scholarly journals Manipulation of colloids by optical and electrical control of disclination lines in liquid crystals

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
D. Kasyanyuk ◽  
P. Pagliusi ◽  
A. Mazzulla ◽  
S. Tomylko ◽  
V. Reshetnyak ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Boundary Conditions ◽  
Applied Voltage ◽  
Topological Defects ◽  
Different Boundary Conditions ◽  
Electrical Control ◽  
Micro Particles ◽  
Continuous Displacement ◽  
Anisotropic Fluids

AbstractWe report two viable strategies to assemble and manipulate arrays of nano- and micro-particles by means of topological defects (TDs) in anisotropic fluids. Exploiting different boundary conditions, single TD, 1D arrays of TDs are tailored in liquid crystal twist cells. In a first approach, light-guided control of particles captured in disclination lines is demonstrated involving the use of a photosensitive chiral dopant within a nematic host. In the second one, an applied voltage enables a continuous displacement and deformation of the particles arrays. The reported results open up new possibilities for managing nano- and micro-metric objects over large distances.

scholarly journals Annihilation dynamics of topological defects induced by microparticles in nematic liquid crystals

Soft Matter ◽  
2019 ◽  
Vol 15 (43) ◽  
pp. 8749-8757 ◽  
Author(s):  
Yuan Shen ◽  
Ingo Dierking
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Applied Electric Field ◽  
Topological Defects ◽  
Field Conditions ◽  
Viscous Drag ◽  
Complex Interplay ◽  
Drag Forces ◽  
Micro Particles

The annihilation dynamics of liquid crystal topological defects with micro-particles is governed by a complex interplay between elastic attraction, backflow, viscous drag forces, confinement and applied electric field conditions.

Liquid crystal alignment in cylindrical microcapillaries

2012 ◽  
Vol 20 (1) ◽  
Author(s):  
M. Chychłowski ◽  
O. Yaroshchuk ◽  
R. Kravchuk ◽  
T. Woliński
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Photonic Crystal ◽  
Boundary Conditions ◽  
Photonic Crystal Fibers ◽  
Optical Devices ◽  
Liquid Crystal Alignment ◽  
Disclination Line ◽  
Crystal Alignment ◽  
Crystal Fibers

AbstractA variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

Nano-Sized Fine Droplets of Liquid Crystals for Optical Application

1996 ◽  
Vol 457 ◽  
Author(s):  
Shiro Matsumoto ◽  
Marthe Houlbert ◽  
Takayoshi Hayashi ◽  
Ken-ichi Kubodera
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Liquid Crystals ◽  
Electric Field ◽  
Applied Voltage ◽  
Applied Electric Field ◽  
Uv Curing ◽  
Infrared Region ◽  
High Transparency ◽  
Power Change

ABSTRACTNano-sized fine droplets of liquid crystal (LC) were obtained by phase separation of nematic LC in UV curing polymer. The polymer composite had a high transparency in the infrared region. The fine droplets responded to an electric field causing a change in birefringence. Output power change was brought about by the generated retardation between two polarizations, parallel and perpendicular to the applied electric field. This differs from the composite containing much larger droplets, where output depends on the degree of scattering. The birefringence changed by 0.001 at the applied voltage of 7.5 V/μm.

scholarly journals Stable and Metastable Patterns in Chromonic Nematic Liquid Crystal Droplets Forced with Static and Dynamic Magnetic Fields

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 138 ◽  
Author(s):  
Jordi Ignés-Mullol ◽  
Marc Mora ◽  
Berta Martínez-Prat ◽  
Ignasi Vélez-Cerón ◽  
R. Santiago Herrera ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Boundary Conditions ◽  
Isotropic Phase ◽  
Director Field ◽  
Line Defects ◽  
The One ◽  
Bulk Structures ◽  
Microscopy Images

Spherical confinement of nematic liquid crystals leads to the formation of equilibrium director field configurations that include point and line defects. Driving these materials with flows or dynamic fields often results in the formation of alternative metastable states. In this article, we study the effect of magnetic field alignment, both under static and dynamic conditions, of nematic gems (nematic droplets in coexistence with the isotropic phase) and emulsified nematic droplets of a lyotropic chromonic liquid crystal. We use a custom polarizing optical microscopy assembly that incorporates a permanent magnet whose strength and orientation can be dynamically changed. By comparing simulated optical patterns with microscopy images, we measure an equilibrium twisted bipolar pattern within nematic gems that is only marginally different from the one reported for emulsified droplets. Both systems evolve to concentric configurations upon application of a static magnetic field, but behave very differently when the field is rotated. While the concentric texture within the emulsified droplets is preserved and only displays asynchronous oscillations for high rotating speeds, the nematic gems transform into a metastable untwisted bipolar configuration that is memorized by the system when the field is removed. Our results demonstrate the importance of boundary conditions in determining the dynamic behavior of confined liquid crystals even for configurations that share similar equilibrium bulk structures.

scholarly journals Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

2017 ◽  
Vol 114 (9) ◽  
pp. 2137-2142 ◽  
Author(s):  
Yunfeng Li ◽  
Elisabeth Prince ◽  
Sangho Cho ◽  
Alinaghi Salari ◽  
Youssef Mosaddeghian Golestani ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Self Assembly ◽  
Soft Matter ◽  
Cholesteric Liquid Crystal ◽  
Topological Defects ◽  
Spatial Inhomogeneity ◽  
Cholesteric Phase ◽  
Anisotropic Surface ◽  
Linear Defects

An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two self-assembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids.

scholarly journals Holographic Characteristics of Photopolymers Containing Different Mixtures of Nematic Liquid Crystals

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 325 ◽  
Author(s):  
Sandra Fenoll ◽  
Francisco Brocal ◽  
José David Segura ◽  
Manuel Ortuño ◽  
Augusto Beléndez ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Electric Field ◽  
Diffraction Efficiency ◽  
Applied Voltage ◽  
Nematic Liquid Crystals ◽  
Variable Electric Field ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed

A holographic polymer dispersed liquid crystal (HPDLC) is used to record holographic diffraction gratings. Several mixtures of nematic liquid crystals (LC) are used as components of the HPDLC to evaluate their influence in static and dynamic basic properties. The diffraction efficiency obtained in the reconstruction of the holograms is evaluated to compare the influence of the different LC. Additionally, the samples are exposed to a variable electric field and the diffracted light intensity as a function of the applied voltage is measured to evaluate the influence of the LC. The results obtained show significant differences depending on the LC incorporated to the photopolymer.

scholarly journals Smart Window Based on Angular-Selective Absorption of Solar Radiation with Guest–Host Liquid Crystals

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 131
Author(s):  
Seong-Min Ji ◽  
Seung-Won Oh ◽  
Tae-Hoon Yoon
Keyword(s):  
Liquid Crystal ◽  
Energy Consumption ◽  
Liquid Crystals ◽  
Solar Radiation ◽  
Applied Voltage ◽  
Incident Light ◽  
Selective Absorption ◽  
Smart Window ◽  
Direct Sunlight ◽  
Smart Windows

In this study, we analyzed angular-selective absorption in a guest–host liquid crystal (GHLC) cell for its application in smart windows. For reducing the energy consumption, angular-selective absorption is desired because the light transmitted through windows during the daytime is predominantly incident obliquely from direct sunlight. Owing to the absorption anisotropy of guest dichroic dyes, a GHLC cell can absorb the obliquely incident light, while allowing people to see through windows in a normal view. Therefore, the cell can provide a comfortable environment for occupants, and reduce the energy required for cooling by blocking the solar heat incident from the oblique direction. The GHLC cell can be switched between the transparent and opaque states for a normal view. The rising (falling) time was 6.1 (80.5) ms when the applied voltage was 10 V.

scholarly journals Expulsion of disclinations in nematic liquid crystals

2003 ◽  
Vol 14 (1) ◽  
pp. 39-59 ◽  
Author(s):  
PAOLO BISCARI ◽  
TIMOTHY J. SLUCKIN
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Boundary Conditions ◽  
Half Space ◽  
Nematic Liquid Crystal ◽  
Nematic Liquid Crystals ◽  
Critical Value ◽  
Repulsive Force ◽  
Anchoring Strength ◽  
Strong Anchoring

We study the interactions between a nematic liquid crystal disclination and the surface of the half-space which bounds it. When strong anchoring conditions are applied on the boundary, the biaxial core of the disclination affects the repulsive force that tends to drive the disclination away from the surface. If we replace the strong boundary conditions with an anchoring potential, the surface-disclination interaction depends on the surface extrapolation length. In particular, the nematic may expel the disclination if the anchoring strength is below a critical value.

Geometric stabilisation of topological defects on micro-helices and grooved rods in nematic liquid crystals

Soft Matter ◽  
2018 ◽  
Vol 14 (48) ◽  
pp. 9819-9829 ◽  
Author(s):  
Maryam Nikkhou ◽  
Igor Muševič
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Nematic Liquid Crystals ◽  
Topological Defects ◽  
Geometric Shape ◽  
Oppositely Charged

We demonstrate how the geometric shape of a rod in a nematic liquid crystal can stabilise a large number of oppositely charged topological defects.

Switching and induced flow effects in chiral smectic C liquid crystals

1997 ◽  
Vol 8 (3) ◽  
pp. 263-270 ◽  
Author(s):  
GEORGE I. BLAKE ◽  
FRANK M. LESLIE ◽  
MIKE J. TOWLER
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Boundary Conditions ◽  
Continuum Theory ◽  
Parallel Plates ◽  
Smectic C ◽  
Induced Flow ◽  
Flow Effects

We consider a chiral smectic C liquid crystal confined between parallel plates in the bookshelf geometry. Using a recently proposed continuum theory for such materials the behaviour of the cell is discussed when an electric field is applied and subsequently removed from the cell. We examine both symmetric and asymmetric boundary conditions for the director.

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