scholarly journals Interactions on the Interface between Two Liquid Crystal Materials

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 393 ◽  
Author(s):  
Rok Geršak ◽  
Simon Čopar
Keyword(s):  
Numerical Simulation ◽  
Liquid Crystal ◽  
Boundary Conditions ◽  
Chemical Treatment ◽  
Molecular Orientation ◽  
Glass Plate ◽  
External Fields ◽  
Intrinsic Properties ◽  
Director Field ◽  
Surface Alignment

In liquid crystal applications, boundary conditions are essential to ensuring suitable bulk molecular orientation and a deterministic response to external fields. Be it confinement to a droplet or a shell, a glass plate, or an interface with air or another liquid, proper surface alignment must be ensured—mechanically by rubbing, by chemical treatment that adds a layer of aligning molecules, by using photoalignment or even by leaving the surface untreated, using the intrinsic properties of the substrate itself. The anchoring can be classified as unidirectional (perpendicular homeotropic, or at oblique angles), or degenerate (planar or pre-tilted). However, if both substances at the interface are anisotropic, more diverse behaviour is expected. Here, we present a numerical simulation of a nematic droplet in a nematic host, and investigate behaviour of the director field and defects at the interface for different interfacial couplings. Finally, we compare the simulations to experimental images of discotic droplets in a calamitic nematic host.

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 Monte Carlo Simulation of the Director Field of a Nematic Liquid Crystal with Three Elastic Coefficients

1996 ◽  
Vol 51 (1-2) ◽  
pp. 1-9 ◽  
Author(s):  
T. Gruhn ◽  
S. Hess
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Free Energy ◽  
Liquid Crystal ◽  
External Field ◽  
Boundary Conditions ◽  
Nematic Liquid Crystal ◽  
Director Field ◽  
Fixed Boundary ◽  
Elastic Coefficients

Abstract In this article, a Monte Carlo simulation is presented, which generates the equilibrium director field of a nematic liquid crystal under the influence of an external field and fixed boundary conditions. The liquid crystal is characterized by a set of directors on a spatially fixed lattice. The simulation is based on an expression for the Frank free energy with three elastic coefficients. The chosen discretisation conserves the nematic symmetry, which means n and - n are equivalent. The results for several Frederiks geometries with homogeneous and spatially modulated external fields are shown, as well as an investigation of a capillary with homeotropic boundary conditions. Further we compare our method with the Lebwohl-Lasher model and introduce an extension of the latter which distinguishes between splay-, twist-and bend-configurations.

A MONTE CARLO SIMULATION OF CONFINED MAGNETIC SYSTEMS WITH RADIAL BOUNDARY CONDITIONS

1995 ◽  
Vol 09 (16) ◽  
pp. 989-997
Author(s):  
CESARE CHICCOLI ◽  
PAOLO PASINI ◽  
FRANCO SEMERIA ◽  
CLAUDIO ZANNONI
Keyword(s):  
Computer Simulation ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Liquid Crystal ◽  
Boundary Conditions ◽  
Heisenberg Model ◽  
Magnetic System ◽  
Magnetic Ordering ◽  
Magnetic Systems ◽  
Surface Alignment

We present a computer simulation of a confined magnetic system. We study a Heisenberg model microsphere with radial boundary conditions, the influence of the homeo-tropic surface alignment on the magnetic ordering inside the sphere and the consequent changes induced in the thermodynamic behavior. Comparisons with the case of nematic liquid crystal droplets are provided.

Temperature influence on homogeneous instabilities in stationary shear flow of nematic liquid crystal with weak surface anchoring

2010 ◽  
Vol 7 ◽  
pp. 191-201
Author(s):  
I.Sh. Nasibullayev ◽  
O.V. Urina
Keyword(s):  
Liquid Crystal ◽  
Shear Flow ◽  
Nematic Liquid Crystal ◽  
Effect Of Temperature ◽  
External Fields ◽  
Temperature Influence ◽  
Surface Anchoring ◽  
Weak Surface ◽  
Surface Coupling

Plane stationary shear flow of the nematic liquid crystal with weak surface anchoring is investigated. The effect of temperature, external fields, and the nature of the surface coupling on the formation of orientation instabilities is investigated.

scholarly journals Dynamic tuning of the director field in liquid crystal shells using block copolymers

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
JungHyun Noh ◽  
Yiwei Wang ◽  
Hsin-Ling Liang ◽  
Venkata Subba Rao Jampani ◽  
Apala Majumdar ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Block Copolymers ◽  
Director Field ◽  
Dynamic Tuning

Shape Optimization and Strength Evaluation of Metal Welded Bellows Wave of Mechanical Seal

2008 ◽  
Vol 33-37 ◽  
pp. 1377-1382 ◽  
Author(s):  
Halida Musha ◽  
Mamtimin Gheni ◽  
Buhalqam
Keyword(s):  
Numerical Simulation ◽  
Bone Mass ◽  
Boundary Conditions ◽  
Shape Optimization ◽  
Reaction Diffusion ◽  
Mechanical Seal ◽  
Forming Process ◽  
Strength Evaluation ◽  
Fem Method ◽  
Initial Load

In this paper, the iBone (Imitation Bone) model which is coupled with Turing reaction-diffusion system and FEM, is used. The numerical simulation of bone forming process by considering the osteoclasts and osteoblasts process are conducted. The bone mass is increased with increase of the initial load value, then fibula and femur bones are obtained respectively by keeping the required bone forming value. The new S shape wave of metal welded bellow of mechanical seal are designed based on the the optimization results through this method. The S shape and V shape both were analyzed with FEM method. The same boundary conditions were given for two types of wave. The results are shown that the stresses mainly concentrated on the welded area. It is interesting that the value of the stresses of the two types of wave basically same. However, compressibility of the two types of wave is very different at the same computation stage. The compressibility of S shape wave was higher than V shape.

A Chiral Director Field in the Nematic Liquid Crystal Phase Induced by a Poly(.gamma.-benzyl glutamate) Chemical Reaction Alignment Film

Langmuir ◽  
1995 ◽  
Vol 11 (12) ◽  
pp. 4838-4843 ◽  
Author(s):  
Shigeru Machida ◽  
Taeko I. Urano ◽  
Kenji Sano ◽  
Yasushi Kawata ◽  
Kazuyuki Sunohara ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Chemical Reaction ◽  
Crystal Phase ◽  
Liquid Crystal Phase ◽  
Director Field
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