the external stress and dimensions of the films. These patterns disappear reversibly when the external stress is relaxed.