Nematic Liquid Crystal System Research Articles

Asymptotic behavior of solutions to the compressible nematic liquid crystal system in ℝ3

In this paper, we study a nematic liquid crystals system in three-dimensional whole space ℝ3 and obtain the time decay rates of the higher-order spatial derivatives of the solution by the method of spectral analysis and energy estimates if the initial data belongs to L1ℝ3 additionally.

Comparative study of nanoparticles doped in Liquid Crystal Polymer System

A comparative study of three nanoparticles Zn, ZnO and CuO doped in Nematic Liquid Crystal Polymer System (NLCPS) with different concentration was studied. The NLCPS combines the orientational ordering properties of liquid crystals, polymer and nanoparticles. The investigations were performed using Polarizing Microscopic Studies (PMS) and Fabry Perot Spectroscopic Studies (FPSS). After doping Zn, ZnO and CuO nanoparticles with liquid crystal polymer system, the response was studied at high temperature. The phase transition temperatures obtained by FPSS were confirmed by PMS. LCPS is useful for displays and may also be used for tunable wavelength filters, tunable liquid-crystal lenses and polarization-independent phase modulators.

Thermal and electro-optical properties of cerium-oxide-doped liquid-crystal devices

ABSTRACTDoping with cerium (IV) oxide (CeO2) nanoparticles can significantly enhance the thermal stability and electro-optical (EO) properties of nematic liquid crystal (NLC) systems. Thermal stability was improved without aggregation and reduction of transmittance by adding CeO2 nanoparticles in a liquid crystal medium. In particular, the EO properties greatly improved in CeO2-dispersed NLC cells. The threshold voltage reduced from 3.027 to 2.279 V and the response time decreased from 13.097 to 9.970 ms with increased CeO2 nanoparticles in the NLC cells. The improved properties of liquid crystals doped with CeO2 nanoparticles depend on the anchoring energy and the electric field of the CeO2-dispersed liquid crystal displays.

Global existence of weak solutions to the non-isothermal nematic liquid crystals in 2D

In this article, we prove the global existence of weak solutions to the non-isothermal nematic liquid crystal system on ▪2, on the basis of a new approximate system which is different from the classical Ginzburg-Landau approximation. Local in space energy inequalities are employed to recover the estimates on the second order spatial derivatives of the director fields locally in time, which cannot be derived from the basic energy balance. It is shown that these weak solutions satisfy the temperature equation, and also the total energy equation but away from at most finite many “singular” times, at which the energy concentration occurs and the director field losses its second order derivatives.

The Kinematic Effects of the Defects in Liquid Crystal Dynamics

AbstractHere we investigate the kinematic transports of the defects in the nematic liquid crystal system by numerical experiments. The model is a shear flow case of the viscoelastic continuummodel simplified fromthe Ericksen-Leslie system. The numerical experiments are carried out by using a difference method. Based on these numerical experiments we find some interesting and important relationships between the kinematic transports and the characteristics of the flow. We present the development and interaction of the defects. These results are partly consistent with the observation from the experiments. Thus this scheme illustrates, to some extent, the kinematic effects of the defects.

Hysteresis-free, energy efficient twisted nematic liquid crystal systems based on IB-irradiated gallium-doped tin oxide films

We successfully demonstrated the high performance of liquid crystal (LC) devices without capacitance hysteresis using ion-beam (IB)-irradiated GaSnO in solution. This method is widely used for obtaining inorganic films, although it yields poor crystallinity, owing to its cost effectiveness and high flexibility in combining materials. Atomic force microscopy and X-ray photoelectron spectroscopy analyses determined that IB irradiation on the films had an effect, which enabled the elucidation of the mechanism for LC alignment. Strong IB irradiation on GaSnO induced the formation of spherical particles on the films and rearrangement of the chemical bonds (linkage of Ga–Sn–O and gradually oxidized films), which could preserve the anisotropic characteristics to unidirectionally align LC molecules on the surface. Because rough surfaces effectively increase the electric field, the strongly restructured GaSnO surface led to a decrease in threshold voltages. Moreover, strong IB irradiation effectively released volume charges when the states of LC molecules were switched “on” and “off”, which is attributed to a reduction in oxygen bonding derived from hydroxyl groups responsible for capturing neutral electrons. Therefore, an IB-irradiated GaSnO film is appropriate as an alternative alignment layer for advanced, energy efficient, hysteresis-free LC display devices. We successfully demonstrated the high performance of liquid crystal (LC) devices without capacitance hysteresis using ion-beam (IB)-irradiated GaSnO in solution. This method is widely used for obtaining inorganic films, although it yields poor crystallinity, owing to its cost effectiveness and high flexibility in combining materials. (a) Schematic of the IB irradiation of the solution-derived GaSnO film. (b) Alignment state of the LCs as a function of IB intensity. (c) Transmittance graph using the crystal rotation method to calculate the pretilt angle. (d) Transmittance as a function of voltage of the twisted nematic (TN) cells fabricated from IB-irradiated GaSnO at different intensities compared to the rubbed PI method (e) Capacitance of the TN cells fabricated from IB-irradiated GaSnO at 2200 eV, which exhibited hysteresis-free characteristic of TN cells. Because rough surfaces effectively increase the electric field, the strongly restructured GaSnO surface led to a decrease in threshold voltages. Moreover, strong IB irradiation effectively released volume charges when the states of LC molecules were switched “on” and “off”, which is attributed to a reduction in oxygen bonding derived from hydroxyl groups responsible for capturing neutral electrons. Therefore, an IB-irradiated GaSnO film is appropriate as an alternative alignment layer for advanced, energy efficient, hysteresis-free LC display devices.

Global well‐posedness of the nonhomogeneous incompressible liquid crystals systems

This paper examines the initial‐value problem for the nonhomogeneous incompressible nematic liquid crystals system with vacuum. This paper establishes two main results. The first result is involved with the global strong solutions to the 2D liquid crystals system in a bounded smooth domain. Our second result is concerned with the small data global existence result about the 3D system in the whole space. In addition, the local existence and a blow‐up criterion of strong solutions are also mentioned. Copyright © 2016 John Wiley & Sons, Ltd.

The n-alcohols liquid doping effect on the twisted nematic liquid crystals

We present a simple and efficient way to improve the performance of the twisted nematic liquid crystal (LC) system by doping a small amount of n-alcohols. The LCs modified by n-hexanol demonstrates the optimum electro-optical properties of lower driving voltage and shorter response time. Our measurements indicate that the liquid dopant n-alcohols can be used to modify LCs for lowering zenithal anchoring energy relative to undoped LCs. Without the drawbacks of precipitation and aggregation that the nanoparticles could have, the method of doping n-alcohol liquids provides a more stable and reliable choice to apply in the various LC display systems.

Nickel Oxide Nanoparticles Doped Liquid Crystal System for Superior Electro-Optical Properties.

We examined the properties of nematic liquid crystal (N-LC) systems with dispersed nickel oxide nanoparticles (NPs). Uniform LC alignments with regular pretilt angles were achieved on rubbed polymer surface regardless of NiO nanoparticles concentration. We confirmed the electro-optical characteristics of twisted nematic (TN) cells containing NiO nanoparticles on rubbed polymer surface, which exhibited lower threshold voltages and faster response times with less capacitance hysteresis than pure LC cells. It is clear that the response time of TN cells on rubbed polymer surfaces decreases with increasing the NiO nanoparticles concentration. These results demonstrate the relationship between NP doping concentration and trapping of impurity ions, and were confirmed by a software simulation of electric flux and field density. NiO nanoparticles in the LC cells focused the electric field flux and strengthened the electric field. Further, NiO nanoparticles in LC medium trapped charged ionic impurities and suppressed the screen effect, leading to a stronger electric field and the van der Waals interactions between LC molecules and the alignment layers.

Tuning phase retardation behaviour of nematic liquid crystal using quantum dot

We here report on the phase retardation behavior of nematic liquid crystal (NLC) doped with CdSe quantum dot (QD). A study of birefringence and relative permittivity in 4-octyl-4′-cyanobiphenyl (8CB) NLC and its variation with doping of QDs has been presented. The study shows improvement of NLC ordering after addition of QDs. The observed higher value of birefringence in QD doped NLC system has been attributed to improved alignment due to additional order in NLC by self assembled QDs. The improved order of NLC system has also been explained by a schematic illustration for pristine and QD doped NLC system. Study of relative permittivity has also revealed the ordering effect in QD dispersed NLC system.

Function Spaces for Liquid Crystals

We consider the relationship between three continuum liquid crystal theories: Oseen-Frank, Ericksen and Landau-de Gennes. It is known that the function space is an important part of the mathematical model and by considering various function space choices for the order parameters $s$, ${\bf n}$, and ${\bf Q}$, we establish connections between the variational formulations of these theories. We use these results to derive a version of the Oseen-Frank theory using special functions of bounded variation. This proposed model can describe both orientable and non-orientable defects. Finally we study a number of frustrated nematic and cholesteric liquid crystal systems and show that the model predicts the existence of point and surface discontinuities in the director.

The Electro-Optical Properties of Twisted Nematic Liquid Crystals Modified by N-Alcohols

We present a simple and efficient way to improve the performance of the twisted nematic liquid crystal (LC) system by doping a small amount of n-alcohols. The LCs modified by n-hexanol demonstrates the optimum electro-optical properties of lower driving voltage and shorter response time. Our measurements indicate that the n-alcohols can be treated as surfactants to modify LCs for lowering zenithal anchoring energy relative to undoped LCs. Without the drawbacks of precipitation and aggregation that the nanoparticles could have, the method of doping n-alcohol liquids provides a more stable and reliable choice to apply in the various LC display systems.

Decay of the nematic liquid crystal system

In this paper, we study the time-decay rates of the solution to the Cauchy problem for a nematic liquid crystals system via a refined pure energy method. In particular, the optimal decay rates of the higher-order spatial derivatives of the solution are obtained. The negative Sobolev norms are shown to be preserved along time evolution and enhance the decay rates. Copyright © 2015 John Wiley & Sons, Ltd.

Space–time derivative estimates of the Koch–Tataru solutions to the nematic liquid crystal system in Besov spaces

In recent paper [7], Y. Du and K. Wang (2013) proved that the global-in-time Koch–Tataru type solution (u,d) to the n-dimensional incompressible nematic liquid crystal flow with small initial data (u0,d0) in BMO−1×BMO has arbitrary space–time derivative estimates in the so-called Koch–Tataru space norms. The purpose of this paper is to show that the Koch–Tataru type solution satisfies the decay estimates for any space–time derivative involving some borderline Besov space norms. More precisely, for the global-in-time Koch–Tataru type solution (u,d) to the nematic liquid crystal flow with initial data (u0,d0)∈BMO−1×BMO and ‖u0‖BMO−1+[d0]BMO≤ε for some small enough ε>0, and for any positive integers k and m, one has‖tk+m2(∂tk∇mu,∂tk∇m∇d)‖L˜∞(R+,B˙∞,∞−1)∩L˜1(R+;B˙∞,∞1)≤ε. Furthermore, we shall give that the solution admits a unique trajectory which is Hölder continuous with respect to space variables.

Photoalignable Radical Initiator for Anisotropic Polymerization in Liquid Crystalline Media

A rod-shaped azobenzene derivative possessing a 2-benzoyl-2-propanol moiety (Az-PIni) was synthesized. This molecule was highly compatible with calamitic nematic liquid crystal (LC) systems and showed dual photofunctions as a photocommander for the alignment of LCs upon linearly polarized light (LPL) irradiation and a photoinitiator for the radical polymerization in these media. The dual photofunctions were achieved simultaneously by irradiation with 365 nm LPL, or stepwisely with 436 nm LPL for the photoalignment, and successively with 254 nm light for the photoinitiated polymerization. In a nematic LC cell, these combined processes provided a persistent uniform alignment. When a polymerizable LC monomer film was coated on an elastomeric sheet, the anisotropic photopolymerization of the photoaligned monomer initiated by Az-PIni led to a uniformly aligned wrinkle formation via polymerization shrinkage.

Global solutions to the 3D incompressible nematic liquid crystal system

In this paper, we consider the global well-posedness of the Cauchy problem of the 3D incompressible nematic liquid crystal system with initial data in the critical Besov space B2,112(R3)×B2,132(R3). In particular, we prove that there exists a positive constant C0 such that the nematic liquid crystal system has a unique global solution with initial data (u0,d0)=(u0h,u03,d0) which satisfies((1+1νμ)‖d0−d¯0‖B2,132+1ν‖u0h‖B2,112)exp⁡{C0ν2(‖u03‖B2,112+1μ)2}≤c0, for some c0 sufficiently small, where d¯0 is a constant vector with |d¯0|=1. Here ν and μ are two positive viscosity constants.

Dielectric Behavior of ZnO Nano Particle Dispersed Nematic Liquid Crystal

In the present study the measurement of the dielectric properties of a pure nematic liquid crystal and nano-nematic composite system in the planar and homeotropic mode has been reported. The motivation of the work is to establish the effect of nano particle, having semiconducting nature, on nematic liquid crystals. The magnitude of dielectric permittivity has decreased due to the addition of ZnO nano particles in LC for both the alignments. The addition of ZnO nano particle (NP) results in shifting of the absorption band of dielectric spectra to the higher side of the frequency of hometropic alignment, whereas for the planar alignment, the band shifts towards the lower frequency side. The shifting of relaxation band in the nano-nematic composite system suggests that a strong interaction occurs between the LC molecules and nano particles. The different concentrations of ZnO nano particle play an important role in the variation of different dielectric parameters for both the types of alignment.

Precession Mechanism of Nematic Liquid Crystal Droplets under Low Power Optical Tweezers

Optical tweezers is a magnificent tool for microscopic manipulation. Owing to few piconewton noninvasive trapping force, the tiny objects from micro sand beads down to living bacteria can be trapped under optical tweezers system. Liquid crystals (LC) are materials that enriched of optical properties providing various phemomena that can be applied for technology. In this report, we applied optical tweezers to nematic liquid crystal system for the optical manipulation study. 5CB (4-cyano-4’-pentylbiphenyl) was used with an appropriate surfactant to prepare nematic liquid crystal (NLC) droplets at room temperature. NLC droplets in radial and bipolar configurations can be formed. They react with light angular momentum and reveal dynamic and static changes through spinning and changing of internal configuration. Several recent articles reported spinning dynamics of NLC droplets under high power trapping (more than a few hundred milliwatts), however, high power caused disturbance in internal configuration of droplets. Dynamic changes of droplet under low power trapping (lower than 100 mW) conducting so far were reported unsuccessful. Here we report the first investigation on behaviour of radial NLC droplet under low power optical trap. The configuration of droplets was not disturbed under low power trapping. We investigated the dynamic behaviour of non-disturbed NLC droplet in low power optical trap.

Nonlinear refractive index induced collision and propagation of nematicons

Nematic liquid crystals (NLCs) have proved to be excellent materials for nonlinear optics and its applications because of their large nonresonant nonlinearity and their extended spectral transparency. We demonstrate the exemplary collision scenario of both optical solitons and nematicons induced by the nonlinear refractive index in nematic liquid crystals. We invoke Hirota's bilinearization method for two coupled partial differential equations governing the dynamics of self-focusing of a laser light in a nematic liquid crystal system. We believe that this type of collision of optical solitons and nematicons reveals the many possibilities of all-optical switching schemes for spatial demultiplexing, network reconfiguration and logic gates.

Shape changing nonlocal molecular deformations in a nematic liquid crystal system

The nature of nonlinear molecular deformations in a homeotropically aligned nematic liquid crystal (NLC) is presented. We start from the basic dynamical equation for the director axis of a NLC with elastic deformation and mapped onto a integro-differential perturbed Nonlinear Schrödinger equation which includes the nonlocal term. By invoking the modified extended tangent hyperbolic function method aided with symbolic computation, we obtain a series of solitary wave solutions. Under the influence of the nonlocality induced by the reorientation nonlinearity due to fluctuations in the molecular orientation, the solitary wave exhibits shape changing property for different choices of parameters. This intriguing property as a result of the relation between the coherence of the solitary deformation and the nonlocality reveals a strong need for a deeper understanding in the theory of self-localization in NLC systems.