LC Cell Research Articles

Experimental observation of the generation of cutoff solitons in a discreteLCnonlinear electrical line

We address the problem of supratransmission of waves in a discrete nonlinear system, driven at one end by a periodic excitation at a frequency lying above the phonon band edge. In an experimental electrical transmission line made of 200 inductance-capacitance LC cells, we establish the existence of a voltage threshold for a supratransmission enabling the generation and propagation of cut-off solitons within the line. The decisive role of modulational instability in the onset and development of the process of generation of cut-off solitons is clearly highlighted. The phenomenon of dissipation is identified as being particularly harmful for the soliton generation, but we show that its impact can be managed by a proper choice of the amplitude of the voltage excitation of the system.

Abstract 3442: Non-canonical Wnt pathway stimulation in response to LiCl is related to suppression of cell proliferation in histologically distinct human tumors

Abstract Disturbances in cellular proliferation are a fundamental characteristic of malignancy, and have often been associated with dysregulation of the Wnt/B-catenin canonical pathway (CAN). The activity of the CAN pathway is subject to regulation by the non-canonical pathway (N-CAN) which stimulates cellular differentiation. The N-CAN pathway which has been described as a negative regulator of the CAN pathway has not been well studied in human cancers and its activity as a possible negative regulator of cellular proliferation in different tumor histologies is not known. The purpose of this study was to characterize the activation of the N-CAN pathway in relationship to tumor cell proliferation in histologically diverse human tumors. LiCl, a known activator of the CAN pathway was used to investigate effects on proliferation of different human tumors along with its capacity to regulate expression of various Wnt pathway signaling components. Cancer cells were derived from surgical specimens obtained from patients with colorectal (CRC), pancreatic (PC), renal (RCC), breast (BC), stomach (SC) and lung (LC) cancers. Cultured cells were treated with LiCl (20 mM) for 72h. Cell proliferation was determined using the MTS assay and gene expression determined using commercially available quantitative RT-PCR Wnt pathway gene expression arrays. Significant inhibition (p<0.05) of proliferation by LiCl was exhibited by all cell types except LC cells. Furthermore, suppression of proliferation was inversely correlated with upregulation of N-CAN components in all tumor types with failure to upregulate N-CAN components in LC cells. The transmembrane protein, VANGL2, which forms a receptor complex for the N-CAN pathway was upregulated significantly in 1 of 2 PC specimens and in RCC and SC cells (mean 17 fold vs. media alone). In cells with increased VANGL2 expression, PRICKLE1 (N-CAN component that interacts with VANGL2), and FRZB, an inhibitor of the CAN pathway were increased by 2.8 and 4.9 folds respectively. In these cells, additional N-CAN components such as NKD1, DAAM1, and CAN inhibitor Wif1 were increased in some, but not all histologies. In contrast, there was no effect on VANGL2 expression in CRC, 1 of 2 PC cells, and BC cells whereas upregulation of additional N-CAN genes and CAN inhibitors was observed in all tumors that demonstrated inhibition of proliferation in response to LiCl. In cancers without VANGL2 increase there was an increase in expression of the N-CAN component NKD1 (6.6 folds) and decreased expression of β-catenin (2.4 folds). Other changes in Wnt pathway genes in these cells that were observed in some but not all cell types included increased expression of FRZB and WIF1. This study demonstrates differential effects of N-CAN pathway components on the proliferation of histologically distinct human tumors. Citation Format: Donald P. Braun, Adriana Rosales, Irshad Ali. Non-canonical Wnt pathway stimulation in response to LiCl is related to suppression of cell proliferation in histologically distinct human tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3442. doi:10.1158/1538-7445.AM2014-3442

On the stability of homogeneous orientation in the plane-parallel cell of a liquid crystal doped with nanoparticles

We consider the problems of homogenous orientations stability of molecules in a nematic liquid crystal (NLC) doped with a small amount of cholesteric LC. We studied LC cells with homeotropic and twisted orientation of molecules on the cell boundaries. The problems are solved using the Noether theorem for LC. According to this theorem, invariance of free energy expression with respect to translation leads to conservation of the momentum flux, while invariance with respect to the rotation group leads to conservation of the angular momentum flux. These conservation laws are used to determine thresholds of stability of homogenous orientation of molecules in the above-mentioned mixture and the influence of nanoparticles on these thresholds.

Dynamic Switching of the Circularly Polarized Luminescence of Disubstituted Polyacetylene by Selective Transmission through a Thermotropic Chiral Nematic Liquid Crystal

AbstractThe circularly polarized luminescence (CPL) of chiral disubstituted liquid‐crystalline polyacetylene (di‐LCPA) can be dynamically switched and amplified from left‐ to right‐handed CPL and vice versa through the selective transmission of CPL across a thermotropic chiral nematic liquid crystal (N*‐LC) phase. By combining a chiral di‐LCPA CPL‐emitting film with an N*‐LC cell and tuning the selective reflection band of the N*‐LC phase to coincide with the CPL emission band, a CPL‐switchable cell was constructed. The phase change induced by the thermotropic N*‐LC cell by varying the temperature leads to a change in the selective transmission of CPL, which enables the dynamic switching and amplification of CPL. It is anticipated that CPL‐switchable devices might find applications in switchable low‐threshold lasers and optical memory devices.

Dynamic switching of the circularly polarized luminescence of disubstituted polyacetylene by selective transmission through a thermotropic chiral nematic liquid crystal.

The circularly polarized luminescence (CPL) of chiral disubstituted liquid-crystalline polyacetylene (di-LCPA) can be dynamically switched and amplified from left- to right-handed CPL and vice versa through the selective transmission of CPL across a thermotropic chiral nematic liquid crystal (N*-LC) phase. By combining a chiral di-LCPA CPL-emitting film with an N*-LC cell and tuning the selective reflection band of the N*-LC phase to coincide with the CPL emission band, a CPL-switchable cell was constructed. The phase change induced by the thermotropic N*-LC cell by varying the temperature leads to a change in the selective transmission of CPL, which enables the dynamic switching and amplification of CPL. It is anticipated that CPL-switchable devices might find applications in switchable low-threshold lasers and optical memory devices.

Reflection spectra of distorted cholesteric liquid crystal structures in cells with interdigitated electrodes

We studied the appearance of second- and third-order Bragg reflections in cholesteric liquid crystals (CLCs) in cells where the electric field was perpendicular to the helical axis. Second-order reflections with reflectance values as large as 80% of the first-order one were observed in the gap regions of alignment cells with interdigitated electrodes for CLC mixtures with pitches in the range 0.5-1.0 μm upon application of a field. The characterization was enabled by local probing of the CLC using a microspectrophotometer. LC cells that are transparent in the visible spectrum in the off-state and become colored upon application of a field due the second- or third-order reflection band appearance were demonstrated. The spectral position of the higher-order Bragg reflections can also be tuned by adjusting the magnitude of the electric field.

Phase Retardation Difference of Liquid Crystal Cells with Symmetric and Asymmetric Boundary Conditions

Phase retardation ΔΦ values for the LC cells with homogeneous and inhomogeneous LC director distribution vs. the LC pretilt angle θ0 on the cell's substrates has been simulated. Cases of symmetric and hybrid cells with both positive and negative optical anisotropy LC with θ0 values in the range from 0 to 90° and θ0 > 90° are reviewed.

Low voltage fast response display using dual π‐cells with quarter‐wave thickness

AbstractIn this paper, a design for a fast response display consisting of dual π‐cells is investigated. The thickness of each liquid crystal cell layer is only half of a single LC cell device with the same retardation change, which results in about one quarter of the response time for a single π‐cell device. While this result is obviously anticipated, an additional advantage is that a good viewing angle can be achieved by using negative C plates, which allows a lower cost device with a more uniform black state across the area of the display than the case of a single cell compensated by a discotic compensator. We also propose a solution to solve parallax issue from two‐layer structure of liquid crystal cell, and it opens a window of opportunity for a device with two‐layer structure.

Study of dynamics and relaxation optical response of nematic liquid crystals doped with CdSe/ZnS quantum dots

This study is devoted to the dynamics of the electro-optical response and relaxation time of LC cells with a nematic liquid crystal doped with CdSe/ZnS semiconductor quantum dots (QDs) and homogeneously oriented by rubbed polyimide. The influence of the nanoparticle concentration as well as the parameters of the alternating electric field has been studied. Experimental dependence of the response and relaxation time on the concentration of QDs was obtained. The increase of concentration of QDs in the range of 0.5–1.5 mg/ml results in a reduction of the optical response time. The threshold voltage reduced twice with increasing QD concentration up to 1.5 mg/ml as compared with the pure LC. For the first time it was shown that applying of unipolar square wave electric field to the LC cell reduces the optical response time even twice regardless to the frequency of the alternating electric field compared to bipolar square wave voltage.

Investigating electro-optical properties of a nematic liquid crystal cell with planar anchoring boundary condition for various thicknesses: A Monte Carlo study

Monte Carlo (MC) simulations and the Mueller matrix formalism were applied to investigate electro optical properties of a LC cell with planar boundary conditions for various thicknesses. Field dependent global order parameter and the optical transmissions were analyzed in common. Three characteristic regions of the periodicity of optical transmissions as a function of polarizer angle and the external field were identified.

High-resistance liquid-crystal lens array for rotatable 2D/3D autostereoscopic display

A 2D/3D switchable and rotatable autostereoscopic display using a high-resistance liquid-crystal (Hi-R LC) lens array is investigated in this paper. Using high-resistance layers in an LC cell, a gradient electric-field distribution can be formed, which can provide a better lens-like shape of the refractive-index distribution. The advantages of the Hi-R LC lens array are its 2D/3D switchability, rotatability (in the horizontal and vertical directions), low driving voltage (~2 volts) and fast response (~0.6 second). In addition, the Hi-R LC lens array requires only a very simple fabrication process.

Reversible Capacitance Change of Nematic Liquid Crystal Cell Doped with Semiconductor CdSe/ZnS Quantum Dots

Electrical characteristics of the nematic LC cells with 3.5 nm semiconductor CdSe/ZnS quantum dots (QDs) were investigated. We observed variation of the LC cell capacitance with QDs concentration about 0.18 wt. %. The capacitance grown to three orders of magnitude at primary measuring under voltages below the Fredericks threshold and then it dropped. Repeated tests shown that the capacitance maximum of dependence decreased and disappeared after repeated measurements of the LC cell. The maximum arose again after applying to the LC cell of the alternating-current electric field with voltage of 30 V at a frequency of 1 kHz for 10 minutes. Changing of the capacitance was observed in the result of mobile ions interactions of liquid crystal with QDs in the electric field. That contributed to an aggregation and moving charged nanoparticles in the direction of substrates of LC cell as well as their reverse motion to a centre under action of applied voltage onto the LC cell.

Intracavity polarization control in mode-locked Er-doped fibre lasers using liquid crystals

AbstractIn this paper we present a novel configuration of an NPR mode-locked Er-doped laser. This new optical setup uses voltage controlled LC cells to replace standard retarders (quarter-and half-waveplates) inside the laser cavity. Using this novel, mechanical-adjustment-free setup a mode-locking was obtained with sub-500 fs pulse duration and an average power exceeding 40 mW. Presented results show that using simple LC cells, an optical layout of an NPR mode-locked laser can be greatly simplified.

Luminescence modulation in liquid crystalline phases containing a dispiro[fluorene-9,11′-indeno[1,2-b]fluorene-12′,9′′-fluorene] core

Luminescence modulations of a bulky dispiro[fluorene-9,11′-indeno[1,2-b]fluorene-12′,9′′-fluorene] (DSF-IF) core embedded in thermotropic liquid crystal phases.

Single-substrate polymer-stabilized blue phase liquid crystal display

We demonstrated a single-substrate polymer-stabilized blue phase liquid crystal (PSBP LC) display using a bar-coating technique. The BP temperature range and the electro-optical (EO) properties of PSBP LC cells fabricated on a single-substrate of glass, polycarbonate (PC) and polyethylene terephthalate (PET) were investigated. It was found that PSBP LC cells fabricated on the single-substrate of glass, PC, and PET exhibited a narrower BP temperature range in comparison with the conventional PSBP LC cell. This is necessary to improve the mechanical stability, the thermal stability and the EO performance of the single-substrate PSBP LC cells.

Residual DC voltage-free behaviour of liquid crystal system with nickel nanoparticle dispersion

In this study, we report on characterisation of residual DC voltage in homogeneously aligned nematic liquid crystal (N-LC) system with ferromagnetic Ni nanoparticles. A residual DC is greatly reduced in the N-LC cell as the increase of Ni particle concentration in LC mixture. The relationship between the doping concentration in Ni nanoparticles and the trapping of impurity ions was examined. In addition, the N-LC cells had faster response times and lower driving voltages, which translated to better electro-optical (EO) characteristics, than pure LC cells.

Achromatic optical compensation using dispersion of uniaxial films for elimination of off-axis light leakage in a liquid crystal cell

We propose an achromatic optical-compensation method using uniaxial films to eliminate the off-axis light leakage at the dark state in a homogeneously aligned liquid crystal cell. Three uniaxial films with different dispersion characteristics are used so that they can compensate each other to achieve achromatic effective phase retardation at off-axis. The retardation values are optimized with the aid of the Poincaré sphere and through numerical research. A contrast ratio of higher than 2000∶1 is predicted over the entire ±60° viewing cone for a homogeneously aligned LC cell with zero pretilt angle.

용액 공정 기반의 다중 적층된 HfO2박막 상에서의 액정 배향

Effect of multi-stacked layer (MSL), 0.1 mol (M) and 0.3 mol (M) hafnium oxide (<TEX>$HfO_2$</TEX>) alignment layers were fabricated via a solution-process for LCs orientation. The solutions were spin-coated and annealed in a furnace. MSL consists of three sub-layers using 0.1 M solution, mono-layer (ML) is composed of 0.3 M <TEX>$HfO_2$</TEX> solution. Then ion-beam irradiation was treated with 1.8 keV for 2 min. <TEX>$HfO_2$</TEX>-based LC cells were investigated through photographs, pre-tilt angle using crystal rotation method, X-ray photoelectron spectroscopy (XPS) measurement, and surface roughness using atomic force microscopy(AFM) for their characteristic research. Good LC orientation characteristics were observed on MSL <TEX>$HfO_2$</TEX> surface. The LC alignment mechanism on MSL <TEX>$HfO_2$</TEX> and ML <TEX>$HfO_2$</TEX> surfaces was attributed to van der Waals (VDW) interaction between the LC molecular and substrate surface.

PB12 Nn*-LCを用いた双安定LCDのポリマー壁による表示保持時間の改善(ディスプレイ,ポスター発表,2013年日本液晶学会討論会)

PB12 Nn*-LCを用いた双安定LCDのポリマー壁による表示保持時間の改善(ディスプレイ,ポスター発表,2013年日本液晶学会討論会)

P.90: Optical Properties of LC Cells with Hybrid Orientation and Negative Birefringence

AbstractPhase retardation ΔΦ values for the LC cells with homogeneous and inhomogeneous LC director distribution vs the LC pretilt angle θ0 on the cell's substrates, namely for hybrid cells with different LC pretilt angles at every substrate and films with negative optical anisotropy materials.