scholarly journals Optical manipulation of the nematic director field around microspheres covered with an azo-dendrimer monolayer

2014 ◽  
Vol 22 (17) ◽  
pp. 20087 ◽  
Author(s):  
Pemika Hirankittiwong ◽  
Nattaporn Chattham ◽  
Jumras Limtrakul ◽  
Osamu Haba ◽  
Koichiro Yonetake ◽  
...  
Keyword(s):  
Optical Manipulation ◽  
Director Field ◽  
Nematic Director

One dimensional model of dye-doped nematic layer for holography

2006 ◽  
Vol 14 (2) ◽  
Author(s):  
G. Derfel ◽  
M. Buczkowska ◽  
J. Parka
Keyword(s):  
Ion Concentration ◽  
Dimensional Model ◽  
Director Field ◽  
One Dimensional ◽  
Ion Concentrations ◽  
Electrically Conducting ◽  
Nematic Director ◽  
Extraordinary Refractive Index ◽  
Director Orientation ◽  
Coated Electrodes

AbstractThe layer of electrically conducting nematic liquid crystal doped with photosensitive dye and confined between polyimide coated electrodes can serve as a diffraction grating. In this paper, the deformations of the nematic director field induced in such a system by external voltage were studied numerically by means of one-dimensional model. The dissociation and recombination of ions were taken into account according to weak electrolyte model. The director orientation in the deformed layers and the distributions of the electric field and of the ion concentrations were calculated for blocking and for conducting electrodes. The effective extraordinary refractive index was also determined as a function of average ion concentration.

scholarly journals Nematic Liquid Crystal Locking Menisci

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Milan Svetec ◽  
Mitja Slavinec
Keyword(s):  
Differential Equation ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Coordinate System ◽  
Point Defects ◽  
Cylindrical Tube ◽  
Curvilinear Coordinate System ◽  
Director Field ◽  
Nematic Director ◽  
Curvilinear Coordinate

We study meniscus driven locking of point defects of nematic liquid crystals confined within a cylindrical tube with free ends. Curvilinear coordinate system is introduced in order to focus on the phenomena of both (convex and concave) types of menisci. Frank's description in terms of the nematic director field is used. The resulting Euler-Lagrange differential equation is solved numerically. We determine conditions for the defects to be trapped by the meniscus.

scholarly journals Self-organized dynamics and the transition to turbulence of confined active nematics

2019 ◽  
Vol 116 (11) ◽  
pp. 4788-4797 ◽  
Author(s):  
Achini Opathalage ◽  
Michael M. Norton ◽  
Michael P. N. Juniper ◽  
Blake Langeslay ◽  
S. Ali Aghvami ◽  
...  
Keyword(s):  
Chaotic Dynamics ◽  
Topological Defects ◽  
Transition To Turbulence ◽  
Director Field ◽  
Self Organized ◽  
Nematic Director ◽  
Double Spiral ◽  
Circular Flows ◽  
Periodic Dynamics

We study how confinement transforms the chaotic dynamics of bulk microtubule-based active nematics into regular spatiotemporal patterns. For weak confinements in disks, multiple continuously nucleating and annihilating topological defects self-organize into persistent circular flows of either handedness. Increasing confinement strength leads to the emergence of distinct dynamics, in which the slow periodic nucleation of topological defects at the boundary is superimposed onto a fast procession of a pair of defects. A defect pair migrates toward the confinement core over multiple rotation cycles, while the associated nematic director field evolves from a distinct double spiral toward a nearly circularly symmetric configuration. The collapse of the defect orbits is punctuated by another boundary-localized nucleation event, that sets up long-term doubly periodic dynamics. Comparing experimental data to a theoretical model of an active nematic reveals that theory captures the fast procession of a pair of +1/2 defects, but not the slow spiral transformation nor the periodic nucleation of defect pairs. Theory also fails to predict the emergence of circular flows in the weak confinement regime. The developed confinement methods are generalized to more complex geometries, providing a robust microfluidic platform for rationally engineering 2D autonomous flows.

Visualization of Nematic Director Field With the RGB Color System

2012 ◽  
Vol 553 (1) ◽  
pp. 50-57 ◽  
Author(s):  
Maja Milfelner ◽  
Milan Ambrožič ◽  
Marjan Krašna ◽  
Matej Cvetko ◽  
Aleksander Zidanšek ◽  
...  
Keyword(s):  
Director Field ◽  
Nematic Director ◽  
Color System

Highly Ordered Helical Nanofilament Assembly Aligned by a Nematic Director Field

2013 ◽  
Vol 23 (21) ◽  
pp. 2701-2707 ◽  
Author(s):  
Fumito Araoka ◽  
Go Sugiyama ◽  
Ken Ishikawa ◽  
Hideo Takezoe
Keyword(s):  
Director Field ◽  
Nematic Director

scholarly journals Optically driven translational and rotational motions of microrod particles in a nematic liquid crystal

2015 ◽  
Vol 112 (6) ◽  
pp. 1716-1720 ◽  
Author(s):  
Alexey Eremin ◽  
Pemika Hirankittiwong ◽  
Nattaporn Chattham ◽  
Hajnalka Nádasi ◽  
Ralf Stannarius ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Uv Light ◽  
Director Field ◽  
Uv Light Irradiation ◽  
Nematic Director ◽  
Different Types ◽  
Liquid Crystal Matrix ◽  
Coated Surface ◽  
Rotational Motions ◽  
Director Reorientation

A small amount of azo-dendrimer molecules dissolved in a liquid crystal enables translational and rotational motions of microrods in a liquid crystal matrix under unpolarized UV light irradiation. This motion is initiated by a light-induced trans-to-cis conformational change of the dendrimer adsorbed at the rod surface and the associated director reorientation. The bending direction of the cis conformers is not random but is selectively chosen due to the curved local director field in the vicinity of the dendrimer-coated surface. Different types of director distortions occur around the rods, depending on their orientations with respect to the nematic director field. This leads to different types of motions driven by the torques exerted on the particles by the director reorientations.

scholarly journals A generalized density-modulated twist-splay-bend phase of banana-shaped particles

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Massimiliano Chiappini ◽  
Marjolein Dijkstra
Keyword(s):  
Nematic Phase ◽  
Director Field ◽  
Polar Order ◽  
Modulated Phases ◽  
Smectic Phases ◽  
Nematic Director ◽  
Curved Rods ◽  
Nematic Phases

AbstractIn 1976, Meyer predicted that bend distortions of the nematic director field are complemented by deformations of either twist or splay, yielding twist-bend and splay-bend nematic phases, respectively. Four decades later, the existence of the splay-bend nematic phase remains dubious, and the origin of these spontaneous distortions uncertain. Here, we conjecture that bend deformations of the nematic director can be complemented by simultaneous distortions of both twist and splay, yielding a twist-splay-bend nematic phase. Using theory and simulations, we show that the coupling between polar order and bend deformations drives the formation of modulated phases in systems of curved rods. We find that twist-bend phases transition to splay-bend phases via intermediate twist-splay-bend phases, and that splay distortions are always accompanied by periodic density modulations due to the coupling of the particle curvature with the non-uniform curvature of the splayed director field, implying that the twist-splay-bend and splay-bend phases of banana-shaped particles are actually smectic phases.

scholarly journals Nematic director fields and topographies of solid shells of revolution

2018 ◽  
Vol 474 (2210) ◽  
pp. 20170566 ◽  
Author(s):  
Mark Warner ◽  
Cyrus Mostajeran
Keyword(s):  
Inverse Problem ◽  
Integral Equation ◽  
Gaussian Curvature ◽  
Energy Cost ◽  
Shape Change ◽  
Mechanical Deformation ◽  
Surfaces Of Revolution ◽  
Shells Of Revolution ◽  
Director Field ◽  
Nematic Director

We solve the forward and inverse problems associated with the transformation of flat sheets with circularly symmetric director fields to surfaces of revolution with non-trivial topography, including Gaussian curvature, without a stretch elastic cost. We deal with systems slender enough to have a small bend energy cost. Shape change is induced by light or heat causing contraction along a non-uniform director field in the plane of an initially flat nematic sheet. The forward problem is, given a director distribution, what shape is induced? Along the way, we determine the Gaussian curvature and the evolution with induced mechanical deformation of the director field and of material curves in the surface (proto-radii) that will become radii in the final surface. The inverse problem is, given a target shape, what director field does one need to specify? Analytic examples of director fields are fully calculated that will, for specific deformations, yield catenoids and paraboloids of revolution. The general prescription is given in terms of an integral equation and yields a method that is generally applicable to surfaces of revolution.

Sign in / Sign up

Export Citation Format

Share Document