Papers by Keyword: Liquid Crystal

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Authors: Filiz Karaomerlioglu, Sevket Simsek, Amirullah M. Mamedov, Ekmel Ozbay
Abstract: Photonic crystals (PCs) have many applications in order to control light-wave propagation. A novel type of two-dimensional anisotropic PC is investigated band gap and optical properties as a hollow semiconductor nanorod with nematicliquid crystals (LC). The PC structure composed of an anisotropic nematicLC in semiconductor square hollow nanorod is designed using the plane wave expansion (PWE) method and finite-difference time-domain (FDTD) method. It has been used 5CB (4-pentyl-4`-cyanobiphenyl) as LC core, and Tellurium (Te) as square hollow nanorod material.The PC with hollow Tenanorod with nematicLC is compared with the PC with solid Tenanorodand the PC with hollow Tenanorod.
Authors: Xin De Tang, Nian Feng Han, Jing Xu
Abstract: A2BA2-type amphiphilic liquid crystalline block copolymers containing azobenzene were synthesized by atom transfer radical polymerization (ATRP). The macroinitiator prepared by the esterification reaction between poly(ethylene glycol) (PEG) and 2,2-dichloroacetyl chloride was used to initiate the ATRP of 6-[4-(4-ethoxyphenylazo)phenoxy]hexyl methacrylate (M6C). The resulting macroinitiator and block copolymers were characterized by 1H NMR, gel permeation chromatography (GPC). Polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) preliminarily revealed the liquid crystalline property of these block copolymers. These novel amphiphilic liquid crystalline block copolymers are promising in some areas, such as optical data storage, optical switch, and molecular devices.
Authors: Wen Ni Tan, Che Rose Laili, Suhaimi Hamdan
Abstract: In this work, liquid crystal emulsion with aloe vera (AV) was formulated and characterised its physical properties. A direct titration method was used to determine the composition of liquid crystal emulsion in a system consisting of water/mixed Tween 80: Span 85/hexane. AV gel was added to produce AV liquid crystal emulsion (AVLCE), which was then subjected to various characterisation such as microscopic analysis, stability test, rheological test and particle size analysis. Results showed that the application of AVCLE employed better performances in terms of stability, particle size and moisturizing. This study suggest that the formulated AVLCE may be suitable to be used as topical application on wounded skin.
Authors: J.Y. Duquesne, G. Bellessa
Authors: Li Ying Wu, Jian Zhang, Yun Fang
Abstract: For laser beam steering, a pure optical-electric system without mechanical or inertial parts is used. The new device is a Liquid Crystal Optical Phased Array (LCOPA). Supplying electric field to liquid crystal cell with electrodes, the extraordinary refractive index changes, which results in phase shift that modulates the direction of incident beam. The advantages of this device are small size, less energy consuming, programmable and addressable control. A one dimensional device is designed and tested. The resolution of the steering angle is 20 μrad, the range is ±2o. The effect of flyback region and phase valley on diffraction efficiency is also discussed briefly.
Authors: Qing Lan Ma, Bao Gai Zhai, Rui Xiong, Yuan Ming Huang
Abstract: Rod-like liquid crystals N-(4-methoxybenzylidene)-4-n-alkoxybenzenamine (MBnBA, n = 1, 2, 10) were synthesized and then were investigated by differential scanning calorimetry, polarizing optical microscopy, ultraviolet-visible spectrophotometry and fluorescence spectroscopy. Our results demonstrated that the dilute tetrahydrofuran solutions of each member in the family of MBnBA could give off blue fluorescence under the 325 nm excitation. The calculated electronic structures revealed that the fluorescence recorded at 469 nm (2.65 eV) was the result of π* → n transitions in the molecules of the synthesized liquid crystals MBnBA.
Authors: Andreas K. Schaper, S.R. Zhao, A. Kutoglu
Authors: Ji Wei Zhou, Guang Ming Ke, Bin Wang, Wei Dong Liu, Rui Xing Li
Abstract: The paper reports the methods for making a novel optical device consisted of photo alignment nematic liquid crystal films and polarizers. The color shift of the device depends on not only the viewing angle but also the viewing orientation. The retardation and intensity of the reflected light are theoretically calculated on the basis of Jones Matrix, and a spectral-RGB transition program is introduced to display colorful results directly. The theoretical results show excellent agreement with experimental data. It is an effective method for predicting interference color and optimizing key parameters of the device. The device can be used to protect valuable documents against fraud because of its special optical variable effects which is caused by interference of polarized light.
Authors: Chin Fhong Soon, Mohamad A. Genedy, Mansour Youseffi, Morgan C.T. Denyer
Abstract: The ability of a cell to adhere and transmit traction forces to a surface reveals the cytoskeleton integrity of a cell. Shear sensitive liquid crystals were discovered with new function in sensing cell traction force recently. This liquid crystal has been previously shown to be non-toxic, linear viscoelastic and sensitive to localized exerted forces. This paper reports the possibility of extending the application of the proposed liquid crystal based cell force sensor in sensing traction forces of osteoblast-like (MG-63) and human keratinocyte (HaCaT) cell lines exerted to the liquid crystal sensor. Incorporated with cell force measurement software, force distributions of both cell types were represented in force maps. For these lowly contractile cells, chondrocytes expressed regular forces (10 – 90 nN, N = 200) around the circular cell body whereas HaCaT projected forces (0 – 200 nN, N = 200) around the perimeter of poly-hedral shaped body. These forces are associated with the organisation of the focal adhesion expressions and stiffness of the LC substrate. From the results, liquid crystal based cell force sensor system is shown to be feasible in detecting forces of both MG63 and HaCaT.
Authors: João P. Borges, M.H. Godinho
Abstract: In an attempt to improve the mechanical properties of an all-cellulose based composite we made solid flexible films containing microcrystalline cellulose fibres produced by a shearing casting technique. To an anisotropic (liquid crystalline) solution of 2-hydroxypropylcellulose (HPC) in N,N – dimethylacetamide (60 w/w %) were added AVICEL fibres (0, 2, 4, 6, 10, 12 w/wHPC %). After homogenization these solutions were poured into a Teflon plate and sheared at a constant rate of 5 mm/s. The cellulosic microfibres in the liquid crystalline polymer medium were partially aligned by shear flow. Mechanical and morphological properties of the films were investigated using tensile tests, polarized optical microscopy and scanning electron microscopy. The mechanical properties of these films, as expected, are higher than those of the films produced from an isotropic solution of HPC. The results show that the orientation of the microfibres, and the mesoscopic properties, can be tuned by adjusting the topography of the nematic matrix in the micro-nano scale.
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