Electrically driven hybrid instabilities in smectic C liquid crystal films

Abstract

Novel static hybrid instabilities in smectic C liquid (SmC) crystal films are described. The Frederiks transition, well known for nematic liquid crystals, also takes place in smectic C layers, but here it is spatially periodic and coupled to undulations of the smectic layer. The Helfrich-Hurault undulational instability, typical for smectic A liquid crystals, occurs in SmC liquid crystals too, but the wave vector of the undulation of the layers is oblique to the applied external field. In addition, this modified Helfrich-Hurault instability not only involves layer undulations, but also contains deformations of the director field, which are typical for the Frederiks transition. The coupled deformations depend on all three coordinate axis, thus characterizing 3-dimensional patterns. There are parameter ranges, where both types of static instabilities, which differ by the spatial wavenumber, compete with each other near codimension-2 bifurcations.

On the application of finite differences, method of lines and pseudo‐spectral methods to smectic‐C liquid crystals

“…We note from Figure 8 that the steady state solution is reached without oscillations at the boundaries. These results compare well to those obtained by Ried et al (2000) in which electrically driven hybrid instabilities in SmC liquid crystal films are described.…”

Layer distortions induced by a magnetic field in planar samples of smectic C liquid crystals

“…The techniques used here may be of relevance to work on electrically driven instabilities in thin films of SmC or SmC* liquid crystals and in this context the reader should consult the work of Ried et al [33,34]. There is also a comprehensive study of electrically driven effects and electroconvection by Pleiner et al [35].…”

“…It is easily verified that sin 2 yzcos 2 y~1 to second order in a when a|0. Inserting equations (34) and (35) into the expression (30) and using (31) and (32) allows c to be evaluated to second order in the first …”

Fabrication of functionalized Optical microstructures

“…The so called soft lithography is able to transfer micrometric patterns to a substrate by using an elastomeric stamp or mold, typically made of polydimethylsiloxane (PDMS) [2,3]. More recently, other approaches have been developed for generating self-patterned structures by using destabilizing forces produced by electric fields, namely electrohydrodynamic (EHD) lithography [4], or by temperature gradients [5], or also by mechanical stress [6]. EHD lithography is very effective for fabricating polymeric structures with high accuracy at micro-and nano-scale.…”