A Gallery of Meniscus Patterns of Free-Standing Smectic Films

Abstract

Spontaneously formed stripe patterns covering the menisci of free-standing smectic films have been described already about 40 years ago, but there was no comprehensive optical investigation of their textures so far. Recently, atomic force microscopy, interferometry and polarised light microscopy studies have cast doubts at their classical interpretation as surface-splay induced domains. That interpretation is not able to explain several basic features of the striped domains. Here, we review some characteristic properties of the stripe domains and related patterns, i.e. textures that decorate regions with film thickness gradients. We discuss changes during phase transitions of the smectic films to collect information on the complex internal structure of the observed patterns.

Deep Holes in Free-Standing Smectic C Films

“…3 and 4). The characteristic texture of radial stripes strongly resembles the static structures observed in film menisci or regions of inhomogeneous thickness [2,3,[9][10][11][12][13]. It can be shown experimentally that both textures are related to the same inner director structure: When the hole boundary reaches the outer film meniscus, the structures in the wedged zone merge with the characteristic meniscus patterns.…”

“…The meniscus of smectic C or C * films is often decorated with more or less complex spontaneous patterns [2,3,[9][10][11][12][13], the origin and internal structure of some of these patterns still being under debate [2,3,13]. Striped patterns can form in regions with sufficiently large film thickness and sufficiently strong film thickness gradient (dislocation density).…”

Labyrinthine instability in freely suspended films of a polarization-modulated smectic phase

“…These patterns are attributed to flexoelectric instabilities in phases with a high spontaneous polarization. Striped patterns were also observed in lyotropic systems [5,15] and menisci of the freely suspended films [16][17][18][19][20].…”

Freely Floating Smectic Films

“…An important advantage of smectic bubbles over soap bubbles, in experiments, is their stability. [12] Of particular interest is the investigation of the dynamics of inclusions in such films, [13] which allows the elucidation of details of the dynamics of 2D fluids and membranes. Smectic freely suspended films (FSFs) can be prepared with well-defined thicknesses that are uniform on the scale of single molecular layers.…”

“…For example, the use of smectic FSFs facilitates the study of the coupling between director and flow fields in quasi-2D fluids [10,11] and of the formation of spontaneous patterns. [12] Of particular interest is the investigation of the dynamics of inclusions in such films, [13] which allows the elucidation of details of the dynamics of 2D fluids and membranes. [14,15] Here, we describe a new type of experiment, related to the shape dynamics of smectic films.…”