Nematic liquid crystals on sinusoidal channels: the zigzag instability
| Autor: | José M. Romero-Enrique, Margarida M. Telo da Gama, Nuno Silvestre |
|---|---|
| Přispěvatelé: | Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear |
| Rok vydání: | 2016 |
| Předmět: |
Materials science
Sinusoidal channels FOS: Physical sciences 02 engineering and technology Condensed Matter - Soft Condensed Matter 01 natural sciences Instability Topological defect Topological defects Liquid crystal 0103 physical sciences Perpendicular General Materials Science 010306 general physics Anisotropy Condensed matter physics Elastic instabilities Texture (cosmology) Disclination 021001 nanoscience & nanotechnology Condensed Matter Physics Condensed Matter::Soft Condensed Matter Zigzag Nematic liquid crystals Soft Condensed Matter (cond-mat.soft) 0210 nano-technology |
| Zdroj: | idUS. Depósito de Investigación de la Universidad de Sevilla instname |
| ISSN: | 1361-648X |
| Popis: | Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau–de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear. Portugal, Fundación para la Ciencia y la Tecnología UID / FIS / 00618/2013 Portugal, Fundación para la Ciencia y la Tecnología EXCEL / FIS-NAN / 0083/2012 España, Ministerio de Economía y Competitividad FIS2012-32455 Junta de Andalucía P09-FQM-4938 |
| Databáze: | OpenAIRE |
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