Undulation instabilities in the meniscus of smectic membranes

TL;DR

This paper investigates undulation patterns in the meniscus of ferroelectric smectic-C* films, revealing temperature-dependent striped structures and proposing a model to explain these instabilities.

Contribution

It provides the first detailed characterization of undulation instabilities in smectic membranes and introduces a simple model to explain their formation and behavior.

Findings

Undulated structures are observed in ferroelectric smectic-C* films.

The undulations depend on meniscus thickness and temperature.

The instability is absent in smectic-A phase.

Abstract

Using optical microscopy, phase shifting interferometry and atomic force microscopy, we demonstrate the existence of undulated structures in the meniscus of ferroelectric smectic-C* films. The meniscus is characterized by a periodic undulation of the smectic-air interface, which manifests itself in a striped pattern. The instability disappears in the untilted smectic-A phase. The modulation amplitude and wavelength both depend on meniscus thickness. We study the temperature evolution of the structure and propose a simple model that accounts for the observed undulations.