WorldWideScience

Sample records for biological liquid crystal

  1. Liquid Crystals

    Science.gov (United States)

    1990-01-01

    Thermochromic liquid crystals, or TLCs, are a type of liquid crystals that react to changes in temperature by changing color. The Hallcrest/NASA collaboration involved development of a new way to visualize boundary layer transition in flight and in wind tunnel testing of aircraft wing and body surfaces. TLCs offered a new and potentially better method of visualizing the boundary layer transition in flight. Hallcrest provided a liquid crystal formulation technique that afforded great control over the sensitivity of the liquid crystals to varying conditions. Method is of great use to industry, government and universities for aerodynamic and hydrodynamic testing. Company's principal line is temperature indicating devices for industrial use, such as non-destructive testing and flaw detection in electric/electronic systems, medical application, such as diagnostic systems, for retail sale, such as room, refrigerator, baby bath and aquarium thermometers, and for advertising and promotion specials. Additionally, Hallcrest manufactures TLC mixtures for cosmetic applications, and liquid crystal battery tester for Duracell batteries.

  2. Biological Macromolecule Crystallization Database

    Science.gov (United States)

    SRD 21 Biological Macromolecule Crystallization Database (Web, free access)   The Biological Macromolecule Crystallization Database and NASA Archive for Protein Crystal Growth Data (BMCD) contains the conditions reported for the crystallization of proteins and nucleic acids used in X-ray structure determinations and archives the results of microgravity macromolecule crystallization studies.

  3. Liquid crystal tunable photonic crystal dye laser

    OpenAIRE

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron; Kristensen, Anders

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.

  4. Liquid crystal tunable photonic crystal dye laser

    DEFF Research Database (Denmark)

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron;

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.......We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  5. Holographic liquid crystal devices

    OpenAIRE

    Pavani, Kotakonda, (Thesis)

    2009-01-01

    Liquid crystals have become natural candidates for use in electro-optic devices for their ability to change the orientation of the director with the application of an electric field, and exhibiting large range of refractive index. The aim of the work presented in this thesis is to fabricate liquid crystal optoelectronic devices such as electrically switchable liquid crystal diffraction gratings and polarization rotators by exploiting the holographic surface relief effect in photopolymer and b...

  6. Thermotropic Ionic Liquid Crystals

    OpenAIRE

    Sabine Laschat; Axenov, Kirill V

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  7. Dynamics in liquid crystals

    International Nuclear Information System (INIS)

    Five types of reorientational motions for molecules in liquid crystals are discussed on the basis of a comparison of the neutron scattering and the dielectric relaxation methods. 18 refs., 7 figs., 2 tabs. (author)

  8. Living liquid crystals

    OpenAIRE

    Zhou, Shuang; Sokolov, Andrey; Lavrentovich, Oleg D.; Aranson, Igor S.

    2014-01-01

    Collective motion of self-propelled organisms or synthetic particles often termed active fluid has attracted enormous attention in broad scientific community because of it fundamentally non-equilibrium nature. Energy input and interactions among the moving units and the medium lead to complex dynamics. Here we introduce a new class of active matter, living liquid crystals (LLCs) that combine living swimming bacteria with a lyotropic liquid crystal. The physical properties of LLCs can be contr...

  9. Liquid crystalline biopolymers: A new arena for liquid crystal research

    International Nuclear Information System (INIS)

    This paper gives a brief introduction to liquid crystals on the basis of biopolymers and reviews literature on liquid crystalline behaviour of biopolymers both in vitro and in vivo in relation to their implications in the fields of biology, medicine and material science. Knowledge in the field of biological liquid crystals is crucial for understanding complex phenomena at supramolecular level which will give information about processes involved in biological organization and function. The understanding of the interaction of theses crystals with electric, magnetic, optical and thermal fields will uncover mechanisms of near quantum-energy detection capabilities of biosystems

  10. Instabilities in liquid crystals

    International Nuclear Information System (INIS)

    This thesis contains theoretical work dealing with the effects of magnetic and electric fields on samples of nematic, smectic A and smectic C liquid crystals. Some background material along with the continuum theory is introduced in Chapter 2. In Chapter 3 we consider the effect on the director within an infinite sample of nematic liquid crystal which is subjected to crossed electric and magnetic fields. In particular we examine the stability of the travelling waves which describe the director motion by considering the behaviour of the stable perturbations as time increases. The work of Chapter 4 examines a bounded sample of smectic A liquid crystal in two dimensions which is subjected to a magnetic field. It can be shown that layer undulations may occur after a critical threshold is reached. The effects of various forms of pressure are also studied and in the case when pressure is included it is shown that layer undulations will always occur regardless of the field strength. Chapter 5 extends the work of Chapter 4 to three dimensions. We consider the effect of adding a dynamical term and study the stability of these solutions. Also we examine how the layers undulate when the sample of smectic A liquid crystal is confined to various cylindrical geometries and subjected to a magnetic field and a uniform pressure. In Chapter 6 we consider a sample of smectic C liquid crystal which is subjected to an oscillatory electric field. The motion of the c-director is complicated and we examine the differences which occur for differing dielectric anisotropies. Finally, in Chapter 7 we study how a sample of smectic C liquid crystal behaves when it is subjected to a uniform shear flow within the smectic plane. We find travelling wave solutions for the behaviour of the c-director and adapt these solutions to incorporate the effects of an applied field. (author)

  11. Thermoelectricity in liquid crystals

    Science.gov (United States)

    Mohd Said, Suhana; Nordin, Abdul Rahman; Abdullah, Norbani; Balamurugan, S.

    2015-09-01

    The thermoelectric effect, also known as the Seebeck effect, describes the conversion of a temperature gradient into electricity. A Figure of Merit (ZT) is used to describe the thermoelectric ability of a material. It is directly dependent on its Seebeck coefficient and electrical conductivity, and inversely dependent on its thermal conductivity. There is usually a compromise between these parameters, which limit the performance of thermoelectric materials. The current achievement for ZT~2.2 falls short of the expected threshold of ZT=3 to allow its viability in commercial applications. In recent times, advances in organic thermoelectrics been significant, improving by over 3 orders of magnitude over a period of about 10 years. Liquid crystals are newly investigated as candidate thermoelectric materials, given their low thermal conductivity, inherent ordering, and in some cases, reasonable electrical conductivity. In this work the thermoelectric behaviour of a discotic liquid crystal, is discussed. The DLC was filled into cells coated with a charge injector, and an alignment of the columnar axis perpendicular to the substrate was allowed to form. This thermoelectric behavior can be correlated to the order-disorder transition. A reasonable thermoelectric power in the liquid crystal temperature regime was noted. In summary, thermoelectric liquid crystals may have the potential to be utilised in flexible devices, as a standalone power source.

  12. Liquid crystal display

    International Nuclear Information System (INIS)

    An improved liquid crystal display device is described which can display letters, numerals and other necessary patterns in the night time using a minimized amount of radioactive material. To achieve this a self-luminous light source is placed in a limited region corresponding to a specific display area. (U.K.)

  13. Liquid crystal orientation control in photonic liquid crystal fibers

    Science.gov (United States)

    Chychlowski, M. S.; Nowinowski-Kruszelnicki, E.; Woliński, T. R.

    2011-05-01

    Similarly to liquid crystal displays technology in photonic liquid crystal fibers (PLCFs) a molecular orientation control is a crucial issue that influences proper operation of PLCF-based devices. The paper presents two distinct configurations: planar and radial escaped orientation of the LC molecules inside capillaries as well as methods of their application to photonic liquid crystal fibers. Possibilities of LC orientation control influence both: attenuation and transmitting spectra of the PLCF The orienting method is based on creation of an additional orienting layer on the inner surface of the capillary or air hole of the photonic liquid crystal fiber. Aligning materials used in the experiment are commercially available polyimides SE1211 and SE130 which induce liquid crystal homeotropic and planar anchoring conditions. The orienting layer increase an order parameter of the liquid crystal improving propagation properties and stability of photonic liquid crystal fiber-based devices.

  14. Liquid Crystal Motion Picture Projector①

    Institute of Scientific and Technical Information of China (English)

    SHIYongji

    1997-01-01

    A liquid crystal moving picture projector and method are described.Light incident on a liquid crystal display-type device is selectively scattered or transmitted by respective portions of liquid crystal display,and a projection mechanism projects an image formed by either such scattered light or such transmitted light.A liquid cystal moving picture projector includes a liquid crystal display for creating characteristics of an image,and projecttion optics for projecting images sequentially created by the display.The display includes a liquid crystal material capable of temporary storing information at respective areas.The temporary storage may be a function of charge storing directly on liquid crystal material.A method of projecting plural images in sequence includes:creating an image or characteristics of an image in a liquid crystal material,storing such image in such liquid crystal material,directing light at such liquid crystal material,projecting such image as a function of light transmitted through or scattered by such liquid crystal material,and creating a further image in such liquid crystal material for subsequent projection.

  15. Nematic liquid crystal bridges

    Science.gov (United States)

    Doss, Susannah; Ellis, Perry; Vallamkondu, Jayalakshmi; Danemiller, Edward; Vernon, Mark; Fernandez-Nieves, Alberto

    We study the effects of confining a nematic liquid crystal between two parallel glass plates with homeotropic boundary conditions for the director at all bounding surfaces. We find that the free surface of the nematic bridge is a surface of constant mean curvature. In addition, by changing the distance between the plates and the contact angle with the glass plates, we transition between loops and hedgehogs that can be either radial or hyperbolic.

  16. Textures of liquid crystals

    CERN Document Server

    Dierking, Ingo

    2006-01-01

    A unique compendium of knowledge on all aspects of the texture of liquid crystals, providing not just detailed information on texture formation and determination, but also an in-depth discussion of different characterization methods. Experts as well as graduates entering the field will find all the information they need in this handbook, while the magnitude of the color images make it valuable hands-on-reference.

  17. Living liquid crystals.

    Science.gov (United States)

    Zhou, Shuang; Sokolov, Andrey; Lavrentovich, Oleg D; Aranson, Igor S

    2014-01-28

    Collective motion of self-propelled organisms or synthetic particles, often termed "active fluid," has attracted enormous attention in the broad scientific community because of its fundamentally nonequilibrium nature. Energy input and interactions among the moving units and the medium lead to complex dynamics. Here, we introduce a class of active matter--living liquid crystals (LLCs)--that combines living swimming bacteria with a lyotropic liquid crystal. The physical properties of LLCs can be controlled by the amount of oxygen available to bacteria, by concentration of ingredients, or by temperature. Our studies reveal a wealth of intriguing dynamic phenomena, caused by the coupling between the activity-triggered flow and long-range orientational order of the medium. Among these are (i) nonlinear trajectories of bacterial motion guided by nonuniform director, (ii) local melting of the liquid crystal caused by the bacteria-produced shear flows, (iii) activity-triggered transition from a nonflowing uniform state into a flowing one-dimensional periodic pattern and its evolution into a turbulent array of topological defects, and (iv) birefringence-enabled visualization of microflow generated by the nanometers-thick bacterial flagella. Unlike their isotropic counterpart, the LLCs show collective dynamic effects at very low volume fraction of bacteria, on the order of 0.2%. Our work suggests an unorthodox design concept to control and manipulate the dynamic behavior of soft active matter and opens the door for potential biosensing and biomedical applications. PMID:24474746

  18. Antiferroelectric liquid crystals

    OpenAIRE

    Benguigui, L.; Hardouin, F.

    1981-01-01

    Dielectric investigations have been undertaken in two thermotropic liquid crystal systems exhibiting a smectic A2 phase (i.e. with the layer spacing equal to twice the molecular length). The postulated antiferroelectric ordering has been supported by these measurements. There are anomalies in the dielectric constants ε∥ and ε〉 at the N-S A2 transition and an unusual low frequency relaxation, with a slight temperature dependence, appears around this transition and in the S A phases of these sy...

  19. Voxelated liquid crystal elastomers

    Science.gov (United States)

    Ware, Taylor H.; McConney, Michael E.; Wie, Jeong Jae; Tondiglia, Vincent P.; White, Timothy J.

    2015-02-01

    Dynamic control of shape can bring multifunctionality to devices. Soft materials capable of programmable shape change require localized control of the magnitude and directionality of a mechanical response. We report the preparation of soft, ordered materials referred to as liquid crystal elastomers. The direction of molecular order, known as the director, is written within local volume elements (voxels) as small as 0.0005 cubic millimeters. Locally, the director controls the inherent mechanical response (55% strain) within the material. In monoliths with spatially patterned director, thermal or chemical stimuli transform flat sheets into three-dimensional objects through controlled bending and stretching. The programmable mechanical response of these materials could yield monolithic multifunctional devices or serve as reconfigurable substrates for flexible devices in aerospace, medicine, or consumer goods.

  20. Nonlinear dynamical phenomena in liquid crystals

    International Nuclear Information System (INIS)

    Because of the existence of the orientational order and anisotropy in liquid crystals, strong nonlinear phenomena and singular behaviors, such as solitary wave, transient periodic structure, chaos, fractal and viscous fingering, can be excited by a very small disturbance. These phenomena and behaviors are in connection with physics, biology and mathematics. 12 refs, 6 figs

  1. Adaptive Liquid Crystal Windows

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, Bahman; Bodnar, Volodymyr

    2011-12-31

    Energy consumption by private and commercial sectors in the U.S. has steadily grown over the last decade. The uncertainty in future availability of imported oil, on which the energy consumption relies strongly, resulted in a dramatic increase in the cost of energy. About 20% of this consumption are used to heat and cool houses and commercial buildings. To reduce dependence on the foreign oil and cut down emission of greenhouse gases, it is necessary to eliminate losses and reduce total energy consumption by buildings. To achieve this goal it is necessary to redefine the role of the conventional windows. At a minimum, windows should stop being a source for energy loss. Ideally, windows should become a source of energy, providing net gain to reduce energy used to heat and cool homes. It is possible to have a net energy gain from a window if its light transmission can be dynamically altered, ideally electronically without the need of operator assistance, providing optimal control of the solar gain that varies with season and climate in the U.S. In addition, the window must not require power from the building for operation. Resolution of this problem is a societal challenge and of national interest and will have a broad global impact. For this purpose, the year-round, allclimate window solution to provide an electronically variable solar heat gain coefficient (SHGC) with a wide dynamic range is needed. AlphaMicron, Inc. (AMI) developed and manufactured 1ft × 1ft prototype panels for the world’s first auto-adjusting Adaptive Liquid Crystal Windows (ALCWs) that can operate from sunlight without the need for external power source and demonstrate an electronically adjustable SHGC. This novel windows are based on AlphaMicron’s patented e-Tint® technology, a guesthost liquid crystal system implemented on flexible, optically clear plastic films. This technology is suitable both for OEM and aftermarket (retro-fitting) lamination to new and existing windows. Low level of

  2. Fundamentals of liquid crystal devices

    CERN Document Server

    Yang, Deng-Ke

    2014-01-01

    Revised throughout to cover the latest developments in the fast moving area of display technology, this 2nd edition of Fundamentals of Liquid Crystal Devices, will continue to be a valuable resource for those wishing to understand the operation of liquid crystal displays. Significant updates include new material on display components, 3D LCDs and blue-phase displays which is one of the most promising new technologies within the field of displays and it is expected that this new LC-technology will reduce the response time and the number of optical components of LC-modules. Prof. Yang is a pion

  3. Bicontinuous liquid crystals

    CERN Document Server

    Lynch, Mathew L

    2005-01-01

    PrefaceIntroduction AcknowledgmentsBicontinuous Cubic Liquid Crystalline Materials: A Historical Perspective and Modern Assessment; Kr̄e LarssonIntermediate Phases; Michael C. Holmes and Marc S. LeaverCubic Phases and Human Skin: Theory and Practice; Steven Hoath and Lars NorlňThe Relationship between Bicontinuous Inverted Cubic Phases and Membrane Fusion; D.P. SiegelAspects of the Differential Geometry and Topology of Bicontinuous Liquid-Crystalline Phases; Robert W. CorkeryNovel L3 Phases and Their Macroscopic Properties; R. Beck and H. HoffmannBicontinuous Cubic Phases of Lipids with Entra

  4. Research on colored lyotropic liquid crystals

    Institute of Scientific and Technical Information of China (English)

    WEI Xilian; YIN Baolin; SUN Dezhi; LIU Jie; WANG Zhongni; LI Ganzuo

    2005-01-01

    Splendidly colored lyotropic liquid crystals formed in the ternary system of a novel cationic surfactant, 3-p-nonylphenoxy-2-hydroxypropyl trimethyl ammonium bromide (NPTAB)-n-butanol-water system, had been observed under polarized light microscope. Small-angle X-ray scattering (SAXS), 2H (deuterium) quadrupolar splitting (2H NMR) were employed to confirm the structures of these liquid crystals. The structural transformation of these special lyotropic liquid crystals had been confirmed by differential scanning calorimetry (DSC). The influences of liquid crystal film thickness, temperature and conserving time on the color of liquid crystals have been investigated. It is also theoretically discussed for forming and changing of liquid crystal color.

  5. Fast response liquid crystal devices

    Science.gov (United States)

    Wu, Yung-Hsun

    Liquid crystal (LC) has been widely used for displays, spatial light modulators, variable optical attenuators (VOAs) and other tunable photonic devices. The response time of these devices is mainly determined by the employed liquid crystal material. The response time of a LC device depends on the visco-elastic coefficient (gamma1/K11), LC cell gap (d), and applied voltage. Hence, low visco-elastic coefficient LC materials and thinner cell gap are favorable for reducing the response time. However, low visco-elastic coefficient LCs are usually associated with a low birefringence because of shorter molecular conjugation. For display applications, such as LCD TVs, low birefringence (Deltanthick cell gap which, in turn, increases the response time. How to obtain fast response for the LC devices is a fundamentally important and technically challenging task. In this dissertation, we investigate several methods to improve liquid crystal response time, for examples, using dual-frequency liquid crystals, polymer stabilized liquid crystals, and sheared polymer network liquid crystals. We discover a new class of material, denoted as sheared polymer network liquid crystal (SPNLC) which exhibits a submillisecond response time. Moreover, this response time is insensitive to the LC cell gap. This is the first LC device exhibiting such an interesting property. Chapters 1 and 2 describe the motivation and background of this dissertation. From chapter 3 to chapter 6, dual-frequency liquid crystals and polymer network methods are demonstrated as examples for the variable optical attenuators. Variable optical attenuator (VOA) is a key component in optical communications. Especially, the sheared PNLC VOA shows the best result; its dynamic range reaches 43 dB while the response time is in the submillisecond range at 1550 nm wavelength, which is 50 times faster than the commercial LC-based VOA. In Chapter 7, we report a new device called axially-symmetric sheared polymer network liquid

  6. Thermotropic liquid crystals recent advances

    CERN Document Server

    Ramamoorthy, Ayyalusammy

    2007-01-01

    Covers developments in the field of thermotropic liquid crystals and and assesses their functional importance. This text includes chapters covering the applications of high-resolution methods, such as solid-state NMR, that have been used to understand the high-resolution structure, dynamics, orientation, and orientational order of these molecules.

  7. Infrared Sensor with Liquid Crystal Chopper

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An infrared sensor using the liquid crystal chopper is presented. The infrared sensor is designed to detect infrared rays with a pyroelectric element used as a liquid crystal chopper in such an infrared sensor or the like.

  8. Hierarchical Organization in Liquid Crystal-in-Liquid Crystal Emulsions

    OpenAIRE

    Mushenheim, Peter C.; Abbott, Nicholas L.

    2014-01-01

    We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4′-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field dir...

  9. Optical trapping in liquid crystals

    Science.gov (United States)

    Simoni, F.; Lucchetti, L.; Criante, L.; Bracalente, F.; Aieta, F.

    2010-08-01

    Optical trapping and manipulation of micrometric silica particles dispersed in a nematic liquid crystal is reported. Several kind of samples are considered: homeotropic and planar undoped cells and homeotropic and planar cells doped by a small amount of the azo-dye Methyl-Red. The incident light intensity is over the threshold for optical reorientation of the molecular director. The refractive index of the dispersed particles is lower than the ones of the liquid crystal therefore the usual conditions for laser trapping and manipulation are not fulfilled. Nevertheless optical trapping is possible and is closely related to the optical nonlinearity of the hosting liquid crystal1. Trapping in doped and undoped cells are compared and it is shown that in the first case intensity lower by more than one order of magnitude is required as compared to the one needed in undoped samples. The effect is faster and the structural forces are of longer range. The formation of bubble-gum like defects in doped samples under certain experimental conditions is also reported and discussed.

  10. Liquid crystals in biotribology synovial joint treatment

    CERN Document Server

    Ermakov, Sergey; Eismont, Oleg; Nikolaev, Vladimir

    2016-01-01

    This book summarizes the theoretical and experimental studies confirming the concept of the liquid-crystalline nature of boundary lubrication in synovial joints. It is shown that cholesteric liquid crystals in the synovial liquid play a significant role in the mechanism of intra-articular friction reduction. The results of structural, rheological and tribological research of the creation of artificial synovial liquids - containing cholesteric liquid crystals in natural synovial liquids - are described. These liquid crystals reproduce the lubrication properties of natural synovia and provide a high chondroprotective efficiency. They were tested in osteoarthritis models and in clinical practice.

  11. Liquid crystal applications and uses, v.3

    CERN Document Server

    Bahadur, Birenda

    1992-01-01

    This book reviews comprehensively the technological, scientific, artistic and medical applications of liquid crystals. It starts with the basics of liquid crystals and covers electro-optical, thermo-optical, colour, polymeric, lyotropic, and scientific applications of liquid crystalline materials. It discusses the fabrication and operational principles of a full range of liquid crystal displays including dynamic scattering, twisted nematic, supertwisted nematic, dichroic, smectic A, ferroelectric, polymer dispersed, light valve, active matrix, etc., in detail. It also covers the emerging appli

  12. Liquid crystal applications and uses, v.2

    CERN Document Server

    Bahadur, Birenda

    1991-01-01

    This book reviews comprehensively the technological, scientific, artistic and medical applications of liquid crystals. It starts with the basics of liquid crystals and covers electro-optical, thermo-optical, colour, polymeric, lyotropic, and scientific applications of liquid crystalline materials. It discusses the fabrication and operational principles of a full range of liquid crystal displays including dynamic scattering, twisted nematic, supertwisted nematic, dichroic, smectic A, ferroelectric, polymer dispersed, light valve, active matrix, etc., in detail. It also covers the emerging appli

  13. Liquid crystal applications and uses, v.1

    CERN Document Server

    Bahadur, Birenda

    1990-01-01

    This book reviews comprehensively the technological, scientific, artistic and medical applications of liquid crystals. It starts with the basics of liquid crystals and covers electro-optical, thermo-optical, colour, polymeric, lyotropic, and scientific applications of liquid crystalline materials. It discusses the fabrication and operational principles of a full range of liquid crystal displays including dynamic scattering, twisted nematic, supertwisted nematic, dichroic, smectic A, ferroelectric, polymer dispersed, light valve, active matrix, , in detail. It also covers the emerging applicati

  14. Liquid crystals of polyelectrolyte networks

    International Nuclear Information System (INIS)

    The Onsager theory of nematic liquid crystals is extended to rigid polyelectrolytes cross-linked by polyvalent ions. Recent synchrotron x-ray diffraction experiments showed that dilute, birefringent networks are formed under these conditions. The application of Onsager theory to this system leads to the prediction of the existence of a range of exotic mesophases such as the 'cubatic,' the 'tetratic,' and the 'trigatic.' The exotic network phases appear on the border of regions of phase coexistence of network phase with isotropic material (at low polyvalent ion concentration) and with dense bundles (at high polyvalent ion concentration)

  15. Charge carrier transport in liquid crystals

    International Nuclear Information System (INIS)

    The materials exhibiting charge carrier mobility ranging from 10−3 to 0.1 cm2/Vs, i.e., between those of amorphous and crystalline materials, had been missing before the 1990s when the electronic conduction in liquid crystals was discovered. Since then, various liquid crystalline materials including discotic and calamitic liquid crystals have been studied in order to clarify their charge carrier transport properties in liquid crystalline mesophases. In this article, the historical background of the discovery of electronic conduction in liquid crystals, intrinsic and extrinsic conductions, unique properties of the charge carrier transport, the effect of molecular alignment on it, and the conduction mechanism in liquid crystalline mesophases are shortly described on the basis of the experimental and theoretical studies accumulated in these two decades, noting that the missing materials were liquid crystals. - Highlights: • Liquid crystals exhibit charge mobility ranging from 10–3 to 0.1 cm2/Vs. • Electronic (intrinsic) and ionic (extrinsic) conductions in liquid crystals • Unique charge carrier transport properties in liquid crystals • Effect of molecular alignment in mesophases on charge carrier transport • Conduction mechanism in smectic liquid crystals

  16. Biased liquid crystal photonic bandgap fiber

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Alkeskjold, Thomas Tanggaard;

    2008-01-01

    We simulate the director structure of all capillaries in a biased photonic crystal fiber infiltrated with liquid crystals. Various mode simulations for different capillaries show the necessity to consider the entire structure.......We simulate the director structure of all capillaries in a biased photonic crystal fiber infiltrated with liquid crystals. Various mode simulations for different capillaries show the necessity to consider the entire structure....

  17. Nanoscopic Manipulation and Imaging of Liquid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Rosenblatt, Charles S. [Case Western Reserve Univ., Cleveland, OH (United States)

    2014-02-04

    This is the final project report. The project’s goals centered on nanoscopic imaging and control of liquid crystals and surfaces. We developed and refined techniques to control liquid crystal orientation at surfaces with resolution as small as 25 nm, we developed an optical imaging technique that we call Optical Nanotomography that allows us to obtain images inside liquid crystal films with resolution of 60 x 60 x 1 nm, and we opened new thrust areas related to chirality and to liquid crystal/colloid composites.

  18. Thermal Inspection of GFRP using Liquid Crystal

    International Nuclear Information System (INIS)

    Flaws in GFRP(Glass Fiber Reinforced Plastics) were thermally detected using cholesteric liquid crystals. Presence of flaws changes the thermal conductivity of GFRP, and disturbs heat flow. When a uniform heat source is applied, the surface temperature of flawed region is different from that of sound region. The surface temperature distributions were measured by thermo-optic properties of liquid crystal. Since the colors of liquid crystal indicate temperature distribution of GFRP surface, the thermal disturbance by flaws could be detected. The locations of flaws in GFRP could be determined from the distribution of liquid crystal colors

  19. Biased liquid crystal infiltrated photonic bandgap fiber

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Scolari, Lara;

    2009-01-01

    A simulation scheme for the transmission spectrum of a photonic crystal fiber infiltrated with a nematic liquid crystal and subject to an external bias is presented. The alignment of the biased liquid crystal is simulated using the finite element method to solve the relevant system of coupled...... partial differential equations. From the liquid crystal alignment the full tensorial dielectric permittivity in the capillaries is derived. The transmission spectrum for the photonic crystal fiber is obtained by solving the generalized eigenvalue problem deriving from Maxwell’s equations using a vector...... element based finite element method. We demonstrate results for a splay aligned liquid crystal infiltrated into the capillaries of a four-ring photonic crystal fiber and compare them to corresponding experiments....

  20. Biaxiality of chiral liquid crystals

    International Nuclear Information System (INIS)

    Using extended deGennes-Ginzburg-Landau free energy expansion in terms of the anisotropic part of the dielectric tensor field Qαβ(χ) a connection between the phase biaxiality and the stability of various chiral liquid crystalline phases is studied. In particular the cholesteric phase, the cubic Blue Phases and the phases characterized by an icosahedral space group symmetry are analysed in detail. Also a general question concerning the applicability of the mean-field approximation in describing the chiral phases is addressed. By an extensive study of the model over a wide range of the parameters a new class of phenomena, not present in the original deGennes-Ginzburg-Landau model, has been found. These include: a) re-entrant phase transitions between the cholesteric and the cubic blue phases and b) the existence of distinct phases of the same symmetry but of different biaxialities. The phase biaxiality serves here as an extra scalar order parameter. Furthermore, it has been shown that due to the presence of the competing bulk terms in the free energy, the stable phases may acquire a large degree of biaxiality, also in liquid crystalline materials composed of effectively uniaxial molecules. A study of icosahedral space group symmetries gives a partial answer to the question as to whether an icosahedral quasicrystalline liquid could be stabilized in liquid crystals. Although, in general, the stability of icosahedral structures could be enhanced by the extra terms in the free energy no absolutely stable icosahedral phase has been found. (author). 16 refs, 3 figs, 1 tab

  1. Nanoemulsions versus lyotropic liquid crystals

    Directory of Open Access Journals (Sweden)

    Hema Chaudhary

    2014-01-01

    Full Text Available Nanoemulsions have gained great accolade in pharmaceutical and food industries, because of integer features, such as optical clarity, ease of preparation, thermodynamic stability, and increased surface area. They are isotropic, non-equilibrium, kinetically stable system of oil, defined blend of surfactant and co-surfactant and water, which serve as vehicles for the delivery of active pharmaceutical ingredients as well as other bio-actives. Both high and low-energy methods have already been exploited to design this system. This review clarify the recurrent confusions found in the literature regarding the difference between nanoemulsions and lyotropic liquid crystals, components, method of preparation, evaluation parameters, and stability issues, which have been described and also the significance of pseudo-ternary phase diagram has been addressed.

  2. Optical Response of a Liquid Crystal modulator

    International Nuclear Information System (INIS)

    The progress in liquid crystal device technology has led to the development of different electro-optical displays from simple digital watchs to high information content computer screens. In these electro-optical systems modulation of light by means of a liquid crystal device is very important subject both from the point of fundamental physics and for possible technological applications. In this study we describe a liquid crystal modulator which consists of a thin film of liquid crystal contained between parallel conductive glass plates. The surfaces of the plates are treated so that the liquid crystal molecules are parallel to the surfaces but twists about an axis normal to the surfaces by an angle of 90 degree from one substrate to the other. In a liquid crystal modulator the dielectric and optical anisotropies are used to modulate a laser beam passing through the film. If an electric field is applied across the film the molecules realign parallel to the electric field to form the homeotropic structure which has no optical modulation effect. Thus, the electric field-dependent transmission of the liquid crystal modulator is characterized. We also analyze the response behavior of the liquid crystal modulator

  3. Demonstrations with a Liquid Crystal Shutter

    Science.gov (United States)

    Kraftmakher, Yaakov

    2012-01-01

    The experiments presented show the response of a liquid crystal shutter to applied electric voltages and the delay of the operations. Both properties are important for liquid crystal displays of computers and television sets. Two characteristics of the shutter are determined: (i) the optical transmittance versus applied voltage of various…

  4. Liquid Crystals In Education – The Basics

    OpenAIRE

    Cepic, Mojca

    2012-01-01

    The introduction of teaching about liquid crystals is discussed from several points of view: the rationale why to teach them, the basics about liquid crystals or what the teacher should teach about them, the fundamental pre-knowledge of students required, the set of experiments accompanying the teaching and the brief report on the already performed testing of the teaching module.

  5. Liquid Crystal Cells Based on Photovoltaic Substrates

    Science.gov (United States)

    Lucchetti, L.; Kushnir, K.; Zaltron, A.; Simoni, F.

    2016-02-01

    Liquid crystal cells with LiNbO3:Fe crystals as substrates, are described. The photovoltaic field generated by the substrates is able to reorient the liquid crystal director thus giving rise to a phase shift on the light propagating through the cell, as in liquid crystal light valves. The process does not require the application of an external electric field, thus being potentially useful for applications requiring a high degree of compactness. An efficient optical switch with a high transmission contrast, based on the described optically-induced electric field, is also proposed.

  6. Liquid crystal device and method thereof

    Science.gov (United States)

    Shiyanovskii, Sergij V; Gu, Mingxia; Lavrentovich, Oleg D

    2012-10-23

    The invention provides a liquid crystal device and method thereof. Subsequent to applying a first electrical voltage on a liquid crystal to induce a reorientation of the liquid crystal, a second electrical voltage with proper polarity is applied on the liquid crystal to assist the relaxation of the reorientation that was induced by the first electrical voltage. The "switch-off" phase of the liquid crystal can therefore be accelerated or temporally shortened, and the device can exhibit better performance such as fast response to on/off signals. The invention can be widely used LCD, LC shutter, LC lens, spatial light modulator, telecommunication device, tunable filter, beam steering device, and electrically driven LC device, among others.

  7. Computer simulation of liquid crystals

    International Nuclear Information System (INIS)

    In this thesis computer simulations of liquid crystal systems were performed focusing on the isotropic-nematic interface and on the effects of confinement. A range of idealised and atomistic models were employed using both Monte-Carlo and Molecular Dynamics techniques. The structure of the planar isotropic - nematic (I-N) interface was investigated using constant volume Monte-Carlo simulation of systems of hard-ellipsoids confined between parallel hard walls. The nematic phase is observed to wet the hard walls, establishing two planar I-N interfaces per simulation box. The microscopic pressure tensor in the vicinity of the interface was calculated for both planar and normal alignment of the nematic. The surface tension, calculated directly from the pressure tensor, is lowest in the case of planar alignment indicating that this is the preferred alignment at the interface. The form of the transverse pressure across the interface is dramatically different for the two orientations. For the case of planar alignment we observe a large tension (low transverse pressure) on the nematic side and a small compressive region (high transverse pressure) on the isotropic side. For the case of normal alignment we see a large compression on the nematic side followed by tension on the isotropic side. Comparisons are made with the results of Onsager theory, showing excellent agreement. Gay-Berne particles confined to very thin films are investigated using constant pressure Monte-Carlo simulation. Orientational wetting is again observed at the liquid-wall interface. For homeotropic alignment at the wall we observe strong layering of particles into planes parallel to the walls and long-range orientational order which persists well beyond the range of the fluid-wall interaction. The average system order parameter is strongly dependent on the film thickness, the order being highest when the film thickness is commensurate with the formation of an integral number of molecular layers. An

  8. Temperature sensing with thermochromic liquid crystals

    Science.gov (United States)

    Smith, C. R.; Sabatino, D. R.; Praisner, T. J.

    A review of the most recent developments in the application of thermochromic liquid crystals to fluid flow temperature measurement is presented. The experimental aspects including application, illumination, recording, and calibration of liquid crystals on solid surfaces, as well as in fluid suspensions, are discussed. Because of the anisotropic optical properties of liquid crystals, on-axis lighting/viewing arrangements, combined with in-situ calibration techniques, generally provide the most accurate temperature assessments. However, where on-axis viewing is not possible, calibration techniques can be employed, which reduce the uncertainty associated with off-axis viewing and lighting arrangements. It has been determined that the use of hue definitions that display a linear trend across the color spectrum yield the most accurate correlation with temperature. The uncertainty of both wide-band and narrow-band thermochromic liquid crystal calibration techniques can be increased due to hysteresis effects, which occur when the temperature of the liquid crystals exceeds their maximum activation temperature. Although liquid crystals are commonly used to provide time-mean temperature measurements, techniques are available which allow the monitoring of temporal changes. Selected examples illustrating the use of thermochromic liquid crystals are shown, and a survey of reported temperature measurement uncertainties is presented.

  9. Temperature sensing with thermochromic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Smith, C.R.; Sabatino, D.R.; Praisner, T.J. [Lehigh Univ., Bethlehem, PA (United States)

    2001-02-01

    A review of the most recent developments in the application of thermochromic liquid crystals to fluid flow temperature measurement is presented. The experimental aspects including application, illumination, recording, and calibration of liquid crystals on solid surfaces, as well as in fluid suspensions, are discussed. Because of the anisotropic optical properties of liquid crystals, on-axis lighting/viewing arrangements, combined with in-situ calibration techniques, generally provide the most accurate temperature assessments. However, where on-axis viewing is not possible, calibration techniques can be employed, which reduce the uncertainty associated with off-axis viewing and lighting arrangements. It has been determined that the use of hue definitions that display a linear trend across the color spectrum yield the most accurate correlation with temperature. The uncertainty of both wide-band and narrow-band thermochromic liquid crystal calibration techniques can be increased due to hysteresis effects, which occur when the temperature of the liquid crystals exceeds their maximum activation temperature. Although liquid crystals are commonly used to provide time-mean temperature measurements, techniques are available which allow the monitoring of temporal changes. Selected examples illustrating the use of thermochromic liquid crystals are shown, and a survey of reported temperature measurement uncertainties is presented. (orig.)

  10. Lipid decorated liquid crystal pressure sensors

    Science.gov (United States)

    Lopatkina, Tetiana; Popov, Piotr; Honaker, Lawrence; Jakli, Antal; Mann, Elizabeth; Mann's group Collaboration; Jakli's group Collaboration

    Surfactants usually promote the alignment of liquid crystal (LC) director parallel to the surfactant chains, and thus on average normal to the substrate (homeotropic), whereas water promotes tangential (planar) alignment. A water-LC interface is therefore very sensitive to the presence of surfactants, such as lipids: this is the principle of LC-based chemical and biological sensing introduced by Abbott et al.Using a modified configuration, we found that at higher than 10 micro molar lipid concentration, the uniformly dark texture seen for homeotropic alignment between left-, and right-handed circular polarizers becomes unstable and slowly brightens again. This texture shows extreme sensitivity to external air pressure variations offering its use for sensitive pressure sensors. Our analysis indicates an osmotic pressure induced bending of the suspended films explaining both the birefringence and pressure sensitivity. In the talk we will discuss the experimental details of these effects. This work was financially supported by NSF DMR No. DMR-0907055.

  11. Two distinct crystallization processes in supercooled liquid

    Science.gov (United States)

    Tane, Masakazu; Kimizuka, Hajime; Ichitsubo, Tetsu

    2016-05-01

    Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquid does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport.

  12. STATIC AND DYNAMIC THEORIES OF LIQUID CRYSTALS

    Institute of Scientific and Technical Information of China (English)

    林芳华; 刘春

    2001-01-01

    The study of liquid crystals givesrise to many fascinating but difficult mathematical problems. The purpose of this paper is to briefly summarize some recent advances, as well as to describe the present state of art of the theory of liquid crystals.For the static theory, we emphasis on the theory of defects and the theory of Smectic A materials. We will also study the Ericksen-Leslie theory for the liquid crystal flow.The well-posedness as well as the motion of the defects will be discussed.

  13. Instability of liquid crystal elastomers

    Science.gov (United States)

    An, Ning; Li, Meie; Zhou, Jinxiong

    2016-01-01

    Nematic liquid crystal elastomers (LCEs) contract in the director direction but expand in other directions, perpendicular to the director, when heated. If the expansion of an LCE is constrained, compressive stress builds up in the LCE, and it wrinkles or buckles to release the stored elastic energy. Although the instability of soft materials is ubiquitous, the mechanism and programmable modulation of LCE instability has not yet been fully explored. We describe a finite element method (FEM) scheme to model the inhomogeneous deformation and instability of LCEs. A constrained LCE beam working as a valve for microfluidic flow, and a piece of LCE laminated with a nanoscale poly(styrene) (PS) film are analyzed in detail. The former uses the buckling of the LCE beam to occlude the microfluidic channel, while the latter utilizes wrinkling or buckling to measure the mechanical properties of hard film or to realize self-folding. Through rigorous instability analysis, we predict the critical conditions for the onset of instability, the wavelength and amplitude evolution of instability, and the instability patterns. The FEM results are found to correlate well with analytical results and reported experiments. These efforts shed light on the understanding and exploitation of the instabilities of LCEs.

  14. Hierarchical organization in liquid crystal-in-liquid crystal emulsions.

    Science.gov (United States)

    Mushenheim, Peter C; Abbott, Nicholas L

    2014-11-21

    We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4'-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field director of the DSCG phase. We determine that this coupling of orientations does not result from either anisometric LC droplet shape or interfacial ionic phenomena but rather is consistent with the influence of van der Waals interactions that arise from the anisotropic polarizabilities of nematic 5CB (Δn = +0.18) and DSCG (Δn = -0.02) phases. We also find that it is possible to rotate and uniformly align the nematic droplets by using a weak magnetic field (B ∼ 0.3 T). An analysis of the dynamics of relaxation of the orientations of the 5CB droplets following removal of the magnetic field reveals the DSCG and 5CB droplets to be coupled by energies of ∼10(4) kT, consistent with a simple theoretical estimate of the influence of anisotropic van der Waals interactions. We also observed the nematic 5CB droplets to form dimers and larger assemblies mediated by the elasticity of the nematic DSCG. Overall, these results reveal that LC-in-LC emulsions define a new class of hierarchically ordered soft matter in which both thermotropic and lyotropic LCs are coupled in their ordering. PMID:25278032

  15. Polymer single crystal membrane from liquid/liquid interface

    Science.gov (United States)

    Wang, Wenda; Li, Christopher; Soft Matter Research Group-Drexel University Team

    2013-03-01

    Vesicles, mimicking the structure of cell membrane at the molecular scale, are small membrane-enclosed sacks that can store or transport substances. The weak mechanical properties and the nature of environment-sensitivity of the current available vesicles: liposomes, polymersomes, colloidsomes limit their applications as an excellent candidate for targeting delivery of drugs/genes in biomedical engineering and treatment. Recently, we developed an emulsion-based method to grow curved polymer single crystals. Varying the polymer concentration and/or the emulsification conditions (such as surfactant concentration, water-oil volume ratio), curved crystals with different sizes and different openness could be obtained. This growing process was attributed to polymer crystal growth along the liquid/liquid interface. In addition, the liquid/liquid interfacial crystal growth is promising for synthesis of enclosed hollow sphere.

  16. Liquid Crystal Quantitative Temperature Measurement Technique

    Institute of Scientific and Technical Information of China (English)

    Wei Lu; Zongshan Wu

    2001-01-01

    Quantitatve temperature measurement using wide band thermochromic liquid crystals is an "area" thermal measurement technique. This technique utilizes the feature that liquid crystal changes its reflex light color with variation of temperature and applies an image capturing and processing system to calibrate the characteristic curve of liquid crystal's color-temperature. Afterwards, the technique uses this curve to measure the distribution of temperature on experimental model. In this paper, firstly, each part of quantitative temperature measurement system using liquid crystal is illustrated and discussed. Then the technique is employed in a long duration hypersonic wind tunnel, and the quantitative result of the heat transfer coefficient along laminar plate is obtained.Additionally, some qualitative results are also given. In the end, comparing the experimental results with reference enthalpy theoretical results, a conclusion of thermal measurement accuracy is drawn.

  17. Multidimensional optics and dynamics of liquid crystals

    Science.gov (United States)

    Tang, Shouping

    2007-12-01

    In this dissertation, we present an alternative description of multidimensional optics in liquid crystals and uniaxial media, and a systematical investigation on the dynamic properties of twist nematic devices and ECB devices including flow. We also present our investigation on the backflow and dynamic properties of nematic liquid crystals in modulated electric fields. Based on the understanding to backflow and dynamics of liquid crystals, the dynamics of colloidal particles dispersed in nematic liquid crystals and the flow-induced dynamic optical crosstalk between pixels in nematic liquid crystal devices are also studied. The alternative description of multidimensional optics combines the geometrical optics approximation (GOA) with the beam propagation method (BPM). The general treatment of this approach is developed both theoretically and numerically. The investigation on the dynamic properties of twist nematic devices and ECB devices with consideration of backflow is done experimentally, theoretically and numerically. The calculation results are compared with the experimental results, and the optical responses due to backflow are discussed in detail. The investigation on the backflow and dynamic properties of a nematic liquid crystal in modulated electric fields includes director, flow and the shift of liquid crystal fluid. Especially, an important phenomenon, reverseswitching, is shown in this investigation. The dynamics of colloidal particles dispersed in a nematic cela is studied experimentally and by computer simulation. The polarity of director distortions determines the direction of lift force, and the backflow is responsible for the horizontal translational motion. The optical crosstalk between pixels demonstrates the significance of switching-induce flow in pixilated devices. The electrical switching of a pixel in a twisted nematic device can induce an optical response in neighboring pixels. These phenomena are studied in detail, both experimentally and

  18. Topological Defects in Liquid Crystal Films

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi-Shi; ZHAO Li; ZHANG Xin-Hui; SI Tie-Yan

    2007-01-01

    A topological theory of liquid crystal films in the presence of defects is developed based on the φ-mapping topological current theory. By generalizing the free-energy density in "one-constant" approximation, a covariant freeenergy density is obtained, from which the U(1) gauge field and the unified topological current for monopoles and strings in liquid crystals are derived. The inner topological structure of these topological defects is characterized by the winding numbers of φ-mapping.

  19. Liquid crystal boojum-colloids

    International Nuclear Information System (INIS)

    Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

  20. Molecular Models of Liquid Crystal Elastomers

    Science.gov (United States)

    Rajshekhar

    Liquid crystal elastomers combine the elastic properties of conventional rubbers with the optical properties of liquid crystals. This dual nature gives rise to unusual physical properties, including the stress induced transition from a polydomain state, consisting of multiple nematic regions with independent orientations, to a monodomain state consisting of a single nematic region with a uniform director. We propose several molecular-scale coarse-grained models of liquid crystal elastomers with varying degrees of resolution. The models employ the Gay-Berne soft potential, and exhibit the chain connectivity of a diamond network. Simulation results show that these models are able to capture the polydomain state exhibited by liquid crystal elastomers in the absence of any external stress. When subjected to uniaxial stress, our models exhibit a polydomain to monodomain transition. We explain that the polydomain state occurs through the aggregation of liquid crystal molecules assisted by crosslinking sites, and conclude that the transition mechanism to the monodomain state is based on the reorientation of nematic domains along the direction of applied stress. Our modeling efforts are primarily focused on three models. The first two models consider the effects of rigid and flexible crosslinkers in liquid crystal elastomers with a diamond topology for chain connectivity. The third model deviates from the diamond network topology and adopts a random network topology.

  1. Tetratic, triatic and nematic liquid crystals on a complex plane

    Science.gov (United States)

    Manyuhina, Oksana; Bowick, Mark

    Liquid crystals are elastic materials able to resolve geometric and topological frustration by creating disclinations, discontinuities in their continuous orientation field. The strength and the nature of disclinations depend on the symmetry of elements forming liquid crystal phase. Several examples of confined nematic (director field), triatic (Y-field) and tetratic (cross-field) liquid crystals will be considered to show that their ground state contains topological defects. Next, we analyze shape variation of the boundary, enclosing different defect textures. We argue that topological defects can capture essential features of macroscopic shape and relate it to microscopic order, providing a natural way to connect different length scales and to account for large deformations in soft and biological systems. Soft Matter Program of Syracuse University.

  2. 21 CFR 880.6970 - Liquid crystal vein locator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  3. Electro-osmosis in nematic liquid crystals

    Science.gov (United States)

    Tovkach, O. M.; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J.

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.

  4. Liquid crystal quantitative temperature measurement technique

    Science.gov (United States)

    Lu, Wei; Wu, Zongshan

    2001-10-01

    Quantitative temperature measurement using wide band thermochromic liquid crystals is an “area” thermal measurement technique. This technique utilizes the feature that liquid crystal changes its reflex light color with variation of temperature and applies an image capturing and processing system to calibrate the characteristic curve of liquid crystal’s color-temperature. Afterwards, the technique uses this curve to measure the distribution of temperature on experimental model. In this paper, firstly, each part of quantitative temperature measurement system using liquid crystal is illustrated and discussed. Then the technique is employed in a long duration hypersonic wind tunnel, and the quantitative result of the heat transfer coefficient along laminar plate is obtained. Additionally, some qualitative results are also given. In the end, comparing the experimental results with reference enthalpy theoretical results, a conclusion of thermal measurement accuracy is drawn.

  5. Key Developments in Ionic Liquid Crystals

    Science.gov (United States)

    Alvarez Fernandez, Alexandra; Kouwer, Paul H. J.

    2016-01-01

    Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material? PMID:27196890

  6. Effect of the Surface Affinity of Liquid Crystals and Monomers on the Orientation of Polymer-Dispersed Liquid Crystal

    Science.gov (United States)

    Lee, Ji-Hoon; Yoon, Tae-Hoon

    2013-09-01

    We investigated the effect of the surface affinity of liquid crystals and reactive monomers on liquid crystal orientation. Liquid crystals and monomers having different contact angles with the vertical alignment polyimide were mixed and photo-polymerized using a UV light. Liquid crystals with smaller contact angles and reactive monomers with greater contact angles promoted a uniform vertical orientation of liquid crystals with a vertical polymer morphology. On the other hand, liquid crystals with greater contact angles and monomers with smaller contact angles resulted in a deformed liquid crystal orientation with an elliptical polymer structure.

  7. An Overview of Biological Macromolecule Crystallization

    Directory of Open Access Journals (Sweden)

    Irene Russo Krauss

    2013-05-01

    Full Text Available The elucidation of the three dimensional structure of biological macromolecules has provided an important contribution to our current understanding of many basic mechanisms involved in life processes. This enormous impact largely results from the ability of X-ray crystallography to provide accurate structural details at atomic resolution that are a prerequisite for a deeper insight on the way in which bio-macromolecules interact with each other to build up supramolecular nano-machines capable of performing specialized biological functions. With the advent of high-energy synchrotron sources and the development of sophisticated software to solve X-ray and neutron crystal structures of large molecules, the crystallization step has become even more the bottleneck of a successful structure determination. This review introduces the general aspects of protein crystallization, summarizes conventional and innovative crystallization methods and focuses on the new strategies utilized to improve the success rate of experiments and increase crystal diffraction quality.

  8. Polymer dispersed ferroelectric liquid crystal devices

    International Nuclear Information System (INIS)

    Recently polymer dispersed ferroelectric liquid crystal (PDFLC) materials have become a field of great interest because of their potential for practical device applications. The PDFLCs are possible alternatives for fast-switching displays which are more stable and flexible than surface-stabilized ferroelectric liquid crystal devices. The PDFLC composites consist of micron-sized droplets of ferroelectric symmetric-C* liquid crystal dispersed throughout a polymer matrix. If appropriately aligned, the PDFLC cells can be switched between a translucent state and a transparent state by application of an electric field. The electro-optical switching is achieved by a voltage dependent optical retardation when the cell is placed between crossed polarizers. In this study we investigated the electro-optical behavior of novel ferroelectric liquid crystal droplets embedded in a photo curable polymer. The PDFLC cells were obtained by photo polymerization-induced phase separation (PIPS) process. Alignment of the cells was obtained by a shear force using a stepper-motor driven translation stage during the photo polymerization. An Argon ion laser was used to induce the phase separation. In the cells the surface interaction forces unwound the helical structure of the ferroelectric liquid crystal inside the micro droplets, thus switching occurred between two stable states on coupling to the spontaneous polarization

  9. Charge transfer reactions in nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wiederrecht, G.P. [Argonne National Lab., IL (United States). Chemistry Div.; Wasielewski, M.R. [Argonne National Lab., IL (United States). Chemistry Div.]|[Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; Galili, T.; Levanon, H. [Hebrew Univ. of Jerusalem (Israel). Dept. of Physical Chemistry

    1998-07-01

    Ultrafast transient absorption studies of intramolecular photoinduced charge separation and thermal charge recombination were carried out on a molecule consisting of a 4-(N-pyrrolidino)naphthalene-1,8-imide donor (PNI) covalently attached to a pyromellitimide acceptor (PI) dissolved in the liquid crystal 4{prime}-(n-pentyl)-4-cyanobiphenyl (5CB). The temperature dependencies of the charge separation and recombination rates were obtained at temperatures above the nematic-isotropic phase transition of 5CB, where ordered microdomains exist and scattering of visible light by these domains is absent. The authors show that excited state charge separation is dominated by molecular reorientation of 5CB perpendicular to the director within the liquid crystal microdomains. They also show that charge recombination is adiabatic and is controlled by the comparatively slow collective reorientation of the liquid crystal microdomains relative to the orientation of PNI{sup +}-PI{sup {minus}}. They also report the results of time resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of supramolecular compounds dissolved in oriented liquid crystal solvents. These studies permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal.

  10. Biological treatment of thin-film transistor liquid crystal display (TFT-LCD) wastewater using aerobic and anoxic/oxic sequencing batch reactors.

    Science.gov (United States)

    Lei, Chin-Nan; Whang, Liang-Ming; Chen, Po-Chun

    2010-09-01

    The amount of pollutants produced during manufacturing processes of thin-film transistor liquid crystal display (TFT-LCD) substantially increases due to an increasing production of the opto-electronic industry in Taiwan. This study presents the treatment performance of one aerobic and one anoxic/oxic (A/O) sequencing batch reactors (SBRs) treating synthetic TFT-LCD wastewater containing dimethyl sulfoxide (DMSO), monoethanolamine (MEA), and tetra-methyl ammonium hydroxide (TMAH). The long-term monitoring results for the aerobic and A/O SBRs demonstrate that stable biodegradation of DMSO, MEA, and TMAH can be achieved without any considerably adverse impacts. The ammonium released during MEA and TMAH degradation can also be completely oxidized to nitrate through nitrification in both SBRs. Batch studies on biodegradation rates for DMSO, MEA, and TMAH under anaerobic, anoxic, and aerobic conditions indicate that effective MEA degradation can be easily achieved under all three conditions examined, while efficient DMSO and TMAH degradation can be attained only under anaerobic and aerobic conditions, respectively. The potential odor problem caused by the formation of malodorous dimethyl sulfide from DMSO degradation under anaerobic conditions, however, requires insightful consideration in treating DMSO-containing wastewater. PMID:20705321

  11. Viscoelastic modes in chiral liquid crystals

    Indian Academy of Sciences (India)

    K A Suresh

    2003-08-01

    Viscoelastic properties of liquid crystals are very important for applications like display technology. However, there are not many direct techniques to study them. In this review, we describe our studies on the viscoelastic modes of some chiral liquid crystals using dynamic light scattering. We discuss viscoelastic modes corresponding to the C director fluctuations in the chiral smectic C phase and the behaviour of the Goldstone-mode near the chiral smectic C–smectic A phase transition. In cholesteric liquid crystals, we consider the director fluctuations in a wavevector range comparable to the inverse pitch of the cholesteric. Here, the study of the scattered light in the vicinity of the Bragg reflection using a novel geometry will be presented.

  12. Diastereomeric liquid crystal domains at the mesoscale

    Science.gov (United States)

    Chen, Dong; Tuchband, Michael R.; Horanyi, Balazs; Korblova, Eva; Walba, David M.; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.

    2015-08-01

    In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

  13. Photonics and lasing in liquid crystals

    Directory of Open Access Journals (Sweden)

    Alison D. Ford

    2006-07-01

    Full Text Available Lasers were invented some 40 years ago and are now used in a plethora of applications. Stable liquid crystals were discovered at about the same time, and are now the basis of a large display industry. Both technologies involve photonics, the former in the creation and use of light and the latter in the control and manipulation of light. However, it is only recently that these two mature technologies have been combined to form liquid-crystal lasers, heralding a new era for these photonic materials and the potential for novel applications. We summarize the characteristics of liquid crystals that lead to laser devices, the wide diversity of possible laser systems, and the properties of the light produced.

  14. Ultrabroadband terahertz spectroscopy of a liquid crystal

    DEFF Research Database (Denmark)

    Vieweg, N.; Fischer, B. M.; Reuter, M.;

    2012-01-01

    present the frequency dependent index of refraction and the absorption coefficients of the nematic liquid crystal 5CB over a frequency range from 0.3 THz to 15 THz using a dispersion-free THz time-domain spectrometer system based on two-color plasma generation and air biased coherent detection (ABCD). We......Liquid crystals (LCs) are becoming increasingly important for applications in the terahertz frequency range. A detailed understanding of the spectroscopic parameters of these materials over a broad frequency range is crucial in order to design customized LC mixtures for improved performance. We...

  15. Liquid crystals for holographic optical data storage

    DEFF Research Database (Denmark)

    Matharu, Avtar; Jeeva, S.; Ramanujam, P.S.

    2007-01-01

    A tutorial review is presented to inform and inspire the reader to develop and integrate strong scientific links between liquid crystals and holographic data storage, from a materials scientist's viewpoint. The principle of holographic data storage as a means of providing a solution to the inform......A tutorial review is presented to inform and inspire the reader to develop and integrate strong scientific links between liquid crystals and holographic data storage, from a materials scientist's viewpoint. The principle of holographic data storage as a means of providing a solution......, is discussed. Polymeric liquid crystals play an important role in the development of materials for holographic storage and photoresponsive materials based on azobenzene are targeted for discussion due to their ease of photo- reversion between trans- and cis- states. Although the final polymer may not be liquid...... causing cis - trans-isomerisation can be used to control helix pitch. A brief mention of liquid crystals is also made since these materials may be of future interest since they are optically transparent and amenable to photo- induced anisotropy....

  16. Optical solitons in liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yung, Y.S.; Lam, L. (National Semiconductor Corp., Santa Clara, CA (USA); Los Alamos National Lab., NM (USA))

    1989-01-01

    In this paper, we will discuss theoretically the possible existence of optical solitons in the isotropic liquid and in the nematic phase. For the same compound, when heated, the nematic phase will go through a first order transition at temperature T{sub c} to the isotropic liquid phase. As temperature increases from below T{sub c}, the orientation order parameter, Q, decreases, drops to zero abruptly at T{sub c} and remains zero for T > T{sub c}. 10 refs., 1 fig.

  17. Tunable Photonic Band Gaps In Photonic Crystal Fibers Filled With a Cholesteric Liquid Crystal

    Institute of Scientific and Technical Information of China (English)

    Thomas; Tanggaard; Larsen; David; Sparre; Hermann; Anders; Bjarklev

    2003-01-01

    A photonic crystal fiber has been filled with a cholesteric liquid crystal. A temperature sensitive photonic band gap effect was observed, which was especially pronounced around the liquid crystal phase transition temperature.

  18. Angular velocity response of nanoparticles dispersed in liquid crystal

    Science.gov (United States)

    Huang, Pin-Chun; Shih, Wen-Pin

    2013-06-01

    A hybrid material of nanoparticles dispersed in liquid crystal changed capacitance after spinning beyond threshold angular velocity. Once the centrifugal force of nanoparticles overcomes the attractive force between liquid crystals, the nanoparticles begin to move. The order of highly viscous liquid crystals is disturbed by the nanoparticles' penetrative movement, and the dielectric constant of the liquid crystal cell changes as a result. We found that the angular velocity response of nanoparticles dispersed in liquid crystal with higher working temperature and nanoparticles' density provided higher sensitivity. The obtained results are important for the continuous improvement of liquid-crystal-based inertial sensors or nano-viscometers.

  19. A theory of the nematic liquid crystals

    International Nuclear Information System (INIS)

    A theory of the nematic phase of liquid crystals is presented, taking explicit account of the geometry of the molecule. The three broad peaks of the neutron scattering structure factor are explained. Expressions of the order parameters (average value of Psub(2L)) are given and they can be extracted by comparison with scattering experiments. (author)

  20. Randomized Grain Boundary Liquid Crystal Phase

    Science.gov (United States)

    Chen, D.; Wang, H.; Li, M.; Glaser, M.; Maclennan, J.; Clark, N.

    2012-02-01

    The formation of macroscopic, chiral domains, in the B4 and dark conglomerate phases, for example, is a feature of bent-core liquid crystals resulting from the interplay of chirality, molecular bend and molecular tilt. We report a new, chiral phase observed in a hockey stick-like liquid crystal molecule. This phase appears below a smectic A phase and cools to a crystal phase. TEM images of the free surface of the chiral phase show hundreds of randomly oriented smectic blocks several hundred nanometers in size, similar to those seen in the twist grain boundary (TGB) phase. However, in contrast to the TGB phase, these blocks are randomly oriented. The characteristic defects in this phase are revealed by freeze-fracture TEM images. We will show how these defects mediate the randomized orientation and discuss the intrinsic mechanism driving the formation of this phase. This work is supported by NSF MRSEC Grant DMR0820579 and NSF Grant DMR0606528.

  1. Cholesteric liquid crystals as multi-purpose sensor materials

    Energy Technology Data Exchange (ETDEWEB)

    Lisetski, L. N. [National Academy of Sciences of Ukraine, Kharkov (Ukraine)

    2005-03-15

    New possibilities are discussed for Cholesteric Liquid Crystals (CLC) as sensor materials for detection of ionizing radiation, biologically active UV radiation, and the presence of hazardous vapors in atmosphere. A distinguishing property of CLC-based detectors is their 'bioequivalence', i.e., mechanisms of their response to external factors essentially imitate the corresponding mechanisms of biological tissues. Such detectors can ensure sufficiently high sensitivity to make feasible their use as alarm indicators or in biophysical studies. Specific examples are given of sensor compositions and their response characteristics.

  2. Cholesteric liquid crystals as multi-purpose sensor materials

    International Nuclear Information System (INIS)

    New possibilities are discussed for Cholesteric Liquid Crystals (CLC) as sensor materials for detection of ionizing radiation, biologically active UV radiation, and the presence of hazardous vapors in atmosphere. A distinguishing property of CLC-based detectors is their 'bioequivalence', i.e., mechanisms of their response to external factors essentially imitate the corresponding mechanisms of biological tissues. Such detectors can ensure sufficiently high sensitivity to make feasible their use as alarm indicators or in biophysical studies. Specific examples are given of sensor compositions and their response characteristics

  3. James Fergason, a Pioneer in Advancing of Liquid Crystal Technology

    OpenAIRE

    Sparavigna, Amelia Carolina

    2013-01-01

    James Lee Fergason (1934 - 2008) focused his research on the liquid crystals. His studies correspond to a relevant part of the history of soft matter science and technology of liquid crystals. Here a discussion of some of his researches.

  4. Liquid crystals: a new topic in physics for undergraduates

    OpenAIRE

    Pavlin, Jerneja; Vaupotič, Nataša; Čepič, Mojca

    2012-01-01

    The paper presents a teaching module about liquid crystals. Since liquid crystals are linked to everyday student experiences and are also a topic of a current scientific research, they are an excellent candidate of a modern topic to be introduced into education. We show that liquid crystals can provide a file rouge through several fields of physics such as thermodynamics, optics and electromagnetism. We discuss what students should learn about liquid crystals and what physical concepts they s...

  5. Application of liquid crystals in thermal nondestructive evaluation

    International Nuclear Information System (INIS)

    In recent years, thermal nondestructive evaluation using Cholestric liquid crystals have found wide applications in industry. Thermography using Cholesteric liquid crystals can be used for detection of nonbonds in metallic composites, hot spots in electronic circuits and preliminary examination of welded pressure vessels. This paper presents the results of experiments on thermography of components using encapsulated liquid crystals. (author)

  6. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  7. Liquid crystals for holographic optical data storage.

    Science.gov (United States)

    Matharu, Avtar S; Jeeva, Shehzad; Ramanujam, P S

    2007-12-01

    A tutorial review is presented to inform and inspire the reader to develop and integrate strong scientific links between liquid crystals and holographic data storage, from a materials scientist's viewpoint. The principle of holographic data storage as a means of providing a solution to the information storage demands of the 21st century is detailed. Holography is a small subset of the much larger field of optical data storage and similarly, the diversity of materials used for optical data storage is enormous. The theory of polarisation holography which produces holograms of constant intensity, is discussed. Polymeric liquid crystals play an important role in the development of materials for holographic storage and photoresponsive materials based on azobenzene are targeted for discussion due to their ease of photo-reversion between trans- and cis-states. Although the final polymer may not be liquid crystalline, irradiation can induce ordered domains. The mesogens act in a co-operative manner, enhancing refractive indices and birefringences. Surface relief gratings are discussed as a consequence of holographic storage. Cholesteric polymers comprising azobenzene are briefly highlighted. Irradiation causing cis-trans-isomerisation can be used to control helix pitch. A brief mention of liquid crystals is also made since these materials may be of future interest since they are optically transparent and amenable to photo-induced anisotropy. PMID:17982514

  8. Optical characterization of lyotropic chromonic liquid crystals

    Science.gov (United States)

    Liu, Hui

    Lyotropic chromonic liquid crystals (LCLCs) represent a special class of lyotropic mesophases markedly different from conventional amphiphilic mesogens. Materials forming LCLCs are composed of plank-like molecules with a polyaromatic central core and hydrophilic ionic groups at the periphery. The individual molecules tend to assemble into rodlike aggregates that form the N phase once the concentration exceeds about 0.1M. The LCLC materials show a tremendous potential for applications in optics as self-assembling polarizing and compensating films and in the area of real-time biological sensing. The emerging applications require an understanding of basic properties of LCLC. This work addresses these needs by providing the optical characterization of LCLC. We studied in detail the optical anisotropic properties of three different nematic LCLCs: disodium cromoglycate (DSCG), Blue 27, and Violet 20. We determined the birefringence of these three materials as the function of the temperature T and wavelength lambda and the corresponding dependencies of the absorption coefficients for Blue 27 and Violet 20. The birefringence is negative and significantly lower in the absolute value as compared to the birefringence of typical thermotropic N materials. We determined the scalar order parameter of the nematic phase of Blue 27 and its temperature dependence. The scalar order parameter is close to the one predicted by the classic Onsager theory for solutions of rigid rods. However, this similarity is not complete, as the measured scalar order parameter depends on temperature. The I-N pretransitional fluctuations in an aqueous solution of DSCG were studied by light scattering. We obtained the correlation length of the orientational order-parameter fluctuations of isotropic DSCG solution. The pretransitional behavior of light scattering does not completely follow the classic Landau-de Gennes model. This feature is explained by the variable length of DSCG aggregates as a function

  9. Carbon-13 NMR studies of liquid crystals

    International Nuclear Information System (INIS)

    High resolution, proton decoupled 13C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = less than P2(costheta) greater than are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so, with temperature in the smectic-A phase. In the nematic series studied, the ordering exhibits an even-odd alternation along the series and qualitative agreement with a recent theory due to Marcelja is found. In both phases, the spectra show that the molecule rotates rapidly about its long axis. Tentative conclusions about molecular conformational motion and 14N spin relaxation are presented for both nematic and smectic-A phases. In the smectic-A phase, the sample is rotated about an axis perpendicular to H0 and the resulting spectra are dicusssed. The theory of observed chemical shifts in liquid crystals is discussed and equations are derived which relate the nmr spectra of liquid-crystals to the order parameters. A model for the smectic-C phase due to Luz and Meiboom and Doane is described and lineshapes are determined on the basis of this model for special cases. The dependence of the order parameters on the molecular potential which give rise to the various degrees of order in the different liquid crystalline phases is examined. To a good approximation the functional dependence of the order parameters on the molecular potential is shown to be a simple one in the limit of small tilt angle in the smectic-C phase

  10. Pulsed laser deposition of liquid crystals

    OpenAIRE

    Gonzalo de los Reyes, José; Dyer, P. E.; Hird, M.

    1997-01-01

    Thin films of 4-cyano-4’-pentylbiphenyl ~5CB! liquid crystal have been fabricated by pulsed laser deposition. The suitability of different lasers ~ArF, KrF and CO2) has been investigated over a range of fluence using visible-UV and infrared absorption and optical microscopy to characterise the films. High performance liquid chromatography ~HPLC! and matrix assisted laser desorption ionization mass spectroscopy ~MALDI-MS! were used to assess the extent of decomposition of the films. The result...

  11. Angular effects on thermochromic liquid crystal thermography

    Science.gov (United States)

    Kodzwa, Paul M.; Eaton, John K.

    2007-12-01

    This paper directly discusses the effects of lighting and viewing angles on liquid crystal thermography. This is because although thermochromic liquid crystals (TLCs) are a widely-used and accepted tool in heat transfer research, little effort has been directed to analytically describing these effects. Such insight is invaluable for the development of effective mitigation strategies. Using analytical relationships that describe the perceived color shift, a systematic manner of improving the performance of a TLC system is presented. This is particularly relevant for applications where significant variations in lighting and/or viewing angles are expected (such as a highly curved surface). This discussion includes an examination of the importance of the definition of the hue angle used to calibrate the color of a TLC-painted surface. The theoretical basis of the validated high-accuracy calibration approach reported by Kodzwa et al. (Exp Fluids s00348-007-0310-6, 2007) is presented.

  12. Angular effects on thermochromic liquid crystal thermography

    Energy Technology Data Exchange (ETDEWEB)

    Kodzwa, Paul M.; Eaton, John K. [Stanford University, Department of Mechanical Engineering, Flow Physics and Computation, Stanford, CA (United States)

    2007-12-15

    This paper directly discusses the effects of lighting and viewing angles on liquid crystal thermography. This is because although thermochromic liquid crystals (TLCs) are a widely-used and accepted tool in heat transfer research, little effort has been directed to analytically describing these effects. Such insight is invaluable for the development of effective mitigation strategies. Using analytical relationships that describe the perceived color shift, a systematic manner of improving the performance of a TLC system is presented. This is particularly relevant for applications where significant variations in lighting and/or viewing angles are expected (such as a highly curved surface). This discussion includes an examination of the importance of the definition of the hue angle used to calibrate the color of a TLC-painted surface. The theoretical basis of the validated high-accuracy calibration approach reported by Kodzwa et al. (Exp Fluids s00348-007-0310-6, 2007) is presented. (orig.)

  13. Errors in thermochromic liquid crystal thermometry

    International Nuclear Information System (INIS)

    This article experimentally investigates and assesses the errors that may be incurred in the hue-based thermochromic liquid crystal thermochromic liquid crystal (TLC) method, and their causes. The errors include response time, hysteresis, aging, surrounding illumination disturbance, direct illumination and viewing angle, amount of light into the camera, TLC thickness, digital resolution of the image conversion system, and measurement noise. Some of the main conclusions are that: (1) The 3x8 bits digital representation of the red green and blue TLC color values produces a temperature measurement error of typically 1% of the TLC effective temperature range, (2) an eight-fold variation of the light intensity into the camera produced variations, which were not discernable from the digital resolution error, (3) this temperature depends on the TLC film thickness, and (4) thicker films are less susceptible to aging and thickness nonuniformities

  14. Errors in thermochromic liquid crystal thermometry

    Science.gov (United States)

    Wiberg, Roland; Lior, Noam

    2004-09-01

    This article experimentally investigates and assesses the errors that may be incurred in the hue-based thermochromic liquid crystal thermochromic liquid crystal (TLC) method, and their causes. The errors include response time, hysteresis, aging, surrounding illumination disturbance, direct illumination and viewing angle, amount of light into the camera, TLC thickness, digital resolution of the image conversion system, and measurement noise. Some of the main conclusions are that: (1) The 3×8 bits digital representation of the red green and blue TLC color values produces a temperature measurement error of typically 1% of the TLC effective temperature range, (2) an eight-fold variation of the light intensity into the camera produced variations, which were not discernable from the digital resolution error, (3) this temperature depends on the TLC film thickness, and (4) thicker films are less susceptible to aging and thickness nonuniformities.

  15. Macroscopic dynamics of polar nematic liquid crystals.

    Science.gov (United States)

    Brand, Helmut R; Pleiner, Harald; Ziebert, Falko

    2006-08-01

    We present the macroscopic equations for polar nematic liquid crystals. We consider the case where one has both, the usual nematic director, n[over ] , characterizing quadrupolar order as well as the macroscopic polarization, P , representing polar order, but where their directions coincide and are rigidly coupled. In this case one has to choose P as the independent macroscopic variable. Such equations are expected to be relevant in connection with nematic phases with unusual properties found recently in compounds composed of banana-shaped molecules. Among the effects predicted, which are absent in conventional nematic liquid crystals showing only quadrupolar order, are pyro-electricity and its analogs for density and for concentration in mixtures as well as a flow alignment behavior, which is more complex than in usual low molecular weight nematics. We also discuss the formation of defect structures expected in such systems. PMID:17025458

  16. Biaxial nematic liquid crystals theory, simulation and experiment

    CERN Document Server

    Luckhurst, Geoffrey R

    2015-01-01

    Liquid Crystals are a state of matter that have properties between those of conventional liquid and those of a solid crystal. Thermotropic liquid crystals react to changes in temperature or, in some cases, pressure. The reaction of lyotropic liquid crystals, which are used in the manufacture of soaps and detergents, depends on the type of solvent they are mixed with. Since the accidental discovery of the chiral nematic (ordered) phase in 1888 many liquid crystal phases have been found, sometimes by chance and sometimes by design. The existence of one such phase was predicted by Freiser in 197

  17. Laser Propagation in Biaxial Liquid Crystal Polymers

    OpenAIRE

    Choate, Eric P.; Zhou, Hong

    2011-01-01

    We examine the propagation of a laser beam through a liquid crystal polymer (LCP) layer using the finite-difference time-domain (FDTD) method. Anchoring conditions on supporting glass plates induce an orientational structure in the LCP between the plates. The orientation can deflect energy away from the direction of propagation of the incident beam when the optical axis or major director of a uniaxial medium is neither parallel nor orthogonal to the incident beam. The maximum e...

  18. Laser pulse shaping with liquid crystals

    OpenAIRE

    Martín Pereda, José Antonio; Muriel Fernández, Miguel Ángel

    1983-01-01

    A method of unpolarized laser pulses shaping is reported. The basis of the method is the use of an hybrid optical bistable device with nematic liquid-crystals, similar to the one previously reported by us. A sample of the input light constrols, by an asymmetrical electronic comparator, a 1 x 2 electro-optical total switch. The output pulses are reshaped and maintain the same polarization properties as the input light. From triangular input light signals, symmetriacl and asymmetrical output pu...

  19. Characterization of polymer-liquid crystal blends

    OpenAIRE

    DOINA MACOCINSCHI; CRISTOFOR I. SIMIONESCU; DANIELA FILIP

    2001-01-01

    Blends of semi-crystalline polymers (polyethylene adipate and two poly(ester-urethane) s) with liquid crystal cholesteryl palmitate with different compositions were prepared by solution casting. One of the poly(ester-urethane)s was based on 2,4-tolylene diisocyanate (TDI) and the other one on 4,4-diphenylmethane diisocyanate (MDI). The miscibility and phase transition were investigated over the whole range of concentration by differential scanning calorimetry and polarizing optical microscopy.

  20. Direct liquid crystal templating of mesoporous silica

    OpenAIRE

    Gordon-Smith, Tobias James

    2003-01-01

    The work described in this thesis is concerned with the development of ordered mesoporous silicas by direct templating from lyotropic liquid crystal phases of the surfactants Pluronic PI23, Pluronic F127, CTAB and Brij 78. The factors affecting the regularity, morphology, pore diameter and wall thickness of the templated mesoporous silicas were examined by exploring the reaction composition space and plotting the structural properties on TMOS/surfactant/water ternary diagrams. ...

  1. Simulations of liquid crystals in Poiseuille flow

    OpenAIRE

    Denniston, Colin; Orlandini, Enzo; Yeomans, J. M.

    2000-01-01

    Lattice Boltzmann simulations are used to explore the behavior of liquid crystals subject to Poiseuille flow. In the nematic regime at low shear rates we find two possible steady state configurations of the director field. The selected state depends on both the shear rate and the history of the sample. For both director configurations there is clear evidence of shear-thinning, a decrease in the viscosity with increasing shear rate. Moreover, at very high shear rates or when the order paramete...

  2. Liquid Crystal Microlenses for Autostereoscopic Displays

    Directory of Open Access Journals (Sweden)

    José Francisco Algorri

    2016-01-01

    Full Text Available Three-dimensional vision has acquired great importance in the audiovisual industry in the past ten years. Despite this, the first generation of autostereoscopic displays failed to generate enough consumer excitement. Some reasons are little 3D content and performance issues. For this reason, an exponential increase in three-dimensional vision research has occurred in the last few years. In this review, a study of the historical impact of the most important technologies has been performed. This study is carried out in terms of research manuscripts per year. The results reveal that research on spatial multiplexing technique is increasing considerably and today is the most studied. For this reason, the state of the art of this technique is presented. The use of microlenses seems to be the most successful method to obtain autostereoscopic vision. When they are fabricated with liquid crystal materials, extended capabilities are produced. Among the numerous techniques for manufacturing liquid crystal microlenses, this review covers the most viable designs for its use in autostereoscopic displays. For this reason, some of the most important topologies and their relation with autostereoscopic displays are presented. Finally, the challenges in some recent applications, such as portable devices, and the future of three-dimensional displays based on liquid crystal microlenses are outlined.

  3. In Situ Adsorption Studies at the Solid/Liquid Interface:Characterization of Biological Surfaces and Interfaces Using SumFrequency Generation Vibrational Spectroscopy, Atomic Force Microscopy,and Quartz Crystal Microbalance

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, D.C.

    2006-05-16

    Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and quartz crystal microbalance (QCM) have been used to study the molecular surface structure, surface topography and mechanical properties, and quantitative adsorbed amount of biological molecules at the solid-liquid interface. The molecular-level behavior of designed peptides adsorbed on hydrophobic polystyrene and hydrophilic silica substrates has been examined as a model of protein adsorption on polymeric biomaterial surfaces. Proteins are such large and complex molecules that it is difficult to identify the features in their structure that lead to adsorption and interaction with solid surfaces. Designed peptides which possess secondary structure provide simple model systems for understanding protein adsorption. Depending on the amino acid sequence of a peptide, different secondary structures ({alpha}-helix and {beta}-sheet) can be induced at apolar (air/liquid or air/solid) interfaces. Having a well-defined secondary structure allows experiments to be carried out under controlled conditions, where it is possible to investigate the affects of peptide amino acid sequence and chain length, concentration, buffering effects, etc. on adsorbed peptide structure. The experiments presented in this dissertation demonstrate that SFG vibrational spectroscopy can be used to directly probe the interaction of adsorbing biomolecules with a surface or interface. The use of well designed model systems aided in isolation of the SFG signal of the adsorbing species, and showed that surface functional groups of the substrate are sensitive to surface adsorbates. The complementary techniques of AFM and QCM allowed for deconvolution of the effects of surface topography and coverage from the observed SFG spectra. Initial studies of biologically relevant surfaces are also presented: SFG spectroscopy was used to study the surface composition of common soil bacteria for use in bioremediation of nuclear

  4. In Situ Adsorption Studies at the Solid/Liquid Interface: Characterization of Biological Surfaces and Interfaces Using Sum Frequency Generation Vibrational Spectroscopy, Atomic Force Microscopy, and Quartz Crystal Microbalance

    International Nuclear Information System (INIS)

    Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and quartz crystal microbalance (QCM) have been used to study the molecular surface structure, surface topography and mechanical properties, and quantitative adsorbed amount of biological molecules at the solid-liquid interface. The molecular-level behavior of designed peptides adsorbed on hydrophobic polystyrene and hydrophilic silica substrates has been examined as a model of protein adsorption on polymeric biomaterial surfaces. Proteins are such large and complex molecules that it is difficult to identify the features in their structure that lead to adsorption and interaction with solid surfaces. Designed peptides which possess secondary structure provide simple model systems for understanding protein adsorption. Depending on the amino acid sequence of a peptide, different secondary structures (α-helix and β-sheet) can be induced at apolar (air/liquid or air/solid) interfaces. Having a well-defined secondary structure allows experiments to be carried out under controlled conditions, where it is possible to investigate the affects of peptide amino acid sequence and chain length, concentration, buffering effects, etc. on adsorbed peptide structure. The experiments presented in this dissertation demonstrate that SFG vibrational spectroscopy can be used to directly probe the interaction of adsorbing biomolecules with a surface or interface. The use of well designed model systems aided in isolation of the SFG signal of the adsorbing species, and showed that surface functional groups of the substrate are sensitive to surface adsorbates. The complementary techniques of AFM and QCM allowed for deconvolution of the effects of surface topography and coverage from the observed SFG spectra. Initial studies of biologically relevant surfaces are also presented: SFG spectroscopy was used to study the surface composition of common soil bacteria for use in bioremediation of nuclear waste

  5. Adsorption phenomena and anchoring energy in nematic liquid crystals

    CERN Document Server

    Barbero, Giovanni

    2005-01-01

    Despite the large quantity of phenomenological information concerning the bulk properties of nematic phase liquid crystals, little is understood about the origin of the surface energy, particularly the surface, interfacial, and anchoring properties of liquid crystals that affect the performance of liquid crystal devices. Self-contained and unique, Adsorption Phenomena and Anchoring Energy in Nematic Liquid Crystals provides an account of new and established results spanning three decades of research into the problems of anchoring energy and adsorption phenomena in liquid crystals.The book contains a detailed discussion of the origin and possible sources of anchoring energy in nematic liquid crystals, emphasizing the dielectric contribution to the anchoring energy in particular. Beginning with fundamental surface and anchoring properties of liquid crystals and the definition of the nematic phase, the authors explain how selective ion adsorption, dielectric energy density, thickness dependence, and bias voltage...

  6. Guided mode studies of smectic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hodder, B

    2000-03-01

    Recently there has been considerable interest in the use of ferroelectric liquid crystals in low power, fast switching display devices. At present the voltage switching process in surface stabilised ferroelectric liquid crystal (SSFLC) devices is not fully understood and a convenient theory for such cells has yet to be found. It is the primary aim of this work to characterise the optic tensor configuration (director profile) in thin cells ({approx} 3.5 {mu}m) containing ferroelectric liquid crystal (FLC) material. These results form a benchmark by which continuum theories may be tested. Polarised microscopy is, perhaps, the most common optical probe of liquid crystal cells. It should be appreciated that this technique is fundamentally limited, as the results are deduced from an integrated optical response of any given cell, and cannot be used to spatially resolve details of the director profile through the cell. The guided mode techniques used in this study are the primary non-integral probe and enable detailed spatial resolution of the director profilewithin liquid crystal cells. Analysis of guided mode data from cells containing homeotropically aligned FLC reveals the temperature dependence of the optical biaxiality and cone angle for a 40% chiral mixture of the commercially available FLC SCE8*. From these optical biaxiality measurements the temperature dependence of the biaxial order parameter C is determined. Guided mode studies of cells containing homogeneously aligned SCE8* (the conventional alignment for SSFLC devices) reveal the 0V equilibrium director profile from which a cone and chevron model is constructed. Subsequent studies of voltage induced elastic deformations of the director profile are presented and compared with a single elastic constant continuum theory which is shown to be inadequate. Optical guided mode techniques are not directly sensitive to the smectic layer configuration but X-ray scattering is. Here, for the first time, results are

  7. Single Molecule Studies on Dynamics in Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Daniela Täuber

    2013-09-01

    Full Text Available Single molecule (SM methods are able to resolve structure related dynamics of guest molecules in liquid crystals (LC. Highly diluted small dye molecules on the one hand explore structure formation and LC dynamics, on the other hand they report about a distortion caused by the guest molecules. The anisotropic structure of LC materials is used to retrieve specific conformation related properties of larger guest molecules like conjugated polymers. This in particular sheds light on organization mechanisms within biological cells, where large molecules are found in nematic LC surroundings. This review gives a short overview related to the application of highly sensitive SM detection schemes in LC.

  8. Liquid crystal nanocomposites produced by mixtures of hydrogen bonded achiral liquid crystals and functionalized carbon nanotubes

    Science.gov (United States)

    Katranchev, B.; Petrov, M.; Keskinova, E.; Naradikian, H.; Rafailov, P. M.; Dettlaff-Weglikowska, U.; Spassov, T.

    2014-12-01

    The liquid crystalline (LC) nature of alkyloxybenzoic acids is preserved after adding of any mesogenic or non-mesogenic compound through hydrogen bonding. However, this noncovalent interaction provokes a sizable effect on the physical properties as, e. g. melting point and mesomorphic states. In the present work we investigate nanocomposites, prepared by mixture of the eighth homologue of p-n-alkyloxybenzoic acids (8OBA) with single-walled carbon nanotubes (SWCNT) with the purpose to modify the optical properties of the liquid crystal. We exercise optical control on the LC system by inserting SWCNT specially functionalized by carboxylic groups. Since the liquid crystalline state combines order and mobility at the molecular (nanoscale) level, molecular modification can lead to different macroscopical nanocomposite symmetry. The thermal properties of the functionalized nanocomposite are confirmed by DSC analyses. The mechanism of the interaction between surface-treated nanoparticles (functionalized nanotubes) and the liquid crystal 8OBA bent- dimer molecules is briefly discussed.

  9. Cholesteric liquid crystal photonic crystal lasers and photonic devices

    Science.gov (United States)

    Zhou, Ying

    This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser

  10. Liquid Crystals and Photonic Bandgap Fiber Components

    DEFF Research Database (Denmark)

    Weirich, Johannes; Wei, Lei; Scolari, Lara;

    Liquid Crystal(LC)filled Photonic Crystal Fibers(PCFs) represent a promising platform for the design and the fabrication of tunable all-in fiber devices. Tunability is achieved by varying the refractive index of the LC thermally, optically or electrically. In this contribution we present important...... parts of the LC theory as well as an application of a LC infiltrated PCF subject to an external electrostatic field. The fiber is placed between two electrodes and the voltage is increased step by step leading to the reorientation of the LC in the fiber capillaries. This mechanism can be used to produce...... a swichable polarizer, and an on chip LC photonic bandgap fiber polarimeter is presented, which admits strong attenuation of one polarization direction while the other one is nearly unaffected....

  11. Stochastic rotation dynamics for nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kuang-Wu, E-mail: jeff.lee@ds.mpg.de; Mazza, Marco G., E-mail: marco.mazza@ds.mpg.de [Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen (Germany)

    2015-04-28

    We introduce a new mesoscopic model for nematic liquid crystals (LCs). We extend the particle-based stochastic rotation dynamics method, which reproduces the Navier-Stokes equation, to anisotropic fluids by including a simplified Ericksen-Leslie formulation of nematodynamics. We verify the applicability of this hybrid model by studying the equilibrium isotropic-nematic phase transition and nonequilibrium problems, such as the dynamics of topological defects and the rheology of sheared LCs. Our simulation results show that this hybrid model captures many essential aspects of LC physics at the mesoscopic scale, while preserving microscopic thermal fluctuations.

  12. Carbon Nanoparticles in Nematic Liquid Crystals

    Institute of Scientific and Technical Information of China (English)

    S.Eren San; Mustafa Okutan; O(g)uz K(o)ysal; Yusuf Yer-li

    2008-01-01

    Fullerene G60,C70,single-walled and multi-walled carbon nanotubes and graphene sheets are doped to nematic liquid crystal(LC)host in the same percentage.Planar samples of these mixtures are prepared and our measurements constitute an optimization basis for possible applications.Fullerene balls are found to be the best compatible material for optical aims and reorientation of LC molecules,while the carbon nanotubes experience some reorientation possibility in LC media and graphene layers are good barriers to preserve reorientation.

  13. The limits of flexoelectricity in liquid crystals

    Directory of Open Access Journals (Sweden)

    F. Castles

    2011-09-01

    Full Text Available The flexoelectric conversion of mechanical to electrical energy in nematic liquid crystals is investigated using continuum theory. Since the electrical energy produced cannot exceed the mechanical energy supplied, and vice-versa, upper bounds are imposed on the magnitudes of the flexoelectric coefficients in terms of the elastic and dielectric coefficients. For conventional values of the elastic and dielectric coefficients, it is shown that the flexoelectric coefficients may not be larger than a few tens of pC/m. This has important consequences for the future use of such flexoelectric materials in devices and the related energetics of distorted equilibrium structures.

  14. Thermal diode made by nematic liquid crystal

    Science.gov (United States)

    Melo, Djair; Fernandes, Ivna; Moraes, Fernando; Fumeron, Sébastien; Pereira, Erms

    2016-09-01

    This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed.

  15. Computer simulation of confined liquid crystal dynamics

    CERN Document Server

    Webster, R E

    2001-01-01

    are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results...

  16. Adaptive lens using liquid crystal concentration redistribution

    Science.gov (United States)

    Ren, Hongwen; Lin, Yi-Hsin; Wu, Shin-Tson

    2006-05-01

    An adaptive lens using electrically induced liquid crystal (LC)/monomer concentration redistribution is demonstrated. In the absence of an electric field, the LC/monomer mixture is homogeneously distributed. Application of an inhomogeneous electric field causes the LC molecules to diffuse towards the high field region and the liquid monomer towards the low field region. On the other hand, the LC molecules tend to diffuse from high to low concentration direction in order to balance the concentration change. A gradient LC concentration is thus obtained. Using the gradient LC concentration, we demonstrate a tunable-focus lens. Compared with a conventional LC lens, our lens has advantages in small astigmatism and without light scattering, but its response time is slower.

  17. Tuning fluidic resistance via liquid crystal microfluidics.

    Science.gov (United States)

    Sengupta, Anupam

    2013-01-01

    Flow of molecularly ordered fluids, like liquid crystals, is inherently coupled with the average local orientation of the molecules, or the director. The anisotropic coupling-typically absent in isotropic fluids-bestows unique functionalities to the flowing matrix. In this work, we harness this anisotropy to pattern different pathways to tunable fluidic resistance within microfluidic devices. We use a nematic liquid crystalline material flowing in microchannels to demonstrate passive and active modulation of the flow resistance. While appropriate surface anchoring conditions-which imprint distinct fluidic resistances within microchannels under similar hydrodynamic parameters-act as passive cues, an external field, e.g., temperature, is used to actively modulate the flow resistance in the microfluidic device. We apply this simple concept to fabricate basic fluidic circuits, which can be hierarchically extended to create complex resistance networks, without any additional design or morphological patterning of the microchannels. PMID:24256819

  18. Control of liquid crystal molecular orientation using ultrasound vibration

    Science.gov (United States)

    Taniguchi, Satoki; Koyama, Daisuke; Shimizu, Yuki; Emoto, Akira; Nakamura, Kentaro; Matsukawa, Mami

    2016-03-01

    We propose a technique to control the orientation of nematic liquid crystals using ultrasound and investigate the optical characteristics of the oriented samples. An ultrasonic liquid crystal cell with a thickness of 5-25 μm and two ultrasonic lead zirconate titanate transducers was fabricated. By exciting the ultrasonic transducers, the flexural vibration modes were generated on the cell. An acoustic radiation force to the liquid crystal layer was generated, changing the molecular orientation and thus the light transmission. By modulating the ultrasonic driving frequency and voltage, the spatial distribution of the molecular orientation of the liquid crystals could be controlled. The distribution of the transmitted light intensity depends on the thickness of the liquid crystal layer because the acoustic field in the liquid crystal layer is changed by the orientational film.

  19. Electro-optical switching by liquid-crystal controlled metasurfaces.

    Science.gov (United States)

    Decker, Manuel; Kremers, Christian; Minovich, Alexander; Staude, Isabelle; Miroshnichenko, Andrey E; Chigrin, Dmitry; Neshev, Dragomir N; Jagadish, Chennupati; Kivshar, Yuri S

    2013-04-01

    We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-crystal reorientation. PMID:23571978

  20. Electro-optical switching by liquid-crystal controlled metasurfaces

    CERN Document Server

    Decker, Manuel; Minovich, Alexander; Staude, Isabelle; Miroshnichenko, Andrey E; Chigrin, Dmitry; Neshev, Dragomir N; Jagadish, Chennupati; Kivshar, Yuri S

    2013-01-01

    We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-crystal reorientation.

  1. Multistability in planar liquid crystal wells

    KAUST Repository

    Luo, Chong

    2012-06-08

    A planar bistable liquid crystal device, reported in Tsakonas, is modeled within the Landau-de Gennes theory for nematic liquid crystals. This planar device consists of an array of square micrometer-sized wells. We obtain six different classes of equilibrium profiles and these profiles are classified as diagonal or rotated solutions. In the strong anchoring case, we propose a Dirichlet boundary condition that mimics the experimentally imposed tangent boundary conditions. In the weak anchoring case, we present a suitable surface energy and study the multiplicity of solutions as a function of the anchoring strength. We find that diagonal solutions exist for all values of the anchoring strength W≥0, while rotated solutions only exist for W≥W c>0, where W c is a critical anchoring strength that has been computed numerically. We propose a dynamic model for the switching mechanisms based on only dielectric effects. For sufficiently strong external electric fields, we numerically demonstrate diagonal-to-rotated and rotated-to-diagonal switching by allowing for variable anchoring strength across the domain boundary. © 2012 American Physical Society.

  2. Instability of crystal helium surface in superfluid liquid flow

    International Nuclear Information System (INIS)

    Stability of crystal growth under liquid normal drop on boundary was studied. One determined threshold speed of instability initiation that under low temperatures turned to be far less than sound speed. One examined stability of shape of cylindrical crystal in liquid flow parallel to crystal axis. One studied experimentally behavior of atomic-irregular surface of crystal helium in liquid jet within 1-1.4 K temperature range where one detected initiation of instability. Observation showed that below face transition level the basal face (0001) was stable in liquid jet

  3. Electrically tunable liquid crystal photonic bandgap fiber laser

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Scolari, Lara; Wei, Lei;

    2010-01-01

    We demonstrate electrical tunability of a fiber laser by using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate an all......-spliced laser cavity based on a liquid crystal photonic bandgap fiber mounted on a silicon assembly, a pump/signal combiner with single-mode signal feed-through and an ytterbium-doped photonic crystal fiber. The laser cavity produces a single-mode output and is tuned in the range 1040-1065nm by applying...

  4. Mesomorphism and electrochemistry of thienoviologen liquid crystals.

    Science.gov (United States)

    Cospito, S; Beneduci, A; Veltri, L; Salamonczyk, M; Chidichimo, G

    2015-07-21

    The thienoviologen series 4,4'-(2,2'-bithiophene-5,5'-diyl)bis(1-alkylpridinium)X2, with = counterion is a new class of electron acceptor materials which show very interesting electrochromic and electrofluorescence properties. Depending on the length, m, of the promesogenic alkyl chains, and on the counterion, thienoviologens might become liquid crystals. Here, we present the mesomorphic behaviour, and the electrochemical and spectroelectrochemical properties in solution of new thienoviologens of the series and (I = iodide; NTf2(-) = bis(tri-fuoromethylsulfonyl)imide) with m = 8, 12. Interestingly, we found that only the compounds are liquid crystals, exhibiting a calamitic behaviour in contrast to the homologous compounds of the series with m = 9-11 and X = NTf2(-), which showed columnar rectangular mesophases. The electrochemical study here reported allowed us to explain for the first time the anomalous behaviour of these thienoviologens already observed in cyclic voltammetry, where two apparently irreversible redox processes occur. This can be explained by a comproportionation reaction in which the neutral species rapidly reduces the dication to the radical-cation, due to its strong reducing power. Electrochemical reduction of the thienoviologens causes electrochromism since a new absorption band, occurring at 660 nm in the electronic spectra, appears with the negative potential bias applied. With a LUMO level of 3.64 eV, similar to those of the C60 and of other n-type materials, these compounds can find applications in several electronics devices, where their liquid crystalline properties can be used to control film morphology and geometry, provided they have good electron mobility. PMID:26082287

  5. Isotropization of nematic liquid crystals by TMDSC

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei; Dadmun, M.; Zhang, Ge; Boller, A.; Wunderlich, B. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry]|[Oak Ridge National Lab., TN (United States)

    1997-12-01

    Temperature-modulated differential scanning calorimetry (TMDSC) and traditional DSC are used to study the transition between the nematic liquid crystalline state and the isotropic liquid for two small molecules [4,4{prime}-azoxyanisole and N,N`-bis(4-n-octyloxybenzal)-1,4-phenylenediamine] and one macromolecule (4,4{prime}-dihydroxy-{alpha}-methylstilbene copolymerized with a 1:1 molar mixture of 1,7-dibromoheptane and 1,9-dibromononane). The DSC measurements with 4,4{prime}-azoxyanisole were used for temperature calibration with varying heating and cooling rates. Quasi-isothermal TMDSC with small temperature amplitude and standard TMDSC with underlying heating and cooling rates were utilized to analyze the breadth of the transitions. It could be verified that the isotropization transition of a nematic liquid crystal is, indeed, reversible for all three molecules. The nature of the transition changes, however, from relatively sharp, for small, rigid molecules, to about three kelvins wide for the small molecule with flexible ends, to as broad as 20 K for the macromolecule. It was also demonstrated that quantitative heats of fusion of sharp transitions can be extracted from TMDSC, but only from the time-domain heat-flow signal.

  6. Dispersion properties of transverse anisotropic liquid crystal core photonic crystal fibers

    Science.gov (United States)

    Karasawa, Naoki

    2016-04-01

    The dispersion properties of liquid crystal core photonic crystal fibers for different core diameters have been calculated by a full vectorial finite difference method. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica and a central hole is filled with liquid crystal to create a core. In this study, three types of transverse anisotropic configurations, where liquid crystal molecules are oriented in a transverse plane, and a planar configuration, where liquid crystal molecules are oriented in a propagation direction, are considered. The large changes of the dispersion properties are found when the orientation of the liquid crystal molecules is changed from a planar configuration to a uniform configuration, where all molecules are oriented in the same direction in a transverse plane. Since the orientation of liquid crystal molecules may be controlled by applying an electric field, it could be utilized for various applications including the spectral control of supercontinuum generation.

  7. Chromatic dispersion of liquid crystal infiltrated capillary tubes and photonic crystal fibers

    DEFF Research Database (Denmark)

    Rasmussen, Per Dalgaard; Lægsgaard, Jesper; Bang, Ole

    2006-01-01

    We consider chromatic dispersion of capillary tubes and photonic crystal fibers infiltrated with liquid crystals. A perturbative scheme for inclusion of material dispersion of both liquid crystal and the surrounding waveguide material is derived. The method is used to calculate the chromatic...

  8. Microscopic theory of liquid crystal rheology

    Science.gov (United States)

    Sarman, Sten

    1995-07-01

    We propose a new expression for the irreversible entropy production of a nematic liquid crystal subject to a velocity gradient. This is done by adding a contribution due to the streaming angular velocity, ω, which is distinct from the contribution from the angular velocity of the director, Ω. This removes the inconsistency between the isotropic fluid entropy production and the liquid crystal entropy production. The new entropy production means that the traditional viscosity coefficients must be replaced by a new set of coefficients. This can be done in a few different ways depending on how one defines the thermodynamic forces and fluxes. We derive equilibrium fluctuation relations for the viscosities by applying linear response theory. One finds that it is very important to select the proper equilibrium ensemble in order to obtain simple expressions, i.e., linear combinations of time correlation function integrals (TCFI's), for the viscosities. It turns out that the thermodynamic forces must be given external parameters whereas the fluxes must be fluctuating phase functions. This means that one sometimes must use equilibrium ensembles where Ω and ω are constrained to be zero. Most TCFI's are the same in those ensembles as in ordinary equilibrium ensembles such as the canonical or isokinetic ensemble. There are relations between those TCFI's that are different. It is particularly convenient to constrain Ω to be zero because this makes a director based coordinate system an inertial frame. It also prevents the director reorientation from affecting the tails of the time correlation functions. In order to test some of the fluctuation relations numerically, we have evaluated them for a nematic liquid crystal phase of an oblate version of the Gay-Berne fluid. We have compared the ordinary isokinetic ensemble to an ensemble where Ω has been constrained to be zero by performing equilibrium molecular dynamics (EMD) simulations. The results were either the same or

  9. Role of Lifshitz Invariants in Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Amelia Sparavigna

    2009-06-01

    Full Text Available The interaction between an external action and the order parameter, via a dependence described by a so-called Lifshitz invariant, is very important to determine the final configuration of liquid crystal cells. The external action can be an electric field applied to the bulk or the confinement due to free surfaces or cell walls. The Lifshitz invariant includes the order parameter in the form of an elastic strain. This coupling between elastic strains and fields, inserted in a Landau-Ginzburg formalism, is well known and gives rise to striction effects causing undulations in the director configuration. We want to discuss here the role of Lifshitz coupling terms, following an approach similar to that introduced by Dzyaloshinskii for magnetic materials. Case studies on nematics in planar and cylindrical cells are also proposed.

  10. Fork gratings based on ferroelectric liquid crystals.

    Science.gov (United States)

    Ma, Y; Wei, B Y; Shi, L Y; Srivastava, A K; Chigrinov, V G; Kwok, H-S; Hu, W; Lu, Y Q

    2016-03-21

    In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices. PMID:27136779

  11. Liquid Crystal Tunable Metamaterial Perfect Absorber

    CERN Document Server

    Shrekenhamer, David; Padilla, Willie J

    2012-01-01

    We present experimental demonstration of electronically tunable metamaterial perfect absorbers in the terahertz regime. By incorporation of active liquid crystal into strategic locations within the metamaterial unit cell we are able to modify the absorption by 30 percent at 2.62 THz, as well as tune the resonant absorption over 4 percent in bandwidth. Numerical full-wave simulations match well to experiments and clarify the underlying mechanism, i.e. a simultaneous tuning of both the electric and magnetic response that allows for the preservation of the resonant absorption. These results show that the fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.

  12. Synthesis of azobenzene-containing liquid crystalline gelator for use in liquid crystal gels

    Institute of Scientific and Technical Information of China (English)

    Guang Wang; Xiao Liang Zhao; Yue Zhao

    2008-01-01

    A liquid crystalline gelator containing the azobenzene chromophore was synthesized for the first time; it was used to form self-assembled network in nematic liquid crystals resulting in liquid crystal gels with distinct features.? 2008 Guang Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

  13. Global dynamics in a liquid crystal flow

    International Nuclear Information System (INIS)

    The results of an experimental study of cellular flow in a small aspect ratio nematic liquid crystal cell are presented. The purpose was to investigate the role that dynamical systems theory can play in describing the behaviour of a complex fluid system on a microscopic scale. Initial investigations are concerned with primary flows consisting of either six or eight convection cells. These developed smoothly from the undisturbed nematic with variation in the control parameter and possessed maximum symmetry consistent with the flow domain. As the external forcing was increased spontaneous symmetry-breaking occurred, giving rise to a multiplicity of solutions. Two different oscillatory flows could also be realised, and it is shown that each was the result of a Hopf bifurcation affected by noise internal to the system. The study is then extended to consider codimension-2 points in the solution set. A Takens-Bogdanov point is identified, and this was the organising centre for global dynamics in a surrounding region of parameter space. Behaviour in accordance with a degenerate Hopf bifurcation of codimension-2 is also described. Here, the degenerate bifurcation point was the origin of two lines of Hopf bifurcations, one supercritical and one subcritical, and a line of periodic folds. Finally, a detailed study of global dynamics in the liquid crystal cell is presented. Pattern dynamics in accordance with an imperfect gluing bifurcation are described, and the effect of inevitable physical imperfections is shown to give rise to complex periodic and aperiodic solutions. A systematic investigation of chaotic dynamics is also given, and the behaviour is related to a system governed by ordinary differential equations that was studied by Sil'nikov. (author)

  14. Substrate-induced bulk alignment of liquid crystals

    DEFF Research Database (Denmark)

    Zhang, Zhengping; Chakrabarti, A.; Mouritsen, Ole G.;

    1996-01-01

    The Gay-Berne model for liquid crystals in the presence of a substrate surface is studied using the hybrid Monte Carlo method. A simple non-mean-field substrate-molecule potential is proposed to describe the effects of rubbed polymer-coated substrates on the liquid crystals. Effects of the...

  15. Simulation of a Liquid Crystal at a Polymer Surface

    Science.gov (United States)

    Doerr, T. P.; Taylor, P. L.

    2002-03-01

    Atomistic molecular dynamics simulations of anchoring of the liquid crystals 5CB and 8CB at the surface of polyvinyl alcohol have been performed. Simulations were performed with various substrate configurations in order to investigate the microscopic origins of rubbing induced orientation. Multiple initial configurations for the liquid crystal were also used to check dependence on initial conditions. Connection is made with experiments.

  16. Liquid Crystal-based Beam Steering Technologies for NASA Applications

    Science.gov (United States)

    Pouch, John; Nguyen, Hung; Miranda, Felix; Bos, Philip; Lavrentovich, Oleg; Wang, Xinghua; Pishnyak, Oleg; Kreminska, Liubov; Golovin, Andrii

    2006-01-01

    Liquid crystal-based beam steering devices can provide electronic beam scanning to angles above 1 milliradian, sub-microradian beam pointing accuracy, as well as wave-front correction to maintain output optical beam quality. The liquid crystal technology effort will be summarized, and the potential application of the resulting devices to NASA space-based scenarios will be described.

  17. Novel ion-containing liquid crystals and liquid crystalline polymers

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, P.

    1992-01-01

    The properties of main chain polymeric liquid crystals (PLC's) based on trans-1,2-bis(4,4[prime]-pyridyl)ethylene mesogens, alkyl spacers and various counterions are described. The mesomorphic properties of model compounds are also described. Some of these are based on [open quotes]Siamese twin[close quotes] systems with the 4-alkoxystilbazole mesogen similar to the trans-1,2-bis(4,4[prime]-pyridyl)ethylene used in the polymer. Some model compounds are low molecular mass monomer analogues of the polymer. The structural parameters investigated were the length of the flexible spacer, the nature of the mesogen, the ionic density of the system and the nature and size of the counterion. The introduction of ionic sites into a main chain PLC's far from inhibiting appears to promote mesophase formation and enhance the stability of the mesophase. The phenomena described here involve high transition temperatures strong odd-even oscillations and supercooling effects. The twins and polymers display a great variety of smectic mesophases, the nature of which depends strongly on the nature of the counterion. Large organic counterions such as methylsulfonates promote the formation of smectic mesophases, sometimes of lower order (S[sub A] or S[sub C]) whilst toluenesulfonate promote often higher order smectic polymorphism. The polymers display also lyotropic liquid crystallinity.

  18. A polarization independent liquid crystal phase modulation adopting surface pinning effect of polymer dispersed liquid crystals

    Science.gov (United States)

    Lin, Yi-Hsin; Tsou, Yu-Shih

    2011-12-01

    A polarization-independent liquid crystal (LC) phase modulation using the surface pinning effect of polymer dispersed liquid crystals (SP-PDLC) is demonstrated. In the bulk region of the SP-PDLC, the orientations of LC directors are randomly dispersed; thus, any polarization of incident light experiences the same averaged refractive index. In the regions near glass substrates, the LC droplets are pinned. The orientations of top and bottom droplets are orthogonal. Two eigen-polarizations of an incident light experience the same phase shift. As a result, the SP-PDLC is polarization independent. Polarizer-free microlens arrays of SP-PDLC are also demonstrated. The SP-PDLC has potential for application in spatial light modulators, laser beam steering, and electrically tunable microprisms.

  19. Advection of nematic liquid crystals by chaotic flow

    CERN Document Server

    O'Naraigh, Lennon

    2016-01-01

    Consideration is given to the effects of inhomogeneous shear flow (both regular and chaotic) on nematic liquid crystals in a planar two-dimensional geometry. The Landau-de Gennes equation coupled to an externally-prescribed flow field is the basis for the study: this is solved numerically in a periodic spatial domain. The focus is on a limiting case where the advection is passive, such that variations in the liquid-crystal properties do not feed back into the equation of motion for the uid velocity. The numerical simulations demonstrate that the coarsening of the liquid-crystal domains is arrested by the ow. The nature of the arrest is different depending on whether the flow is regular or chaotic. For the specific case where tumbling is important, the flow has a strong effect on the the liquid-crystal morphology: this provides a mechanism for controlling the shape of the liquid-crystal domains.

  20. Simulation of liquid crystals. Disclinations and surface modification

    CERN Document Server

    Downton, M

    2001-01-01

    In this thesis we investigate the behaviour of molecular models liquid crystals in several different situations. Basic introductory material on liquid crystals and computer simulations is discussed in the first two chapters, we then discuss the research. The third chapter investigates the interaction between a liquid crystal and a modified surface. A confined system of hard spherocylinders in a slab geometry is examined. The surface consists of planar hard walls with elongated molecules grafted perpendicularly onto them. The concentration of grafted molecules is varied to give different surfaces. Several different behaviours are found including planar, homeotropic and tilted anchorings of the liquid crystal. Molecular dynamics simulations of a nematic liquid crystal in slab geometry with twisted boundary conditions are performed. By arranging the initial configuration suitably it is possible to create a simulation cell with two regions of opposite twist separated by a strength half disclination line. The prop...

  1. Nuclear Magnetic Resonance Quantum Computing Using Liquid Crystal Solvents

    CERN Document Server

    Yannoni, C S; Vandersypen, L M K; Miller, D C; Kubinec, M G; Chuang, I L; Yannoni, Costantino S.; Sherwood, Mark H.; Vandersypen, Lieven M.K.; Miller, Dolores C.; Kubinec, Mark G.; Chuang, Isaac L.

    1999-01-01

    Liquid crystals offer several advantages as solvents for molecules used for NMR quantum computing (NMRQC). The dipolar coupling between nuclear spins manifest in the NMR spectra of molecules oriented by a liquid crystal permits a significant increase in clock frequency, while short spin-lattice relaxation times permit fast recycling of algorithms, and save time in calibration and signal-enhancement experiments. Furthermore, the use of liquid crystal solvents offers scalability in the form of an expanded library of spin-bearing molecules suitable for NMRQC. These ideas are demonstrated with the successful execution of a 2-qubit Grover search using a molecule ($^{13}$C$^{1}$HCl$_3$) oriented in a liquid crystal and a clock speed eight times greater than in an isotropic solvent. Perhaps more importantly, five times as many logic operations can be executed within the coherence time using the liquid crystal solvent.

  2. Tunable bandpass filter based on photonic crystal fiber filled with multiple liquid crystals

    DEFF Research Database (Denmark)

    Scolari, Lara; Tartarini, G.; Borelli, E.; Alkeskjold, Thomas Tanggaard; Mulvad, Hans Christian Hansen; Bassi, Paolo; Bjarklev, Anders Overgaard

    A tunable bandpass filter based on a photonic crystal fiber filled with two different liquid crystals is demonstrated. 130 nm bandwidth tunability is achieved by tuning the temperature from 30degC to 90degC....

  3. Distributed optical fibre devices based on liquid crystal infiltrated photonic crystal fibers

    OpenAIRE

    Alkeskjold, Thomas Tanggaard; Broeng, Jes; Hermann, D.S.; Bjarklev, Anders Overgaard

    2004-01-01

    We describe a new class of hybrid photonic crystal fibers, which are liquid crystal infiltrated fibers. Using these fibers, we demonstrate 'distributed' tunable filter and switching functionalities operating by the photonic bandgap effect.

  4. Liquid Crystal Devices for Optical Communications and Sensing Applications

    OpenAIRE

    Mathews, Sunish

    2011-01-01

    This thesis is focussed on the design and development of liquid crystal based tunable photonic devices for applications in optical communications and optical sensing, with an emphasis on all-fiber device configuration. The infiltration of liquid crystals into photonic crystal fiber provides a suitable common platform to design and fabricate simple and compact all-fiber tunable photonic devices which can be easily integrated with optical fiber networks and sensing systems. Based on the infiltr...

  5. Magnetic, electric and optic properties of liquid crystals

    International Nuclear Information System (INIS)

    We study the nematic liquid crystals of thermotrop type. We also studied the crystals whose mesomorphism occured both at temperature increasing and decreasing and during the supercooling phase (monotrope). Investigation results performed by us have had in view the following: clearing up and experimental support of a new mechanism of nuclear relaxation in liquid crystals, proposed by author; usage of experimental techniques and methods for to characterize and test some mesomorph media used in very important applications, such as color TV. (author)

  6. Electro-optical switching by liquid-crystal controlled metasurfaces

    OpenAIRE

    Decker, Manuel; Kremers, Christian; Minovich, Alexander; Staude, Isabelle; Miroshnichenko, Andrey E.; Chigrin, Dmitry; Neshev, Dragomir N.; Jagadish, Chennupati; Kivshar, Yuri S.

    2013-01-01

    We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-cry...

  7. A NEW METHOD TO ALIGN LIQUID CRYSTAL MOLECULES BY LINEAR PHOTO-POLYMERIZATION FOR LIQUID CRYSTAL DISPLAY

    Institute of Scientific and Technical Information of China (English)

    LIANG ZHAO-YAN; FANG KUN; XUAN LI; HUANG XI-MIN; DING BAO-QUAN; LU RAN; ZHAO YING-YING

    2000-01-01

    A new technique to uniformly align liquid crystal molecules is presented.The technique is based on producing an anisotropic surface on the glass substrate coated with photo-polymers by photo-polymerization of linear polarized UVlight.The orientation of liquid crystal molecules is governed by the direction of the polarized vector of UV-light.Using this method,we have studied the photo-polymer PSi-CM aligning LC 6710A molecules.The liquid crystal microscopic texture between crossed polarizers,optical retardation from liquid crystal layers and electro-optical properties of twisted nematic liquid crystal display cell are obtained,which was prepared with one side -photo-alignment and the other siderebbed substrate.

  8. Liquid crystal drops in suspensions of colloidal plates

    NARCIS (Netherlands)

    Verhoeff, A.A.

    2011-01-01

    This thesis deals with liquid crystalline phases and in particular liquid crystal drops in suspensions of colloidal gibbsite platelets. In Part I we deal with some general aspects of liquid crystalline phases in suspensions of gibbsite platelets, to provide a basic framework for the research describ

  9. H-Bond stabilized columnar discotic liquid crystals

    NARCIS (Netherlands)

    Paraschiv, I.

    2007-01-01

    Since 1977, more than 2300 publications on discotic (disk-like) liquid crystalline materials have appeared. Discotic liquid crystals, which usually consist of polyaromatic molecules surrounded by long peripheral alkyl tails, can form liquid crystalline mesophases in a wide temperature range. Within

  10. Simulating human photoreceptor optics using a liquid-filled photonic crystal fiber

    OpenAIRE

    Rativa, Diego; Vohnsen, Brian

    2011-01-01

    We introduce a liquid-filled photonic crystal fiber to simulate a retinal cone photoreceptor mosaic and the directionality selective mechanism broadly known as the Stiles-Crawford effect. Experimental measurements are realized across the visible spectrum to study waveguide coupling and directionality at different managed waveguide parameters. The crystal fiber method is a hybrid tool between theory and a real biological sample and a valuable addition as a retina model for real eye simulations.

  11. Liquid crystal adaptive lens with circular electrodes

    Science.gov (United States)

    Sun, Yi

    The liquid crystal adaptive lens (LCAL) developed in this research is an electro-optical device using a set of electrodes to grade the refractive index across its aperture. Adjusting the applied voltages permits continuous control of focal length. The first effort at developing an LCAL using circular electrodes to provide a simpler architecture than previous devices using linear electrodes is presented in this dissertation. A theoretical study for an LCAL with circular electrodes is performed. The liquid crystal behavior and the applied voltage profile required for different focal lengths is discussed. Numerical simulation of the refractive index change and the Point Spread Function is developed to study the aberrations and predict performance with circular electrode geometry. A Fresnel lens phase profile is applied to yield a lens with a useful F-number, and a previously unexplored aberration is identified and characterized. An LCAL prototype was designed with a set of high-density electrodes in the conductive ladder meshing configuration, which results in a small number of externally controlled electrodes. A new electronic controller was designed and built with a fast response and accurate output to apply the voltage set to the LCAL. An electro-optical feedback control system based on LabVIEW software was developed to optimize control output voltages using signals from a CID camera. A prototype LCAL was designed with a 7.86 mm diameter aperture and a focal length adjustable from 0.2 m to infinity. It was fabricated on a glass substrate with two layers of transparent electrodes, insulating layers, and vias to connect the two conducting layers. The special fabrication challenges involved are discussed. Focusing experiments were performed by auto-dithering using the electro-optical feedback control system. The point spread function measurement results are presented, demonstrating that the focal spot size reaches the diffraction limit, but astigmatism created by the

  12. New scintillating media based on liquid crystals for particle detectors

    CERN Document Server

    Barnik, M I; Vasilchenko, V G; Golovkin, S V; Medvedkov, A M; Soloviev, A S

    2000-01-01

    The study results of optical, photoluminiscent and scintillation properties of a liquid crystal 4-pentyl-4'-cyanobiphenyl are presented. The scintillation light output of this liquid crystal is about 35% of crystal anthracene, its main decay time constants are 4 and 14 ns, and the maximum of light emission spectrum is about 400 nm. The light output of a dissolution of green emitting light scintillation dopant R6 in the liquid crystal is about 120% of crystal anthracene. The light output of the frozen dissolution measured at -112 deg. C is about 2.5 times higher as observed at +20 deg. C. In the uniaxially oriented liquid crystal, the predominant intensity direction of emitted light is pointed perpendicular to the liquid crystal director and an appreciable part of the emitted light is elliptically polarized. The possibility to use scintillation properties of liquid crystals is considered both for the improvement of existing particle detector characteristics and for the creation of new gated particle detectors.

  13. Computer simulation of confined liquid crystal dynamics

    International Nuclear Information System (INIS)

    Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show /that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer lilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. (author)

  14. Rupture and recoil of bent-core liquid crystal filaments.

    Science.gov (United States)

    Salili, S M; Ostapenko, T; Kress, O; Bailey, C; Weissflog, W; Harth, K; Eremin, A; Stannarius, R; Jákli, A

    2016-05-25

    The recoil process of free-standing liquid crystal filaments is investigated experimentally and theoretically. We focus on two aspects, the contraction speed of the filament and a spontaneously formed undulation instability. At the moment of rupture, the filaments buckle similarly to the classical Euler buckling of elastic rods. The tip velocity decays with decreasing filament length. The wavelength of buckling affinely decreases with the retracting filament tip. The energy gain related to the decrease of the total length and surface area of the filaments is mainly dissipated by layer rearrangements during thickening of the fibre. A flow back into the meniscus is relevant only in the final stage of the recoil process. We introduce a model for the quantitative description of the filament retraction speed. The dynamics of this recoil behaviour may find relevance as a model for biology-related filaments. PMID:27140824

  15. Role of nucleation of bile liquid crystal in gallstone formation

    Institute of Scientific and Technical Information of China (English)

    Hai-Ming Yang; Jie Wu; Jin-Yi Li; Lin Gu; Min-Fei Zhou

    2003-01-01

    AIM: To explore the role of bile liquid crystal in the process of gallbladder stone formation and to provide bases for preventing and treating cholelithiasis.METHODS: 46 guinea pigs, half males and half females,were randomly divided into control group and stone-causing group. Normal feed and stoneleading feed were used respectively to raise guinea pigs in the control group and stone-causing group. The guinea pigs were killed in three batches during the raising period. Under polarizing microscope, the pattern changes of bile liquid crystal in the gallbladder biles of the guinea pigs in the control group and stone-causing group were dynamicly observed respectively in single-blind trial.RESULTS: It was found that there were few crystals in the guinea pigs′biles of the control group, and their Malta cross was small and scattered, and existed in single form. With the increase of the feeding days, bile liquid crystals grew and Malta cross became bigger with their distribution densified, denser somewhere, but always existed in single form. While those of the stone-causing group had more bile liquid crystals, Malta cross was big and merged in strings.With the increase of the feeding days, bile liquid crystals grew in amount and strings of Malta cross increased and became bigger. The crosses in strings were arranged more and more regularly and they gradually changed into stone crystals.CONCLUSION: Formation of gallbladder stone is a process of nucleation from different substances, and the causing-stone gallbladder bile is a constantly supersaturated solution, and bile liquid crystal is a nucleation factor in the formation of gallbladder stones. The process of nucleation includes gathering, merging and phase-changing of bile liquid crystals.The process of gathering, merging of bile liquid crystal is the key to nucleation.

  16. Liquid crystal photoalignment material based on chloromethylated polyimide

    International Nuclear Information System (INIS)

    We report a liquid crystal photoalignment material with high photosensitivity and excellent thermal stability. The chloromethylated aromatic polyimide exhibited defect-free homogeneous alignment of liquid crystals upon irradiation of polarized deep ultraviolet (UV) for 50 s. The aligning ability of the film was retained up to 210 deg. C, and the cell containing liquid crystals could be stored at 85 deg. C for more than 14 days without any deterioration. FT-IR and UV-vis spectra confirmed that the alignment was induced by photodecomposition of polyimide, drastically accelerated by the introduction of chloromethyl side group

  17. Liquid crystals beyond displays chemistry, physics, and applications

    CERN Document Server

    Li, Quan

    2012-01-01

    The chemistry, physics, and applications of liquid crystals beyond LCDs Liquid Crystals (LCs) combine order and mobility on a molecular and supramolecular level. But while these remarkable states of matter are most commonly associated with visual display technologies, they have important applications for a variety of other fields as well. Liquid Crystals Beyond Displays: Chemistry, Physics, and Applications considers these, bringing together cutting-edge research from some of the most promising areas of LC science. Featuring contributions from respected researchers from around the globe, th

  18. A liquid crystal thermography calibration with true color image processing

    Institute of Scientific and Technical Information of China (English)

    Yu Rao; Shusheng Zang; Minghai Huang

    2009-01-01

    Liquid crystal thermography is a high-resolution,non-intrusive optical technique for full-field temperature measurement.We present the detailed calibration data for the thermochromic liquid crystal(TLC)with a usefill range of 41-60 ℃.The calibration is done with true color image processing by using an isothermal calibrator.The hue-temperature curve of the TLC is obtained,and the measurement uncertainty is analyzed.Combined with the image noise reduction technique of a 5×5 median filter,the measurement accuracy of the liquid crystal thermography can be significantly improved by approximately 57.1%.

  19. Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Joanna Ptasinski

    2014-03-01

    Full Text Available In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths.

  20. Thermochromic liquid crystals in heat transfer research

    Science.gov (United States)

    Stasiek, Jan A.; Kowalewski, Tomasz A.

    2002-06-01

    In recent years Thermochromic Liquid Crystals (TLC) have been successfully used in non-intrusive heat transfer and fluid mechanics studies. Thin coatings of TLC's at surfaces is utilized to obtain detailed heat transfer data of steady or transient process. Application of TLC tracers allows instantaneous measurement of the temperature and velocity fields for two-dimensional cross-section of flow. Computerized flow visualization techniques allow automatic quantification of temperature of the analyzed surface or the visualized flow cross-section. Here we describe our experience in applying the method to selected problems studied in our laboratory. They include modeling flow configurations in the differentially heated inclined cavity with vertical temperature gradient simulating up-slope flow as well as thermal convection under freezing surface. The main aim of these experimental models is to generate reliable experimental database on velocity and temperature fields for specific flow. The methods are based on computerized true-color analysis of digital images for temperature measurements and modified Particle Image Velocimetry and Thermometry (PIVT) used to obtain the flow field velocity.

  1. Liquid crystal elastomer strips as soft crawlers

    Science.gov (United States)

    DeSimone, Antonio; Gidoni, Paolo; Noselli, Giovanni

    2015-11-01

    In this paper, we speculate on a possible application of Liquid Crystal Elastomers to the field of soft robotics. In particular, we study a concept for limbless locomotion that is amenable to miniaturisation. For this purpose, we formulate and solve the evolution equations for a strip of nematic elastomer, subject to directional frictional interactions with a flat solid substrate, and cyclically actuated by a spatially uniform, time-periodic stimulus (e.g., temperature change). The presence of frictional forces that are sensitive to the direction of sliding transforms reciprocal, 'breathing-like' deformations into directed forward motion. We derive formulas quantifying this motion in the case of distributed friction, by solving a differential inclusion for the displacement field. The simpler case of concentrated frictional interactions at the two ends of the strip is also solved, in order to provide a benchmark to compare the continuously distributed case with a finite-dimensional benchmark. We also provide explicit formulas for the axial force along the crawler body.

  2. Surface Dipole Control of Liquid Crystal Alignment.

    Science.gov (United States)

    Schwartz, Jeffrey J; Mendoza, Alexandra M; Wattanatorn, Natcha; Zhao, Yuxi; Nguyen, Vinh T; Spokoyny, Alexander M; Mirkin, Chad A; Baše, Tomáš; Weiss, Paul S

    2016-05-11

    Detailed understanding and control of the intermolecular forces that govern molecular assembly are necessary to engineer structure and function at the nanoscale. Liquid crystal (LC) assembly is exceptionally sensitive to surface properties, capable of transducing nanoscale intermolecular interactions into a macroscopic optical readout. Self-assembled monolayers (SAMs) modify surface interactions and are known to influence LC alignment. Here, we exploit the different dipole magnitudes and orientations of carboranethiol and -dithiol positional isomers to deconvolve the influence of SAM-LC dipolar coupling from variations in molecular geometry, tilt, and order. Director orientations and anchoring energies are measured for LC cells employing various carboranethiol and -dithiol isomer alignment layers. The normal component of the molecular dipole in the SAM, toward or away from the underlying substrate, was found to determine the in-plane LC director orientation relative to the anisotropy axis of the surface. By using LC alignment as a probe of interaction strength, we elucidate the role of dipolar coupling of molecular monolayers to their environment in determining molecular orientations. We apply this understanding to advance the engineering of molecular interactions at the nanoscale. PMID:27090503

  3. Free surface dynamics of nematic liquid crystal

    Science.gov (United States)

    Cummings, Linda; Kondic, Lou; Lam, Michael; Lin, Te-Sheng

    2014-11-01

    Spreading thin films of nematic liquid crystal (NLC) are known to behave very differently to those of isotropic fluids. The polar interactions of the rod-like molecules with each other, and the interactions with the underlying substrate, can lead to intricate patterns and instabilities that are not yet fully understood. The physics of a system even as simple as a film of NLC spreading slowly over a surface (inclined or horizontal) are remarkably complex: the outcome depends strongly on the details of the NLC's behavior at both the substrate and the free surface (so-called ``anchoring'' effects). We will present a dynamic flow model that takes careful account of such nematic-substrate and nematic-free surface interactions. We will present model simulations for several different flow scenarios that indicate the variety of behavior that can emerge. Spreading over a horizontal substrate may exhibit a range of unstable behavior. Flow down an incline also exhibits intriguing instabilities: in addition to the usual transverse fingering, instabilities can be manifested behind the flowing front in a manner reminiscent of Newtonian flow down an inverted substrate. NSF DMS-1211713.

  4. Liquid crystal devices especially for use in liquid crystal point diffraction interferometer systems

    Science.gov (United States)

    Marshall, Kenneth L. (Inventor)

    2009-01-01

    Liquid crystal point diffraction interferometer (LCPDI) systems that can provide real-time, phase-shifting interferograms that are useful in the characterization of static optical properties (wavefront aberrations, lensing, or wedge) in optical elements or dynamic, time-resolved events (temperature fluctuations and gradients, motion) in physical systems use improved LCPDI cells that employ a "structured" substrate or substrates in which the structural features are produced by thin film deposition or photo resist processing to provide a diffractive element that is an integral part of the cell substrate(s). The LC material used in the device may be doped with a "contrast-compensated" mixture of positive and negative dichroic dyes.

  5. Liquid crystal devices especially for use in liquid crystal point diffraction interferometer systems

    Science.gov (United States)

    Marshall, Kenneth L.

    2009-02-17

    Liquid crystal point diffraction interferometer (LCPDI) systems that can provide real-time, phase-shifting interferograms that are useful in the characterization of static optical properties (wavefront aberrations, lensing, or wedge) in optical elements or dynamic, time-resolved events (temperature fluctuations and gradients, motion) in physical systems use improved LCPDI cells that employ a "structured" substrate or substrates in which the structural features are produced by thin film deposition or photo resist processing to provide a diffractive element that is an integral part of the cell substrate(s). The LC material used in the device may be doped with a "contrast-compensated" mixture of positive and negative dichroic dyes.

  6. Controllable light diffraction in woodpile photonic crystals filled with liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Chih-Hua; Zeng, Hao; Wiersma, Diederik S. [European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Cheng, Yu-Chieh; Maigyte, Lina; Trull, Jose; Cojocaru, Crina [Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa (Spain); Staliunas, Kestutis [Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa (Spain); Institucio Catalana de Reserca i Estudis Avançats (ICREA), passeig Lluis Companys 23, 08010 Barcelona (Spain)

    2015-01-12

    An approach to switching between different patterns of light beams transmitted through the woodpile photonic crystals filled with liquid crystals is proposed. The phase transition between the nematic and isotropic liquid crystal states leads to an observable variation of the spatial pattern transmitted through the photonic structure. The transmission profiles in the nematic phase also show polarization sensibility due to refractive index dependence on the field polarization. The experimental results are consistent with a numerical calculation by Finite Difference Time Domain method.

  7. NATO Advanced Research Workshop on Incommensurate Crystals, Liquid Crystals, and Quasi-Crystals

    CERN Document Server

    Clark, N

    1988-01-01

    In this NATO-sponsored Advanced Research Workshop we succeeded in bringing together approximately forty scientists working in the three main areas of structurally incommensurate materials: incommensurate crystals (primarily ferroelectric insulators), incommensurate liquid crystals, and metallic quasi-crystals. Although these three classes of materials are quite distinct, the commonality of the physics of the origin and descrip­ tion of these incommensurate structures is striking and evident in these proceedings. A measure of the success of this conference was the degree to which interaction among the three subgroups occurred; this was facili­ tated by approximately equal amounts of theory and experiment in the papers presented. We thank the University of Colorado for providing pleasant housing and conference facilities at a modest cost, and we are especially grate­ ful to Ann Underwood, who retyped all the manuscripts into camera-ready form. J. F. Scott Boulder, Colorado N. A. Clark v CONTENTS PART I: INCO...

  8. Liquid crystals: a new topic in physics for undergraduates

    CERN Document Server

    Pavlin, Jerneja; Cepic, Mojca

    2012-01-01

    The paper presents a teaching module about liquid crystals. Since liquid crystals are linked to everyday student experiences and are also a topic of a current scientific research, they are an excellent candidate of a modern topic to be introduced into education. We show that liquid crystals can provide a file rouge through several fields of physics such as thermodynamics, optics and electromagnetism. We discuss what students should learn about liquid crystals and what physical concepts they should know before considering them. In the presentation of the teaching module that consists of a lecture and experimental work in a chemistry and physics lab, we focus on experiments on phase transitions, polarization of light, double refraction and colours. A pilot evaluation of the module was performed among pre-service primary school teachers who have no special preference for natural sciences. The evaluation shows that the module is very efficient in transferring knowledge. A prior study showed that the informally ob...

  9. Magnetic, electrical and optical properties of liquid crystals

    International Nuclear Information System (INIS)

    This thesis lays stress on the study of thermotrop nematic liquid crystals. But the crystals whose mesomorphism is achieved by an increase and decrease in temperature and the crystal category exhibiting a mesomorphism in a deep freezing phase are also studied. The results of the research carried out in the laboratory of ''active media, lasers and matter-radiation interactions'' of the Institute for Physics and Technology of Radiation Apparata as well as in the laboratories of liquid crystals and nuclear magnetic resonance of the Polytechnical Institute of Bucharest during seven years have had in view two main objectives: to elucidate and prove experimentally a new mechanism of nuclear relaxation in liquid crystals, proposed by the author; to use the current experimental techniques and methods applied in the above-mentioned laboratories to characterize and test some foreign mesomorphic media which are synthesized locally, providing a wide range of applications, such as colour television. (author)

  10. Nonlocal gap soliton in liquid infiltrated photonic crystal fibres

    DEFF Research Database (Denmark)

    Bennet, F.H.; Rosberg, C.R.; Rasmussen, Per Dalgaard;

    We report on the observation of nonlocal gap solitons in infiltrated photonic crystal fibres. We employ the thermal defocusing nonlinearity of the liquid to study soliton existence and effect of boundaries of the periodic structure.......We report on the observation of nonlocal gap solitons in infiltrated photonic crystal fibres. We employ the thermal defocusing nonlinearity of the liquid to study soliton existence and effect of boundaries of the periodic structure....

  11. Liquid crystal director fluctuations and surface anchoring by molecular simulation

    OpenAIRE

    Andrienko, D.; Germano, G; Allen, M. P.

    2002-01-01

    We propose a simple and reliable method to measure the liquid crystal surface anchoring strength by molecular simulation. The method is based on the measurement of the long-range fluctuation modes of the director in confined geometry. As an example, molecular simulations of a liquid crystal in slab geometry between parallel walls with homeotropic anchoring have been carried out using the Monte Carlo technique. By studying different slab thicknesses, we are able to calculate separately the pos...

  12. Measurement of optical properties of thermochromic liquid-crystals

    International Nuclear Information System (INIS)

    3 kinds of thermochromic liquid-crystals, stabilized by the micro-encapsulation, are investigated by the method of visual observation, spectro-meter and color-meter which measures the tristimulus of the light selectively reflected from the liquid-crystal layers. After the discussion of the optical properties, a new method is successfully examined to correlate the color and temperature using the hue value. (author)

  13. Gaussian Filtering with Tapered Liquid Crystal Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Scolari, Lara; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2006-01-01

    We present a device based on a tapered Liquid Crystal Photonic Bandgap Fiber that allows active all-in-fiber filtering. The resulting Photonic Bandgap Fiber device provides a Gaussian filter covering the wavelength range 1200-1600 nm......We present a device based on a tapered Liquid Crystal Photonic Bandgap Fiber that allows active all-in-fiber filtering. The resulting Photonic Bandgap Fiber device provides a Gaussian filter covering the wavelength range 1200-1600 nm...

  14. Liquid-crystal tunable filter based on sapphire microspheres.

    Science.gov (United States)

    Gilardi, Giovanni; Donisi, Domenico; Serpengüzel, Ali; Beccherelli, Romeo

    2009-11-01

    We design an integrated optoelectronic device based on the whispering-gallery modes of a sapphire microsphere integrated with a liquid-crystal tuning medium to produce a narrowband, electrically tunable, channel-dropping filter. The sapphire microsphere is glued over a diffused waveguide in a glass substrate. At the base of the microsphere, a small volume of liquid crystal is infiltrated. We numerically evaluate the performance of the device and demonstrate a voltage tuning of the narrowband resonances. PMID:19881558

  15. Liquid-Crystal Blazed-Grating Beam Deflector

    OpenAIRE

    Wang, Xu; Wilson, Daniel; Muller, Richard; Maker, Paul; Psaltis, Demetri

    2000-01-01

    A transmission-type nonmechanical multiple-angle beam-steering device that uses liquid-crystal blazed grating has been developed. Sixteen steering angles with a contrast ratio of 18 has been demonstrated. A detailed analysis of the liquid-crystal and poly(methyl methacrylate) blazed-grating deflector was carried out to provide guidance during the deflector’s development. A manufacturing offset compensation technique is proposed to improve the device’s performance greatly. A hybrid approach ut...

  16. Optical detection of sepsis markers using liquid crystal based biosensors

    Science.gov (United States)

    McCamley, Maureen K.; Artenstein, Andrew W.; Opal, Steven M.; Crawford, Gregory P.

    2007-02-01

    A liquid crystal based biosensor for the detection and diagnosis of sepsis is currently in development. Sepsis, a major clinical syndrome with a significant public health burden in the US due to a large elderly population, is the systemic response of the body to a localized infection and is defined as the combination of pathologic infection and physiological changes. Bacterial infections are responsible for 90% of cases of sepsis in the US. Currently there is no bedside diagnostic available to positively identify sepsis. The basic detection scheme employed in a liquid crystal biosensor contains attributes that would find value in a clinical setting, especially for the early detection of sepsis. Utilizing the unique properties of liquid crystals, such as birefringence, a bedside diagnostic is in development which will optically report the presence of biomolecules. In a septic patient, an endotoxin known as lipopolysaccharide (LPS) is released from the outer membrane of Gram-negative bacteria and can be found in the blood stream. It is hypothesized that this long chained molecule will cause local disruptions to the open surface of a sensor containing aligned liquid crystal. The bulk liquid crystal ampli.es these local changes at the surface due to the presence of the sepsis marker, providing an optical readout through polarizing microscopy images. Liquid crystal sensors consisting of both square and circular grids, 100-200 μm in size, have been fabricated and filled with a common liquid crystal material, 5CB. Homeotropic alignment was confirmed using polarizing microscopy. The grids were then contacted with either saline only (control), or saline with varying concentrations of LPS. Changes in the con.guration of the nematic director of the liquid crystal were observed through the range of concentrations tested (5mg/mL - 1pg/mL) which have been confirmed by a consulting physician as clinically relevant levels.

  17. Columnar liquid crystals in cylindrical nanoconfinement.

    Science.gov (United States)

    Zhang, Ruibin; Zeng, Xiangbing; Kim, Bongseock; Bushby, Richard J; Shin, Kyusoon; Baker, Patrick J; Percec, Virgil; Leowanawat, Pawaret; Ungar, Goran

    2015-02-24

    Axial orientation of discotic columnar liquid crystals in nanopores of inorganic templates, with the columns parallel to the axis of the nanochannels, is considered desirable for applications such as production of molecular wires. Here, we evaluate experimentally the role of the rigidity of the LC columns in achieving such orientation in nanopores where the planar anchoring (i.e., columns parallel to wall surface) is enforced. We studied the columnar phase of several discotic compounds with increasing column rigidity in the following order: dendronized carbazole, hexakis(hexyloxy)triphenylene (HAT6), a 1:1 HAT6-trinitrofluorenone (TNF) complex, and a helicene derivative. Using 2-D X-ray diffraction, AFM, grazing incidence diffraction, and polarized microscopy, we observed that the orientation of the columns changes from circular concentric to axial with increasing column rigidity. Additionally, when the rigidity is borderline, increasing pore diameter can change the configuration from axial back to circular. We derive expressions for distortion free energy that suggest that the orientation is determined by the competition between, on the one hand, the distortion energy of the 2-d lattice and the mismatch of its crystallographic facets with the curved pore wall in the axial orientation and, on the other hand, the bend energy of the columns in the circular configuration. Furthermore, the highly detailed AFM images of the core of the disclinations of strength +1 and +1/2 in the center of the pore reveal that the columns spiral down to the very center of the disclination and that there is no amorphous or misaligned region at the core, as suggested previously. PMID:25626118

  18. Order parameters in smectic liquid crystals

    International Nuclear Information System (INIS)

    This thesis explores some of the important mechanisms for switching in smectic liquid crystals. It is mainly concerned with the interaction of the electric field and various order parameters in smectic phases. Distortion of these order parameters and also the layer structures associated with smectics are discussed in depth. Initial work is concentrated on the electroclinic effect of commercially available FLC mixtures, where experimental results suggest the presence of non-uniformity in the molecular director profile. Two possible models are suggested assuming a variation of the order parameter θ through the cell. The first model assumes that the smectic layers remain bookshelf-like, and the second that the layers tilt in a vertical chevron structure when a cone angle is induced electroclinically or otherwise. The latter model is the first 'order parameter' model of an electric field induced vertical chevron. The presence of non-uniformity in the director profile is sensed by a method similar to wavelength extinction spectroscopy. Investigations are undertaken on racemic smectic materials with high dielectric biaxiality. Modelling of such a material reveals a new electroclinic effect which shows a discrete second order phase transition on application of a field. It is suggested that a bistable electroclinic effect stabilised with a high frequency ac field may be realised if a residual polarisation is present in the high biaxiality material, and that this might be useful in the displays industry. Experimental investigations of such a material confirm the above effects close to the smectic A-C transition. Finally a higher order smectic phase, the smectic I* phase, is considered. The distortion of the hexagonal bond orientational order is investigated experimentally during application of an electric field. The first dynamic model of the switching process is presented, showing good agreement with the experimental results. It is suggested that the bond orientational

  19. A liquid crystal and polymer composite film for liquid crystal lenses

    Science.gov (United States)

    Lin, Yi-Hsin; Chen, Hung-Shan; Wang, Yu-Jen; Chang, Chia-Ming

    2015-03-01

    Liquid crystal (LC) lenses offer novel opportunities for applications of ophthalmic lenses, camera modules, pico projectors, endoscopes, and optical zoom systems owing to electrically tunable lens power. Nevertheless, the tunable lens power and the aperture size of LC lenses are limited by the optical phase resulting from limit birefringence of LC materials. Recently, we developed a liquid crystal and polymer composite film (LCPCF) as a separation layer and an alignment layer for a multi-layered structure of LC lenses in order to enlarge the polarization-independent optical phase modulation. However, the physical properties and mechanical properties of the LCPCF are not clearly investigated. In this paper, we show the mechanical and physical properties of the LCPCF. The anchoring energy of the LCPCF is comparable with the standard rubbing-induced alignment layer. The transmission efficiency is around 97% neglecting the Fresnel reflection. The surface roughness is under 2 nm by using AFM scanning. The bending strength test indicates that the LCPCF can hold the LC material with reasonable deformation. We believe this study provides a deeper insight to the LC lens structure embedded with LCPCF.

  20. Liquid crystals: a new topic in physics for undergraduates

    International Nuclear Information System (INIS)

    This paper presents a teaching module about liquid crystals. Since liquid crystals are linked to everyday student experiences and are also a topic of current scientific research, they are an excellent candidate for a modern topic to be introduced into education. We show that liquid crystals can provide a pathway through several fields of physics such as thermodynamics, optics and electromagnetism. We discuss what students should learn about liquid crystals and what physical concepts they should know before considering them. In the presentation of the teaching module, which consists of a lecture and experimental work in a chemistry and physics laboratory, we focus on experiments on phase transitions, polarization of light, double refraction and colours. A pilot evaluation of the module was performed among pre-service primary school teachers who have no special preference for natural sciences. The evaluation shows that the module is very efficient in transferring knowledge. A prior study showed that the informally obtained pre-knowledge on liquid crystals of the first-year students from several different fields of study was negligible. Since social science students are the least interested in natural sciences, it can be expected that students in any study programme will on average achieve at least as good qualitative knowledge of phenomena related to liquid crystals as the group involved in the pilot study. (paper)

  1. Photorefractivity in polymer-stabilized nematic liquid crystals

    Science.gov (United States)

    Wiederrecht, Gary P.; Wasielewski, Michael R.

    1998-10-01

    Polymer-stabilized liquid crystals, consisting of low concentrations of a polymeric electron acceptor, are shown to exhibit significantly enhanced photorefractive properties. The charge generation and transport properties of these composite systems are strongly modified from nematic liquid crystals doped with electron donors and acceptors. The new composites are produced by polymerizing a small quantity of a 1,4:5,8-naphthalenediimide electron acceptor functionalized with an acrylate group in an aligned nematic liquid crystal. Photopolymerization creates an anisotropic gel-like medium in which the liquid crystal is free to reorient in the presence of a space charge field, while maintaining charge trapping sites in the polymerized regions of the material. The presence of these trapping sites results in the observation of longer lived, higher resolution holographic gratings in the polymer-stabilized liquid crystals than observed in nematic liquid crystals alone. These gratings display Bragg regime diffraction. Asymmetric beam coupling, photo-conductivity, and four-wave mixing experiments are performed to characterize the photophysics of these novel materials.

  2. Tunable photoluminescence of porous silicon by liquid crystal infiltration

    International Nuclear Information System (INIS)

    The photoluminescence (PL) of porous silicon films has been investigated as a function of the amount of liquid crystal molecules that are infiltrated into the constricted geometry of the porous silicon films. A typical nematic liquid crystal 4-pentyl-4'-cyanobiphenyl was employed in our experiment as the filler to modify the PL of porous silicon. It is found that the originally red PL of porous silicon films can be tuned to blue by simply adjusting the amount of liquid crystal molecules in the microchannels of the porous films. The chromaticity coordinates are calculated for the recorded PL spectra. The mechanism of the tunable PL is discussed. Our results have demonstrated that the luminescent properties of porous silicon films can be efficiently tuned by liquid crystal infiltration. - Highlights: → Liquid crystal infiltration can tune the photoluminescence of porous silicon. → Red emission of porous silicon can be switched to blue by the infiltration. → Chromaticity coordinates are calculated for the tuned emissions. → White emission is realized for porous silicon by liquid crystal infiltration.

  3. Lyotropic chromonic liquid crystals: From viscoelastic properties to living liquid crystals

    Science.gov (United States)

    Zhou, Shuang

    Lyotropic chromonic liquid crystal (LCLC) represents a broad range of molecules, from organic dyes and drugs to DNA, that self-assemble into linear aggregates in water through face-to-face stacking. These linear aggregates of high aspect ratio are capable of orientational order, forming, for example nematic phase. Since the microscopic properties (such as length) of the chromonic aggregates are results of subtle balance between energy and entropy, the macroscopic viscoelastic properties of the nematic media are sensitive to change of external factors. In the first part of this thesis, by using dynamic light scattering and magnetic Frederiks transition techniques, we study the Frank elastic moduli and viscosity coefficients of LCLC disodium cromoglycate (DSCG) and sunset yellow (SSY) as functions of concentration c , temperature T and ionic contents. The elastic moduli of splay (K1) and bend (K3) are in the order of 10pN, about 10 times larger than the twist modulus (K2). The splay modulus K1 and the ratio K1/K3 both increase substantially as T decreases or c increases, which we attribute to the elongation of linear aggregates at lower T or higher c . The bend viscosity is comparable to that of thermotropic liquid crystals, while the splay and twist viscosities are several orders of magnitude larger, changing exponentially with T . Additional ionic additives into the system influence the viscoelastic properties of these systems in a dramatic and versatile way. For example, monovalent salt NaCl decreases bend modulus K3 and increases twist viscosity, while an elevated pH decreases all the parameters. We attribute these features to the ion-induced changes in length and flexibility of building units of LCLC, the chromonic aggregates, a property not found in conventional thermotropic and lyotropic liquid crystals form by covalently bound units of fixed length. The second part of the thesis studies a new active bio-mechanical hybrid system called living liquid crystal

  4. NMR STUDIES OF LIQUID CRYSTALS AND MOLECULES DISSOLVED IN LIQUID CRYSTAL SOLVENTS

    Energy Technology Data Exchange (ETDEWEB)

    Drobny, G.P.

    1982-11-01

    This thesis describes several studies in which nuclear magnetic resonance (nmr) spectroscopy has been used to probe the structure, orientation and dynamics of liquid crystal mesogens and molecules dissolved in liquid crystalline phases. In addition, a modern high field nmr spectrometer is described which has been used to perform such nmr studies. Chapter 1 introduces the quantum mechanical formalisms used throughout this thesis and briefly reviews the fundamentals of nuclear spin physics and pulsed nmr spectroscopy. First the density operator is described and a specific form for the canonical ensemble is derived. Then Clebsch-Gordon coefficients, Wigner rotation matrices, and irreducible tensor operators are reviewed. An expression for the equilibrium (Curie) magnetization is obtained and the linear response of a spin system to a strong pulsed r.f. irradiation is described. Finally, the spin interaction Hamiltonians relevant to this work are reviewed together with their truncated forms. Chapter 2 is a deuterium magnetic resonance study of two 'nom' liquid crystals which possess several low temperature mesomorphic phases. Specifically, deuterium quadrupolar echo spectroscopy is used to determine the orientation of the liquid crystal molecules in smectic phases, the changes in molecular orientation and motion that occur at smectic-smectic phase transitions, and the order of the phase transitions. For both compounds, the phase sequence is determined to be isotropic, nematic, smectic A, smectic C, smectic B{sub A}, smectic B{sub C}, and crystalline. The structure of the smectic A phase is found to be consistent with the well-known model of a two dimensional liquid in which molecules are rapidly rotating about their long axes and oriented at right angles to the plane of the layers. Molecules in the smectic C phase are found to have their long axes tilted with respect to the layer normal, and the tilt angle is temperature dependent, increasing from zero at the

  5. NATO Advanced Study Institute on Advances in the Computer Simulations of Liquid Crystals

    CERN Document Server

    Zannoni, Claudio

    2000-01-01

    Computer simulations provide an essential set of tools for understanding the macroscopic properties of liquid crystals and of their phase transitions in terms of molecular models. While simulations of liquid crystals are based on the same general Monte Carlo and molecular dynamics techniques as are used for other fluids, they present a number of specific problems and peculiarities connected to the intrinsic properties of these mesophases. The field of computer simulations of anisotropic fluids is interdisciplinary and is evolving very rapidly. The present volume covers a variety of techniques and model systems, from lattices to hard particle and Gay-Berne to atomistic, for thermotropics, lyotropics, and some biologically interesting liquid crystals. Contributions are written by an excellent panel of international lecturers and provides a timely account of the techniques and problems in the field.

  6. Nonlinear optical studies of liquid crystals and polymers

    Science.gov (United States)

    Hong, Seok-Cheol

    Polymers are indispensable in our life. A life is a continuous event maintained by many complex processes in which biological polymers participate. It also gets help from a variety of natural and synthetic polymers with useful functions. Such functions depend on the chemical and conformational structures of polymers and often largely on the surface structures and properties of polymers. We used second order nonlinear optical techniques (sum frequency vibrational spectroscopy (SFVS) and second harmonic generation (SHG)) to obtain structural information on polymers. We also studied liquid crystal molecules deposited on polymer surfaces. The first part of the thesis is aimed at understanding liquid crystal (LC) alignment on rubbed polymer surfaces by determining the molecular orientations of LC adsorbates and surface polymer chains. The alignment of LCs by rubbed polymers is not only of fundamental interest but also of practical importance because it is a technique enabling production of commercial liquid crystal displays. We observed that rubbing induces alignment of surface polymer chains along the rubbing direction, and there is a strong correlation between the molecular orientations of LC adsorbates and the surface chains of rubbed polymers such as polyvinyl alcohol (PVA) and polyimide (6FDA-6CBO). The latter revealed a relatively large but negative pretilt angle, which is highly unusual. On a rubbed polystyrene (PS) surface, we found that the phenyl side groups of PS are oriented perpendicularly to the rubbing direction at the surface, rendering an LC alignment also perpendicular to the rubbing direction. The second part of the thesis is our discovery of rubbing-induced polar ordering on nylon 11 surfaces. Nylon 11 is known to be ferroelectric. We found that mechanical rubbing can induce strong ferroelectric polarization on an initially amorphous film of nylon 11. The surface chains of rubbed nylon 11 are aligned along the rubbing direction while the induced

  7. Understanding the fabric of protein crystals: computational classification of biological interfaces and crystal contacts

    OpenAIRE

    Capitani, Guido; Duarte, Jose M; Baskaran, Kumaran; Bliven, Spencer; Somody, Joseph C.

    2015-01-01

    Modern structural biology still draws the vast majority of information from crystallography, a technique where the objects being investigated are embedded in a crystal lattice. Given the complexity and variety of those objects, it becomes fundamental to computationally assess which of the interfaces in the lattice are biologically relevant and which are simply crystal contacts. Since the mid-1990s, several approaches have been applied to obtain high-accuracy classification of crystal contacts...

  8. Manipulating lipid membrane architecture by liquid crystal-analog curvature elasticity (Presentation Recording)

    Science.gov (United States)

    Lee, Sin-Doo

    2015-10-01

    Soft matters such as liquid crystals and biological molecules exhibit a variety of interesting physical phenomena as well as new applications. Recently, in mimicking biological systems that have the ability to sense, regulate, grow, react, and regenerate in a highly responsive and self-adaptive manner, the significance of the liquid crystal order in living organisms, for example, a biological membrane possessing the lamellar order, is widely recognized from the viewpoints of physics and chemistry of interfaces and membrane biophysics. Lipid bilayers, resembling cell membranes, provide primary functions for the transport of biological components of ions and molecules in various cellular activities, including vesicle budding and membrane fusion, through lateral organization of the membrane components such as proteins. In this lecture, I will describe how the liquid crystal-analog curvature elasticity of a lipid bilayer plays a critical role in developing a new platform for understanding diverse biological functions at a cellular level. The key concept is to manipulate the local curvature at an interface between a solid substrate and a model membrane. Two representative examples will be demonstrated: one of them is the topographic control of lipid rafts in a combinatorial array where the ligand-receptor binding event occurs and the other concerns the reconstitution of a ring-type lipid raft in bud-mimicking architecture within the framework of the curvature elasticity.

  9. Liquid crystals for organic thin-film transistors

    OpenAIRE

    Iino, Hiroaki; Usui, Takayuki; Hanna, Jun-ichi

    2015-01-01

    Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,...

  10. Magnetic Alignment Study of Rare-Earth-Containing Liquid Crystals

    OpenAIRE

    Galyametdinov, Yury; Haase, Wolfgang; Goderis, Bart; Moors, Dries; Driesen, Kris; Van Deun, Rik; Binnemans, Koen

    2007-01-01

    The liquid-crystalline rare-earth complexes of the type [Ln(LH)3(DOS)3]-where Ln is Tb, Dy, Ho, Er, Tm, or Yb; LH is the Schiff base N-octadecyl-4-tetradecyloxysalicylaldimine; and DOS is dodecylsulfate-exhibit a smectic A phase. Because of the presence of rare-earth ions with a large magnetic anisotropy, the smectic A phase of these liquid crystals can be easier aligned in an external magnetic field than smectic A phases of conventional liquid crystals. The magnetic anisotropy of the [Ln(LH)...

  11. Reflective and transflective liquid crystal displays

    Science.gov (United States)

    Zhou, Fushan

    Recently transflective liquid crystal displays (LCD) received a lot of attention. A transflective display has a transmissive mode and a reflective mode. It combines the high contrast, high brightness of the transmissive mode with energy-saving of reflective mode and has good performance in various illumination conditions. However, state-of-the-art transflective displays have problems such as different electro-optical properties, difficulty in compatibility and optimization of both modes, low efficiency of light utilization, and complexity in structure. This dissertation focuses on finding new designs of transflective displays that address those problems. One way to do this is to study film compensation of LCD. We first studied film compensation of bistable twisted nematic (BTN) LCD. Starting form the reduced (3x3) Mueller matrices, we derived and simplified the conditions that film compensated BTN can be optimized. Based on these relations, electro-optical properties of some particular configurations, and designs of transflective BTN with high brightness and contrast were given. To confirm and get a better understanding of the results, we use the Poincare sphere to analyze film compensated BTN. The key to this approach is the existence of "fixed points". Compared with the matrix approach, this approach is more simple, elegant, and efficient. We then generalized the Poincare sphere approach to a universal approach of LCD. We applied the universal approach to film compensation of ECB and IPS, and the design of achromatic birefringent filters. We also give two more new designs of transflective displays. In the first design, a dichroic mirror is used to split the visible spectrum into two parts used in transmissive and reflective modes, respectively. Both modes can be optimized. It has a simple structure and good light utilization. A design for a full-color transflective display with good performance is also given. In the second design, each pixel is divided into two

  12. Optical waveguide temperature sensor with liquid crystal

    OpenAIRE

    Hotra, Z.; Skoczylas, M.

    2006-01-01

    Наведено результати розроблення та дослідження сенсора температури на основі пластикового оптоволокна та нематичного рідкого кристала. Сенсор характеризується простою конструкцією і легкою адаптацією до різних умов. Використання термо-оптичних ефектів в сенсорах є дуже зручним під час роботи з агресивними середовищами. The construction and obtained results of temperature sensor operation based on plastic optical waveguide and nematic liquid crystal have been presented. Such sensor is characte...

  13. Quantum Dot/Liquid Crystal Nanocomposites in Photonic Devices

    Directory of Open Access Journals (Sweden)

    Andrea L. Rodarte

    2015-07-01

    Full Text Available Quantum dot/liquid crystal nano-composites are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however, we need to control and stabilize nano-particle dispersion in different liquid crystal host phases and understand how the particles behave in an anisotropic fluid. An ideal system will allow for the controlled assembly of either well-defined nano-particle clusters or a uniform particle distribution. In this paper, we investigate mesogen-functionalized quantum dots for dispersion in cholesteric liquid crystal. These nanoparticles are known to assemble into dense stable packings in the nematic phase, and such structures, when localized in the liquid crystal defects, can potentially enhance the coupling between particles and a cholesteric cavity. Controlling the dispersion and assembly of quantum dots using mesogenic surface ligands, we demonstrate how resonant fluid photonic cavities can result from the co-assembly of luminescent nanoparticles in the presence of cholesteric liquid crystalline ordering.

  14. Theoretical analysis of a biased photonic crystal fiber infiltrated with a negative dielectric anisotropy liquid crystal

    DEFF Research Database (Denmark)

    Weirich, Johannes; Wei, Lei; Lægsgaard, Jesper;

    2009-01-01

    We simulate the PBG mode of a biased Photonic Crystal Fiber (PCF) infiltrated with a Liquid Crystal (LC) with negative dielectric anisotropy. We analyse the voltage induced change of the transmission spectrum, dispersion and losses and compare them to the experimental values.......We simulate the PBG mode of a biased Photonic Crystal Fiber (PCF) infiltrated with a Liquid Crystal (LC) with negative dielectric anisotropy. We analyse the voltage induced change of the transmission spectrum, dispersion and losses and compare them to the experimental values....

  15. Molecular dynamics simulations of liquid crystals at interfaces

    International Nuclear Information System (INIS)

    Molecular dynamics simulations of an atomistic model of 4-n-octyl-4'-cyanobiphenyl (8CB) were performed for thin films of 8CB on solid substrates (a pseudopotential representation of the molecular topography of the (100) crystal surface of polyethylene (PE), a highly ordered atomistic model of a pseudo-crystalline PE surface and an atomistic model of a partially orientated film of PE), free standing thin films of 8CB and 8CB droplets in a hexagonal pit. The systems showed strong homeotropic anchoring at the free volume interface and planar anchoring at the solid interface whose strength was dependent upon the surface present. The free volume interface also demonstrated weak signs of smectic wetting of the bulk. Simulations of thin free standing films of liquid crystals showed the ordered nature of the liquid crystals at the two free volume interfaces can be adopted by the region of liquid crystal molecules between the homeotropic layer at each interface only if there is a certain number of liquid crystal molecules present. The perpendicular anchoring imposed by the free volume interface and the solid interface for the thin films on the solid substrates resulted in some evidence for the liquid crystal director undergoing a continual rotation at low temperatures and a definite discontinuous change at higher temperatures. The liquid crystal alignment imparted by these substrates was found to depend upon the topography of the surface and not the direction of the polymer chains in the substrate. The liquid crystal was found to order via an epitaxy-like mechanism. The perpendicular anchoring results in a drop in the order - disorder transition temperature for the molecules in the region between the homeotropic layer at the free volume interface and the planar layers at the solid interface. An increase in the size of this region does not alter the transition temperature. The shape of the liquid crystal molecules is dependent upon the degree of order and thus the nematic

  16. Liquid crystal display modes in a nontilted bent-core biaxial smectic liquid crystal

    Science.gov (United States)

    Nagaraj, Mamatha; Panarin, Y. P.; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-11-01

    Liquid crystal display (LCD) modes associated with the rotation of the secondary director in nontilted, biaxial smectic phase of an achiral bent-core compound are demonstrated. For LCDs, we find that at least four display modes are possible using SmAPA phase of the studied material, in which the minor directors in adjacent layers are aligned antiferroelectrically. The advantages of these modes include low driving field (1-2 V/μm), high contrast ratio 1000:1, relatively fast switching time of 0.5 ms and continuous gray scale. The molecular short axis or the polar axis in a negative dielectric, biaxial material is oriented by the in-plane electric field by a combination dielectric biaxiality and polarity at low electric fields and polarity at higher fields.

  17. Do protein crystals nucleate within dense liquid clusters?

    Energy Technology Data Exchange (ETDEWEB)

    Maes, Dominique, E-mail: dommaes@vub.ac.be [Vrije Universiteit Brussel, 1050 Brussels (Belgium); Vorontsova, Maria A. [University of Houston, Houston, TX 77204 (United States); Potenza, Marco A. C.; Sanvito, Tiziano [Universita di Milano, 20133 Milano (Italy); Sleutel, Mike [Vrije Universiteit Brussel, 1050 Brussels (Belgium); Giglio, Marzio [Universita di Milano, 20133 Milano (Italy); Vekilov, Peter G. [Vrije Universiteit Brussel, 1050 Brussels (Belgium); University of Houston, Houston, TX 77204 (United States); University of Houston, Houston, TX 77204 (United States)

    2015-06-27

    The evolution of protein-rich clusters and nucleating crystals were characterized by dynamic light scattering (DLS), confocal depolarized dynamic light scattering (cDDLS) and depolarized oblique illumination dark-field microscopy. Newly nucleated crystals within protein-rich clusters were detected directly. These observations indicate that the protein-rich clusters are locations for crystal nucleation. Protein-dense liquid clusters are regions of high protein concentration that have been observed in solutions of several proteins. The typical cluster size varies from several tens to several hundreds of nanometres and their volume fraction remains below 10{sup −3} of the solution. According to the two-step mechanism of nucleation, the protein-rich clusters serve as locations for and precursors to the nucleation of protein crystals. While the two-step mechanism explained several unusual features of protein crystal nucleation kinetics, a direct observation of its validity for protein crystals has been lacking. Here, two independent observations of crystal nucleation with the proteins lysozyme and glucose isomerase are discussed. Firstly, the evolutions of the protein-rich clusters and nucleating crystals were characterized simultaneously by dynamic light scattering (DLS) and confocal depolarized dynamic light scattering (cDDLS), respectively. It is demonstrated that protein crystals appear following a significant delay after cluster formation. The cDDLS correlation functions follow a Gaussian decay, indicative of nondiffusive motion. A possible explanation is that the crystals are contained inside large clusters and are driven by the elasticity of the cluster surface. Secondly, depolarized oblique illumination dark-field microscopy reveals the evolution from liquid clusters without crystals to newly nucleated crystals contained in the clusters to grown crystals freely diffusing in the solution. Collectively, the observations indicate that the protein-rich clusters in

  18. Electrochemical liquid-liquid-solid (ec-LLS) crystal growth: a low-temperature strategy for covalent semiconductor crystal growth.

    Science.gov (United States)

    Fahrenkrug, Eli; Maldonado, Stephen

    2015-07-21

    This Account describes a new electrochemical synthetic strategy for direct growth of crystalline covalent group IV and III-V semiconductor materials at or near ambient temperature conditions. This strategy, which we call "electrochemical liquid-liquid-solid" (ec-LLS) crystal growth, marries the semiconductor solvation properties of liquid metal melts with the utility and simplicity of conventional electrodeposition. A low-temperature liquid metal (i.e., Hg, Ga, or alloy thereof) acts simultaneously as the source of electrons for the heterogeneous reduction of oxidized semiconductor precursors dissolved in an electrolyte as well as the solvent for dissolution of the zero-valent semiconductor. Supersaturation of the semiconductor in the liquid metal triggers eventual crystal nucleation and growth. In this way, the liquid electrolyte-liquid metal-solid crystal phase boundary strongly influences crystal growth. As a synthetic strategy, ec-LLS has several intrinsic features that are attractive for preparing covalent semiconductor crystals. First, ec-LLS does not require high temperatures, toxic precursors, or high-energy-density semiconductor reagents. This largely simplifies equipment complexity and expense. In practice, ec-LLS can be performed with only a beaker filled with electrolyte and an electrical circuit capable of supplying a defined current (e.g., a battery in series with a resistor). By this same token, ec-LLS is compatible with thermally and chemically sensitive substrates (e.g., plastics) that cannot be used as deposition substrates in conventional syntheses of covalent semiconductors. Second, ec-LLS affords control over a host of crystal shapes and sizes through simple changes in common experimental parameters. As described in detail herein, large and small semiconductor crystals can be grown both homogeneously within a liquid metal electrode and heterogeneously at the interface of a liquid metal electrode and a seed substrate, depending on the particular

  19. Nanoscience with liquid crystals from self-organized nanostructures to applications

    CERN Document Server

    Li, Quan

    2014-01-01

    This book focuses on the exciting topic of nanoscience with liquid crystals: from self-organized nanostructures to applications. The elegant self-organized liquid crystalline nanostructures, the synergetic characteristics of liquid crystals and nanoparticles, liquid crystalline nanomaterials, synthesis of nanomaterials using liquid crystals as templates, nanoconfinement and nanoparticles of liquid crystals are covered and discussed, and the prospect of fabricating functional materials is highlighted. Contributions, collecting the scattered literature of the field from leading and active player

  20. Modeling Textural Processes during Self-Assembly of Plant-Based Chiral-Nematic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Yogesh K. Murugesan

    2010-12-01

    Full Text Available Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal plywood architecture. The emergence of the plywood architecture by directed chiral nematic liquid crystalline self assembly has been postulated as the mechanism that leads to optimal cellulose fibril organization. In natural systems, tissue growth and development takes place in the presence of inclusions and secondary phases leaving behind characteristic defects and textures, which provide a unique testing ground for the validity of the liquid crystal self-assembly postulate. In this work, a mathematical model, based on the Landau-de Gennes theory of liquid crystals, is used to simulate defect textures arising in the domain of self assembly, due to presence of secondary phases representing plant cells, lumens and pit canals. It is shown that the obtained defect patterns observed in some plant cell walls are those expected from a truly liquid crystalline phase. The analysis reveals the nature and magnitude of the viscoelastic material parameters that lead to observed patterns in plant-based helicoids through directed self-assembly. In addition, the results provide new guidance to develop biomimetic plywoods for structural and functional applications.

  1. Programmable agile beam steering based on a liquid crystal prism

    International Nuclear Information System (INIS)

    To meet the application need for agile precision beam steering, a novel liquid crystal prism device with a simple structure, convenient control, low cost and applicable performance is presented, and analysed theoretically and experimentally. The relationships between the optical path and the thickness of the liquid crystal cell under different voltages are investigated quantitatively by using a theoretical model. Analysis results show that the optical path profile of the liquid crystal prism has a quasi-linear slope and the standard deviation of the linear slope is less than 16 nm. The slope ratio can be changed by a voltage, which achieves the programmable beam steering and control. Practical liquid crystal prism devices are fabricated. Their deflection angles and wavefront profiles with different voltages are experimentally tested. The results are in good agreement with the simulated results. The results imply that the agile beam steering in a scope of 100 μrad with a micro-rad resolution is substantiated in the device. The two-dimensional beam steering is also achieved by cascading two liquid crystal prism devices. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  2. Photonics of liquid-crystal structures: A review

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Blinov, L. M.; Barnik, M. I.; Lazarev, V. V.; Umanskii, B. A.; Shtykov, N. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2011-07-15

    The original results of studies of the electro-optical and laser effects which have been performed at the Laboratory of Liquid Crystals of the Institute of Crystallography, Russian Academy of Sciences, over the last few years are reviewed. Cholesteric liquid crystals as vivid representatives of photonic structures and their behavior in an electric field are considered in detail. The formation of higher harmonics in the periodic distribution of the director field in a helical liquid crystal structure and, correspondingly, the new (anharmonic) mode of electro-optical effects are discussed. Another group of studies is devoted to bistable light switching by an electric field in chiral nematics. Polarization diffraction gratings controlled by an electric field are also considered. The results of studies devoted to microlasers on various photonic structures with cholesteric and nematic liquid crystals are considered in detail. Particular attention is given to the new regime: leaky-mode lasing. Designs of liquid crystal light amplifiers and their polarization, field, and spectral characteristics are considered in the last section.

  3. Photonics of liquid-crystal structures: A review

    International Nuclear Information System (INIS)

    The original results of studies of the electro-optical and laser effects which have been performed at the Laboratory of Liquid Crystals of the Institute of Crystallography, Russian Academy of Sciences, over the last few years are reviewed. Cholesteric liquid crystals as vivid representatives of photonic structures and their behavior in an electric field are considered in detail. The formation of higher harmonics in the periodic distribution of the director field in a helical liquid crystal structure and, correspondingly, the new (anharmonic) mode of electro-optical effects are discussed. Another group of studies is devoted to bistable light switching by an electric field in chiral nematics. Polarization diffraction gratings controlled by an electric field are also considered. The results of studies devoted to microlasers on various photonic structures with cholesteric and nematic liquid crystals are considered in detail. Particular attention is given to the new regime: leaky-mode lasing. Designs of liquid crystal light amplifiers and their polarization, field, and spectral characteristics are considered in the last section.

  4. Thermal and Optical Characterization of Polymer-Dispersed Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Robert A. Shanks

    2012-01-01

    Full Text Available Liquid crystals are compounds that display order in the liquid state above the melting temperature and below the mesogenic isotropic temperature. Polymer-dispersed liquid crystals (PDLCs are composite materials in which liquid crystalline material is dispersed within a polymer matrix to form micron-sized droplets. The aim was to prepare several cholesteryl esters or alkoxybenzoic acid PDLCs and characterise thermal and optical properties. Differential scanning calorimetry and polarized optical microscopy were employed. The matrix polymer was a one-component UV-curable epoxy-acrylate resin. PDLCs were formed through entropy controlled phase separation resulting from UV-initiated crosslinking. The liquid crystals, both as mesogenic moieties and as dispersed droplets, exhibited various textures according to their molecular order and orientation. These textures formed in constrained regions separated by phase boundaries that occurred at temperatures characteristic of each liquid crystal used. The PDLC phase transitions occurred at temperatures lower than those exhibited by the mesogenic components in the neat state.

  5. Biological upgrading of coal liquids. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-02-01

    A large number of bacterial enrichments have been developed for their ability to utilize nitrogen and sulfur in coal liquids and the model compound naphtha. These bacteria include the original aerobic bacteria isolated from natural sources which utilize heteroatom compounds in the presence of rich media, aerobic nitrogen-utilizing bacteria and denitrifying bacteria. The most promising isolates include Mix M, a mixture of aerobic bacteria; ER15, a pyridine-utilizing isolate; ERI6, an aniline-utilizing isolate and a sewage sludge isolate. Culture optimization experiments have led to these bacteria being able to remove up to 40 percent of the sulfur and nitrogen in naphtha and coal liquids in batch culture. Continuous culture experiments showed that the coal liquid is too toxic to the bacteria to be fed without dilution or extraction. Thus either semi-batch operation must be employed with continuous gas sparging into a batch of liquid, or acid extracted coal liquid must be employed in continuous reactor studies with continuous liquid flow. Isolate EN-1, a chemical waste isolate, removed 27 percent of the sulfur and 19 percent of the nitrogen in fed batch experiments. Isolate ERI5 removed 28 percent of the nitrogen in coal liquid in 10 days in fed batch culture. The sewage sludge isolate removed 22.5 percent of the sulfur and 6.5 percent of the nitrogen from extracted coal liquid in continuous culture, and Mix M removed 17.5 percent of the nitrogen from medium containing extracted coal liquid. An economic evaluation has been prepared for the removal of nitrogen heteroatom compounds from Wilsonville coal liquid using acid extraction followed by fermentation. Similar technology can be developed for sulfur removal. The evaluation indicates that the nitrogen heteroatom compounds can be removed for $0.09/lb of coal liquid treated.

  6. Crystal-liquid interfacial free energy via thermodynamic integration

    Energy Technology Data Exchange (ETDEWEB)

    Benjamin, Ronald; Horbach, Jürgen, E-mail: horbach@thphy.uni-duesseldorf.de [Institut für Theoretische Physik II: Soft Matter, Heinrich Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf (Germany)

    2014-07-28

    A novel thermodynamic integration (TI) scheme is presented to compute the crystal-liquid interfacial free energy (γ{sub cl}) from molecular dynamics simulation. The scheme is applied to a Lennard-Jones system. By using extremely short-ranged and impenetrable Gaussian flat walls to confine the liquid and crystal phases, we overcome hysteresis problems of previous TI schemes that stem from the translational movement of the crystal-liquid interface. Our technique is applied to compute γ{sub cl} for the (100), (110), and (111) orientation of the crystalline phase at three temperatures under coexistence conditions. For one case, namely, the (100) interface at the temperature T = 1.0 (in reduced units), we demonstrate that finite-size scaling in the framework of capillary wave theory can be used to estimate γ{sub cl} in the thermodynamic limit. Thereby, we show that our TI scheme is not associated with the suppression of capillary wave fluctuations.

  7. Nonlinear optics, active plasmonics and metamaterials with liquid crystals

    Science.gov (United States)

    Khoo, Iam Choon

    2014-03-01

    Nematic liquid crystals possess large and versatile optical nonlinearities suitable for photonics applications spanning the femtoseconds to milliseconds time scales, and across a wide spectral window. We present a comprehensive review of the physical properties and mechanisms that underlie these multiple time scales nonlinearities, delving into individual molecular electronic responses as well as collective ordered-phase dynamical processes. Several exemplary theoretical formalisms and feasibility demonstrations of ultrafast all-optical transmission switching and tunable metamaterials and plasmonic photonic structures where the liquid crystal constituents play the critical role of enabling the processes are discussed. Emphasis is placed on all-optical processes, but we have also highlighted cases where electro-optical means could provide additional control, flexibility and enhancement possibility. We also point out how another phase of chiral nematic, namely, Blue-Phase liquid crystals could circumvent some of the limitations of nematic and present new possibilities.

  8. Thin aligned organic polymer films for liquid crystal devices

    International Nuclear Information System (INIS)

    This project was designed to investigate the possibility of producing alignment layers for liquid crystal devices by cross-linking thin films containing anisotropic polymer bound chromophores via irradiation with polarised ultraviolet light. Photocross-linkable polymers find use in microelectronics, liquid crystal displays, printing and UV curable lacquers and inks; so there is an increasing incentive for the development of new varieties of photopolymers in general. The synthesis and characterisation of two new photopolymers that are suitable as potential alignment layers for liquid crystal devices are reported in this thesis. The first polymer contains the anthracene chromophore attached via a spacer unit to a methacrylate backbone and the second used a similarly attached aryl azide group. Copolymers of the new monomers with methyl methacrylate were investigated to establish reactivity ratios in order to understand composition drift during polymerisation. (author)

  9. Thin aligned organic polymer films for liquid crystal devices

    CERN Document Server

    Foster, K E

    1997-01-01

    This project was designed to investigate the possibility of producing alignment layers for liquid crystal devices by cross-linking thin films containing anisotropic polymer bound chromophores via irradiation with polarised ultraviolet light. Photocross-linkable polymers find use in microelectronics, liquid crystal displays, printing and UV curable lacquers and inks; so there is an increasing incentive for the development of new varieties of photopolymers in general. The synthesis and characterisation of two new photopolymers that are suitable as potential alignment layers for liquid crystal devices are reported in this thesis. The first polymer contains the anthracene chromophore attached via a spacer unit to a methacrylate backbone and the second used a similarly attached aryl azide group. Copolymers of the new monomers with methyl methacrylate were investigated to establish reactivity ratios in order to understand composition drift during polymerisation.

  10. Study of liquid crystal composite systems by neutron scattering

    International Nuclear Information System (INIS)

    X-ray is one of the most important tools to characterise the structure of smectic and columnar liquid crystals. X-ray scattering profile can provide information about the smectic layer spacing, alignment and tilt direction of the director with respect to the layer normal. In these investigations the X-ray technique is superior to other scattering methods, like neutron or light scattering. Although the smectic layer spacing (∼ 30 A) is accessible also for small-angle-neutron-scattering (SANS) studies, it requires much more material than X-ray. SANS measurements, however can become very useful, or even unavoidable to get information about the structure of some liquid crystal composites, or about the molecular dynamics of certain highly symmetric smectic phases. Neutron scattering studies carried out in Saclay and in Budapest on liquid crystal composites are reviewed. (author)

  11. Liquid-Crystal-Enabled Active Plasmonics: A Review

    Directory of Open Access Journals (Sweden)

    Guangyuan Si

    2014-02-01

    Full Text Available Liquid crystals are a promising candidate for development of active plasmonics due to their large birefringence, low driving threshold, and versatile driving methods. We review recent progress on the interdisciplinary research field of liquid crystal based plasmonics. The research scope of this field is to build the next generation of reconfigurable plasmonic devices by combining liquid crystals with plasmonic nanostructures. Various active plasmonic devices, such as switches, modulators, color filters, absorbers, have been demonstrated. This review is structured to cover active plasmonic devices from two aspects: functionalities and driven methods. We hope this review would provide basic knowledge for a new researcher to get familiar with the field, and serve as a reference for experienced researchers to keep up the current research trends.

  12. Substrate-induced gliding in a nematic liquid crystal layer

    Science.gov (United States)

    Mema, E.; Kondic, L.; Cummings, L. J.

    2015-12-01

    We consider the interaction between nematic liquid crystals (NLCs) and polymer substrates. Such substrates can interact with NLCs, exhibiting a phenomenon known as director gliding: the preferred orientation of the NLC molecules at the interface changes on time scales that are slow relative to the elastic relaxation time scale of the NLC. We present two models for gliding, inspired by experiments that investigate the interaction between the NLC and a polymer substrate. These models, though simple, lead to nontrivial results, including loss of bistability under gliding. Perhaps surprisingly, we find that externally imposed switching between the steady states of a bistable system may reverse the effect of gliding, preventing loss of bistability if switching is sufficiently frequent. Our findings may be of relevance to a variety of technological applications involving liquid crystal devices, and particularly to a new generation of flexible liquid crystal displays that implement polymeric substrates.

  13. Selective crystallization of tank supernatant liquid

    Energy Technology Data Exchange (ETDEWEB)

    Herting, D.

    1996-10-01

    The objective of this task is to demonstrate the feasibility of selectively removing sodium nitrate (NaNO{sub 3}) from Hanford Site tank waste by a large-scale fractional crystallization process. Two thirds of all the nuclear waste stored in Hanford`s underground storage tanks is sodium nitrate (mass basis, excluding water). Fractional crystallization can remove essentially nonradioactive NaNO{sub 3} and other sodium salts from the waste, thereby reducing the volume of low-level waste glass by as much as 90%.

  14. Synthesis and mesomorphic properties of rigid-core ionic liquid crystals

    NARCIS (Netherlands)

    Kouwer, P.H.J.; Swager, T.M.

    2007-01-01

    Ionic liquid crystals combine the unique solvent properties of ionic liquids with self-organization found for liquid crystals. We report a detailed analysis of the structure-property relationship of a series of new imidazolium-based liquid crystals with an extended aromatic core. Investigated parame

  15. Molecular dynamics simulations of liquid crystals at interfaces

    CERN Document Server

    Shield, M

    2002-01-01

    Molecular dynamics simulations of an atomistic model of 4-n-octyl-4'-cyanobiphenyl (8CB) were performed for thin films of 8CB on solid substrates (a pseudopotential representation of the molecular topography of the (100) crystal surface of polyethylene (PE), a highly ordered atomistic model of a pseudo-crystalline PE surface and an atomistic model of a partially orientated film of PE), free standing thin films of 8CB and 8CB droplets in a hexagonal pit. The systems showed strong homeotropic anchoring at the free volume interface and planar anchoring at the solid interface whose strength was dependent upon the surface present. The free volume interface also demonstrated weak signs of smectic wetting of the bulk. Simulations of thin free standing films of liquid crystals showed the ordered nature of the liquid crystals at the two free volume interfaces can be adopted by the region of liquid crystal molecules between the homeotropic layer at each interface only if there is a certain number of liquid crystal mole...

  16. Chemistry of Discotic Liquid Crystals From Monomers to Polymers

    CERN Document Server

    Kumar, Sandeep

    2010-01-01

    Compiling the scattered literature into a single seminal work, this book describes the basic design principles, synthesis, and mesomorphic properties of discotic liquid crystals. Of fundamental importance as models for the study of energy and charge migration in self-organized systems, discotic liquid crystals find functional application as one-dimensional conductors, photoconductors, light emitting diodes, photovoltaic solar cells, field-effect transistors, and gas sensors. This book highlights the scientific concepts behind the hierarchical self-assembly of these disc-shaped molecules alongs

  17. Low voltage blue phase liquid crystal for spatial light modulators.

    Science.gov (United States)

    Peng, Fenglin; Lee, Yun-Han; Luo, Zhenyue; Wu, Shin-Tson

    2015-11-01

    We demonstrated a low-voltage polymer-stabilized blue phase liquid crystal (BPLC) for phase-only modulation with a liquid-crystal-on-silicon (LCoS). A new device configuration was developed, which allows the incident laser beam to traverse the BPLC layer four times before exiting the LCoS. As a result, the 2π phase change voltage is reduced to below 24 V in the visible region. The response time remains relatively fast (∼3  ms). The proposed device configuration enables widespread applications of BPLC spatial light modulators. PMID:26512528

  18. Investigating the orientational order in smectic liquid crystals

    Science.gov (United States)

    Wang, Shun

    This thesis is composed of two projects. The first one is the investigation of a reversed phase sequence, which subsequently leads to the discovery of a novel Smectic-C liquid crystal phase. The 10OHFBBB1M7 (10OHF) compound shows a reversed phase sequence with the SmC*d4 phase occurring at a higher temperature than the SmC* phase. This phase sequence is stabilized by moderate doping of 9OTBBB1M7 (C9) or 11OTBBB1M7 (C11). To further study this unique phase sequence, the mixtures of 10OHFBBB1M7 and its homologs have been characterized by optical techniques. In order to perform the resonant X-ray diffraction experiment, we have added C9 and C11 compounds to the binary mixtures and pure 10OHF. In two of the studied mixtures, a new smectic-C* liquid crystal phase with six-layer periodicity has been discovered. Upon cooling, the new phase appears between the SmC*a phase having a helical structure and the SmC*d4 phase with four-layer periodicity. The SmC*d6 phase shows a distorted clock structure. Three theoretical models have predicted the existence of a six-layer phase. However, our experimental findings are not consistent with the theories. The second project involves the mixtures of liquid crystals with different shapes. The role of different interactions in stabilizing the antiferroelectric smectic liquid crystal phases have been a long-standing questions in the community. By mixing the antiferroelectric smectic liquid crystal with achiral liquid crystal molecules with rod and hockey-stick shapes, distinct different behaviors are obtained. In the case of the mixtures of chiral smectic liquid crystals with rod-like molecules, all the smectic-C* variant phases vanish with a small amount of doping. However, the hockey-stick molecule is much less destructive compared to the rod-like molecule. This suggests that the antiferroelectric smectic liquid crystal molecules may have a shape closer to a hockey-stick rather than a rod.

  19. Electrically modulated transparent liquid crystal-optical grating projection

    DEFF Research Database (Denmark)

    Buss, Thomas; Smith, Cameron; Kristensen, Anders

    2013-01-01

    A transparent, fully integrated electrically modulated projection technique is presented based on light guiding through a thin liquid crystal layer covering sub-wavelength gratings. The reported device operates at 10 V with response times of 4.5 ms. Analysis of the liquid crystal alignment shows...... that director-reorientation occurs over timescales on the order of 90 μs close to the grating surface. The technology is suitable for next generation heads-up-displays and reconfigurable multilayer photonic integrated circuits. © 2013 Optical Society of America....

  20. A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Ingo Dierking

    2014-05-01

    Full Text Available The polymer stabilized state of ferroelectric liquid crystals (FLC is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as well as the dielectric modes. It was found that the data can largely be explained by assuming an elastic interaction between the polymer network strands and the liquid crystal molecules. The elastic interaction parameter was determined; and increases linearly with increasing polymer concentration.

  1. A study on thermo-camera using liquid crystal

    International Nuclear Information System (INIS)

    Some cholesteric liquid crystals change their color according to temperature and are used to show temperature distribution on a surface qualitatively. The present study developed a quantitative method by which temperature distribution can be displayed just like an infra-red thermo-camera. At first, the theoretical ground is presented. The spectral properties of liquid crystal and optical filters are determined. Calibration methods are described and the accuracy of this method is evaluated as 0.2 deg C, and the order of resolution is 0.01 deg C. For application, temperature distributions on heated surfaces attached by a cylinder are measured in detail. (author)

  2. Supercontinuum generation in fibers infiltrated with liquid crystals

    DEFF Research Database (Denmark)

    Rasmussen, Per Dalgaard; Bang, Ole; Lægsgaard, Jesper;

    2006-01-01

    Supercontinuum generation in a capillary tube infiltrated with a nematic liquid crystal is investigated theoretically in the near infrared region. A liquid crystal with a high electronic nonlinearity is chosen, which makes it possible to generate 100 nm wide supercontinua using IO ps pulses with...... peak power 1.5 kW in a 10 cm long waveguide. The possibility of tuning the spectrum of the generated Supercontinuum by changing the dispersion of the waveguide is also considered. It is found that the broadening of the spectrum in both the normal and anomalous regime is mainly due to self phase...

  3. Locomotion in a liquid crystal near a wall

    Science.gov (United States)

    Powers, Thomas; Krieger, Madison; Spagnolie, Saverio

    2015-11-01

    Recent observations of bacteria swimming in nematic liquid crystal solution motivate the theoretical study of how swimming speed depends on liquid crystal properties. We consider the Taylor sheet near a wall, in which propulsion is achieved by the propagation of traveling waves along the length of the swimmer. Using the lubrication approximation, we determine how swimming speed depends on the Ericksen number, which is the ratio of elastic to viscous stresses. We also study the effect of anchoring strength, at the surface of the swimmer and the surface of the wall. Supported by NSF-CBET 1437195.

  4. Photoresponsive Liquid Crystals Based on Dihydroazulene

    DEFF Research Database (Denmark)

    Petersen, Anne Ugleholdt

    The main focus of this thesis was a study upon photoresponsive liquid crystalline materials,with a starting point on the photoactive compound dihydroazulene (DHA). It has been shown thatsome DHAs with liquid crystalline properties can be synthesized, having an aliphatic substituent atthe 2-position....... Irradiation of such a DHA in the nematic phase gave partial conversion to avinylheptafulvene (VHF), not showing any changes in the mesophase, though a higher alignmentwas obtained when this sample was irradiated in its liquid crystalline state.Photomicrographs of the DHA under crossed polarizers before...... irradiation, after irradiation and when allowed toclose back to the DHAFor a disubstituted DHAs, with substituents in both the 2- and 7-positions, it was shown thatthese materials were unstable when heated above 100 °C, leading to side reactions, whichcomplicated analysis of the system. When doped into a...

  5. Hydrothermal decomposition of liquid crystal in subcritical water

    International Nuclear Information System (INIS)

    Highlights: • Hydrothermal technology can effectively decompose the liquid crystal of 4-octoxy-4'-cyanobiphenyl. • The decomposition rate reached 97.6% under the optimized condition. • Octoxy-4'-cyanobiphenyl was mainly decomposed into simple and innocuous products. • The mechanism analysis reveals the decomposition reaction process. - Abstract: Treatment of liquid crystal has important significance for the environment protection and human health. This study proposed a hydrothermal process to decompose the liquid crystal of 4-octoxy-4′-cyanobiphenyl. Experiments were conducted with a 5.7 mL stainless tube reactor and heated by a salt-bath. Factors affecting the decomposition rate of 4-octoxy-4′-cyanobiphenyl were evaluated with HPLC. The decomposed liquid products were characterized by GC-MS. Under optimized conditions i.e., 0.2 mL H2O2 supply, pH value 6, temperature 275 °C and reaction time 5 min, 97.6% of 4-octoxy-4′-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment

  6. Hydrothermal decomposition of liquid crystal in subcritical water

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Xuning [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, No. 1239 Siping Road, Shanghai 200092 (China); Shanghai Cooperative Centre for WEEE Recycling, Shanghai Second Polytechnic University, No. 2360 Jinhai Road, Shanghai 201209 (China); He, Wenzhi, E-mail: hithwz@163.com [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, No. 1239 Siping Road, Shanghai 200092 (China); Li, Guangming; Huang, Juwen; Lu, Shangming; Hou, Lianjiao [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, No. 1239 Siping Road, Shanghai 200092 (China)

    2014-04-01

    Highlights: • Hydrothermal technology can effectively decompose the liquid crystal of 4-octoxy-4'-cyanobiphenyl. • The decomposition rate reached 97.6% under the optimized condition. • Octoxy-4'-cyanobiphenyl was mainly decomposed into simple and innocuous products. • The mechanism analysis reveals the decomposition reaction process. - Abstract: Treatment of liquid crystal has important significance for the environment protection and human health. This study proposed a hydrothermal process to decompose the liquid crystal of 4-octoxy-4′-cyanobiphenyl. Experiments were conducted with a 5.7 mL stainless tube reactor and heated by a salt-bath. Factors affecting the decomposition rate of 4-octoxy-4′-cyanobiphenyl were evaluated with HPLC. The decomposed liquid products were characterized by GC-MS. Under optimized conditions i.e., 0.2 mL H{sub 2}O{sub 2} supply, pH value 6, temperature 275 °C and reaction time 5 min, 97.6% of 4-octoxy-4′-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment.

  7. Bubble migration in a compacting crystal-liquid mush

    Science.gov (United States)

    Boudreau, Alan

    2016-04-01

    Recent theoretical models have suggested that bubbles are unlikely to undergo significant migration in a compaction crystal mush by capillary invasion while the system remains partly molten. To test this, experiments of bubble migration during compaction in a crystal-liquid mush were modeled using deformable foam crystals in corn syrup in a volumetric burette, compacted with rods of varying weights. A bubble source was provided by sodium bicarbonate (Alka-Seltzer®). Large bubbles (>several crystal sizes) are pinched by the compacting matrix and become overpressured and deformed as the bubbles experience a load change from hydrostatic to lithostatic. Once they begin to move, they move much faster than the compaction-driven liquid. Bubbles that are about the same size as the crystals but larger than the narrower pore throats move by deformation or breaking into smaller bubbles as they are forced through pore restrictions. Bubbles that are less than the typical pore diameter generally move with the liquid: The liquid + bubble mixture behaves as a single phase with a lower density than the bubble-free liquid, and as a consequence it rises faster than bubble-free liquid and allows for faster compaction. The overpressure required to force a bubble through the matrix (max grain size = 5 mm) is modest, about 5 %, and it is estimated that for a grain size of 1 mm, the required overpressure would be about 25 %. Using apatite distribution in a Stillwater olivine gabbro as an analog for bubble nucleation and growth, it is suggested that relatively large bubbles initially nucleate and grow in liquid-rich channels that develop late in the compaction history. Overpressure from compaction allows bubbles to rise higher into hotter parts of the crystal pile, where they redissolve and increase the volatile content of the liquid over what it would have without the bubble migration, leading to progressively earlier vapor saturation during crystallization of the interstitial liquid

  8. Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core photonic crystal fiber

    CERN Document Server

    Zito, Gianluigi

    2013-01-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a pre-polymer/LC solution infiltrated into the hollow channels of a solid core photonic crystal fiber (PCF). The fabrication process and effects related to the photonic bandgap guidance into the infiltrated PCF, and characterization of the PLC-FBG are discussed. Experimental data here presented, demonstrate that the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending sensitivities. The microscopic behavior of the polymer/liquid crystal phase separation inside the PCF capillaries is examined using scanning electron microscopy, while further discussed.

  9. A polarization-independent liquid crystal phase modulation using polymer-network liquid crystal with orthogonal alignment layers

    Science.gov (United States)

    Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih; Lin, Yi-Hsin

    2012-10-01

    A polarization-independent liquid crystal (LC) phase modulation using polymer-network liquid crystals with orthogonal alignments layers (T-PNLC) is demonstrated. T-PNLC consists of three layers. LC directors in the two layers near glass substrates are orthogonal to each other. In the middle layer, LC directors are perpendicular to the glass substrate. The advantages of such T-PNLC include polarizer-free, larger phase shift (~0.4π rad) than the residual phase type (<0.05π rad), and low operating voltage (< 30Vrms). It does not require bias voltage for avoiding scattering because the refractive index of liquid crystals matches that of polymers. The phase shift of T-PNLC is affected by the cell gap and the curing voltages. The potential applications are laser beam steering, spatial light modulators and electrically tunable micro-lens arrays.

  10. Phase separation of monomer in liquid crystal mixtures and surface morphology in polymer-stabilized vertical alignment liquid crystal displays

    Energy Technology Data Exchange (ETDEWEB)

    Lyu, Jae Jin; Lee, Jun Hyup; Kim, Kyeong Hyeon [Development Center, LCD Business, SAMSUNG Electronics Co. LTD., Tangjeong-Myeon, Asan, Chungnam 336-741 (Korea, Republic of); Kikuchi, Hirotsuku; Higuchi, Hiroki [Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-Koen, Kasuga 816-8580 (Japan); Kim, Dae Hyun; Lee, Seung Hee, E-mail: jsquare.lyu@samsung.com, E-mail: lsh1@chonbuk.ac.kr [Department of BIN Fusion Technology and Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)

    2011-08-17

    The polymer-stabilized vertically aligned (PS-VA) liquid crystal display (LCD) driving mode has high potential for manufacturing low power consuming displays due to the higher transmittance and fast response as compared with the existing patterned vertically aligned and multi-domain vertically aligned modes. In this paper we have investigated the reaction mechanisms of monomer-liquid crystal blends to form a surface pre-tilt angle of liquid crystal in vertical alignment LCD associated with a fishbone electrode structure. The observed sizes of polymer bumps formed on the substrates were found to be dependent on the exposed UV wavelength and were almost equal in both top and bottom substrates. When a large UV wavelength was used, the phase separation mechanism of monomer in PS-VA mode was found nearly isotropic rather than anisotropic in contrast to the previous studies.

  11. Simulation of nuclear magnetic resonance spectra of liquid crystals, polymers liquid crystals and conventional polymers

    International Nuclear Information System (INIS)

    The aim of this study is the simulation and the exploitation of NMR spectra of nematic liquid crystals and of polymers. The NMR forms of lines are analysed owing to two complementary models. The first (single conformation model) describes the purely molecular contribution (geometry and internal movements in the molecule), the second the contribution of collective movements (visco elastic modes). Recallings on the NMR method and the orientational order notion within the nematic phase, are given in the first part, where these two models are also described. In a second part these models are applied to data relative to nematic molecules of weak molecular mass and to nematic polymers. This application allows to obtain informations on the structure and the internal movements of the molecule, the orientational order prevailing within the phase and the visco-elastic properties of the studied material. At last it is demonstrated that extension of these models to NMR data of polymers which don't present nematic phase in pure phase allows to obtain similar informations if we consider that their amorphous phase presents locally a nematic order. 136 refs., 46 figs., 4 tabs

  12. Simple system for evaluating retardation of liquid crystal cells using grating type liquid crystal polarization splitters

    Science.gov (United States)

    Honma, Michinori; Nose, Toshiaki

    2016-04-01

    We propose a unique optical system for measuring the retardation of birefringent films using a pair of liquid crystal (LC) gratings; that is, the examined birefringent films are inserted between two LC gratings. Because the LC grating functions as a polarization beam splitter for circularly polarized light, the proposed system is optically equivalent to the measurement system using a pair of two circular polarizers. First, the polarization splitting performance of the LC grating is discussed. It is found that a sufficiently high voltage (such that the retardation is less than a half wavelength) has to be applied for the almost pure circularly polarized diffracted light. Next, the measurement of the retardation of a homogeneous LC cell as an examined birefringent film was demonstrated using the proposed method. The proposed method is revealed to have the same measurement performance as that of the conventional method using a pair of linear polarizers and has an advantage that there is no need for the optic axis of the test birefringent specimen to be set at a specific angle.

  13. Photocontrol of fluid slugs in liquid crystal polymer microactuators.

    Science.gov (United States)

    Lv, Jiu-An; Liu, Yuyun; Wei, Jia; Chen, Erqiang; Qin, Lang; Yu, Yanlei

    2016-01-01

    The manipulation of small amounts of liquids has applications ranging from biomedical devices to liquid transfer. Direct light-driven manipulation of liquids, especially when triggered by light-induced capillary forces, is of particular interest because light can provide contactless spatial and temporal control. However, existing light-driven technologies suffer from an inherent limitation in that liquid motion is strongly resisted by the effect of contact-line pinning. Here we report a strategy to manipulate fluid slugs by photo-induced asymmetric deformation of tubular microactuators, which induces capillary forces for liquid propulsion. Microactuators with various shapes (straight, 'Y'-shaped, serpentine and helical) are fabricated from a mechanically robust linear liquid crystal polymer. These microactuators are able to exert photocontrol of a wide diversity of liquids over a long distance with controllable velocity and direction, and hence to mix multiphase liquids, to combine liquids and even to make liquids run uphill. We anticipate that this photodeformable microactuator will find use in micro-reactors, in laboratory-on-a-chip settings and in micro-optomechanical systems. PMID:27604946

  14. Ultra-fast solid state electro-optical modulator based on liquid crystal polymer and liquid crystal composites

    International Nuclear Information System (INIS)

    A different generation of polymer-dispersed liquid crystals (PDLCs) based on a liquid crystalline polymer host is reported wherein the fluid behavior of the reactive mesogenic monomer is an enabler to concentration windows (liquid crystal polymer/liquid crystal) (and subsequent morphologies) not previously explored. These liquid crystal (LC) polymer/LC composites, LCPDLCs, exhibit excellent optical and electro-optical properties with negligible scattering losses in both the ON and OFF states. These systems thus have application in systems where fast phase modulation of optical signal instead of amplitude control is needed. Polarized optical microscopy and high resolution scanning electron microscopy confirm a bicontinuous morphology composed of aligned LC polymer coexisting with a phase separated LC fluid. Operating voltages, switching times, and spectra of LCPDLCs compare favourably to conventional PDLC films. The LCPDLCs exhibit a low switching voltage (4–5 V/μm), symmetric and submillisecond (200 μs) on/off response times, and high transmission in both the as formed and switched state in a phase modulation geometry

  15. Liquid Crystal Gel Reduces Age Spots by Promoting Skin Turnover

    Directory of Open Access Journals (Sweden)

    Mina Musashi

    2014-07-01

    Full Text Available Studies have shown that liquid crystals structurally resembling the intercellular lipids in the stratum corneum can beneficially affect the skin when applied topically by stimulating the skin’s natural regenerative functions and accelerating epidermal turnover. In the present study, the effects of applying low concentrations of a liquid crystal gel of our own creation were evaluated using epidermal thickening in mouse skin as an assay for effective stimulation of epidermal turnover. A liquid crystal gel was also applied topically to human facial skin, and analysis was conducted using before-and-after photographs of age spots, measurements of L* values that reflect degree of skin pigmentation, single-layer samples of the stratum corneum obtained via tape-stripping, and measurements of trans-epidermal water loss that reflect the status of the skin’s barrier function. The results suggested that cost-effective creams containing as low as 5% liquid crystal gel might be effective and safely sold as skin care products targeting age spots and other problems relating to uneven skin pigmentation.

  16. LIQUID CRYSTAL AS ACCELERANT IN DRUG ABSORPTION FROM TOPICAL FORMULATIONS

    Directory of Open Access Journals (Sweden)

    Trivedi Nirali

    2011-04-01

    Full Text Available Topical drug delivery has been one of the major research fields in the area of drug therapy for last few decades. However inspite of its large therapeutic potential market success has been limited. It provides the several advantages over the oral drug delivery. Percutaneous absorption involves the passage of the drug molecule from the skin surface into the stratum corneum under the influence of a concentration gradient and its subsequent diffusion through the stratum corneum and underlying epidermis, through the dermis, and into the blood circulation. Liquid crystal phase has emerged as a novel material for preparation of topical drug delivery systems. It fulfills the requirements for making drug loading and drug absorption faster from the site of application of topical formulations. Liquid crystal has got many phases in itself which can be further exploited to get a better and more efficient drug delivery system. Also a variety of areas in medical and electronics streamline can find its application. There is also a wide scope in respect to the methods by which these liquid crystals can be prepared. Different methods give rise to different kinds of liquid crystals. Topical formulations have emerged as a very useful drug delivery system as it bypasses the first pass metabolism. Also the absorption of drugs depends on the percutaneous absorption of drug from the area of application. Hence it’s required to choose such a vehicle which enhances the absorption of drug from the formulation.

  17. A statistical calibration technique for thermochromic liquid crystals

    Science.gov (United States)

    Roesgen, T.; Totaro, R.

    2002-09-01

    A novel approach is proposed for the color calibration of thermochromic liquid crystals. Based on a statistical interpretation, a linear transform of the native (R, G, B) values can replace the customary hue mapping. The transform coefficients are computed through a proper orthogonal decomposition, providing complete data decorrelation and optimal information compression.

  18. A statistical calibration technique for thermochromic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Roesgen, T.; Totaro, R. [Institute of Fluid Dynamics, Swiss Federal Institute of Technology, ETH Zentrum, Sonneggstrasse 3, 8092 Zurich (Switzerland)

    2002-11-01

    A novel approach is proposed for the color calibration of thermochromic liquid crystals. Based on a statistical interpretation, a linear transform of the native (R, G, B) values can replace the customary hue mapping. The transform coefficients are computed through a proper orthogonal decomposition, providing complete data decorrelation and optimal information compression. (orig.)

  19. Flexoelectricity in an oxadiazole bent-core nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, S., E-mail: Sarabjot.Kaur@manchester.ac.uk; Panov, V. P.; Gleeson, H. F. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Greco, C.; Ferrarini, A. [Department of Chemical Sciences, University of Padua, Padua I-35131 (Italy); Görtz, V. [Department of Chemistry, University of York, York YO10 5DD (United Kingdom); Department of Chemistry, University of Lancaster, Lancaster LA1 4YB (United Kingdom); Goodby, J. W. [Department of Chemistry, University of York, York YO10 5DD (United Kingdom)

    2014-12-01

    We have determined experimentally the magnitude of the difference in the splay and bend flexoelectric coefficients, |e{sub 1} − e{sub 3}|, of an oxadiazole bent-core liquid crystal by measuring the critical voltage for the formation of flexodomains together with their wave number. The coefficient |e{sub 1} − e{sub 3}| is found to be a factor of 2–3 times higher than in most conventional calamitic nematic liquid crystals, varying from 8 pCm{sup −1} to 20 pCm{sup −1} across the ∼60 K—wide nematic regime. We have also calculated the individual flexoelectric coefficients e{sub 1} and e{sub 3}, with the dipolar and quadrupolar contributions of the bent-core liquid crystal by combining density functional theory calculations with a molecular field approach and atomistic modelling. Interestingly, the magnitude of the bend flexoelectric coefficient is found to be rather small, in contrast to common expectations for bent-core molecules. The calculations are in excellent agreement with the experimental values, offering an insight into how molecular parameters contribute to the flexoelectric coefficients and illustrating a huge potential for the prediction of flexoelectric behaviour in bent-core liquid crystals.

  20. Orientational bistability in ferronematic liquid crystals with negative diamagnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Zakhlevnykh, A.N., E-mail: anz@psu.ru; Petrov, D.A.

    2015-11-01

    In the framework of continuum theory we study magnetic field induced orientational transitions in a ferronematic, i.e. suspension of single-domain magnetic particles in a nematic liquid crystal. We consider the case of negative diamagnetic susceptibility anisotropy of a liquid crystal and soft planar coupling of impurity particles with a liquid crystal matrix. We found tricritical behavior of the threshold transition in a magnetic field from perturbed state into uniform planar state. This transition can be the first or second order, depending on the parameter of the magnetic phase segregation. We analytically derive the expression for the tricritical segregation parameter that determines the character of a transition. We show that ferronematic has a large magneto-optical non-linearity which is the result of the director reorientation under external field. Comparison of results of numerical calculations with experimental data has been carried out. - Highlights: • We study orientational and magnetooptical properties of ferronematics. • We obtain the phase diagram for soft coupling of nanoparticles and liquid crystal. • We examine the character of magnetic field induced orientational transitions. • We found tricritical behavior of the transition from perturbed to uniform state. • We study the optical phase lag and the capacity of ferronematic cell.

  1. Alignment of liquid crystals : on geometrically and chemically modified surfaces

    NARCIS (Netherlands)

    Zhang, Jing

    2013-01-01

    This thesis consists of two main parts. The first part describes a new model to explain the complex role of surface materials and surface geometry in the liquid crystal (LC) alignment, which has been a subject of intensive debate over the last 40 years. The second part presents a potentially cost ef

  2. Liquid crystals detect voids in fiber glass laminates

    Science.gov (United States)

    Hollar, W. T.

    1967-01-01

    Liquid crystal solution nondestructively detects voids or poor bond lines in fiber glass laminates. A thin coating of the solution is applied by spray or brush to the test article surface, and when heated indicates the exact location of defects by differences in color.

  3. On asymptotic isotropy for a hydrodynamic model of liquid crystals

    Czech Academy of Sciences Publication Activity Database

    Dai, M.; Feireisl, Eduard; Rocca, E.; Schimperna, G.; Schonbek, M.E.

    2016-01-01

    Roč. 97, 3-4 (2016), s. 189-210. ISSN 0921-7134 Grant ostatní: European Research Council(XE) MATHEF(320078) Keywords : liquid crystal * Q-tensor description * long-time behavior Subject RIV: BA - General Mathematics Impact factor: 0.528, year: 2014 http://content.iospress.com/articles/asymptotic-analysis/asy1348

  4. Novel Ferroelectric Liquid Crystals with Very Large Spontaneous Polarization

    Science.gov (United States)

    Nakauchi, Jun; Uematsu, Mioko; Sakashita, Keiichi; Kageyama, Yoshitaka; Hayashi, Seiji; Ikemoto, Tetsuya; Mori, Kenji

    1989-07-01

    Several ferroelectric liquid crystals derived from a new optically active (2S, 5R)-2-hydroxy-5-hexyl-δ-valerolactone have been synthesized, and their mesomorphic and ferroelectric properties have been investigated. Very large spontaneous polarization (Ps) has been observed in these compounds, one of which shows an extremly large Ps value: as high as 320 nC/cm2.

  5. Light-scattering study of a polymer nematic liquid crystal

    Science.gov (United States)

    Taratuta, Victor G.; Hurd, Alan J.; Meyer, Robert B.

    1985-07-01

    We study the relaxation of thermally excited orientation fluctuations in a polymer nematic liquid crystal using photon correlation spectroscopy. The material studied is poly-γ-benzyl glutamate at a concentration just above the isotropic to nematic transition point. The relaxation rates of elastic deformation modes exhibit large anisotropies. Quantitative measurements of ratios of Frank elastic constants and Leslie viscosities are described.

  6. Polarization studies on stretched polymer dispersed ferroelectric liquid crystal films

    Czech Academy of Sciences Publication Activity Database

    Manila-Maximean, D.; Hamplová, Věra; Rosu, C.; Glogarová, Milada; Klosowicz, S.; Bena, R.

    2001-01-01

    Roč. 366, - (2001), s. 395-402. ISSN 1058-725X Institutional research plan: CEZ:AV0Z1010914 Keywords : PDFLC * ferroelectric liquid crystals * polarization * polymers * mechanical stretching Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.457, year: 2001

  7. Photoalignment - an alternative aligning technique for Liquid Crystal Displays

    Directory of Open Access Journals (Sweden)

    M.M. Chrzanowski

    2011-09-01

    Full Text Available Purpose: The main aim of this work is to present our investigation in the field of photoalignment. In this work we introduce useful photoalignment techniques and discuss in detail the results of photocrosslinking and photodegradation in photosensitive polymer materials.Design/methodology/approach: We describe the new procedure investigated in our laboratory for the following materials: HD-4100, HD-4110 and HD-8820 (DuPont Microsystems as well as the characteristics obtained for the thin polyimide layers: optical homogeneity, thickness, surface tension.Findings: Polyimide layers obtained on the glass/ITO substrates which were irradiated using linearly polarised ultraviolet light show the aligning properties for liquid crystal layers. The proposed new technology is fairly fine to obtain 2-3 cm2 layers.Research limitations/implications: The liquid crystal material alignment quality is not perfect, but the works are still in progress. In the next step we will try to use silan-derivative adhesion promoters to lower the aligning layers thickness. This solution will probably also have a big influence on the aligning layers homogeneity.Practical implications: We discuss an alternative technique of the rubbing method for composition of liquid crystal displays. Liquid crystal displays are widely used for many industrial and commercial applications. Multimedia and graphics and medical-imaging systems require top quality images. Such an image can be obtained under the condition of good liquid crystal alignment. Rubbing is a method conventionally used for these purposes. Unfortunately this technique has some disadvantages that are particularly visible in new generation displays. The usage of photodephiniable materials opens the route to obtain an appropriate molecular tilt and controlled anchoring energy as well as preparing layers that are suitable to providing diversified optical axes in one liquid crystal cell.Originality/value: Agents investigated in the

  8. Photorefractive nonlinearity in pure and doped liquid crystals

    Science.gov (United States)

    Chen, Kan

    Detailed theoretical analysis and experimental investigation of the photorefractive (PR) effect in liquid crystals (LC) are presented. The photorefractive nonlinearity arises from the formation of spatially modulated space charge field. Two main mechanisms contribute space charge field in liquid crystals. One comes from the formation and the subsequent dissociation of charge transfer complexes between the liquid crystal and the dopant, which produces mobile charge carriers. The generation and redistribution of charge carriers, induced by external dc voltage and inhomogeneous illumination, form the space charge field. Second source comes from the so-called Carr-Helfrich effect, which states that transverse space charge field can be induced by liquid crystal dielectric and conductivity anisotropy under external applied field. Assisted by the space charge field, large optical nonlinearity can be obtained in liquid crystals. Liquid crystal molecular reorientation occurs under the combined action of internal space charge field and external dc field. The subsequent birefringent grating accounts for photorefractive diffraction and beam coupling. Its orientational feature is investigated and evidenced by facts, such as, polarization anisotropy observed in probe diffraction, external threshold behavior, asymmetric two beam coupling, and geometrical dependence of diffraction efficiency. In parallel with the effort to understand basic mechanisms governing photorefractive effect in liquid crystals, we've also attempted to enhance PR performance, mainly by chemical doping. The doping effect, both organic (C60, single walled nanotubes (SWNT)), and inorganic doping (e.g., CdSe nanorodes), is studied. Substantial improvement of photorefractive response can be observed in our doping samples, in terms of larger diffraction efficiency and higher beam coupling gain. Although the underline mechanism is still intricate in molecular level, we believe the enhanced photo-charge generation

  9. Liquid crystals. Oligomeric and polymeric materials for soft photonic technologies

    International Nuclear Information System (INIS)

    The current pace of today's information technologies might lead the casual observer to believe that this is all new. However the reality is that, as with most things, this is really a long evolution of processes based on tried, tested and re-adapted techniques. This thesis represents 12 years of predominantly technology driven research and covers a whole range of characterising, evaluating and fabricating devices based on liquid crystalline systems. Firstly polymer liquid crystals are discussed with respect to the fabrication of a flexible substrate display based on standard printing techniques and this is shown to have improved display viewing properties over a standard polymer dispersed liquid crystal (PDLC) device. Following on from this work is presented that involves the production of regular grid arrays in isotropic polymers that are used as control structures in nematic liquid crystal systems. This progresses onto a now patented device that allows the production of robust ferroelectric devices based on PDLC technology. Whilst the development of production techniques is important for the advancement of devices it would not be possible to keep up the pace without continued research into the basic liquid crystalline systems. The final chapter reviews work currently under supervision of the author based on flexoelectric effects in symmetric bimesogens. These materials possess responses times of the order of ∼100μs with an effective optic axis switching angle that is linear with the applied field and can be in well in excess of 90 deg. (author)

  10. Droplet Breakup of the Nematic Liquid Crystal MBBA

    CERN Document Server

    Nachman, Benjamin

    2012-01-01

    Droplet breakup is a well studied phenomena in Newtonian fluids. One property of this behavior is that, independent of initial conditions, the minimum radius exhibits power law scaling with the time left to breakup tau. Because they have additional structure and shear dependent viscosity, liquid crystals pose an interesting complication to such studies. Here, we investigate the breakup of a synthetic nematic liquid crystal known as MBBA. We determine the phase of the solution by using a cross polarizer setup in situ with the liquid bridge breakup apparatus. Consistent with previous studies of scaling behavior in viscous-inertial fluid breakup, when MBBA is in the isotropic phase, the minimum radius decreases as tau^{1.03 \\pm 0.04}. In the nematic phase however, we observe very different thinning behavior. Our measurements of the thinning profile are consistent with two interpretations. In the first interpretation, the breakup is universal and consists of two different regimes. The first regime is characterize...

  11. Liquid crystal alignment on excimer laser irradiated polyimide

    International Nuclear Information System (INIS)

    Grating and photoinduced anisotropic modifications are made to polyimide layers to promote homogeneous and pretilted nematic liquid crystal alignment. Gratings are etched into the polyimide by irradiating a phase mask of period 1.1 μm with the output from a KrF excimer laser of wavelength 248 nm with fluences above the threshold required for ablation. Grating depths from 10 to 190 nm have been achieved using a simple pulse from the laser, and the liquid crystal azimuthal anchoring energy is determined as a function of the grating depth. Values up to 1.3 x 10-5 Jm-2 are found. Discrepancies are found when comparisons are made between experimental data and a theory based upon elastic strain energy minimisation. A modified theory taking finite polar anchoring into account shows better agreement. Polarised excimer laser radiation at normal incidence is used to induce an anisotropy which gives rise to homogeneous liquid crystal alignment. The strength of the azimuthal anchoring energy is similar to that produced by grating alignment. Spectroscopic analysis reveals that the alignment originates from the stronger depletion of polyimide chains parallel to the exposure polarisation direction. The dependence of beam fluence and exposure time on the anchoring energy is measured, and the degradation mechanism of the polyimide is investigated as a function of the exposure. We find that oxidative degradation takes place. We also use these techniques to identify the chemical composition of the polyimide material. Pretilted liquid crystal alignment has also been achieved, with pretilt angles up to 3.7 deg. A tilted polymer distribution is generated by oblique exposure of the polyimide to an elliptically polarised beam. We measure the liquid crystal pretilt angle as a function of the angle of incidence, and exposure time and present a theoretical analysis of the polyimide chain azimuthal distribution which agrees with the experimental results. Finally, a simple and novel technique

  12. Structural organization of liquid crystals at liquid crystal-air interface: Synchrotron X-ray reflectivity and computational simulations

    Science.gov (United States)

    Sadati, Monirosadat; Ramezani-Dakhel, Hadi; Bu, Wei; Sevgen, Emre; Liang, Zhu; Erol, Cem; Taheri Qazvini, Nader; Rahimi, Mohammad; Lin, Binhua; Roux, Benoit; Schlossman, Mark; de Pablo, Juan J.

    Numerous applications of liquid crystals (LC) rely on control of molecular orientation at an interface. However, little is known about the precise molecular structure of such interfaces. In this work, we have performed synchrotron X-ray reflectivity measurements accompanied by an advanced theoretical and computational analysis to study the structural organization of liquid crystals at the air-liquid crystal interface. The X-ray reflectivity was measured from two nematic (5CB) and smectic (8CB) liquid crystals at several temperatures, in the nematic phase and above the nematic-isotropic transition. Our computational simulations and X-ray reflectivity results indicate that in the case of 8CB nematic phase, incipient bulk smectic fluctuations are pinned at the interface to form temperature-dependent multilayers at the interface. Such layers can extend far from the interface. However, the interface of 5CB in the nematic phase exhibits a relatively small number of layers. These measurements will be extended to the study of the LC-aqueous electrolyte interfaces to understand the effects of electrostatic interactions and external stimuli on the interfacial anchoring energy and LC orientational ordering.

  13. Time-resolved crystallization of deeply cooled liquid hydrogen isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Kuehnel, Matthias

    2014-02-15

    This thesis serves two main purposes: 1. The introduction of a novel experimental method to investigate phase change dynamics of supercooled liquids 2. First-time measurements for the crystallization behaviour for hydrogen isotopes under various conditions (1) The new method is established by the synergy of a liquid microjet of ∼ 5 μm diameter and a scattering technique with high spatial resolution, here linear Raman spectroscopy. Due to the high directional stability and the known velocity of the liquid filament, its traveling axis corresponds to a time axis static in space. Utilizing evaporative cooling in a vacuum environment, the propagating liquid cools down rapidly and eventually experiences a phase transition to the crystalline state. This temporal evolution is probed along the filament axis, ultimately resulting in a time resolution of 10 ns. The feasibility of this approach is proven successfully within the following experiments. (2) A main object of study are para-hydrogen liquid filaments. Raman spectra reveal a temperature gradient of the liquid across the filament. This behaviour can quantitatively be reconstructed by numerical simulations using a layered model and is rooted in the effectiveness of evaporative cooling on the surface and a finite thermal conductivity. The deepest supercoolings achieved are ∼ 30% below the melting point, at which the filament starts to solidify from the surface towards the core. With a crystal growth velocity extracted from the data the appropriate growth mechanism is identified. The crystal structure that initially forms is metastable and probably the result of Ostwald's rule of stages. Indications for a transition within the solid towards the stable equilibrium phase support this interpretation. The analog isotope ortho-deuterium is evidenced to behave qualitatively similar with quantitative differences being mass related. In further measurements, isotopic mixtures of para-hydrogen and ortho-deuterium are

  14. Morphological control and polarization switching in polymer dispersed liquid crystal materials and devices

    Indian Academy of Sciences (India)

    K K Raina; Pankaj Kumar; Praveen Malik

    2006-11-01

    Liquid crystals dispersed in polymer systems constitute novel class of optical materials. The precise control of the liquid crystal droplet morphology in the polymer matrix is essentially required to meet the prerequisites of display device. Experiments have been carried out to investigate and identify the material properties and processing conditions required for the precise control of the droplet morphology of the dispersed liquid crystal systems. Polarization switching has been studied. Aligned liquid crystal dispersed systems showed higher polarization over unaligned ones.

  15. Electrically controllable liquid crystal photonic bandgap fiber with dual-frequency control

    DEFF Research Database (Denmark)

    Scolari, Lara; Alkeskjold, Thomas Tanggaard; Riishede, Jesper;

    2005-01-01

    We present an electrically tunable liquid crystal photonic bandgap fiber device based on a dual frequency liquid crystal with pre-tilted molecules that allows the bandgaps to be continuously tuned. The frequency dependent behavior of the liquid crystal enables active shifting of the bandgaps toward...

  16. Cubic and Hexagonal Liquid Crystals as Drug Delivery Systems

    Directory of Open Access Journals (Sweden)

    Yulin Chen

    2014-01-01

    Full Text Available Lipids have been widely used as main constituents in various drug delivery systems, such as liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-based lyotropic liquid crystals. Among them, lipid-based lyotropic liquid crystals have highly ordered, thermodynamically stable internal nanostructure, thereby offering the potential as a sustained drug release matrix. The intricate nanostructures of the cubic phase and hexagonal phase have been shown to provide diffusion controlled release of active pharmaceutical ingredients with a wide range of molecular weights and polarities. In addition, the biodegradable and biocompatible nature of lipids demonstrates the minimum toxicity and thus they are used for various routes of administration. Therefore, the research on lipid-based lyotropic liquid crystalline phases has attracted a lot of attention in recent years. This review will provide an overview of the lipids used to prepare cubic phase and hexagonal phase at physiological temperature, as well as the influencing factors on the phase transition of liquid crystals. In particular, the most current research progresses on cubic and hexagonal phases as drug delivery systems will be discussed.

  17. Mixing effects in the crystallization of supercooled quantum binary liquids

    Energy Technology Data Exchange (ETDEWEB)

    Kühnel, M.; Kalinin, A. [Institut für Kernphysik, J. W. Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); Fernández, J. M.; Tejeda, G.; Moreno, E.; Montero, S. [Laboratory of Molecular Fluid Dynamics, Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain); Tramonto, F.; Galli, D. E. [Laboratorio di Calcolo Parallelo e di Simulazioni di Materia Condensata, Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Nava, M. [Laboratorio di Calcolo Parallelo e di Simulazioni di Materia Condensata, Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Computational Science, Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, Via Giuseppe Buffi 13, CH-6900 Lugano (Switzerland); Grisenti, R. E. [Institut für Kernphysik, J. W. Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); GSI - Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany)

    2015-08-14

    By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH{sub 2}) or orthodeuterium (oD{sub 2}) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH{sub 2} and oD{sub 2} crystal growth rates, similarly to what found in our previous work on supercooled pH{sub 2}-oD{sub 2} liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites.

  18. Minimal model for transient swimming in a liquid crystal.

    Science.gov (United States)

    Krieger, Madison S; Dias, Marcelo A; Powers, Thomas R

    2015-08-01

    When a microorganism begins swimming from rest in a Newtonian fluid such as water, it rapidly attains its steady-state swimming speed since changes in the velocity field spread quickly when the Reynolds number is small. However, swimming microorganisms are commonly found or studied in complex fluids. Because these fluids have long relaxation times, the time to attain the steady-state swimming speed can also be long. In this article we study the swimming startup problem in the simplest liquid crystalline fluid: a two-dimensional hexatic liquid crystal film. We study the dependence of startup time on anchoring strength and Ericksen number, which is the ratio of viscous to elastic stresses. For strong anchoring, the fluid flow starts up immediately but the liquid crystal field and swimming velocity attain their sinusoidal steady-state values after a time proportional to the relaxation time of the liquid crystal. When the Ericksen number is high, the behavior is the same as in the strong-anchoring case for any anchoring strength. We also find that the startup time increases with the ratio of the rotational viscosity to the shear viscosity, and then ultimately saturates once the rotational viscosity is much greater than the shear viscosity. PMID:26314259

  19. Minimal model for transient swimming in a liquid crystal

    CERN Document Server

    Krieger, Madison S; Powers, Thomas R

    2015-01-01

    When a microorganism begins swimming from rest in a Newtonian fluid such as water, it rapidly attains its steady-state swimming speed since changes in the velocity field spread quickly when the Reynolds number is small. However, swimming microorganisms are commonly found or studied in complex fluids. Because these fluids have long relaxation times, the time to attain the steady- state swimming speed can also be long. In this article we study the swimming startup problem in the simplest liquid crystalline fluid: a two-dimensional hexatic liquid crystal film. We study the dependence of startup time on anchoring strength and Ericksen number, which is the ratio of viscous to elastic stresses. For strong anchoring, the fluid flow starts up immediately but the liquid crystal field and swimming velocity attain their sinusoidal steady-state values after a time proportional to the relaxation time of the liquid crystal. When the Ericksen number is high, the behavior is the same as in the strong anchoring case for any a...

  20. Superfluorinated Ionic Liquid Crystals Based on Supramolecular, Halogen-Bonded Anions

    OpenAIRE

    Cavallo, Gabriella; Terraneo, Giancarlo; Monfredini, Alessandro; Saccone, Marco; Priimagi, Arri; Pilati, Tullio; Resnati, Giuseppe; Metrangolo, Pierangelo; Bruce, Duncan W

    2016-01-01

    Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [CnF2n+1-I···I···I-CnF2n+1]- are reported. The material system is unique in many ways, demonstrating for the first time 1)ionic, halogen-bonded liquid crystals, and 2)imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation.

  1. Biologically inspired hairy surfaces for liquid repellency

    Science.gov (United States)

    Hsu, Shu-Hau

    Owing to remarkable features, such as self-cleaning, anti-biofouling and drag reduction, interest on rendering surfaces water-repellent has significantly grown within this decade. Attempts on making surfaces "superhydrophobic", where high water contact angle (θc >150°) accompanied with only few degrees of roll-off angle, have been extensively demonstrated through the mimicking of the surface chemistry and morphology of lotus leaves. This appealing phenomenon also exists on another structure from nature: surfaces comprising soft hairs. Although the role of this piliferous integument has long been recognized for providing life, arthropods in particular, waterrepellency, the synthetic superhydrophobic surfaces based on this structure are still very limited. In this study, the goal was to develop a novel liquid-repellent surface by mimicking the hairy exterior of species. The artificial hairy surfaces were prepared by means of pressurized membrane casting, in which thermoplastic sheets were forced to flow into porous membranes at elevated temperature. The G-shaped pillars on the membrane cast polypropylene substrate are particularly similar to the conformation of natural hairs. The principle of this fabrication technique is relatively accessible and is expected to be compatible with large-area fabrication of superhydrophobic interfaces. The artificial hairy surface features perfectly hydrophobic response where no contact angle hysteresis was observed from video assessment. Thus the artificial hairy surface of the current work appears to be the first report to have such extreme hydrophobicity with only structural modification from the original substrate. This ultralow adhesion to water droplet is believed to be attributed to the hydrophobic methyl groups and the mechanical response of the artificial hairs. Liquid repellency of the hairy surfaces was further enhanced by coating with fluorocarbon (CF) layers via deep reactive ion etching (DRIE). The contact angle of

  2. Colorimetric qualification of shear sensitive liquid crystal coatings

    Science.gov (United States)

    Muratore, Joseph J., Jr.

    1993-01-01

    The work that has been done to date on the Shear Sensitive Liquid Crystal Project demonstrated that cholesteric liquid crystal coatings respond to both the direction and magnitude of a shearing force. The response of the coating is to selectively scatter incident white light into a spectrum of colors. Discernible color changes at a fixed angle of observation and illumination are the result of an applied shear stress. The intention was to be able to convert these observable color patterns from a flow visualization technique into a quantitative tool. One of the earlier intentions was to be able to use liquid crystals in dynamic flow fields. This was assumed possible because liquid crystals had made it possible to visualize transients in surface shear forces. Although the transients were visualized by color changes to an order one micro second, the time response of a coating to align to a shearing force is dependent on the magnitude of the change between its initial and final states. Unfortunately, the response is not instantaneous. It is for this reason any future attempt at quantifying the magnitude and directions of a shearing force are limited to surface shear stress vector fields in three dimensional steady state flows. This limitation does not significantly detract from the utility of liquid crystal coatings. The measurement of skin friction in the study of transition on wings, prediction of drag forces, performance assessment, and the investigation of boundary layer behavior is of great importance in aerodynamics. There exist numerous examples of techniques for the measurement of surface shear stress. Most techniques require arduous calibrations and necessitate extensive preparation of the receiving surfaces. However, the main draw back of instruments such as Preston tubes, hot films, buried wire gages, and floating element balances is that they only provide a point measurement. The advantages of capturing global shear data would be appreciable when compared

  3. Thermal tunability of photonic bandgaps in liquid crystal filled polymer photonic crystal fiber

    Science.gov (United States)

    Wang, Doudou; Chen, Guoxiang; Wang, Lili

    2016-05-01

    A highly tunable bandgap-guiding polymer photonic crystal fiber is designed by infiltrating the cladding air holes with liquid crystal 5CB. Structural parameter dependence and thermal tunability of the photonic bandgaps, mode properties and confinement losses of the designed fiber are investigated. Bandgaps red shift as the temperature goes up. Average thermal tuning sensitivity of 30.9 nm/°C and 20.6 nm/°C is achieved around room temperature for the first and second photonic bandgap, respectively. Our results provide theoretical references for applications of polymer photonic crystal fiber in sensing and tunable fiber-optic devices.

  4. Conformational fluctuations affect protein alignment in dilute liquid crystal media

    DEFF Research Database (Denmark)

    Louhivuori, M.; Otten, R.; Lindorff-Larsen, Kresten;

    2006-01-01

    The discovery of dilute liquid crystalline media to align biological macromolecules has opened many new possibilities to study protein and nucleic acid structures by NMR spectroscopy. We inspect the basic alignment phenomenon for an ensemble of protein conformations to deduce relative contributions...

  5. Biological production of liquid fuels from biomass

    Energy Technology Data Exchange (ETDEWEB)

    None

    1982-01-01

    A scheme for the production of liquid fuels from renewable resources such as poplar wood and lignocellulosic wastes from a refuse hydropulper was investigated. The particular scheme being studied involves the conversion of a cellulosic residue, resulting from a solvent delignified lignocellulosic feed, into either high concentration sugar syrups or into ethyl and/or butyl alcohol. The construction of a pilot apparatus for solvent delignifying 150 g samples of lignocellulosic feeds was completed. Also, an analysis method for characterizing the delignified product has been selected and tested. This is a method recommended in the Forage Fiber Handbook. Delignified samples are now being prepared and tested for their extent of delignification and susceptibility to enzyme hydrolysis. Work is continuing on characterizing the cellulase and cellobiase enzyme systems derived from the YX strain of Thermomonospora.

  6. Orientational dynamics and energy landscape features of thermotropic liquid crystals: An analogy with supercooled liquids

    Indian Academy of Sciences (India)

    Biman Jana; Biman Bagchi

    2007-09-01

    Recent optical kerr effect (OKE) studies have revealed that orientational relaxation of rodlike nematogens near the isotropic-nematic (I-N) phase boundary and also in the nematic phase exhibit temporal power law decay at intermediate times. Such behaviour has drawn an intriguing analogy with supercooled liquids. Here, we have investigated the single-particle and collective orientational dynamics of a family of model system of thermotropic liquid crystals using extensive computer simulations. Several remarkable features of glassy dynamics are on display including non-exponential relaxation, dynamical heterogeneity, and non-Arrhenius temperature dependence of the orientational relaxation time. Over a temperature range near the I-N phase boundary, the system behaves like a fragile glass-forming liquid. Using proper scaling, we construct the usual relaxation time versus inverse temperature plot and explicitly demonstrate that one can successfully define a density dependent fragility of liquid crystals. The fragility of liquid crystals shows a temperature and density dependence which is remarkably similar to the fragility of glass forming supercooled liquids. Energy landscape analysis of inherent structures shows that the breakdown of the Arrhenius temperature dependence of relaxation rate occurs at a temperature that marks the onset of the growth of the depth of the potential energy minima explored by the system.

  7. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    International Nuclear Information System (INIS)

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage

  8. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Wahle, Markus, E-mail: markus.wahle@uni-paderborn.de; Kitzerow, Heinz-Siegfried [Department of Chemistry, University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany and Center for Optoelectronics and Photonics Paderborn (CeOPP), Warburger Str. 100, 33098 Paderborn (Germany)

    2015-11-16

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  9. Synthesis, crystal structure and biological activity of novel diester cyclophanes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengfei; Yang, Bingqin; Fang, Xianwen; Cheng, Zhao; Yang, Meipan, E-mail: yangbq@nwu.edu.cn [Department of Chemistry, Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Northwest University, Shaanxi (China)

    2012-10-15

    A series of novel diester cyclophanes was synthesized by esterification of 1,2-benzenedicarbonyl chloride with eight different diols under high dilution conditions. The structures of the compounds were verified by elemental analysis, {sup 1}H nuclear magnetic resonance (NMR), IR spectroscopy and high resolution mass spectrometry (HRMS). The crystal structures of two compounds were characterized by single crystal X-ray diffractometry (XRD). All the new cyclophanes were evaluated for biological activities and the results showed that some of these compounds have low antibacterial or antifungal activities (author)

  10. High-speed imaging polarimetry using liquid crystal modulators

    Directory of Open Access Journals (Sweden)

    Ambs P.

    2010-06-01

    Full Text Available This paper deals with dynamic polarimetric imaging techniques. The basics of modern polarimetry have been known for one and a half century, but no practical high-speed implementation providing the full polarization information is currently available. Various methods are reviewed which prove to be a trade-off between the complexity of the optical set-up and the amount of polarimetric information they provide (ie the number of components of the Stokes vector. Techniques using liquid crystal devices, incepted in the late 1990's, are emphasized. Optical set-ups we implemented are presented. We particularly focus on high-speed techniques (i.e. faster than 200 Hz using ferroelectric liquid crystal devices.

  11. A numerical method for eigenvalue problems in modeling liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Baglama, J.; Farrell, P.A.; Reichel, L.; Ruttan, A. [Kent State Univ., OH (United States); Calvetti, D. [Stevens Inst. of Technology, Hoboken, NJ (United States)

    1996-12-31

    Equilibrium configurations of liquid crystals in finite containments are minimizers of the thermodynamic free energy of the system. It is important to be able to track the equilibrium configurations as the temperature of the liquid crystals decreases. The path of the minimal energy configuration at bifurcation points can be computed from the null space of a large sparse symmetric matrix. We describe a new variant of the implicitly restarted Lanczos method that is well suited for the computation of extreme eigenvalues of a large sparse symmetric matrix, and we use this method to determine the desired null space. Our implicitly restarted Lanczos method determines adoptively a polynomial filter by using Leja shifts, and does not require factorization of the matrix. The storage requirement of the method is small, and this makes it attractive to use for the present application.

  12. Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates

    Science.gov (United States)

    Shuai, M.; Klittnick, A.; Shen, Y.; Smith, G. P.; Tuchband, M. R.; Zhu, C.; Petschek, R. G.; Mertelj, A.; Lisjak, D.; Čopič, M.; Maclennan, J. E.; Glaser, M. A.; Clark, N. A.

    2016-01-01

    Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth's magnetic field. PMID:26817823

  13. Brownian Dynamics of Colloidal Particles in Lyotropic Chromonic Liquid Crystals

    Science.gov (United States)

    Martinez, Angel; Collings, Peter J.; Yodh, Arjun G.

    We employ video microscopy to study the Brownian dynamics of colloidal particles in the nematic phase of lyotropic chromonic liquid crystals (LCLCs). These LCLCs (in this case, DSCG) are water soluble, and their nematic phases are characterized by an unusually large elastic anisotropy. Our preliminary measurements of particle mean-square displacement for polystyrene colloidal particles (~5 micron-diameter) show diffusive and sub-diffusive behaviors moving parallel and perpendicular to the nematic director, respectively. In order to understand these motions, we are developing models that incorporate the relaxation of elastic distortions of the surrounding nematic field. Further experiments to confirm these preliminary results and to determine the origin of these deviations compared to simple diffusion theory are ongoing; our results will also be compared to previous diffusion experiments in nematic liquid crystals. We gratefully acknowledge financial support through NSF DMR12-05463, MRSEC DMR11-20901, and NASA NNX08AO0G.

  14. Liquid crystals for unsteady surface shear stress visualization

    Science.gov (United States)

    Reda, D. C.

    1988-04-01

    Oscillating airfoil experiments were conducted to test the frequency response of thermochromic liquid crystal coatings to unsteady surface shear stresses under isothermal-flow conditions. The model was an NACA-0015 airfoil, exposed to an incompressible flow at a freestream Reynolds number (based on chord) of 1.14 x 1000000. Angle-of-attack forcing functions were sine waves of amplitude + or - 10 deg about each of three mean angles of attack: 0 deg 10 deg, and 20 deg. Frequencies of oscillation were 0.2, 0.6 and 1.2 hertz, corresponding to reduced frequencies of 0.0055, 0.0164 and 0.0328. Data acquisition was accomplished by video recording. Observations showed the liquid crystal technique capable of visualizing high surface shear stress zones over the stated dynamic range in a continuous and reversible manner.

  15. Ultra-broadband wavelength conversion sensor using thermochromic liquid crystals

    Science.gov (United States)

    Chen, Ichun Anderson; Park, S. W.; Chen, G.; Wang, C.; Bethea, C.; Martini, R.; Woolard, D.

    2013-03-01

    Wavelength conversion (WC) imaging is a methodology that employs temperature sensitive detectors to convert photoinduced termperature into a detectable optical signal. One specific method is to use molecular detectors such as thermochromic liquid crystals (TLC), which exhibits thermochromism to observe the surface temperature of an area by observing the apparent color in the visible spectrum. Utilizing this methodology, an ultra-broadband room temperature imaging system was envisioned and realized using off the shelf thermochromic liquid crystals. The thermochromic properties of the sensor were characterized to show a thermochromic coefficient α = 10%/°K and a noise equivalent power (NEP) of 64 μW. With the TLC camera, images of both pulsed and continuous wave (CW) sources spanning 0.6 μm to 150 μm wavelengths were captured to demonstrate its potential as a portable, low-cost, and ultra-broadband imaging tool.

  16. Crystallization in supercooled liquid Cu: Homogeneous nucleation and growth

    Science.gov (United States)

    E, J. C.; Wang, L.; Cai, Y.; Wu, H. A.; Luo, S. N.

    2015-02-01

    Homogeneous nucleation and growth during crystallization of supercooled liquid Cu are investigated with molecular dynamics simulations, and the microstructure is characterized with one- and two-dimensional x-ray diffraction. The resulting solids are single-crystal or nanocrystalline, containing various defects such as stacking faults, twins, fivefold twins, and grain boundaries; the microstructure is subject to thermal fluctuations and extent of supercooling. Fivefold twins form via sequential twinning from the solid-liquid interfaces. Critical nucleus size and nucleation rate at 31% supercooling are obtained from statistical runs with the mean first-passage time and survival probability methods, and are about 14 atoms and 1032 m-3s-1, respectively. The bulk growth dynamics are analyzed with the Johnson-Mehl-Avrami law and manifest three stages; the Avrami exponent varies in the range of 1-19, which also depends on thermal fluctuations and supercooling.

  17. Crystallization in supercooled liquid Cu: Homogeneous nucleation and growth

    Energy Technology Data Exchange (ETDEWEB)

    E, J. C. [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610031 (China); Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Wang, L.; Luo, S. N., E-mail: sluo@pims.ac.cn [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610031 (China); Cai, Y. [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610031 (China); CAS Key Laboratory of Materials Behavior and Design, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China); Wu, H. A., E-mail: wuha@ustc.edu.cn [CAS Key Laboratory of Materials Behavior and Design, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China)

    2015-02-14

    Homogeneous nucleation and growth during crystallization of supercooled liquid Cu are investigated with molecular dynamics simulations, and the microstructure is characterized with one- and two-dimensional x-ray diffraction. The resulting solids are single-crystal or nanocrystalline, containing various defects such as stacking faults, twins, fivefold twins, and grain boundaries; the microstructure is subject to thermal fluctuations and extent of supercooling. Fivefold twins form via sequential twinning from the solid-liquid interfaces. Critical nucleus size and nucleation rate at 31% supercooling are obtained from statistical runs with the mean first-passage time and survival probability methods, and are about 14 atoms and 10{sup 32} m{sup −3}s{sup −1}, respectively. The bulk growth dynamics are analyzed with the Johnson-Mehl-Avrami law and manifest three stages; the Avrami exponent varies in the range of 1–19, which also depends on thermal fluctuations and supercooling.

  18. High contrast reflective liquid crystal display using a thermochromic reflector

    International Nuclear Information System (INIS)

    This paper presents a reflective liquid crystal display (LCD) with a high contrast ratio (CR) combined with mono-type thermochromic materials to solve the low CR of reflective type LCDs. Here, reflective, wide-band, electrically controlled birefringence mode was used as the optical liquid crystal (LC) mode, and a thermochromic material was used as the reflector for the white state and an absorber for the dark state. The combination of LCD and thermochromic material can have a synergistic effect in achieving a better display. By controlling the reflectance of the thermochromic reflector using Joule heating, the proposed reflective LC cell exhibited a high CR of approximately 70:1. The figure was extremely high compared to the approximately 10:1 of a typical reflective LC cell with an optically wide band design. The proposed LC cell configuration is expected to find many outdoor applications which can admit slow response speed. (paper)

  19. Soft Elasticity in Main Chain Liquid Crystal Elastomers

    Directory of Open Access Journals (Sweden)

    Anselm C. Griffin

    2013-06-01

    Full Text Available Main chain liquid crystal elastomers exhibit several interesting phenomena, such as three different regimes of elastic response, unconventional stress-strain relationship in one of these regimes, and the shape memory effect. Investigations are beginning to reveal relationships between their macroscopic behavior and the nature of domain structure, microscopic smectic phase structure, relaxation mechanism, and sample history. These aspects of liquid crystal elastomers are briefly reviewed followed by a summary of the results of recent elastic and high-resolution X-ray diffraction studies of the shape memory effect and the dynamics of the formation of the smectic-C chevron-like layer structure. A possible route to realizing auxetic effect at molecular level is also discussed.

  20. Capillary smectization and layering in a confined liquid crystal.

    Science.gov (United States)

    de Las Heras, D; Velasco, E; Mederos, L

    2005-01-14

    Using density-functional theory, we have analyzed the phase behavior of a model liquid crystal confined between two parallel, planar surfaces (i.e., the so-called slit pore). As a result of confinement, a rich phase behavior arises. The complete liquid-crystal phase diagram of the confined fluid is mapped out as a function of wall separation and chemical potential. Strong commensuration effects in the film with respect to wall separation lead to enhanced smectic ordering, which gives capillary smectization (i.e., formation of a smectic phase in the pore), or frustrated smectic ordering, which suppresses capillary smectization. These effects also produce layering transitions. Our nonlocal density-functional-based analysis provides a unified picture of all the above phenomena. PMID:15698132

  1. High contrast reflective liquid crystal display using a thermochromic reflector

    Science.gov (United States)

    Heo, Kyong Chan; Yi, Jonghoon; Kwon, Jin Hyuk; Seog Gwag, Jin

    2015-02-01

    This paper presents a reflective liquid crystal display (LCD) with a high contrast ratio (CR) combined with mono-type thermochromic materials to solve the low CR of reflective type LCDs. Here, reflective, wide-band, electrically controlled birefringence mode was used as the optical liquid crystal (LC) mode, and a thermochromic material was used as the reflector for the white state and an absorber for the dark state. The combination of LCD and thermochromic material can have a synergistic effect in achieving a better display. By controlling the reflectance of the thermochromic reflector using Joule heating, the proposed reflective LC cell exhibited a high CR of approximately 70:1. The figure was extremely high compared to the approximately 10:1 of a typical reflective LC cell with an optically wide band design. The proposed LC cell configuration is expected to find many outdoor applications which can admit slow response speed.

  2. Compound liquid crystal microlens array with convergent and divergent functions.

    Science.gov (United States)

    Kang, Shengwu; Zhang, Xinyu

    2016-04-20

    Based on the common liquid crystal microlens, a new compound structure for a liquid crystal (LC) microlens array is proposed. The structure consists of two sub LC microlens arrays with properties of light divergence and convergence. The structure has two LC layers: one to form the positive sub lens, one for the negative. The patterned electrode and plane electrode are used in both sub microlens arrays. When two sub microlens arrays are electrically controlled separately, they can diverge or converge the incident light, respectively. As two sub microlens arrays are both applied on the voltage, the focal length of the compound LC microlens becomes larger than that of the LC microlens with a single LC layer. Another feature of a compound LC microlens array is that it can make the target contour become visible under intense light. The mechanisms are described in detail, and the experimental data are given. PMID:27140107

  3. Ferromagnetic Switching of Knotted Vector Fields in Liquid Crystal Colloids.

    Science.gov (United States)

    Zhang, Qiaoxuan; Ackerman, Paul J; Liu, Qingkun; Smalyukh, Ivan I

    2015-08-28

    We experimentally realize polydomain and monodomain chiral ferromagnetic liquid crystal colloids that exhibit solitonic and knotted vector field configurations. Formed by dispersions of ferromagnetic nanoplatelets in chiral nematic liquid crystals, these colloidal ferromagnets exhibit spontaneous long-range alignment of magnetic dipole moments of individual platelets, giving rise to a continuum of the magnetization field M(r). Competing effects of surface confinement and chirality prompt spontaneous formation and enable the optical generation of localized twisted solitonic structures with double-twist tubes and torus knots of M(r), which exhibit a strong sensitivity to the direction of weak magnetic fields ∼1  mT. Numerical modeling, implemented through free energy minimization to arrive at a field-dependent three-dimensional M(r), shows a good agreement with experiments and provides insights into the torus knot topology of observed field configurations and the corresponding physical underpinnings. PMID:26371682

  4. Light-controlled topological charge in a nematic liquid crystal

    Science.gov (United States)

    Nikkhou, Maryam; Škarabot, Miha; Čopar, Simon; Ravnik, Miha; Žumer, Slobodan; Muševič, Igor

    2015-02-01

    Creating, imaging, and transforming the topological charge in a superconductor, a superfluid, a system of cold atoms, or a soft ferromagnet is a difficult--if not impossible--task because of the shortness of the length scales and lack of control. The length scale and softness of defects in liquid crystals allow the easy observation of charges, but it is difficult to control charge creation. Here we demonstrate full control over the creation, manipulation and analysis of topological charges that are pinned to a microfibre in a nematic liquid crystal. Oppositely charged pairs are created through the Kibble-Zurek mechanism by applying a laser-induced local temperature quench in the presence of symmetry-breaking boundaries. The pairs are long-lived, oppositely charged rings or points that either attract and annihilate, or form a long-lived, charge-neutral loop made of two segments with a fractional topological charge.

  5. Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics

    Science.gov (United States)

    Griffin, DeVon W.; Marshall, Keneth L.

    2002-11-01

    The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal

  6. Crystallization in supercooled liquid Cu: Homogeneous nucleation and growth

    International Nuclear Information System (INIS)

    Homogeneous nucleation and growth during crystallization of supercooled liquid Cu are investigated with molecular dynamics simulations, and the microstructure is characterized with one- and two-dimensional x-ray diffraction. The resulting solids are single-crystal or nanocrystalline, containing various defects such as stacking faults, twins, fivefold twins, and grain boundaries; the microstructure is subject to thermal fluctuations and extent of supercooling. Fivefold twins form via sequential twinning from the solid-liquid interfaces. Critical nucleus size and nucleation rate at 31% supercooling are obtained from statistical runs with the mean first-passage time and survival probability methods, and are about 14 atoms and 1032 m−3s−1, respectively. The bulk growth dynamics are analyzed with the Johnson-Mehl-Avrami law and manifest three stages; the Avrami exponent varies in the range of 1–19, which also depends on thermal fluctuations and supercooling

  7. Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates

    Science.gov (United States)

    Shuai, M.; Klittnick, A.; Shen, Y.; Smith, G. P.; Tuchband, M. R.; Zhu, C.; Petschek, R. G.; Mertelj, A.; Lisjak, D.; Čopič, M.; Maclennan, J. E.; Glaser, M. A.; Clark, N. A.

    2016-01-01

    Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth's magnetic field.

  8. Highly birefringent, low-loss liquid crystals for terahertz applications

    Directory of Open Access Journals (Sweden)

    M. Reuter

    2013-07-01

    Full Text Available With growing interest in switchable devices for the THz frequency range, there is a strong demand for liquid crystals (LC exhibiting both a high birefringence and a low absorption. We present the refractive index and absorption coefficient of the liquid crystal mixtures 1852 and 1825 in the frequency range between 0.2 and 2.5 THz. Both mixtures are designed specifically for high birefringence Δn of 0.32 and 0.38, respectively, in the THz region. In addition, they show low absorption coefficients for both ordinary and extraordinary polarization. This low absorbance in combination with the high birefringence makes these LCs particularly well suited for applications in switchable devices for THz optics.

  9. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    Directory of Open Access Journals (Sweden)

    Vasily F. Shabanov

    2013-08-01

    Full Text Available Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

  10. Proton irradiation of liquid crystal based adaptive optical devices

    International Nuclear Information System (INIS)

    To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence (1010p/cm2). The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

  11. Homeotropic alignment of lyotropic chromonic liquid crystals using noncovalent interactions.

    Science.gov (United States)

    Jeong, Joonwoo; Han, Ganghee; Johnson, A T Charlie; Collings, Peter J; Lubensky, Tom C; Yodh, Arjun G

    2014-03-18

    We report on the homeotropic alignment of lyotropic chromonic liquid crystals (LCLCs). Homeotropic anchoring of LCLCs is difficult to achieve, and this challenge has limited development of applications for LCLCs. In this work, homeotropic alignment is achieved using noncovalent interactions between the LCLC molecules and various alignment layers including graphene, parylene films, poly(methyl methacrylate) films, and fluoropolymer films. The LCLC molecules are unique in that they self-assemble via noncovalent interactions in water into elongated aggregates which, in turn, form nematic and columnar liquid crystal (LC) phases. Here we exploit these same noncovalent interactions to induce homeotropic anchoring of the nematic LCLC. Homeotropic alignment is confirmed by polarized optical microscopy and conoscopy. We also report on novel transient stripe textures that occur when an initial flow-induced planar alignment transforms into the equilibrium homeotropic alignment required by boundary conditions. An understanding of this behavior could be important for switching applications. PMID:24559290

  12. Two-Dimensional Spatial Solitons in Nematic Liquid Crystals

    Institute of Scientific and Technical Information of China (English)

    ZHONG Wei-Ping; YANG Zheng-Ping; XIE Rui-Hua; Milivoj Be-lie; Goong Chen

    2009-01-01

    We study the propagation of spatial solitons in nematic liquid crystals, using the self-similar method.Analytical solutions in the form of self-similar solitons are obtained exactly.We confirm the stability of these solutions by direct numerical simulation, and find that the stable spatial solitons can exist in various forms, such as Gaussian solitons, radially symmetric solitons, multipoIe solitons, and soliton vortices.

  13. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    OpenAIRE

    Vasily F. Shabanov; Parshin, Alexander M.; Victor Y. Zyryanov; Gunyakov, Vladimir A.

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with ...

  14. Imaging in natural light with nematic liquid crystals (Presentation Recording)

    Science.gov (United States)

    Galstian, Tigran V.

    2015-10-01

    Nametic liquid crystals (NLC) are most commonly used liquid crystal (LC) materials in various light modulators [1], displays [2] and lenses [3]. However those materials have a fundamental limitation: they are polarization sensitive since the refractive index modulation here is achieved by the electric field induced reorientation of their local anisotropy axis. Thus, the standard imaging optical systems (used in consumer electronic products and dealing with natural light sources [4]) have to use double NLC structures in a cross oriented way and in rather requiring geometrical conditions. We describe a simple but very efficient optical device that allows the dynamic focusing of unpolarized light using a single NLC layer. The operation principle of the proposed device is based on the combination of an electrically variable "single layer lens" with two fixed optical elements for light reflection and 90° polarization flip. Such an approach is made possible thanks to the close integration of thin film wave plate and mirror. Preliminary experimental studies of the obtained electrically variable mirror show very promising results. Several standard camera geometries, using the double layer approach, and possible new geometries, using the reflective approach, will be described. References 1. Gordon D. Love, Wave-front correction and production of Zernike modes with a liquid-crystal spatial light modulator, Applied Optics, Vol. 36, Issue 7, pp. 1517-1524 (1997). 2. P. Yeh and C. Gu, Optics of Liquid Crystal Displays, Wiley, 1999. 3. T. Galstian, Smart Mini-Cameras, CRC Press, Taylor and Francis group, 2013. 4. www.lensvector.com

  15. Surface induced structures in nematic liquid crystal colloids

    OpenAIRE

    Chernyshuk, S. B.; Tovkach, O. M.; Lev, B. I.

    2014-01-01

    We predict theoretically the existence of a class of colloidal structures in nematic liquid crystal (NLC) cells, which are induced by surface patterns on the plates of the cell (like cells with UV-irradiated polyimide surfaces using micron size masks). These bulk structures arise from non-zero boundary conditions for the director distortions at the confining surfaces. In particular, we demonstrate that quadrupole spherical particles (like spheres with boojums or Saturn-ring director configura...

  16. Iris-like tunable aperture employing liquid-crystal elastomers.

    Science.gov (United States)

    Schuhladen, Stefan; Preller, Falko; Rix, Richard; Petsch, Sebastian; Zentel, Rudolf; Zappe, Hans

    2014-11-12

    A liquid-crystal elastomer (LCE) iris inspired by the human eye is demonstrated. With integrated polyimide-based platinum heaters, the LCE material is thermally actuated. The radial contraction direction, similar to a mammalian iris, is imprinted to the LCE by a custom-designed magnetic field. Actuation of the device is reproducible over multiple cycles and controllable at intermediate contraction states. PMID:25209884

  17. Reconfigurable random bit storage using polymer-dispersed liquid crystal

    OpenAIRE

    Horstmeyer, Roarke; Assawaworrarit, Sid; Yang, Changhuei

    2014-01-01

    We present an optical method of storing random cryptographic keys, at high densities, within an electronically reconfigurable volume of polymer-dispersed liquid crystal (PDLC) film. We demonstrate how temporary application of a voltage above PDLC's saturation threshold can completely randomize (i.e., decorrelate) its optical scattering potential in less than a second. A unique optical setup is built around this resettable PDLC film to non-electronically save many random cryptographic bits, wi...

  18. Spinodal dewetting of a nematic liquid crystal film

    Science.gov (United States)

    Braun; Yokoyama

    2000-08-01

    We discuss spinodal dewetting of a nematic film destabilized by Van der Waals forces, focusing on the case of non-antagonistic anchoring conditions. Using physical parameters pertinent to low-molecular-weight thermotropic liquid crystals, we predict a small damping effect. In the presence of an antagonistic applied magnetic field, the anchoring conditions become more significant, and can influence the shape and dynamics of the unstable modes. PMID:11088786

  19. Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells

    OpenAIRE

    VIJ, JAGDISH; Song, Jang-Kun

    2008-01-01

    PUBLISHED Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells controlled by surface anchoring of the alignment layers is investigated for different conditions of alignment on the two opposite surfaces. We show that the critical field Ec, where the speed of the solitary wave becomes zero, is finite for asymmetric alignment on two surfaces. We also show that the polar anchoring energy difference (Deltawp) between the alignment layers can be calculated by measur...

  20. Electronically Reconfigurable Liquid Crystal Based Mm-Wave Polarization Converter

    OpenAIRE

    Doumanis, E.; Goussetis, G.; Dickie, R.; CAHILL, R; Baine, P; Bain, M; V. Fusco; Encinar, J. A.; Toso, G

    2014-01-01

    An electronically tunable reflection polarizer which exploits the dielectric anisotropy of nematic liquid crystals (LC) has been designed, fabricated and measured in a frequency band centered at 130 GHz. The phase agile polarizing mirror converts an incident slant 45° signal upon reflection to right hand circular (RHCP), orthogonal linear (-45 °) or left hand circular (LHCP) polarization depending on the value of the voltage biasing the LC mixture. In the experimental set-up this is achieved ...

  1. ANALISIS CITRA PERMUKAAN THERMOCHROMIC LIQUID CRYSTAL BERDASARKAN NILAI STATISTIK HUE

    OpenAIRE

    Risti Suryantari; - Flaviana

    2014-01-01

    Tujuan dari penelitian ini adalah untuk mengamati perbedaan citra pada permukaan Thermocromic Liquid Crystal (TLC) R25C5W akibat perubahan temperatur. Metode yang digunakan untuk analisis adalah pengolahan citra berbasis morfologi matematika menggunakan perangkat lunak Matlab2013a. Citra asli yang diperoleh dalam bentuk RGB dikonversi menjadi HSV (hue, saturation, value), dengan mengambil komponen hue saja. Proses utama yang digunakan adalah opening dengan struktur elemen (SE) line. Berdasark...

  2. Nematic Liquid Crystal Spatial Light Modulators for Laser Beam Steering

    OpenAIRE

    Hällstig, Emil

    2004-01-01

    Laser beam control is important in many applications. Phase modulating spatial light modulators (SLMs) can be used to electronically alter the phase distribution of an optical wave-front and thus change the direction and shape of a laser beam. Physical constraints set limitations to the SLM and an ideal phase distribution can usually not be realised. In order to understand how such components can be used for non-mechanical beam control three nematic liquid crystal (NLC) SLMs have been thoroug...

  3. Supercoiled DNA; plectonemic structure and liquid crystal formation

    CERN Document Server

    Maarel, J R C; Jesse, W; Backendorf, C; Egelhaaf, S U; Lapp, A

    2003-01-01

    We have investigated the phase behaviour of pUC18 plasmid solutions with phase separation experiments and polarized light microscopy. Furthermore, the configuration of the superhelix is monitored with small-angle neutron scattering. The phase diagram is interpreted with liquid crystal theory including the effects of charge, orientation entropy, excluded volume, as well as the elastic, entropic and electrostatic contributions to the molecular free energy.

  4. An Adaptive Algorithm of Local dimming for Liquid Crystal Displays

    OpenAIRE

    Huaxia Wu; Jianghong Han; Bo Liu; Xin Liu; Xiaobing Zhang

    2012-01-01

    The local dimming backlight technique enables liquid crystal display to present images with high contrast ratio and low power consumption. Considering that it is more important to make sure a high quality of the displayed image when reducing the power consumption, therefore, in this paper the new algorithm chooses RPSNR (the peak signal-to-noise ratio) =30 as the lowest standard to guarantee the quality of image. RPSNR =30 could provide a value that the maximum distortion of the image can be ...

  5. New Photocrosslinking Polymeric Materials for Liquid Crystal Photoalignment

    OpenAIRE

    Mahilny, Uladzimir; Trofimova, Alexandra; Stankevich, Alexander; Tolstik, Alexei; Murauski, Anatoli; Muravsky, Alexander

    2013-01-01

    The photoinduced alignment (photoalignment) of nematic liquid crystals (LC) is of great interest as a contactless technique to create patterned LC aligning layers which have good prospect as basic elements of nonlinear optical devices like controllable waveguide structures with discrete diffraction, statical and dynamical photonic media etc. LC photoalignment on the surface of benzaldehyde polymeric layer caused by photochemical reaction of benzaldehyde side groups is investigated exper...

  6. Cellular solid behaviour of liquid crystal colloids. 2. Mechanical properties

    OpenAIRE

    Anderson, V.J.; Terentjev, E. M.

    2000-01-01

    This paper presents the results of a rheological study of thermotropic nematic colloids aggregated into cellular structures. Small sterically stabilised PMMA particles dispersed in a liquid crystal matrix densely pack on cell interfaces, but reversibly mix with the matrix when the system is heated above Tni. We obtain a remarkably high elastic modulus, G'~10^5 Pa, which is a nearly linear function of particle concentration. A characteristic yield stress is required to disrupt the continuity o...

  7. Lensing effects in a nematic liquid crystal with topological defects.

    Science.gov (United States)

    Sátiro, C; Moraes, F

    2006-06-01

    Light traveling through a liquid crystal with disclinations perceives a geometrical background which causes lensing effects similar to the ones predicted for cosmic objects like global monopoles and cosmic strings. In this paper we explore the effective geometry as perceived by light in such media. The comparison between both systems suggests that experiments can be done in the laboratory to simulate optical properties, like gravitational lensing, of cosmic objects. PMID:16775663

  8. Hydrodynamics and rheology of active liquid crystals: a numerical investigation.

    Science.gov (United States)

    Marenduzzo, D; Orlandini, E; Yeomans, J M

    2007-03-16

    We report numerical studies of the hydrodynamics and rheology of an active liquid crystal. We confirm the existence of a transition between a passive and an active phase, with spontaneous flow in steady state. We explore how the velocity profile changes with activity, and we point out the difference in behavior for flow-aligning and tumbling materials. We find that an active material can thicken or thin under a flow, or even exhibit both behaviors as the forcing changes. PMID:17501095

  9. General elastic interaction in nematic liquid crystals colloids

    OpenAIRE

    Chernyshuk, S. B.; Lev, B. I.

    2009-01-01

    The new free energy functional that describes general elastic interaction between colloidal particles and nematic liquid crystal has been proposed. It generalizes results of the paper \\cite{lupe} on the case of arbitrary orientation of colloidal particles and is valid for arbitrary surface anchoring strength. Formal analogies and differences between electric particles and colloidal particles in LC are found. It is first time shown that spur of the quadrupole moment tensor is different from ze...

  10. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    Science.gov (United States)

    Hanham, S. M.; Watts, C.; Otter, W. J.; Lucyszyn, S.; Klein, N.

    2015-07-01

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ˜4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ˜5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  11. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    International Nuclear Information System (INIS)

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ∼4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ∼5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies

  12. NMR of small solutes in liquid crystals and molecular sieves

    Science.gov (United States)

    Ylihautala, Mika Petri

    The present thesis deals with the nuclear magnetic resonance (NMR) spectroscopy of small solutes applied to the studies of liquid crystals and molecular sieves. In this method, changes induced by the investigated environment to the static spectral parameters (i.e. nuclear shielding, indirect and direct spin-spin coupling and quadrupole coupling) of the solute are measured. The nuclear shielding of dissolved noble gases is utilized for the studies of thermotropic liquid crystals. The relation between the symmetry properties of mesophases and the nuclear shielding is described. The different interaction mechanisms perturbing the observed noble gas nuclear shielding are discussed, particularly, the role of long-range attractive van der Waals interactions is brought out. The suitability of the noble gas NMR spectroscopy to the studies of Iyotropic liquid crystals is investigated in terms of nuclear shielding and quadrupole coupling interactions. In molecular sieve systems, the effect of inter- and intracrystalline motions of solutes on their NMR spectra is discussed. A novel method for the measurement of the intracrystalline motions is developed. The distinctions in the 13C shielding of methane adsorbed in AlPO4-11 and SAPO-11, two structurally similar molecular sieves differing in composition, are indicated.

  13. Liquid crystal thermometry for micro-fluidic applications

    Science.gov (United States)

    Pottebaum, Tait

    2009-11-01

    Liquid crystal thermometry has been implemented in a micro-channel and the performance of the technique quantified. Implementation of the technique is subject to constraints on imaging and illumination configurations similar to the constraints on micro-PIV. In addition, the proximity of the measurements to interfaces and surfaces from which light scatters leads to high noise levels that cannot be reduced by wavelength filtering (such as with fluorescent particles) because the temperature information is contained in the color of the particles. Therefore, circular polarization filtering is used, exploiting the circular dichroism of the thermochromic liquid crystal (TLC). Encapsulated TLC particles were flowed through the micro-channel and subjected to a series of uniform temperatures for calibration. To validate the technique, a temperature gradient was imposed with no flow. Finally, the technique was applied to micro-channel flow with an imposed wall temperature gradient in the flow direction. Liquid crystal thermometry can now be applied to a wide range of micro-fluidic applications.

  14. Liquid crystal film development for plasma mirrors and waveplates

    Science.gov (United States)

    Cochran, G. E.; Poole, P. L.; Willis, C.; Hanna, R. J.; Pytel, K.; Sullivan, K. S.; Andereck, C. D.; Schumacher, D. W.

    2015-11-01

    Many laser-plasma phenomena currently under study depend critically on the quality of the pulse contrast. Costly sacrificial plasma mirrors are now commonly used to improve the temporal laser contrast before target interaction, especially for ion acceleration where high contrast is necessary to achieve interesting new mechanisms. Liquid crystal films were originally developed as variable thickness thin-film targets, and were demonstrated for this purpose in. Varying film formation parameters such as volume, temperature, and draw speed allows thickness control between 10 nm and several 10s of microns, in-situ and under vacuum. Development since that initial work has allowed large area films to be formed, several cm2 in extent, with the same thickness range. The molecular flatness of a freely suspended film renders these films excellent low-cost plasma mirrors, given appropriate formation control. Additionally, the birefringence of the liquid crystal used here permits these films to be used as large area zero-order waveplates at the appropriate thickness. Details on the current state of liquid crystal film application development, including a >1 Hz small area film formation device, will be presented. This work was performed with support from the DARPA PULSE program through a grant from AMRDEC and by the NNSA under contract DE-NA0001976.

  15. Hierarchical spatial heterogeneity in liquid crystals composed of graphene oxides.

    Science.gov (United States)

    Shundo, Atsuomi; Hori, Koichiro; Penaloza, David P; Matsumoto, Yuji; Okumura, Yasushi; Kikuchi, Hirotsugu; Lee, Kyung Eun; Kim, Sang Ouk; Tanaka, Keiji

    2016-08-10

    Graphene oxide (GO) is a class of two-dimensional materials with a thickness of about 1 nm and a broad distribution of lateral dimension commonly approaching several micrometers. A dispersion of GOs in water often forms a liquid crystal, which is expected to be a promising precursor for the fabrication of carbon-based materials with well-ordered structures. To accelerate the application of GO-based liquid crystals, their structures and physical properties at various sizes must be well understood. To that end, we examined the local rheological properties of GO-based liquid crystals in the nematic phase using a particle tracking technique, where local properties can be accessed by observing the thermal motion of embedded probe particles. Particle diffusion was spatially heterogeneous, and depended on the size of the particles. Such a size-dependent heterogeneity can be associated with a hierarchical local environment, which is time-dependent for this system. The anisotropic particle diffusion originated from particles trapped in between the GO layers and in isotropic-like regions. The aggregation states of the GO dispersion composed of nematic and isotropic-like regions were observed using confocal laser scanning microscopy. PMID:27464002

  16. Photorefractivity in liquid crystals doped with a soluble conjugated polymer

    Science.gov (United States)

    Wiederrecht, Gary P.; Svec, Walter A.; Niemczyk, Mark P.; Wasielewski, Michael R.

    1999-10-01

    Photoconductive polymers are doped into liquid crystals to create a new mechanism for space-charge field formation in photorefractive liquid crystal composites. The composites contain poly(2,5-bis(2'-ethylhexyloxy)-1,4- phenylenevinylene) (BEH-PPV) and the electron acceptor N,N'- dioctyl-1,4:5,8-naphthalenediimide, NI. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 micrometers . We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile spaces due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  17. Photorefractivity in liquid crystals doped with a soluble conjugated polymer.

    Energy Technology Data Exchange (ETDEWEB)

    Niemczyk, M. P.; Svec, W. A.; Wasielewski, M. R.; Wiederrecht, G. P.

    1999-07-07

    Photoconductive polymers are doped into liquid crystals to create a new mechanism for space-charge field formation in photorefractive liquid crystal composites. The composites contain poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N{prime}-dioctyl-1,4:5,8-naphthalenediimide, NI. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 {micro}m. We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  18. Structural relaxation in a glassy liquid crystal: MBBA

    International Nuclear Information System (INIS)

    Combined neutron and Raman scattering measurements were performed to analyze the solid polymorphic modifications of a typical nematic liquid crystal substance, MBBA. A glassy solid phase, classified as oriented molecular glass (OMG) may be produced by fast cooling from the nematic phase. A sequence of irreversible phase transitions was observed on reheating OMG. Four different solid modifications were found: two structurally relaxed amorphous 'mesophases' and two crystalline ones. A distinct modification can be found by slow crystallization from the nematic phase and it can be transformed reversibly into an other crystal structure by further cooling. The role of medium range order in the non-crystalline phases and the structural relaxation of the OMG state were analyzed. (author)

  19. Influence of hue origin on the hue-temperature calibration of thermochromic liquid crystals

    Science.gov (United States)

    Sun, J. H.; Leong, K. C.; Liu, C. Y.

    Liquid crystal thermography incorporates a process by which the liquid crystal color, bearing temperature information, is analyzed using image processing techniques to quantify complex temperature distributions on heat transfer surfaces. Previous researches have found that hue can be used to represent the liquid crystal color since there exists a monotonic relation between the hue and temperature of liquid crystals. It is found in this study that the white-light point, which is usually adopted as the hue reference point, does not generally lie at the center of the liquid crystal colors defined on a chromaticity diagram. This results that hue does not have uniform resolution to all liquid crystal colors and a biased error is produced subsequently in the temperature measurement. The non-uniform hue can be corrected by shifting the hue origin to the center of the colors or by a color calibration scheme so that the liquid crystal colors distribute evenly around the white-light point.

  20. IR Sensor Synchronizing Active Shutter Glasses for 3D HDTV with Flexible Liquid Crystal Lenses

    Directory of Open Access Journals (Sweden)

    Jeong In Han

    2013-12-01

    Full Text Available IR sensor synchronizing active shutter glasses for three-dimensional high definition television (3D HDTV were developed using a flexible liquid crystal (FLC lens. The FLC lens was made on a polycarbonate (PC substrate using conventional liquid crystal display (LCD processes. The flexible liquid crystal lens displayed a maximum transmission of 32% and total response time of 2.56 ms. The transmittance, the contrast ratio and the response time of the flexible liquid crystal lens were superior to those of glass liquid crystal lenses. Microcontroller unit and drivers were developed as part of a reception module with power supply for the IR sensor synchronizing active shutter glasses with the flexible liquid crystal lens prototypes. IR sensor synchronizing active shutter glasses for 3D HDTV with flexible liquid crystal lenses produced excellent 3D images viewing characteristics.

  1. Liquid Between Macromolecules in Protein Crystals: Static Versus Dynamics

    Science.gov (United States)

    Chernov, A. A.

    2005-01-01

    Protein crystals are so fragile that they often can not be handled by tweezers. Indeed, measurements of the Young modulus, E, of lysozyme crystals resulted in E approx. equals 0.1 - 1 GPa, the lower figures, 0.1 - 0.5 GPa, being obtained from triple point bending of as-grown and not cross-linked crystals sitting in solution. The bending strength was found to be approx.10(exp -2) E. On the other hand, ultrasound speed and Mandelstam-Raman-Brilloin light scattering experiments led to much higher figures, E approx. equals 2.7 GPa. The lower figures for E were found from static or low frequency crystal deformations measurements, while the higher moduli are based on high frequency lattice vibrations, 10(exp 7) - 10(exp 10) 1/s. The physical reason for the about an order of magnitude discrepancy is in different behavior of water filling space between protein molecules. At slow lattice deformation, the not-bound intermolecular water has enough time to flow from the compressed to expanded regions of the deformed crystal. At high deformation frequencies in the ultra- and hypersound waves, the water is confined in the intermolecular space and, on that scale, behaves like a solid, thus contributing to the elastic crystal moduli. In this case, the reciprocal crystal modulus is expected to be an average of the water protein and water compressibilities (reciprocal compressibilities): the bulk modulus for lysozyme is 26 GPa, for water it is 7 GPa. Anisotropy of the crystal moduli comes from intermolecular contacts within the lattice while the high frequency hardness comes from the bulk of protein molecules and water bulk moduli. These conclusions are based on the analysis of liquid flow in porous medium to be presented.

  2. High sensitive piezoelectric quartz crystal liquid density sensor

    Institute of Scientific and Technical Information of China (English)

    Xue Cai Zhao; Jun Guo Du; Rui Sheng; Qi Kang; Da Zhong Shen

    2010-01-01

    We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC)in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears in the conductance-frequency curve.With gradually increasing liquid density,the additional peak moves from low to high frequency region then disappears.The frequency of the additional resonant peak is sensitive to the change in liquid density.The frequency shift of the additional peak is linear with the liquid density in a given range.For a 5 MHz PQC with a reflection distance of 16 mm for longitudinal wave,the sensitivity to liquid density is 2.61×106 Hz g-1 cm3.The overlap between the primary resonant peak and the additional resonant peak causes a decrease in the intensity of the former and an increase in the intensity of the latter.In a combined impedance analysis method,the changes in surface mass loading,density and viscosity of the liquid were monitored simultaneously by a PQC sensor.

  3. Hard-body models of bulk liquid crystals.

    Science.gov (United States)

    Mederos, Luis; Velasco, Enrique; Martínez-Ratón, Yuri

    2014-11-19

    Hard models for particle interactions have played a crucial role in the understanding of the structure of condensed matter. In particular, they help to explain the formation of oriented phases in liquids made of anisotropic molecules or colloidal particles and continue to be of great interest in the formulation of theories for liquids in bulk, near interfaces and in biophysical environments. Hard models of anisotropic particles give rise to complex phase diagrams, including uniaxial and biaxial nematic phases, discotic phases and spatially ordered phases such as smectic, columnar or crystal. Also, their mixtures exhibit additional interesting behaviours where demixing competes with orientational order. Here we review the different models of hard particles used in the theory of bulk anisotropic liquids, leaving aside interfacial properties and discuss the associated theoretical approaches and computer simulations, focusing on applications in equilibrium situations. The latter include one-component bulk fluids, mixtures and polydisperse fluids, both in two and three dimensions, and emphasis is put on liquid-crystal phase transitions and complex phase behaviour in general. PMID:25335432

  4. Temperature dependences of the electrooptical properties of rodlike nematic liquid crystals doped with hockey-stick-shaped liquid crystals

    Science.gov (United States)

    Yeo, Sunggu; Srivastava, Anoop Kumar; Lee, Hyojin; Lee, Ji-Hoon; Choi, E.-Joon

    2016-01-01

    We investigated the temperature dependences of the dielectric anisotropy, birefringence, order parameter, splay elastic constant, and rotational viscosity of rodlike nematic liquid crystals (RLCs) doped with hockey-stick-shaped liquid crystals (HLCs). Although the order parameter of the HLC-RLC mixtures was similar to that of the pure RLC, the dielectric anisotropy and the birefringence of the mixtures were decreased or increased depending on the structure of the HLC molecule. In addition, the activation energies of the mixtures were different, which implies that the intramolecular structure of the HLC molecule had more influence on the electrooptical properties of the HLC-RLC binary mixtures than the inter-molecular interaction between the HLC and the RLC molecules.

  5. A study of waste liquid crystal display generation in mainland China.

    Science.gov (United States)

    Liu, Zhifeng; Xu, Zeying; Huang, Haihong; Li, Bingbing

    2016-01-01

    The generation of liquid crystal display waste is becoming a serious social problem. Predicting liquid crystal display waste status is the foundation for establishing a recycling network; however, the difficulty in predicting liquid crystal display waste quantity lies in data mining. In order to determine the quantity and the distribution of liquid crystal display waste in China, the four top-selling liquid crystal display products (liquid crystal display TVs, desktop PCs, notebook PCs, and mobile phones) were selected as study objects. Then, the extended logistic model and market supply A method was used to predict the quantity of liquid crystal display waste products. Moreover, the distribution of liquid crystal display waste products in different regions was evaluated by examining the consumption levels of household equipment. The results revealed that the quantity of waste liquid crystal displays would increase rapidly in the next decade. In particular, the predicted quantity of waste liquid crystal displays would rise to approximately 4.262 × 10(9) pieces in 2020, and the total display area (i.e. the surface area of liquid crystal display panels) of waste liquid crystal displays would reach 5.539 × 10(7) m(2). The prediction on the display area of waste liquid crystal display TVs showed that it would account for 71.5% of the total display area by 2020. Meanwhile, the quantity of waste mobile phones would significantly grow, increasing 5.8 times from 2012 to 2020. In terms of distribution, Guangdong is the top waste liquid crystal display-generating province in China, followed by Jiangsu, Shandong, Henan, Zhejiang, and Sichuan. Considering its regional characteristics, Guangdong has been proposed to be the most important location of the recycling network. PMID:26542394

  6. Modelling of switching in ferroelectric liquid crystal devices

    International Nuclear Information System (INIS)

    Smectic C* liquid crystals are now used in many applications such as flat panel displays and laser printer print heads. They are an attractive alternative to the standard nematic liquid crystals because they offer significant improvements in speed, resolution, viewing characteristics, precision and power consumption. Aside from the initial high production costs, the main drawback of the material is the lack of a usable design tool. The liquid crystal has a complex phase structure and a complex interaction with electric fields. Surface stabilisation, the introduction of two close parallel boundaries, induces ferroelectric behaviour, but also increases the structural complexity. As an important step towards a complete design tool, the work presented in this thesis concentrates on the dynamics of switching in a single cell in a typical flat panel display. (Switching refers to the reorientation of the liquid crystal's permanent electric dipole.) Two different switching models are developed from novel equations based on a continuum representation of the liquid crystal. These equations can for the first time describe the display cell in an isolated state, as found in active matrix displays, as well as the applied voltage state common to all displays. Numerical simulations of dynamic behaviour are implemented which show good agreement with published experimental results. At low voltages, cells switch by nucleation and growth of reoriented domains. The Avrami theory of growing phases in two dimensions is adapted to model this, and combined with the continuum equations to give a single dynamic equation relating the domain area to the charge (for an isolated cell) or to the voltage. Empirical relationships are found for the switching times which show two regimes separated by a distinct threshold. A finite difference model is developed to simulate the dynamics of reorientation in one and two dimensions. The model takes into account much of the known structural complexity, for

  7. Liquid-Liquid Phase Separation in Supersaturated Lysozyme Solutions and Associated Precipitate Formation/Crystallization

    Science.gov (United States)

    Muschol, Martin; Rosenberger, Franz

    1997-01-01

    Using cloud point determinations, the phase boundaries (binodals) for metastable liquid-liquid (L-L) separation in supersaturated hen egg white lysozyme solutions with 3%, 5%, and 7% (wlv) NaCl at pH= 4.5 and protein concentrations c between 40 and 400 mg/ml were determined. The critical temperature for the binodal increased approximately linearly with salt concentration. The coexisting liquid phases both remained supersaturated but differed widely in protein concentration. No salt repartitioning was observed between the initial and the two separated liquid phases. After the L-L separation, due to the presence of the high protein concentration phase, crystallization occurred much more rapidly than in the initial solution. At high initial protein concentrations, a metastable gel phase formed at temperatures above the liquid binodal. Both crystal nucleation and gel formation were accelerated in samples that had been cycled through the binodal. Solutions in the gel and L-L regions yielded various types of precipitates. Based on theoretical considerations, previous observations with other proteins, and our experimental results with lysozyme, a generic phase diagram for globular proteins is put forth. A limited region in the (T,c) plane favorable for the growth of protein single crystals is delineated.

  8. Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal

    International Nuclear Information System (INIS)

    Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to 40 wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15 wt% PSEO and 30 wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface

  9. A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell

    Science.gov (United States)

    Lin, Yi-Hsin; Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih

    2012-07-01

    A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell (T-PNLC) is demonstrated. T-PNLC consists of three layers. Liquid crystal (LC) directors in the two layers near glass substrates are orthogonal to each other and those two layers modulate two eigen-polarizations of an incident light. As a result, two eigen-polarizations of an incident light experience the same phase shift. In the middle layer, LC directors are perpendicular to the glass substrate and contribute no phase shift. The phase shift of T-PNLC is electrically tunable and polarization-independent. T-PNLC does not require any bias voltage for operation. The phase shift is 0.28 π rad for the voltage of 30 Vrms. By measuring and analyzing the optical phase shift of T-PNLC at the oblique incidence of transverse magnetic wave, the pretilt angle of LC directors and the effective thickness of three layers are obtained and discussed. The potential applications are spatial light modulators, laser beam steering, and micro-lens arrays.

  10. Digital photofinishing system based on liquid crystal on silicon

    Science.gov (United States)

    Zheng, Minmin; Yan, Huimin; Zhang, Xiuda; Du, Yanli

    2006-01-01

    As the digital camera user base grows, so does the demand for digital imaging services. A new digital photo finishing system based on Liquid Crystal On Silicon (LCOS) is presented. The LCOS panel motherboard is made up of CMOS chip. Three individual streams of light (red, green, blue) are directed to corresponding Polarization Beam Spliter (PBS) to make the S polarization beam arrive at LCOS panel. When the Liquid appears light, the S polarization beam is changed to P polarization beam and reflected to pass through Polarization Beam Spliter. Compared with Thin Film Transistor-Liquid Crystal Display (TFT-LCD), LCOS has many merits including high resolution, high contrast, wide viewing angle, low cost and so on. In this work, we focus on the way in which the images will be displayed on LCOS. A liquid crystal on silicon microdisplay driver circuit for digital photo finishing system has been designed and fabricated using BRILLIAN microdisplay driver lite(MDD-LITE) ASIC and LCOS SXGA (1280×1024 pixel) with a 0.78"(20mm) diagonal active matrix reflective mode LCD. The driver includes a control circuit, which presents serial data, serial clock , write protect signals and control signals for LED, and a mixed circuit which implements RGB signal to input the LCOS. According to a minimum error sum of squares algorithm, we find a minimum offset and then shift RGB optical intensity vs voltage curves right and left to make these three curves almost coincide with each other. The design had great application in the digital photo finishing.

  11. Understanding the fabric of protein crystals: computational classification of biological interfaces and crystal contacts.

    Science.gov (United States)

    Capitani, Guido; Duarte, Jose M; Baskaran, Kumaran; Bliven, Spencer; Somody, Joseph C

    2016-02-15

    Modern structural biology still draws the vast majority of information from crystallography, a technique where the objects being investigated are embedded in a crystal lattice. Given the complexity and variety of those objects, it becomes fundamental to computationally assess which of the interfaces in the lattice are biologically relevant and which are simply crystal contacts. Since the mid-1990s, several approaches have been applied to obtain high-accuracy classification of crystal contacts and biological protein-protein interfaces. This review provides an overview of the concepts and main approaches to protein interface classification: thermodynamic estimation of interface stability, evolutionary approaches based on conservation of interface residues, and co-occurrence of the interface across different crystal forms. Among the three categories, evolutionary approaches offer the strongest promise for improvement, thanks to the incessant growth in sequence knowledge. Importantly, protein interface classification algorithms can also be used on multimeric structures obtained using other high-resolution techniques or for protein assembly design or validation purposes. A key issue linked to protein interface classification is the identification of the biological assembly of a crystal structure and the analysis of its symmetry. Here, we highlight the most important concepts and problems to be overcome in assembly prediction. Over the next few years, tools and concepts of interface classification will probably become more frequently used and integrated in several areas of structural biology and structural bioinformatics. Among the main challenges for the future are better addressing of weak interfaces and the application of interface classification concepts to prediction problems like protein-protein docking. PMID:26508758

  12. Nuclear magnetic resonance study of epoxy- based polymer-dispersed liquid crystal droplets

    CERN Document Server

    Han, J W

    1998-01-01

    In this work, polymer-dispersed liquid crystals (PDLC) samples were prepared and studied by nuclear magnetic resonance. Proton NMR spectra and spin-lattice relaxations of 4-cyano-4'-pentylbiphenyl(5CB) and p-methoxybenzylidene-p-n-butylaniline (MBBA) liquid crystals confined in microdroplets were measured. The experimental results were compared with those of the liquid crystals in the pores of silica-gels and with those of the mixing components. The experimental results indicated that the nematic ordering in the microdroplets differed markedly from that observed in bulk nematic crystals. In addition, we examined spin-lattice relaxation mechanisms. The proton spin-lattice relaxation mechanisms in bulk nematic liquid crystals are well established. However, when nematic liquid crystals are confined in microdroplets, the relaxation mechanisms are expected to be affected. We examined possible relaxation mechanisms to explain the observed increase in the spin-lattice relaxation rate of liquid crystals confined in m...

  13. Soap, science, and flat-screen TVs a history of liquid crystals

    CERN Document Server

    Dunmur, David

    2011-01-01

    The terms 'liquid crystal' or 'liquid crystal display' (LCD) are well-known in the context of flat-screen televisions, but the properties and history of liquid crystals are little understood. This book tells the story of liquid crystals, from their controversial discovery at the end of the nineteenth century, to their eventual acceptance as another state of matter to rank alongside gases, liquids and solids. As their story unfolds, the scientists involved and their works are put into illuminating broader socio-political contexts. In recent years, liquid crystals have had a major impact on the display industry, culminating in the now widely available flat-screen televisions; this development is described in detail over three chapters, and the basic science behind it is explained in simple terms accessible to a general reader. New applications of liquid crystals in materials, bio-systems, medicine and technology are also explained.

  14. Polarization sensitive performance of one dimensional photonic crystal filters with a liquid crystal layer

    Institute of Scientific and Technical Information of China (English)

    HE Jie; SONG Li-tao; WANG Hua-lei; HAN Yi-ang; LI Tao

    2010-01-01

    @@ A tunable photonic crystal (PC) filter is proposed with the twisted nematic (TN) liquid crystal (LC) as a defect layer. The polarization sensitive performance and the eigenmodes are analyzed. The results show that there are two kinds of transmission modes, namely o and e, when the voltage is low. The different modes can be selected by rotating the filter axially. The e mode shifts toward the shorter wavelength side as the applied voltage increases. Then the peaks of two modes merge into each other and the polarization sensitive performance disappears. The photonic band gap is insensitive to the voltage. The tunable range of the filter is 53 nm.

  15. Electrically Rotatable Polarizer Using One-Dimensional Photonic Crystal with a Nematic Liquid Crystal Defect Layer

    Directory of Open Access Journals (Sweden)

    Ryotaro Ozaki

    2015-09-01

    Full Text Available Polarization characteristics of defect mode peaks in a one-dimensional (1D photonic crystal (PC with a nematic liquid crystal (NLC defect layer have been investigated. Two different polarized defect modes are observed in a stop band. One group of defect modes is polarized along the long molecular axis of the NLC, whereas another group is polarized along its short axis. Polarizations of the defect modes can be tuned by field-induced in-plane reorientation of the NLC in the defect layer. The polarization properties of the 1D PC with the NLC defect layer is also investigated by the finite difference time domain (FDTD simulation.

  16. Study of some defects observed in the hexagonal liquid crystals

    International Nuclear Information System (INIS)

    A polarising microscopy study of the disclinations in an hexagonal discotic liquid crystal (hexa-pentoxy-triphenylene) allows us to confirm the theory of the developable domains and the existence of the disclinations as involute of the circle. The absence of the lines S = 1 leads us to propose a model of core in which the energetic instability of these lines is emphasized. The nature of the core is discussed: it is probably filled with hexagonal liquid crystal. Moreover the birefringence Δn is measured and a first estimate of the anchoring energies of the discotic both on the glass and in contact with the air is given. The Michelson interferometry study of the interaction between the disclinations and the free surface has allowed to observe a strong anisotropy of the interfacial tension. At last a study of the walls leads to a classification according to the matching angle and to a first estimate of the penetration distance λ. A similar study has been undertaken in an inverse middle liquid crystalline phase (Na dioctylsulfosuccinate). A strong dependence of the elastic constants with the water concentration is observed. The micellar → hexagonal transition is studied. (author)

  17. Aqueous cholesteric liquid crystals using uncharged rodlike polypeptides.

    Science.gov (United States)

    Bellomo, Enrico G; Davidson, Patrick; Impéror-Clerc, Marianne; Deming, Timothy J

    2004-07-28

    The aqueous, lyotropic liquid-crystalline phase behavior of the alpha-helical polypeptide, poly(N(epsilon)-2-[2-(2-methoxyethoxy)ethoxy]acetyl-lysine) (1), has been studied using optical microscopy and X-ray scattering. Solutions of optically pure 1 were found to form cholesteric liquid crystals at volume fractions that decreased with increasing average chain length. At very high volume fractions, the formation of a hexagonal mesophase was observed. The pitch of the cholesteric phase could be varied by a mixture of enantiomeric samples L-1 and D-1, where the pitch increased as the mixture approached equimolar. The cholesteric phases could be untwisted, using either magnetic field or shear flow, into nematic phases, which relaxed into cholesterics upon removal of field or shear. We have found that the phase diagram of 1 in aqueous solution parallels that of poly(gamma-benzyl glutamate) in organic solvents, thus providing a useful system for liquid-crystal applications requiring water as solvent. PMID:15264844

  18. Self-Assembled Supramolecular Architectures Lyotropic Liquid Crystals

    CERN Document Server

    Garti, Nissim

    2012-01-01

    This book will describe fundamentals and recent developments in the area of Self-Assembled Supramolecular Architecture and their relevance to the  understanding of the functionality of  membranes  as delivery systems for active ingredients. As the heirarchial architectures determine their performance capabilities, attention will be paid to theoretical and design aspects related to the construction of lyotropic liquid crystals: mesophases such as lamellar, hexagonal, cubic, sponge phase micellosomes. The book will bring to the reader mechanistic aspects, compositional c

  19. Infiltration liquid crystal in microstructured polymer optical fibers

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Wei, Lei; Bang, Ole

    2009-01-01

    crystal E7 is then infiltrated into about 6 cm of the length of mPOF by using capillary forces with the duration of 45 minutes. The transmission spectrum is measured by an optical spectrum analyzer with 1 nm resolution, and normalized to that of the unfilled fiber as shown by the solid line. The......POF is butt-coupled to a conventional single mode fiber (SMF) with the broadband light from a supercontinuum source. It is clear to see the colour of the guided modes is red, since some wavelengths are attenuated by the material loss of PMMA in visible region. A positive dielectric anisotropy liquid...

  20. Characterization of some wide viewing angle liquid crystal devices

    Science.gov (United States)

    Liu, Weimin

    2001-08-01

    It is well known that a standard twisted nematic (TN) display, which is most commonly used in flat panel displays, has inherently narrow and non-uniform viewing angle characteristics. Normally black TN (NBTN) displays suffer from problems with chromaticity and contrast for normal and poor grayscale at wide viewing angles. Ideal compensation of the dark state for a NBTN requires a negative birefringence film with a uniformly twisted optical axis distribution. However, such films have not been fabricated to date. In our work we approximate the twisted structure of compensation film for NBTN displays by stacking several layers of polymer film having in- plane negative retardation. Using only 4 layers of film we obtain much wider viewing cone and higher contrast compare to uncompensated NBTN. The chromaticity is also greatly improved over the uncompensated cell. Modeling of liquid crystal displays is an efficient and economical way to LCD characterization and optimization without assembling a large number of test cells. It has become a useful tool for the development of new display modes. In the past, optical simulation of LCDs has mainly relied on one-dimensional models. As the liquid crystal technology advances, multidimensional modeling is required for better understanding of optical behavior at smaller feature sizes. In our work, a generalized geometrical optics approach (GOA) has been applied to liquid crystal devices with multiple dimensions. It is faster than other approaches (e.g. FDTD) and proved to be a useful design tool for optimization of liquid crystal devices in more than one-dimension. We performed detailed characterization of the electrically-induced optical compensation (EOC) mode for information display applications. This mode shows very wide viewing angle and excellent grayscale performance when a negative birefringent compensation film is added. Using GOA, we investigated the detailed transmission profile and the viewing angle properties of EOC

  1. Polarization converters based on axially symmetric twisted nematic liquid crystal.

    Science.gov (United States)

    Ko, Shih-Wei; Ting, Chi-Lun; Fuh, Andy Y-G; Lin, Tsung-Hsien

    2010-02-15

    An axially symmetric twisted nematic liquid crystal (ASTNLC) device, based on axially symmetric photoalignment, was demonstrated. Such an ASTNLC device can convert axial (azimuthal) to azimuthal (axial) polarization. The optical properties of the ASTNLC device are analyzed and found to agree with simulation results. The ASTNLC device with a specific device can be adopted as an arbitrary axial symmetric polarization converter or waveplate for axially, azimuthally or vertically polarized light. A design for converting linear polarized light to axially symmetric circular polarized light is also demonstrated. PMID:20389369

  2. Graphene electrodes for adaptive liquid crystal contact lenses.

    Science.gov (United States)

    Kaur, S; Kim, Y-J; Milton, H; Mistry, D; Syed, I M; Bailey, J; Novoselov, K S; Jones, J C; Morgan, P B; Clamp, J; Gleeson, H F

    2016-04-18

    The superlatives of graphene cover a whole range of properties: electrical, chemical, mechanical, thermal and others. These special properties earn graphene a place in current or future applications. Here we demonstrate one such application - adaptive contact lenses based on liquid crystals, where simultaneously the high electrical conductivity, transparency, flexibility and elasticity of graphene are being utilised. In our devices graphene is used as a transparent conductive coating on curved PMMA substrates. The adaptive lenses provide a + 0.7 D change in optical power with an applied voltage of 7.1 Vrms - perfect to correct presbyopia, the age-related condition that limits the near focus ability of the eye. PMID:27137312

  3. Liquid crystal emulsion micro-droplet WGM resonators

    Czech Academy of Sciences Publication Activity Database

    Ježek, Jan; Pilát, Zdeněk; Brzobohatý, Oto; Jonáš, A.; Aas, M.; Kiraz, A.; Zemánek, Pavel

    Bellingham : SPIE, 2014, 944108:1-9. ISBN 9781628415568. ISSN 0277-786X. [Polish-Slovak-Czech Optical Conference on Wave and Quantum Aspects of Contemporary Optics /19./. Jelenia Góra (PL), 08.09.2014-12.09.2014] R&D Projects: GA TA ČR TA03010642; GA MŠk(CZ) LO1212; GA MŠk(CZ) LD14069; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : liquid crystals * resonators * optical trapping * water * laser s Subject RIV: BH - Optics , Masers, Laser s

  4. Viscosity of Liquid Crystal Mixtures in the Presence of Electroconvection

    Science.gov (United States)

    Nagaya, Tomoyuki; Satou, Yuki; Goto, Yoshitomo; Hidaka, Yoshiki; Orihara, Hiroshi

    2016-07-01

    We have experimentally investigated the viscosity of nematic liquid crystal mixtures of p-methoxybenzylidene-p'-n-butylaniline (MBBA) and p-ethoxybenzylidene-p'-cyanoaniline (EBCA) in the presence of electroconvection under an ac electric field with 60 Hz. Although the viscosity of the mixtures with negative dielectric anisotropy shows a characteristic decrease in the high-voltage regime, that with positive dielectric anisotropy shows a monotonic increase as the applied voltage is increased. The experimental results suggest that the decrease in viscosity observed only for the mixtures with negative dielectric anisotropy is attributed to the negative contribution of electric stress caused by the anisotropic director distribution of the turbulent state.

  5. Liquid Crystal Photonic bandgap Fibers: Modeling and Devices

    DEFF Research Database (Denmark)

    Weirich, Johannes

    In this PhD thesis an experimental and numerical investigation of liquid crystal infiltrated photonic bandgap fibers (LCPBGs) is presented. A simulation scheme for modeling LCPBG devices including electrical tunability is presented. New experimental techniques, boundary coating and the applications...... of monomer added LCs, are investigated. Waveplates based on LCPBGs and a tunable polarization maintaining filter are developed. An on-chip tunable notch filter based on long period gratings is presented. Furthermore, the application of a LCPBG device for the electrical control of a fiber laser is...

  6. Experimental studies of the transient fluctuation theorem using liquid crystals

    Indian Academy of Sciences (India)

    Soma Datta; Arun Roy

    2009-05-01

    In a thermodynamical process, the dissipation or production of entropy can only be positive or zero, according to the second law of thermodynamics. However, the laws of thermodynamics are applicable to large systems in the thermodynamic limit. Recently a fluctuation theorem, known as the transient fluctuation theorem (TFT), which generalizes the second law of thermodynamics to small systems has been proposed. This theorem has been tested in small systems such as a colloidal particle in an optical trap. We report for the first time an analogous experimental study of TFT in a spatially extended system using liquid crystals.

  7. Polarization holographic device using photoreactive polymer liquid crystals

    International Nuclear Information System (INIS)

    Optical phase gratings were fabricated from photo-crosslinkable polymer liquid crystals with mesogenic 4-(4-methoxycinnamoyloxy)biphenyl side groups by irradiating with 325 nm interference lights and subsequent annealing at elevated temperatures. Recorded phase gratings were verified after the annealing process, although no gratings were observed immediately after the exposure. The characteristics of the phase gratings were strongly dependent on the polarization states of the two recording beams, and the resultant gratings involve not only linear birefringence caused by the reorientation of the mesogenic groups but also surface relief modulation generated by the molecular migration. Copyright (2003) AD-TECH - International Foundation for the Advancement of Technology Ltd

  8. Self-polarizing terahertz liquid crystal phase shifter

    Directory of Open Access Journals (Sweden)

    Xiao-wen Lin

    2011-09-01

    Full Text Available Using sub-wavelength metallic gratings as both transparent electrodes and broadband high-efficiency polarizers, a highly-compact self-polarizing phase shifter is demonstrated by electrically tuning the effective birefringence of a nematic liquid crystal cell. The metal grating polarizers ensure a good polarizing efficiency in the range of 0.2 to 2 THz. Phase shift of more than π/3 is achieved in a 256 μm-thick cell with a saturation root mean square voltage of around 130 V in this integrated device.

  9. Point diffraction interferometer with a liquid crystal monopixel

    OpenAIRE

    Ramírez, Claudio; Otón Martínez, Eva; Iemmi, Claudio; Moreno, Ignacio; Bennis, Noureddine; Otón Sánchez, José Manuel; Campos, Juan

    2013-01-01

    In this work a novel point diffraction interferometer based on a variable liquid crystal wave plate (LCWP) has been implemented. The LCWP consists of a 3x3 cm2 monopixel cell with parallel alignment. The monopixel cell was manufactured such that the electrode covers the entire surface except in a centered circular area of 50 μm of diameter. This circle acts as a point perturbation which diffracts the incident wave front giving rise to a spherical reference wave. By applying a voltage to the L...

  10. Effects of weak shear on hyperswollen lyotropic smectic liquid crystals

    International Nuclear Information System (INIS)

    We have developed a Zimm-type viscometer specially designed for the simultaneous measurements of the structure factor and the viscosity of hyperswollen lyotropic liquid crystals under a very weak shear. We have investigated the shear effects on the layer undulation fluctuation in the lamellar structure and the transition from the anisotropic lamellar to the isotropic sponge phase. We have found a significant difference in the rheological properties between the lamellar and the sponge phase: The former exhibits non-Newtonian flow behavior, while the latter exhibits Newtonian behavior

  11. Feedback control of flow alignment in sheared liquid crystals

    OpenAIRE

    Strehober, David A.; Schöll, Eckehard; Klapp, Sabine H. L.

    2013-01-01

    Based on a continuum theory, we investigate the manipulation of the non-equilibrium behavior of a sheared liquid crystal via closed-loop feedback control. Our goal is to stabilize a specific dynamical state, that is, the stationary "flow-alignment", under conditions where the uncontrolled system displays oscillatory director dynamics with in-plane symmetry. To this end we employ time-delayed feedback control (TDFC), where the equation of motion for the ith component, q_i(t), of the order para...

  12. Singularities and nonuniqueness in cylindrical flow of nematic liquid crystals

    OpenAIRE

    Van Hout, R.; Vilucchi, E

    2001-01-01

    The subject of this paper is the behavior of the director field of a nematic liquid crystal in flow through a tube with circular cross-section. Both the flow and the director field are assumed to have cylindrical symmetry. The requirement of finite Frank-Oseen energy forces ``admissible" director fields to be axially directed at the location of the symmetry axis. Thus, the angle between the axis and the director field at the location of the axis amounts to $k\\pi$, $k$ being an ...

  13. Liquid Crystal Thermography Measurement Uncertainty Analysis and Its Application to Turbulent Heat Transfer Measurements

    Directory of Open Access Journals (Sweden)

    Yu Rao

    2012-01-01

    Full Text Available Liquid crystal thermography is an advanced nonintrusive measurement technique, which is capable of providing a high-accuracy continuous temperature field measurement, especially for a complex structured heat transfer surface. The first part of the paper presents a comprehensive introduction to the thermochromic liquid crystal material and the related liquid crystal thermography technique. Then, based on the aythors' experiences in using the liquid crystal thermography for the heat transfer measurement, the parameters affecting the measurement uncertainty of the liquid crystal thermography have been discussed in detail through an experimental study. The final part of the paper describes the applications of the steady and transient liquid crystal thermography technique in the study of the turbulent flow heat transfer related to the aeroengine turbine blade cooling.

  14. Enhanced Biological Phosphorus Removal for Liquid Dairy Manure

    OpenAIRE

    Hong, Yanjuan

    2009-01-01

    Enhanced biological phosphorus removal (EBPR) has been widely used in municipal wastewater treatment, but no previous studies have examined the application of EBPR to treat dairy manure. This study was conducted to evaluate the (i) performance of pilot-scale EBPR systems treating liquid dairy manure, to balance the ratio of nitrogen to phosphorus in manure to meet crop nutrient requirements, (ii) effects of dissolved oxygen and solids retention time on the efficiency of EBPR, and (iii) effect...

  15. Miscibility and alignment effects of mixed monolayer cyanobiphenyl liquid-crystal-capped gold nanoparticles in nematic cyanobiphenyl liquid crystal hosts.

    Science.gov (United States)

    Qi, Hao; Kinkead, Brandy; Marx, Vanessa M; Zhang, Huai R; Hegmann, Torsten

    2009-06-01

    Against the rule: Liquid crystal hosts (5CB and 8CB) are doped with different thiol decorated gold nanoparticles (see figure). The "simple" hexanethiol and dodecanethiol capped nanoparticles (Au1 and Au2) are more compatible to the nematic cyanobiphenyl liquid crystals than nanoparticles capped simultaneously with alkylthiols and a nematic cyanobiphenyl thiol (Au3 and Au4).This study focuses on the miscibility of liquid crystal (LC) decorated gold nanoparticles (NPs) in nematic LCs. To explore if LC functional groups on the gold NP corona improve the compatibility (miscibility) with structurally related LC hosts, we examined mixtures of two LC hosts, 5CB and 8CB, doped at 5 wt % with different types of gold NPs. Four alkanethiol-capped NPs were synthesized; two homogeneously coated with alkanethiols (Au1 with C(6)H(13)SH and Au2 with C(12)H(25)SH), and two that were additionally capped at a different ratio with a mesogenic cyanobiphenyl end-functionalized alkanethiol HS10OCB (C(6)H(13)SH + HS10OCB for Au3 and C(12)H(25)SH + HS10OCB for Au4). Investigating these mixtures in the bulk for settling of the NPs, and in thin films using polarized optical microscopy (POM) between untreated glass slides as well as POM studies and electro-optic tests in planar ITO/polyimide test cells, reveal that the alkanethiol capped NPs Au1 and Au2 are more compatible with the two polar cyanobiphenyl hosts in comparison to the NPs decorated with the cyanobiphenyl moieties. All NPs induce homeotropic alignment in 5CB and 8CB between untreated glass slides, with Au1 and Au2 showing characteristic birefringent stripes, and Au3 and A4 exhibiting clear signs of aggregation. In rubbed polyimide cells, however, Au3 and Au4 fail to induce homeotropic alignment and show clear signs of macroscopic aggregation. PMID:19334026

  16. Investigation of the liquid crystal alignment layer: effect on electrical properties

    OpenAIRE

    Asma Abderrahmen et al

    2008-01-01

    We investigate the electrical behavior of a symmetric liquid crystal (LC) cell: elecrode-silane-LC-silane-electrode. The silane (chlorodimethyloctadecyl-silane) layer induces a homeotropic orientation of the nematic liquid crystal (NLC) molecules. The wettability technique is used to detect the change of the surface energy of the electrode upon cleaning and silane layer deposition. We report on the dynamic impedance measurements of the nematic liquid crystal cell. It is found that the silane ...

  17. Security devices based on liquid crystals doped with a colour dye

    OpenAIRE

    Carrasco Vela, Carlos; Quintana Arregui, Patxi Xabier; Otón, E.; Geday, Morten Andreas; Otón Sánchez, José Manuel

    2011-01-01

    Liquid crystal properties make them useful for the development of security devices in applications of authentication and detection of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices. Employing liquid crystal and dichroic colorants, we have developed devices that show, with the aid of a polarizer, multiple images on each side of the device. Rubbed polyimide is used as alignment layer on each substrate of the LC ce...

  18. A Novel Microwave Tunable Band-Pass Filter Integrated Power Divider Based on Liquid Crystal

    OpenAIRE

    Yupeng Liu; Di Jiang; Lei Xia; Ruimin Xu

    2015-01-01

    This paper proposes a novel microwave continuous adjustable band-pass filter integrated power divider based on nematic liquid crystals (LCs). The proposed power divider uses liquid crystal (LC) as the dielectric material. It can realize phase shift by changing the dielectric anisotropy, when biasing the high anisotropy nematic liquid crystal. It is mainly used in microwave frequencies. It has a large number of advantages compared to conventional filter integrated power divider, such as low lo...

  19. Adaptive micro-optical phase modulators based on liquid crystal technology

    OpenAIRE

    Algorri Genaro, José Francisco

    2015-01-01

    This thesis began with the project “Advanced Devices of Liquid Crystal and Electroluminescent Organic Diodes. Hybrid Applications for 3D Vision” funded by the Spanish government. The goal of this project was the development of optical devices to achieve 3D vision in portable devices without glasses or external elements. In order to achieve the goals of this project, solutions based on liquid crystal are considered. Specifically, adaptive micro-optical phase modulators based on liquid crystal ...

  20. The Reflective Type of Electronic Whiteboard Based on Cholesteric Liquid Crystal Display Technology

    OpenAIRE

    TianHua Li

    2013-01-01

    The study analyzes the basic principle and structure of cholesteric liquid crystal display technology and concludes features and requirements of reflective type of electronic whiteboard based on cholesteric liquid crystal display technology. The design of drive circuit of reflective type of electronic whiteboard; the make-up of large reflective type of cholesteric liquid crystal homogeneous display screen as the display equipment of electronic whiteboard; and the adoption of C language to edi...

  1. Electrooptical characteristics of the novelty system: ionic doped liquid crystal - conductive polymer

    OpenAIRE

    Mykytyuk, T.; Aksimentyeva, O.; Stakhira, P.; Cherpak, V.; Fechan, A.; Konopelnik, O.; Fomenko, V.; Hlushyk, I.

    2004-01-01

    Taking into account that ionic-doped liquid crystals are conductive and the conductance depends on dopant concentration, we suggested using ionic-doped liquid crystals as a electrolytic medium in a described configuration of cell. The application of an ionic doped liquid crystal as electrolytic medium in electrochromic device were investigated. Polyaniline is a conductive polymer and has electrochromic effect in an electrolytic medium under the applied voltage. The spectral investigation of t...

  2. Photoluminescence analysis of self induced planer alignment in azo dye dispersed nematic liquid crystal complex

    International Nuclear Information System (INIS)

    We have developed azo dye doped nematic liquid crystal complex for advanced photonic liquid crystal display technology aspects. Disperse orange azo dye self introduced planer alignment in the nematic liquid crystal without any surface anchoring treatment. Planer alignment was characterized by optical polarizing microscopy. The electro-optical switching response of dye disperse planer aligned nematic cell was investigated as a function of applied voltage with the help of photoluminescence spectrophotometer for the tuning of photoluminescence contrast

  3. Correlation measurements of light transmittance in polymer dispersed liquid crystals

    Science.gov (United States)

    Maksimyak, P. P.; Nehrych, A. L.

    2015-11-01

    The methods of correlation optics are for the first time applied to study structure of liquid crystal (LC) - polymer (P) composites at various concentrations of LC and P. Their phase correlation function (PCF) was obtained considering LC-P composite as a random phase screen. The amplitude of PCF contains information about number of LC domains and structure of LC director inside of them, while a half-width of this function is connected with a size of these domains. We studied unpowered and powered composite layers with a thickness of 5 μm. As liquid crystal and polymer were used nematic LC E7 from Merck and photopolymer composition NOA65 from Norland. Concentration of polymer φP was varied in a range 10-55 vol. %. In good agreement with previous studies by SEM technique we detected monotone decrease of LC domains with concentration of polymer. With application of electric field, amplitude of PCF behaves differently for the samples with different polymer content. For the samples with φP>35 vol. % (samples having morphology of polymer dispersed LC), this dependence is monotonic. In turn, if φPfact is explained by transformation of orientational defects of LC phase with the applied voltage.

  4. Adding Mono- and Multivalent Ions to Lyotropic Chromonic Liquid Crystals

    Science.gov (United States)

    Tortora, Luana; Park, Heung-Shik; Antion, Kelly; Woolwerton, Chris; Finotello, Daniele; Lavrentovich, Oleg

    2006-03-01

    Lyotropic Chromonic Liquid Crystals (LCLCs) are a distinct class of liquid crystals formed in aqueous solutions by molecules with rigid polyaromatic cores and ionic groups at the periphery [1-4]. The phase diagrams of these materials should depend on entropic factors (as in the Onsager model) and electrostatic interactions. Using optical polarizing microscopy, we studied the effects of mono- and multivalent ions on the phase diagrams of Blue 27 [3] and Sunset Yellow [2]. The monovalent ions change the temperatures of phase transitions, as described in [4], while the effect of multivalent ions is more dramatic and, in addition to the changed temperatures of phase transitions by tens of degrees, it often involves condensation of LCLC aggregates into domains with birefringence much higher than that in a normal nematic phase. Work supported by OBR B-7844. [1]J. Lydon, Current Opin. Colloid & Interface Sci. 3, 458 (1998);8, 480-489 (2004); [2]V. R. Horowitz, L. A. Janowitz, A. L. Modic, P. J. Heiney, and P. J. Collings, 2005, Phys. Rew. E 72, 041710; [3]Yu. A. Nastishin, H. Liu, T. Schneider, T., V. Nazarenko, R. Vasyuta, S. V. Shiyanovskii, and O. D. Lavrentovich, 2005, Phys. Rev. E 72, 041711; [4]A.F. Kostko, B. H. Cipriano, O. A. Pinchuk, L. Ziserman, M. A. Anisimov, D. Danino, and S. R. Raghavan. J. Phys. Chem. B 109, 19126-19133 (2005)

  5. Control of active liquid crystals with a magnetic field.

    Science.gov (United States)

    Guillamat, Pau; Ignés-Mullol, Jordi; Sagués, Francesc

    2016-05-17

    Living cells sense the mechanical features of their environment and adapt to it by actively remodeling their peripheral network of filamentary proteins, known as cortical cytoskeleton. By mimicking this principle, we demonstrate an effective control strategy for a microtubule-based active nematic in contact with a hydrophobic thermotropic liquid crystal. By using well-established protocols for the orientation of liquid crystals with a uniform magnetic field, and through the mediation of anisotropic shear stresses, the active nematic reversibly self-assembles with aligned flows and textures that feature orientational order at the millimeter scale. The turbulent flow, characteristic of active nematics, is in this way regularized into a laminar flow with periodic velocity oscillations. Once patterned, the microtubule assembly reveals its intrinsic length and time scales, which we correlate with the activity of motor proteins, as predicted by existing theories of active nematics. The demonstrated commanding strategy should be compatible with other viable active biomaterials at interfaces, and we envision its use to probe the mechanics of the intracellular matrix. PMID:27140604

  6. Optical switch based on the electrically controlled liquid crystal interface.

    Science.gov (United States)

    Komar, Andrei A; Tolstik, Alexei L; Melnikova, Elena A; Muravsky, Alexander A

    2015-06-01

    The peculiarities of the linearly polarized light beam reflection at the interface within the bulk of a nematic liquid crystal (NLC) cell with different orientations of the director are analyzed. Two methods to create the interface are considered. Combination of the planar and homeotropic orientations of the NLC director is realized by means of a spatially structured electrode under the applied voltage. In-plane patterned azimuthal alignment of the NLC director is created by the patterned rubbing alignment technique. All possible orthogonal orientations of the LC director are considered; the configurations for realization of total internal reflection are determined. The revealed relationship between the propagation of optical beams in a liquid crystal material and polarization of laser radiation has enabled realization of the spatial separation for the orthogonally polarized light beams at the interface between two regions of NLC with different director orientations (domains). Owing to variations in the applied voltage and, hence, in the refractive index gradient, the light beam propagation directions may be controlled electrically. PMID:26192675

  7. Liquid Crystal Lenses for Correction of Presbyopia - Invited Paper

    Science.gov (United States)

    Li, Guoqiang; Peyghambarian, N.

    2008-01-01

    Correction of presbyopia has been increasingly important. An electro-active lens allows voltage controlled change of the focusing power across the entire aperture. Such a lens must have high light efficiency, relatively large aperture, fast switching time, low driving voltage, and power-failure-safe configuration. New switchable, flat, thin liquid crystal diffractive lenses that meet the above requirements will be presented. The operation principle is based on electrical tuning of the refractive index of a 5 μm-thick layer of nematic liquid crystal using a circular array of photolithographically defined transparent electrodes. The effects of the gaps between the ring electrodes and the fringing field on the lens performance will be analyzed. Lenses with three different designs will be demonstrated: (1) All the ring electrodes for modulating the multi-level phase profile are patterned in one layer with a 1μm gap between the neighboring electrodes. (2) In order to avoid the lateral gaps between the electrodes, a preliminary experiment with interleaved electrode pattern has been performed for a 4-level lens. (3) A robust design is given with three-layer electrode pattern and two-layer via structures for flexible interconnection and no-gap pattern. Designs 1 and 3 allow any even-numbered phase levels greater than 4 and provides the capability of correction for near-, intermediate-, and distance-vision. Such a lens has potential of revolutionizing the field of presbyopia correction.

  8. Design of Responsive and Active (Soft) Materials Using Liquid Crystals.

    Science.gov (United States)

    Bukusoglu, Emre; Bedolla Pantoja, Marco; Mushenheim, Peter C; Wang, Xiaoguang; Abbott, Nicholas L

    2016-06-01

    Liquid crystals (LCs) are widely known for their use in liquid crystal displays (LCDs). Indeed, LCDs represent one of the most successful technologies developed to date using a responsive soft material: An electric field is used to induce a change in ordering of the LC and thus a change in optical appearance. Over the past decade, however, research has revealed the fundamental underpinnings of potentially far broader and more pervasive uses of LCs for the design of responsive soft material systems. These systems involve a delicate interplay of the effects of surface-induced ordering, elastic strain of LCs, and formation of topological defects and are characterized by a chemical complexity and diversity of nano- and micrometer-scale geometry that goes well beyond that previously investigated. As a reflection of this evolution, the community investigating LC-based materials now relies heavily on concepts from colloid and interface science. In this context, this review describes recent advances in colloidal and interfacial phenomena involving LCs that are enabling the design of new classes of soft matter that respond to stimuli as broad as light, airborne pollutants, bacterial toxins in water, mechanical interactions with living cells, molecular chirality, and more. Ongoing efforts hint also that the collective properties of LCs (e.g., LC-dispersed colloids) will, over the coming decade, yield exciting new classes of driven or active soft material systems in which organization (and useful properties) emerges during the dissipation of energy. PMID:26979412

  9. Viewing angle switching of patterned vertical alignment liquid crystal display

    International Nuclear Information System (INIS)

    Viewing angle control of a patterned vertical alignment (PVA) liquid crystal display using only one panel is investigated. In conventional PVA modes, a vertically aligned liquid crystal (LC) director tilts down in four directions making 45 deg. with respect to crossed polarizers to exhibit a wide viewing angle. In the viewing angle control device, one pixel was divided into two sub-pixels such that the LC director in the main pixel is controlled to be tilted down in multiple directions making an angle with the polarizer, playing the role of main display with the wide viewing angle, while the LC director in the sub-pixel is controlled to be tilted down to the polarizer axis, playing the role of sub-pixel to the viewing angle control for the narrow viewing angle. Using sub-pixel control, light leakage or any type of information such as characters and image can be generated in oblique viewing directions without distorting the image quality in the normal direction, which will prevent others from peeping at the displayed image by overlapping the displayed image with the made image

  10. Generation of harmonics and supercontinuum in nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Nyushkov, B N; Trashkeev, S I; Klementyev, Vasilii M; Pivtsov, V S; Kobtsev, Sergey M

    2013-02-28

    Nonlinear optical properties of nematic liquid crystals (NLC) have been investigated. A technique for efficient laser frequency conversion in a microscopic NLC volume deposited on an optical fibre end face is experimentally demonstrated. An efficient design of a compact NLC-based IR frequency converter with a fibre input and achromatic collimator is proposed and implemented. Simultaneous generation of the second and third harmonics is obtained for the first time under pumping NLC by a 1.56-mm femtosecond fibre laser. The second-harmonic generation efficiency is measured to be about 1 %, while the efficiency of third-harmonic generation is several tenths of percent. A strong polarisation dependence of the third-harmonic generation efficiency is revealed. When pumping NLC by a cw laser, generation of spectral supercontinua (covering the visible and near-IR spectral ranges) is observed. The nonlinear effects revealed can be due to the light-induced change in the orientational order in liquid crystals, which breaks the initial symmetry and leads to formation of disclination structures. The NLC optical nonlinearity is believed to be of mixed orientationalelectronic nature as a whole. (laser optics 2012)

  11. Analog switching in the nanocolloids of ferroelectric liquid crystals

    Science.gov (United States)

    Kumar, Pradeep; Kishore, Avinash; Sinha, Aloka

    2016-06-01

    Nanoparticle (NP) dispersion in liquid crystals (LCs) results in significant changes in the physical properties of the existing LC mixtures. Two ferroelectric liquid crystals (FLCs), 5 F6T and 6 F6T , have been studied for analog switching. The 5 F6T sample is doped with titanium dioxide (T i O2) NPs of two different concentrations of the same average particle size and another FLC 6 F6T is systematically doped with barium titanate (B a T i O3) NPs of two different average particle sizes at the same concentration. The frequency and temperature dependence of the coercive voltage of FLC nanocolloids has been studied. The V-shaped switching was observed in the case of nano-doped FLCs. The value of inversion frequency for the 5 F6T +1.0 wt.% TiO2 doped sample is 30 Hz while it is 24 Hz for the 6 F6T +0.5 wt.% BaTiO3 (particle size 5-10 nm) doped sample. The conductivity measurements show that the conductivity of doped samples is higher than the conductivity of their parental FLCs and can be considered the main reason for the V-shaped switching in the FLC nanocolloids, which was initially absent in their parental FLCs.

  12. Polyimide liquid crystal alignment layers prepared by soft-Lithography

    Institute of Scientific and Technical Information of China (English)

    HE Yaning; LIU Bin; REN Hongfeng; WANG Xiaogong

    2007-01-01

    Elastomeric replicas of surface relief structures were prepared by molding poly(dimethylsiloxane) (PDMS)precursors against photo-inscribed surface-relief-gratings on azo polymer films.The PI solutions were micro-contact printed with the elastomeric PDMS replica on quartz slides.Good surface-relief-grating structures were formed on the quartz slides.The quartz slides covered with surface-reliefgrating polymide (PI) films were then assembled into liquid crystal (LC) cells.The transmittance passing through the cell between crossed polarizers changed periodically with a regular 90°separation of the rotational angle.The pretilt angle of the cell was found to be 2.8°.Results showed that the PI films with surface-relief-grating structures by this micro-contact printing process have good liquid crystal alignment ability.This preparation method of alignment layers can be considered a potentially useful technique in the LC display (LCD)industry in the future.

  13. Low loss liquid crystal photonic bandgap fiber in the near-infrared region

    DEFF Research Database (Denmark)

    Scolari, Lara; Wei, Lei; Gauza, S.;

    2010-01-01

    We infiltrate a photonic crystal fiber with a perdeuterated liquid crystal, which has a reduced infrared absorption. The lowest loss ever reported (about 1 dB) in the middle of the near-infrared bandgap is achieved.......We infiltrate a photonic crystal fiber with a perdeuterated liquid crystal, which has a reduced infrared absorption. The lowest loss ever reported (about 1 dB) in the middle of the near-infrared bandgap is achieved....

  14. Manufacturing, structure and properties of recycled polyethylene terephthalate /liquid crystal polymer/montmorillonite clay nanocomposites

    International Nuclear Information System (INIS)

    Polyethylene terephthalate (PET)/liquid crystal polymer (LCP)/monthmorillonite clay (MMT) compositions were obtained by melt mixing. Their mechanical, structural, rheological and thermal properties were investigated

  15. Ultra-high-resolution time projection chambers with liquid crystal backplanes

    Energy Technology Data Exchange (ETDEWEB)

    Monreal, Benjamin

    2014-10-15

    We investigated the possibility of incorporating a liquid-crystal device into a gas ionization detector. After extensive R&D on several candidate liquid-crystal technologies, we developed some novel materials allowing twisted nematic liquid-crystal layers to be coupled directly to gas ionization counters. However, the resulting structures were unsuitable for large-scale or practical use. We tested several technologies known to result in mechanically-robust liquid crystal electrooptic layers, but found poor behavior in the detector context.

  16. Nonlinear optical studies of liquid crystal alignment on a rubbed polyvinyl alcohol surface

    Science.gov (United States)

    Wei, Xing; Hong, Seok-Cheol; Zhuang, Xiaowei; Goto, Tomohisa; Shen, Y. R.

    2000-10-01

    Sum-frequency vibrational spectroscopy and second-harmonic generation have been used to measure the orientational distributions of the polymer chains and adsorbed 8CB liquid crystal molecules on a rubbed polyvinyl alcohol surface. Results show that the polymer chains at the surface appear to be well aligned by rubbing, and the adsorbed liquid crystal molecules are aligned, in turn, by the surface polymer chains. Strong correlation exists between the orientational distributions of the polymer chains and the liquid crystal molecules, indicating that the surface-induced bulk alignment of a liquid crystal film by rubbed polymer surfaces is via an orientational epitaxylike mechanism.

  17. Liquid crystal-type assembly of native cellulose-glucuronoxylans extracted from plant cell wall.

    Science.gov (United States)

    Reis, D; Vian, B; Chanzy, H; Roland, J C

    1991-01-01

    In numerous plant cell walls, the cellulose microfibrils are arranged in a helicoidal pattern which has been considered as an analog to a cholesteric order. Here, we report on the spontaneous helicoidal organization which occurs in acellular conditions from aqueous suspensions of cellulose. The cellulosic mucilage of mature seeds of quince (Cydonia oblonga L) was studied both in situ (pre-release mucilage) and after water extraction and in in vitro re-assembly (prolonged high speed ultracentrifugation, further progressive dehydration and embedding in LR White methacrylate or hydrosoluble melamine resin). The cellulosic component was characterized by the use of cellobiohydrolase (CBH1) bound to colloidal gold, and the glucuronic acid residues of the xylan matrix were characterized by the use of cationised gold. Inside the seeds, the pre-release mucilage is mostly helicoidal, with the occurrence of more or less ordered domains, which indicate a fluid organization relevant to an actual liquid crystal state. Cytochemical tests revealed the tight association between cellulose and glucuronoxylans, the latter constituting a charged coat around each microfibril. Following the hydration of the seed, a cellulosic suspension was extracted in which microfibrils were totally dispersed. The progressive dehydration of the suspension gave rise to concentrated viscous drops. Ultrastructural observations revealed the occurrence of multidomain organization, from non-ordered to cholesteric-like regions, revealing that the mucilage is at the same time crystalline and liquid. This constitutes the first demonstration that liquid crystal type assemblies can arise from crystalline and biological cellulose in aqueous suspension. It strengthens the hypothesis that a transient liquid crystal state must occur during the cellulose ordering. The possible morphogenetic role of the glucuronoxylans in the cholesteric organization of the cellulose is discussed. PMID:1804508

  18. Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals.

    Science.gov (United States)

    Gharbi, Mohamed Amine; Manet, Sabine; Lhermitte, Julien; Brown, Sarah; Milette, Jonathan; Toader, Violeta; Sutton, Mark; Reven, Linda

    2016-03-22

    Blue phases (BPs), a distinct class of liquid crystals (LCs) with 3D periodic ordering of double twist cylinders involving orthogonal helical director twists, have been theoretically studied as potential templates for tunable colloidal crystals. Here, we report the spontaneous formation of thermally reversible, cubic crystal nanoparticle (NP) assemblies in BPs. Gold NPs, functionalized to be highly miscible in cyanobiphenyl-based LCs, were dispersed in BP mixtures and characterized by polarized optical microscopy and synchrotron small-angle X-ray scattering (SAXS). The NPs assemble by selectively migrating to periodic strong trapping sites in the BP disclination lines. The NP lattice, remarkably robust given the small particle size (4.5 nm diameter), is commensurate with that of the BP matrix. At the BP I to BP II phase transition, the NP lattice reversibly switches between two different cubic structures. The simultaneous presence of two different symmetries in a single material presents an interesting opportunity to develop novel dynamic optical materials. PMID:26900753

  19. Oscillating Frequency Response of a Langasite Crystal Microbalance in Liquid Phase

    Institute of Scientific and Technical Information of China (English)

    Qi KANG; Huai Jin ZHANG; Xue Yong LIU; Da Zhong SHEN

    2005-01-01

    The frequency responses of a langasite crystal microbalance (LCM) in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly used quartz crystal microbalance (QCM). The frequency shifts of the LCM to the changes in mass loading, as well as viscosity and density of the liquid were measured. The LCM was applied to monitor the adsorption process of an ionic liquid film to ethanol vapor.

  20. Pulsed zero field NMR of solids and liquid crystals

    International Nuclear Information System (INIS)

    This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs

  1. Synthesis and thermal behavior of new liquid crystals arylaldoxime esters

    Energy Technology Data Exchange (ETDEWEB)

    Tavares, Aline; Arruda, Barbara C.; Boes, Elvis S.; Stefani, Valter; Stassen, Hubert K.; Campo, Leandra F.; Merlo, Aloir A., E-mail: aloir@iq.ufrgs.br [Instituto de Quimica, Universidade Federal do Rio Grande do Sul, Porto Alegre-RS (Brazil); Bechtold, Ivan H. [Departamento de Fisica, Universidade Federal de Santa Catarina, Florianopolis-SC (Brazil)

    2012-05-15

    We report the synthesis of a series of liquid-crystalline materials based on arylaldoxime esters and the characterization of these materials by {sup 1}H, {sup 13}C NMR, ATR/FT-IR spectroscopy and elemental analysis. The chemical stability and liquid-crystalline as well as photophysical properties of the compounds are described being dependent on the heating/cooling cycles. The changes in chemical stability and the liquid crystals properties of arylaldoxime esters were observed during these thermal cycles by IR analysis. All samples underwent a thermal degradation yielding the corresponding nitriles and carboxylic acid as evidenced by IR and {sup 1}H NMR spectra. Due to the decomposition process, information about the mesomorphic behaviour is lost. The UV-Vis absorption spectra in solution display three absorption bands between 230 and 340 nm. The fluorescence spectra exhibit a broad and structureless emission band located at 430 nm. Ab initio calculations were performed to obtain information on the molecular structure and properties of the title compounds. (author)

  2. (Liquid + liquid), (solid + liquid), and (solid + liquid + liquid) equilibria of systems containing cyclic ether (tetrahydrofuran or 1,3-dioxolane), water, and a biological buffer MOPS

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • MOPS buffer induced liquid phase splitting for mixtures of water with THF or 1,3-dioxolane. • Phase boundaries of LLE, SLE, and SLLE were determined experimentally. • Tie-lines at LLE and at SLLE were also measured. • Phase diagrams of MOPS + water + THF or 1,3-dioxolane are prepared. • LLE tie-line data are correlated satisfactorily with the NRTL model. - Abstract: Two liquid phases were formed as the addition of a certain amount of biological buffer 3-(N-morpholino)propane sulfonic acid (MOPS) in the aqueous solutions of tetrahydrofuran (THF) or 1,3-dioxolane. To evaluate the feasibility of recovering the cyclic ethers from their aqueous solutions with the aid of MOPS, we determined experimentally the phase diagrams of the ternary systems of {cyclic ether (THF or 1,3-dioxolane) + water + MOPS} at T = 298.15 K under atmospheric pressure. In this study, the solubility data of MOPS in water and in the mixed solvents of water/cyclic ethers were obtained from the results of a series of density measurements, while the (liquid + liquid) and the (solid + liquid + liquid) phase boundaries were determined by visually inspection. Additionally, the tie-line results for (liquid + liquid) equilibrium (LLE) and for (solid + liquid + liquid) equilibrium (SLLE) were measured using an analytical method. The reliability of the experimental LLE tie-line results data was validated by using the Othmer–Tobias correlation. These LLE tie-line values were correlated well with the NRTL model. The phase diagrams obtained from this study reveal that MOPS is a feasible green auxiliary agent to recover the cyclic ethers from their aqueous solutions, especially for 1,3-dioxolane

  3. Surface plasmon Raman scattering studies of liquid crystal anchoring on liquid-crystal-based self-assembled monolayers.

    Science.gov (United States)

    Critchley, Kevin; Cheadle, Edward M; Zhang, Hao-Li; Baldwin, Kurt J; Liu, Quanying; Cheng, Yaling; Fukushima, Hitoshi; Tamaki, Takashi; Batchelder, David N; Bushby, Richard J; Evans, Stephen D

    2009-11-26

    We studied the anchoring of 6CB on a series of self-assembled monolayers (SAMs) with a functional group that mimics that of the nematic liquid crystal (LC). The SAMs were first characterized by wetting, Fourier-transform infrared spectroscopy, and surface potential measurements. We found that, in two of these SAMs, the end group dipoles were oriented close to the normal of the surface and that these promoted homeotropic anchoring. In the case of the other SAM, the dipole was oriented parallel to the surface, and planar anchoring was obtained. Raman scattering by adsorbates on thin metal films is enhanced by the electromagnetic fields of surface plasmon polaritons (SPPs). Despite the inherent polarization of SPPs, there have been few reports in which SPP Raman scattering has been used to study molecular orientation. We have developed optical instrumentation to provide efficient excitation and collection of SPP Raman scattered light using attenuated total reflection geometry. The Kretschmann prism coupling configuration was used to excite SPPs on thin (500 A) gold films with adsorbed SAMs of alkanethiols in contact with thin films (50 microm) of the nematic liquid crystal 4'-hexylbiphenyl-4-carbonitrile (6CB, Merck). The anchoring and orientational wetting of the LC 6CB at the interface with omega-functionalized SAMs was studied using this arrangement. In agreement with the results of previous studies, a high-energy surface (-COOH) was found to promote planar anchoring, whereas a low-energy surface (-CF(3)) was found to induce homeotropic anchoring. PMID:19921953

  4. Flat liquid crystal diffractive lenses with variable focus and magnification

    Science.gov (United States)

    Valley, Pouria

    Non-mechanical variable lenses are important for creating compact imaging devices. Various methods employing dielectrically actuated lenses, membrane lenses, and liquid crystal lenses were previously proposed [1-4]. In This dissertation the design, fabrication, and characterization of innovative flat tunable-focus liquid crystal diffractive lenses (LCDL) are presented. LCDL employ binary Fresnel zone electrodes fabricated on Indium-Tin-Oxide using conventional micro-photolithography. The light phase can be adjusted by varying the effective refractive index of a nematic liquid crystal sandwiched between the electrodes and a reference substrate. Using a proper voltage distribution across various electrodes the focal length can be changed between several discrete values. Electrodes are shunted such that the correct phase retardation step sequence is achieved. If the number of 2pi zone boundaries is increased by a factor of m the focal length is changed from f to f/m based on the digitized Fresnel zone equation: f = rm2/2mlambda, where r m is mth zone radius, and lambda is the wavelength. The chromatic aberration of the diffractive lens is addressed and corrected by adding a variable fluidic lens. These LCDL operate at very low voltage levels (+/-2.5V ac input), exhibit fast switching times (20-150 ms), can have large apertures (>10 mm), and small form factor, and are robust and insensitive to vibrations, gravity, and capillary effects that limit membrane and dielectrically actuated lenses. Several tests were performed on the LCDL including diffraction efficiency measurement, switching dynamics, and hybrid imaging with a refractive lens. Negative focal lengths are achieved by adjusting the voltages across electrodes. Using these lenses in combination, magnification can be changed and zoom lenses can be formed. These characteristics make LCDL a good candidate for a variety of applications including auto-focus and zoom lenses in compact imaging devices such as camera

  5. Two-Dimensional NMR Study of a Liquid-Crystal Solution under Magic-Angle Spinning. Conformation of Carboxylic Ionophore Lasalocid A Dissolved in a Lyotropic Liquid Crystal

    Science.gov (United States)

    Kimura, Atsuomi; Kano, Tetsushi; Fujiwara, Hideaki

    1996-07-01

    The conformation of a carboxylic ionophore, lasalocid A, has been determined in a lyotropic liquid crystal by means of magic-angle spinning (MAS) and two-dimensional NMR experiments. The information extracted from ROESY spectra measured under MAS was analyzed according to the distance-geometry algorithm. The liquid crystal used for the solvent is cesium perfluorooctanoate dissolved in D2O, and the resulting structure of lasalocid A is a cyclic one, indicating cation complexation within a hydrophobic region of the liquid crystal. In this way, the two-dimensional MAS NMR experiment is proved to be a useful technique in conformational studies of complex molecules dissolved in lyotropic liquid crystal which may be regarded as offering a membrane-like environment.

  6. Spectroscopic analysis of bosentan in biological samples after a liquid-liquid microextraction

    Science.gov (United States)

    Sajedi-Amin, Sanaz; Assadpour-Zeynali, Karim; Panahi-Azar, Vahid; Kebriaeezadeh, Abbas; Khoubnasabjafari, Maryam; Ansarin, Khalil; Jouyban-Gharamaleki, Vahid; Jouyban, Abolghasem

    2015-01-01

    Introduction:Microextraction processes with UV-Vis measurement have been developed and validated for analysis of bosentan in biological samples. Methods:In this work, liquid–liquid microextraction procedures (DLLME & USAEME) were employed for cleanup, pre-concentration, and determination of bosentan in biological samples by UV-Vis spectroscopy at 270 nm. The method was validated and applied to the determination of bosentan in spiked serum, exhaled breath condensate and urine samples. Results:Various experimental factors including type of extraction and dispersive solvents and their volumes, pH, sonication time and centrifuging time were investigated. Under the optimum conditions, the method was linear in the range of 1.0–5.0 μg.mL-1, with coefficient of determination (R2) of > 0.998. The limit of detection (LOD) was 0.07 mg.L-1. Recovery of the target analyte in biological samples was 106.2%. The method could be easily applied for higher concentration of bosentan and needs more improvement for application in the pharmacokinetic investigations where more sensitive methods are required. Conclusion:A simple, low cost, precise and accurate spectrophotometric analysis of bosentan in biological samples after liquid-liquid microextraction were developed and validated for routine analyses. PMID:26929923

  7. The Effect of Thermal Cycling on Crystal-Liquid Separation During Lunar Magma Ocean Differentiation

    Science.gov (United States)

    Mills, Ryan D.

    2013-01-01

    Differentiation of magma oceans likely involves a mixture of fractional and equilibrium crystallization [1]. The existence of: 1) large volumes of anorthosite in the lunar highlands and 2) the incompatible- rich (KREEP) reservoir suggests that fractional crystallization may have dominated during differentiation of the Moon. For this to have occurred, crystal fractionation must have been remarkably efficient. Several authors [e.g. 2, 3] have hypothesized that equilibrium crystallization would have dominated early in differentiation of magma oceans because of crystal entrainment during turbulent convection. However, recent numerical modeling [4] suggests that crystal settling could have occurred throughout the entire solidification history of the lunar magma ocean if crystals were large and crystal fraction was low. These results indicate that the crystal size distribution could have played an important role in differentiation of the lunar magma ocean. Here, I suggest that thermal cycling from tidal heating during lunar magma ocean crystallization caused crystals to coarsen, leading to efficient crystal-liquid separation.

  8. Reconfigurable random bit storage using polymer-dispersed liquid crystal

    CERN Document Server

    Horstmeyer, Roarke; Yang, Changhuei

    2014-01-01

    We present an optical method of storing random cryptographic keys, at high densities, within an electronically reconfigurable volume of polymer-dispersed liquid crystal (PDLC) film. We demonstrate how temporary application of a voltage above PDLC's saturation threshold can completely randomize (i.e., decorrelate) its optical scattering potential in less than a second. A unique optical setup is built around this resettable PDLC film to non-electronically save many random cryptographic bits, with minimal error, over a period of one day. These random bits, stored at an unprecedented density (10 Gb per cubic millimeter), can then be erased and transformed into a new random key space in less than one second. Cryptographic applications of such a volumetric memory device include use as a crypto-currency wallet and as a source of resettable "fingerprints" for time-sensitive authentication.

  9. Anomalous light transmission by nematic liquid crystal cells

    Science.gov (United States)

    Konshina, E. A.; Fedorov, M. A.; Ivanova, N. L.; Amosova, L. P.

    2008-01-01

    Light transmission through nematic liquid crystal (NLC) cells with a planar alignment and various boundary conditions has been studied as a function of the bias voltage in the regimes of maximum transmittance and complete extinction. The phenomenon of anomalous light leakage in the regime of complete extinction has been observed in the NLC sells with alignment layers of amorphous hydrogenated carbon (a-C:H) and poly(vinyl alcohol) (PVA), in which an anisotropy was induced by rubbing the electrode surface (for a-C:H) and the alignment layer (for PVA). The anomalous transmission is caused by the deformation of nematic molecules, which are situated near the surface, in the direction perpendicular to the direction of rubbing. The magnitude of anomalous transmission increases with the bias voltage. This behavior is explained by the anisotropy of the surface anchoring energy of nematic molecules at the interface.

  10. Measurement of liquid crystal film thickness using interferometry

    International Nuclear Information System (INIS)

    Thickness measurements of thin films having thickness less than 1 µm are difficult to obtain by an interferometer. These difficulties arise from the overlap of the fringes from the upper and lower surfaces of the thin films. This paper presents a new methodology that mediates the consequences of this overlap and then implements it with thickness measurements of liquid crystal (LC) thin films. It takes into consideration the properties of light propagation within these films in order to rectify the images obtained from the interferometer. It assumes that the lower fringe pattern is much stronger that the upper one and hence the latter may be ignored. This occurs in situations where thin films are coated on substrates of significantly higher reflectivity, as happens when an LC thin film is coated on a polished iron substrate. The thickness and topography of LC thin films were experimentally measured with this methodology and were compared with measurements taken by an atomic force microscope

  11. Experimental realization of directed percolation criticality in turbulent liquid crystals.

    Science.gov (United States)

    Takeuchi, Kazumasa A; Kuroda, Masafumi; Chaté, Hugues; Sano, Masaki

    2009-11-01

    This is a comprehensive report on the phase transition between two turbulent states of electroconvection in nematic liquid crystals, which was recently found by the authors to be in the directed percolation (DP) universality class [K. A. Takeuchi, Phys. Rev. Lett. 99, 234503 (2007)]. We further investigate both static and dynamic critical behaviors of this phase transition, measuring a total of 12 critical exponents, 5 scaling functions, and 8 scaling relations, all in full agreement with those characterizing the DP class in 2+1 dimensions. Developing an experimental technique to create a seed of topological-defect turbulence by pulse laser, we confirm in particular the rapidity symmetry, which is a basic but nontrivial consequence of the field-theoretic approach to DP. This provides a clear experimental realization of this outstanding truly out-of-equilibrium universality class, dominating most phase transitions into an absorbing state. PMID:20364956

  12. Glucose sensor using liquid-crystal droplets made by microfluidics.

    Science.gov (United States)

    Kim, Jiyeon; Khan, Mashooq; Park, Soo-Young

    2013-12-26

    Micrometer-sized, 4-cyno-4-pentylbiphenyl (5CB) droplets were developed for glucose detection in an aqueous medium by coating with poly(acrylicacid-b-4-cynobiphenyl-4-oxyundecylacrylate) (PAA-b-LCP) at the 5CB/water interface and covalently immobilizing glucose oxidase (GOx) to the PAA chains. This functionalized liquid-crystal (LC) droplet detected glucose from a radial to bipolar configurational change by polarized optical microscopy under crossed polarizers at concentrations as low as 0.03 mM and response times of ~3 min and showed the selective detection of glucose against galactose. This new and sensitive LC-droplet-based glucose biosensor has the merits of low production cost and easy detection by the naked eye and might be useful for prescreening the glucose level in the human body. PMID:24251831

  13. ANALISIS CITRA PERMUKAAN THERMOCHROMIC LIQUID CRYSTAL BERDASARKAN NILAI STATISTIK HUE

    Directory of Open Access Journals (Sweden)

    Risti Suryantari

    2014-05-01

    Full Text Available Tujuan dari penelitian ini adalah untuk mengamati perbedaan citra pada permukaan Thermocromic Liquid Crystal (TLC R25C5W akibat perubahan temperatur. Metode yang digunakan untuk analisis adalah pengolahan citra berbasis morfologi matematika menggunakan perangkat lunak Matlab2013a. Citra asli yang diperoleh dalam bentuk RGB dikonversi menjadi HSV (hue, saturation, value, dengan mengambil komponen hue saja. Proses utama yang digunakan adalah opening dengan struktur elemen (SE line. Berdasarkan analisis visual pada citra akhir hasil pengolahan citra, tampak bahwa terdapat perbedaan setiap citra untuk berbagai temperatur berdasarkan tingkat kecerahannya. Secara kuantitatif perbedaan tersebut dapat dilihat dari nilai statistiknya. Nilai max dan mean citra hue semakin meningkat seiring dengan meningkatnya temperatur.

  14. Giant soft-memory in liquid crystal nanocomposites

    Science.gov (United States)

    Kempaiah, Ravindra; Liu, Yijing; Nie, Zhihong; Basu, Rajratan

    2016-02-01

    A hybrid nanocomposite comprising 5CB liquid crystal (LC) and block copolymer (BCP) functionalized barium titanate ferroelectric nanoparticles was prepared. This hybrid system exhibits a giant soft-memory effect that was detected by dielectric hysteresis. Spontaneous polarization of ferroelectric nanoparticles couples synergistically with the radially aligned BCP chains to create nanoscopic domains where LC mesogens can align directionally. Such domains can be rotated electromechanically and locked in space even after the removal of the applied electric field. The resulting non-volatile memory is several times larger than the non-functionalized sample and provides an insight into the role of non-covalent polymer functionalization on enhancing the size of the nanoscopic domains.

  15. Transitions through critical temperatures in nematic liquid crystals

    KAUST Repository

    Majumdar, Apala

    2013-08-06

    We obtain estimates for critical nematic liquid crystal (LC) temperatures under the action of a slowly varying temperature-dependent control variable. We show that biaxiality has a negligible effect within our model and that these delay estimates are well described by a purely uniaxial model. The static theory predicts two critical temperatures: the supercooling temperature below which the isotropic phase loses stability and the superheating temperature above which the ordered nematic states do not exist. In contrast to the static problem, the isotropic phase exhibits a memory effect below the supercooling temperature in the dynamic framework. This delayed loss of stability is independent of the rate of change of temperature and depends purely on the initial value of the temperature. We also show how our results can be used to improve estimates for LC material constants. © 2013 American Physical Society.

  16. Induced smectic phases of stoichiometric liquid crystal mixtures.

    Science.gov (United States)

    Sugisawa, Shin-Ya; Tabe, Yuka

    2016-03-16

    We revealed the detailed structures of induced smectic liquid crystal (LC) phases composed of a binary mixture of charge-transfer (CT) LC substances. Although neither of the constituents had highly ordered smectic phases, the mixture exhibited smectic-E (SmE) or smectic-B (SmB) phases when mixed at ratios of 1 : 1 and 2 : 3, respectively. The results of polarized optical microscopy, differential scanning calorimetry, X-ray diffraction, and infrared spectroscopy indicated that the induced smectic phases were stabilized by an exquisite balance between the CT interactions, dipolar interactions, and excluded volume effects. We proposed a possible model for the molecular arrangements in the SmE and SmB phases, which consistently explained the experimental results including the stoichiometric ratios. PMID:26898174

  17. Muscular MEMS—the engineering of liquid crystal elastomer actuators

    Science.gov (United States)

    Petsch, S.; Khatri, B.; Schuhladen, S.; Köbele, L.; Rix, R.; Zentel, R.; Zappe, H.

    2016-08-01

    A new class of soft-matter actuator, the liquid crystal elastomer (LCE), shows promise for application in a wide variety of mechanical microsystems. Frequently referred to as an ‘artificial muscle’, this family of materials exhibits large actuation stroke and generates considerable force, in a compact form which may easily be combined with the structures and devices commonly used in microsystems and MEMS. We show here how standard microfabrication techniques may be used to integrate LCEs into mechanical microsystems and present an in-depth analysis of their mechanical and actuation properties. Using an example from micro-optics and optical MEMS, we demonstrate that their performance and flexibility allows realization of entirely new types of tunable optical functionality.

  18. Infrared sensitive liquid crystal light valve with semiconductor substrate.

    Science.gov (United States)

    Shcherbin, Konstantin; Gvozdovskyy, Igor; Evans, Dean R

    2016-02-10

    A liquid crystal light valve (LCLV) is an optically controlled spatial light modulator that allows recording of dynamic holograms. Almost all known LCLVs operate in the visible range of the spectrum. In the present work we demonstrate a LCLV operating in the infrared. The interaction of signal and pump waves is studied for different applied voltages, grating spacings, and intensities of the recording beams. A fourfold amplification of the weak signal beam is achieved. The amplitude of the refractive index modulation Δn=0.007 and nonlinear coupling constant n₂=-1  cm²/W are estimated from the experimental results. External phase modulation of one of the recording beams is used for a further transient increase of the signal beam gain. PMID:26906379

  19. Liquid Crystal Microlens Using Nanoparticle-Induced Vertical Alignment

    Directory of Open Access Journals (Sweden)

    Shug-June Hwang

    2015-01-01

    Full Text Available The nanoparticle-induced vertical alignment (NIVA of the nematic liquid crystals (LC is applied to achieve an adaptive flat LC microlens with hybrid-aligned nematic (HAN mode by dropping polyhedral oligomeric silsesquioxane (POSS nanoparticle solution on a homogeneous alignment layer. The vertical alignment induced by the POSS nanoparticles resulted in the formation of a hybrid-aligned LC layer with concentric nonuniform distribution of the refractive index in the planar LC cell, which subsequently played the role of the lens, even in the absence of any applied voltages. The dimensions of the concentric HAN structure significantly depend on the volume of the microdroplet and the POSS concentration. The focus effect of this flat microlens was observed while electrically controlling its focal length using the applied voltages from −50 mm to −90 mm.

  20. Some specificities of wetting by cyanobiphenyl liquid crystals

    International Nuclear Information System (INIS)

    The present paper provides an up to date restatement of the wetting behaviour of the series of cyanobiphenyl liquid crystals (LCs) on usual substrates, i.e. oxidized silicon wafers, water and glycerol, at both the macroscopic and microscopic scale, in the nematic range of temperature. We show that on water the systems are close to a wetting transition, especially 5CB and 7CB. In that case, the wetting behaviour is controlled by the presence of impurities. On a mesoscopic scale, we observe for all our (thin LC film-substrate) systems an identical, complex, but well defined general scenario, not accounted for by the available models. In the last part, we present a study on line tension which results from the specific organization of LCs at the edge of the nematic film. We report preliminary results on two-dimensional film coalescence where this line tension plays a major role.

  1. Dielectric Anisotropy of Gold Nanoparticle Colloids in Nematic Liquid Crystals

    Science.gov (United States)

    Visco, Angelo; Foust, Jon; Mahmood, Rizwan

    We present electrical and optical studies of hexanethiol-treated gold nanoparticle (GNPs) colloids in 4-cyano-4 '-pentyl-biphenyl (5CB) liquid crystals. Preliminary data analysis suggests an unusual behavior of sudden drop and then rise in the dielectric anisotropy at a critical concentration of 0.0862% by wt. GNPs and a sudden rise and then drop in the nematic to isotropic transition temperature. Above the critical concentration the data level off to within the uncertainty of the experimental errors. This colloidal system will help us to understand the interaction and the effects of nanoparticles on the self-assembly of LC molecules and the manner in which these particles organize in LC. This study is important for further developments in nanotechnology, sharp and fast display panels, and within the medical field.

  2. Point diffraction interferometer with a liquid crystal monopixel.

    Science.gov (United States)

    Ramírez, Claudio; Otón, Eva; Iemmi, Claudio; Moreno, Ignacio; Bennis, Noureddine; Otón, José Manuel; Campos, Juan

    2013-04-01

    In this work a novel point diffraction interferometer based on a variable liquid crystal wave plate (LCWP) has been implemented. The LCWP consists of a 3x3 cm(2) monopixel cell with parallel alignment. The monopixel cell was manufactured such that the electrode covers the entire surface except in a centered circular area of 50 μm of diameter. This circle acts as a point perturbation which diffracts the incident wave front giving rise to a spherical reference wave. By applying a voltage to the LCWP we can change the phase of the wave front that passes through the monopixel, except at the center. Phase shifting techniques are used in order to calculate the amplitude and phase distribution of the object wave front. The system allows a digital hologram to be obtained, and by using the Fresnel diffraction integral it is possible to digitally reconstruct the different planes that constitute the three dimensional object. PMID:23571901

  3. Spatiotemporal complexity of electroconvection patterns in nematic liquid crystals

    Science.gov (United States)

    Krekhov, Alexei; Dressel, Bernd; Pesch, Werner; Delev, Vladimir; Batyrshin, Eduard

    2015-12-01

    We investigate a number of complex patterns driven by the electroconvection instability in a planarly aligned layer of a nematic liquid crystal. They are traced back to various secondary instabilities of the ideal roll patterns bifurcating at onset of convection, whereby the basic nematohydrodynamic equations are solved by common Galerkin expansion methods. Alternatively these equations are systematically approximated by a set of coupled amplitude equations. They describe slow modulations of the convection roll amplitudes, which are coupled to a flow field component with finite vorticity perpendicular to the layer and to a quasihomogeneous in-plane rotation of the director. It is demonstrated that the Galerkin stability diagram of the convection rolls is well reproduced by the corresponding one based on the amplitude equations. The main purpose of the paper is, however, to demonstrate that their direct numerical simulations match surprisingly well new experiments, which serves as a convincing test of our theoretical approach.

  4. Emerging Applications of Liquid Crystals Based on Nanotechnology

    Directory of Open Access Journals (Sweden)

    Jung Inn Sohn

    2014-03-01

    Full Text Available Diverse functionalities of liquid crystals (LCs offer enormous opportunities for their potential use in advanced mobile and smart displays, as well as novel non-display applications. Here, we present snapshots of the research carried out on emerging applications of LCs ranging from electronics to holography and self-powered systems. In addition, we will show our recent results focused on the development of new LC applications, such as programmable transistors, a transparent and active-type two-dimensional optical array and self-powered display systems based on LCs, and will briefly discuss their novel concepts and basic operating principles. Our research will give insights not only into comprehensively understanding technical and scientific applications of LCs, but also developing new discoveries of other LC-based devices.

  5. Nonlinear flow behaviors of nematic liquid crystals in complex geometries

    Science.gov (United States)

    Araki, Takeaki

    2013-02-01

    We study nematic liquid crystals flowing in a regular-shaped porous medium by means of lattice Boltzmann simulations. With strong anchoring, the director field cannot align uniformly and topological defects are stably formed with a large number of possible configurations. In a quiescent state, each configuration is arrested since the energy barriers between possible configurations are higher than the thermal energy. If the flow speed is slow enough, the defect pattern is not changed from the initial quiescent configuration. Above a critical flow speed, the defect pattern transforms to a new stable configuration. In a regular-shaped porous matrix, there remain regularly aligned disclination loops. This regular pattern is maintained even after the flow is stopped.

  6. Cholesteric Liquid Crystal Based Reflex Color Reflective Displays

    Science.gov (United States)

    Khan, Asad

    2012-02-01

    Bistable color cholesteric liquid crystal displays are unique LCDs that exhibit high reflectivity, good contrast, extremely low power operation, and are amenable to versatile roll-to-roll manufacturing. The display technology, now branded as Reflex has been in commercialized products since 1996. It has been the subject of extensive research and development globally by a variety of parties in both academic and industrial settings. Today, the display technology is in volume production for applications such as dedicated eWriters (Boogie Board), full color electronic skins (eSkin), and displays for smart cards. The flexibility comes from polymerization induced phase separation using unique materials unparalleled in any other display technology. The blend of monomers, polymers, cross linkers, and other components along with nematic liquid crystals and chiral dopants is created and processed in such ways so as to enable highly efficient manufactrable displays using ultra thin plastic substrates -- often as thin as 50μm. Other significant aspects include full color by stacking or spatial separation, night vision capability, ultra high resolution, as well as active matrix capabilities. Of particular note is the stacking approach of Reflex based displays to show full color. This approach for reflective color displays is unique to this technology. Owing to high transparency in wavelength bands outside the selective reflection band, three primarily color layers can be stacked on top of each other and reflect without interfering with other layers. This highly surprising architecture enables the highest reflectivity of any other reflective electronic color display technology. The optics, architecture, electro-topics, and process techniques will be discussed. This presentation will focus on the physics of the core technology and color, it's evolution from rigid glass based displays to flexible displays, development of products from the paradigm shifting concepts to consumer

  7. Thermal tunability of photonic bandgaps in liquid crystal infiltrated microstructured polymer optical fibers

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Wei, Lei; Alkeskjold, Thomas Tanggaard;

    2009-01-01

    We demonstrate the photonic bandgap effect and the thermal tunability of bandgaps in microstructured polymer optical fibers infiltrated with liquid crystal. Two liquid crystals with opposite sign of the temperature gradient of the ordinary refractive index (E7 and MDA-00- 1444) are used to...

  8. treatment of polyimide by an atmospheric pressure plasma of capacitive rf discharge for liquid crystal alignment

    International Nuclear Information System (INIS)

    Uniform planar alignment of liquid crystals is obtained by polyimide films obliquely treated by a stream of argon plasma from capacitive RF discharge at atmospheric pressure. Two liquid crystal alignment modes are discovered differing by their longitudinal or transverse orientation with respect to treatment direction. Optimum parameters of the treatment for obtaining these orientation modes are determined.

  9. Surface-induced and oriented textures of smectic liquid crystals: effect of thin films

    International Nuclear Information System (INIS)

    In this work, the effect of YBa2Cu3O7-x complex compound thin films on the morphological, thermotropical, optical and orientational properties of smectic liquid crystals have been studied. The peculiarities of surface-induced textures and dynamics of their temperature transformations have been investigated. Stable, homogeneous and reproducible oriented textures of smectic liquid crystals have been obtained

  10. Liquid Crystal Phases of Colloidal Platelets and their Use as Nanocomposite Templates

    NARCIS (Netherlands)

    Mourad, M.C.D.

    2009-01-01

    This thesis explores the gelation and liquid crystal phase behavior of colloidal dispersions of platelike particles as well as the use of such dispersions for the generation of nanocomposites. We report on the sol-gel, sol-glass and liquid crystal phase transitions of positively charged colloidal gi

  11. Formation of liquid inclusion induced light scatter in KDP (DKDP) crystals

    Institute of Scientific and Technical Information of China (English)

    孙洵; 孙大亮; 许心光; 王正平; 付有君; 王圣来; 曾红; 李毅平; 于锡玲; 高樟寿

    2001-01-01

    We describe in this paper the formation of liquid inclusion induced light scatter in potassium dihydrogen phosphate (KDP) crystal and deuterated potassium dihydrogen phosphate (DKDP) crystals. The measurement has been done with an atomic force microscope (AFM). The mechanism of formation of liquid inclusion scatter has been proposed and the effect of super-saturation discussed.

  12. Switchable photoluminescence liquid crystal coated bacterial cellulose films with conductive response.

    Science.gov (United States)

    Tercjak, Agnieszka; Gutierrez, Junkal; Barud, Hernane S; Ribeiro, Sidney J L

    2016-06-01

    Three different low molecular weight nematic liquid crystals (LCs) were used to impregnate bacterial cellulose (BC) film. This simple fabrication pathway allows to obtain highly transparent BC based films. The coating of BC film with different liquid crystals changed transmittance spectra in ultraviolet-visible region and allows to design UVC and UVB shielding materials. Atomic force microscopy results confirmed that liquid crystals coated BC films maintain highly interconnected three-dimensional network characteristic of BC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the three-dimensional network of BC nanofibers. Investigated BC films maintain nematic liquid crystal properties being switchable photoluminiscence as a function of temperature during repeatable heating/cooling cycles. Conductive response of the liquid crystal coated BC films was proved by tunneling atomic force microscopy measurement. Moreover, liquid crystal coated BC films maintain thermal stability and mechanical properties of the BC film. Designed thermoresponsive materials possessed interesting optical and conductive properties opening a novel simple pathway of fabrication liquid crystal coated BC films with tuneable properties. PMID:27083359

  13. Regularity of solutions to the liquid crystals systems in R2 and R3

    International Nuclear Information System (INIS)

    In this paper, we establish regularity and uniqueness for solutions to density dependent nematic liquid crystals systems. The results presented extend the regularity and uniqueness for constant density liquid crystals systems, obtained by Lin and Liu (1995 Commun. Pure Appl. Math. XLVIII 501–37)

  14. Nematic quantum liquid crystals of bosons in frustrated lattices

    Science.gov (United States)

    Zhu, Guanyu; Koch, Jens; Martin, Ivar

    2016-04-01

    The problem of interacting bosons in frustrated lattices is an intricate one due to the absence of a unique minimum in the single-particle dispersion where macroscopic number of bosons can condense. Here, we consider a family of tight-binding models with macroscopically degenerate lowest energy bands, separated from other bands by a gap. We predict the formation of exotic states that spontaneously break rotational symmetry at relatively low filling. These states belong to three nematic phases: Wigner crystal, supersolid, and superfluid. The Wigner crystal phase is established exactly at low filling. Supersolid and superfluid phases, at larger filling, are obtained by making use of a projection onto the flat band, construction of an appropriate Wannier basis, and subsequent mean-field treatment. The nematic superfluid that we predict is uniform in real space but has an anisotropic momentum distribution, providing a novel scenario for Bose condensation with an additional nematic order. Our findings open up a promising direction of studying microscopic quantum liquid crystalline phases of bosons.

  15. The Frozen State in the Liquid Phase of Side-Chain Liquid-Crystal Polymers

    International Nuclear Information System (INIS)

    Quenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that cross-links or entanglements are not a necessary condition to provide elasticity in melts

  16. A novel soft-core spherocylinder model for liquid crystals

    Science.gov (United States)

    Zong, Jing; Zhang, Xinghua; Wang, Qiang

    2010-03-01

    Interaction models with soft-core repulsions that allow particle overlapping give orders of magnitude faster/better sampling of configurational space than those with hard-core repulsions (e.g., hard spherocylinders or Gay-Berne potential). While several soft-core spherocylinder models were recently proposed^1, their repulsive interaction depends only on the shortest distance between two spherocylinders. Here we present a novel, computationally efficient soft-core spherocylinder model, which gives exact treatment of the excluded-volume interactions and anisotropic shape of two particles (thus the orientational interaction between them favoring their parallel alignment). It further takes into account the degree of overlap between the two particles, thus superior to other soft-core models. This model has great potential applications in the study of liquid crystals, block copolymers containing rod blocks, and liquid crystalline polymers. [1] Z. E. Hughes et al., Comput. Phys. Commun., 178, 724 (2008); J. S. Lintuvuori and M. R. Wilson, J. Chem. Phys., 128, 044906 (2008).

  17. Discotic liquid crystal derived from zinc tetraaminophthalocyanine and perfluorooctanoic acid

    Science.gov (United States)

    Meng, Fanbao; Zhou, Naiyu; Diao, Na; Du, Chang

    2013-12-01

    A novel kind of metallo-phthalocyanine derivative, zinc 2,9,16,23-tetraaminophthalocyanine perfluorooctanoate (Zn-APc-pFOA), was synthesized from zinc tetraaminophthalocyanine and perfluorooctanoic acid. The chemical structure, liquid crystalline behavior, and electrorheological properties were characterized by the use of various experimental techniques, methods, and instruments, including FT-IR and UV-vis spectroscopy, 1H-NMR, x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, the four-point method, a relative permittivity test instrument, and a rotating viscometer. Zn-APc-pFOA shows a discotic hexagonal columnar mesophase over a wide temperature range. The dielectric constant and conductivity of Zn-APc-pFOA are 11.4 and 6.34 × 10-3 S cm-1, respectively. The 20 V% silicone oil-Zn-APc-pFOA fluid shows an electrorheological (ER) effect. Zn-APc-pFOA is a semiconductor with a high dielectric constant, causing a mismatch of conductivity and dielectric constant between the Zn-APc-pFOA and silicone oil. Furthermore, some synergistic effect could occur between the semiconducting property and the molecular orientation of the discotic liquid crystals in Zn-APc-pFOA suspensions, resulting in a high ER effect.

  18. Mid-infrared gas sensors of liquid crystal type

    International Nuclear Information System (INIS)

    One of the most important tasks in the environmental monitoring field is detection and concentration measurements of different ingredients in natural and artificial mixtures of substances. According to the measuring of value of IR absorption of different gases one can determine their concentration in the environment. That is why there is a great practical and on principle fundamental interest to investigate an opportunity of making the devices which could be used for measuring the absorption of some gases in IR optical range and also would not have such disadvantages as construction complexity, cumbersome embodiments, difficulty in controlling and obligatory presence of the moving parts (mirrors, prisms or gratings). The main element in a sensor of the type proposed is a liquid-crystalline cell, possessing marked dichroism of optical absorption in some spectral range (IR region). By fitting the absorbance and alignment parameters of the LC cell, it is possible to create the effect of the absorption edge shift when varying the magnitude of electric field applied. This leads to some kind of wavelength modulation of an external optical radiation in the pre-determined spectral range. Adding an appropriate light detector to the system described, one can obtain a miniature scanning spectral instrument (sensor) of a liquid crystal type. LC cells with absorption bands in spectral range near 3 μm where some atmospheric hydrocarbons absorb were investigated. The technique for reducing true external spectrum from the signal detected after the modulation process was developed

  19. Molecular organization in liquid crystals: A comparative computational analysis

    International Nuclear Information System (INIS)

    A comparative computational analysis of molecular organization in four-nematogenic acids (nOCAC) having two, four, six, and eight carbon atoms in the alkyl chain is carried out with respect to translatory and orientational motions. The evaluation of the atomic charge and dipole moment at each atomic center is performed through the complete neglect differential overlap (CNDO/2) method. The Rayleigh-Schroedinger perturbation theory, along with the multicentered-multipole expansion method, is employed to evaluate the long-range interactions, while the '6-exp' potential function is assumed for short-range interactions. The total interaction-energy values obtained through these computations are used to calculate the probability of each configuration at the phase transition temperature via the Maxwell-Boltzmann formula. Further, the flexibility of various configurations is studied in terms of variation of probability due to small departures from the most probable configuration. A comparative picture of molecular parameters, such as the total energy, binding energy, and total dipole moment, is given. An attempt is made to explain the nematogenic behavior of these liquid crystals in terms of their relative order and, thereby, to develop a molecular model for the liquid crystallinity.

  20. Carbon Nanotube Liquid Crystals: Nematic Droplets and Coarsening Dynamics

    Science.gov (United States)

    Behabtu, Natnael; Senyuk, Bohdan; Smalyukh, Ivan; Pasquali, Matteo

    2012-02-01

    On a fundamental basis, carbon nanotubes (CNTs) offer a new model molecule to explore the dynamics and phases of rigid rods and test theories. Their large aspect ratio (100 to 100,000) and persistence length (˜ 100 microns) allow exploring the physics of nematic phases with high Frank elastic constant. Moreover, understanding of CNT liquid crystals is key to their rational processing into ordered materials such as fibers. Here we report the formation of elongated nematic droplets of CNTs in chlorosulfonic acid. In nematic droplets, a continuous transition from a homogeneous to bipolar nematic director field is expected theoretically, as a function of droplet volume; yet, experimental determination of such transition has been elusive. We show that CNT nematic droplets display such transition. We study the coarsening dynamics of positive and negative nematic droplets and observe that two or more droplets merge by matching their nematic director. Merging scenarios that lead to defect formation are not observed. Negative tactoids (isotropic phase in liquid crystalline continuum) merge through attractive forces induced by the nematic director distortion with quadrupolar symmetry.

  1. The application of liquid crystal polymers to turbomachinery

    Science.gov (United States)

    Mueller, Mark A.; Schmidt, Ed E.

    1992-02-01

    The Advanced Materials for Turbomachinery program is investigating the use of thermotropic Liquid Crystal Polymers (LCP's) as a housing material in turbopump assemblies. A requirement for this application is the compatibility of the LCP's with the working fluids (propellants) of the turbopump. A study was therefore undertaken to assess the physical and chemical properties of several commercial thermotropic LCP's in both storable and cryogenic propellants. Compatibility tests in storable propellants showed the LCP's to be incompatible with monomethyl hydrazine due to the breakdown of ester linkages in the polymer chains. Several LCP's were found to be compatible with nitrogen tetroxide under ambient conditions. Compatibility tests in oxygen environments determined that, although they have high autoignition temperatures, thermotropic LCP's are sensitive to ignition by means of mechanical impact and have high flame propagation rates. Pneumatic burst testing under ambient and cryogenic (liquid nitrogen) conditions showed that burst pressures generally increased at cryogenic temperatures. However, the burst pressure data showed large standard deviations leading to the conclusion that the mechanical properties of thermotropic LCP's are extremely sensitive to material processing parameters.

  2. Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field.

    Science.gov (United States)

    García-García, Amanda; Vergaz, Ricardo; Algorri, José F; Zito, Gianluigi; Cacace, Teresa; Marino, Antigone; Otón, José M; Geday, Morten A

    2016-01-01

    Single-wall carbon nanotubes (SWCNT) are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules. PMID:27547599

  3. Elastic Properties of Nematic Liquid Crystals Formed by Living and Migrating Cells

    CERN Document Server

    Kemkemer, R; Kaufmann, D; Gruler, H; Kemkemer, Ralf; Kling, Dieter; Kaufmann, Dieter; Gruler, Hans

    1998-01-01

    In culture migrating and interacting amoeboid cells can form nematic liquid crystal phases. A polar nematic liquid crystal is formed if the interaction has a polar symmetry. One type of white blood cells (granulocytes) form clusters where the cells are oriented towards the center. The core of such an orientational defect (disclination) is either a granulocyte forced to be in an isotropic state or another cell type like a monocyte. An apolar nematic liquid crystal is formed if the interaction has an apolar symmetry. Different cell types like human melanocytes (=pigment cells of the skin), human fibroblasts (=connective tissue cells), human osteoblasts (=bone cells), human adipocytes (= fat cells) etc., form an apolar nematic liquid crystal. The orientational elastic energy is derived and the orientational defects (disclination) of nematic liquid crystals are investigated. The existence of half-numbered disclinations show that the nematic phase has an apolar symmetry. The density- and order parameter dependence...

  4. Spectral properties of bacteriochlorophyll c in nematic liquid crystal. Part 1. Monomeric forms of dye

    Science.gov (United States)

    Dudkowiak, A.; Francke, C.; Amesz, J.; Planner, A.; Hanyz, I.; Fraçkowiak, D.

    1996-02-01

    The spectroscopic features of bacteriochlorophyll c and bacteriopheophytin c in a nematic liquid crystal matrix have been investigated. Absorption, circular dichroism, fluorescence and time resolved delayed luminescence spectra have been measured. The pigment is introduced to the liquid crystal from a dry and from a hydrated chloroform solution. In both cases the pigment is in the monomeric form. Hydration of the solvent and the presence or absence of the central Mg atom affect the interaction of the pigment molecules with the liquid crystal matrix, changing the fluorescence anisotropy. A model for the bacteriochlorophyll c orientation in the liquid crystal is proposed and the averaged angles between the transition moments and the liquid crystal orientation axis are determined. A slow process (in the microsecond range) of radiative deactivation of energy absorbed by the pigments is observed. This delayed emission could be due to pigment ionization and delayed charge recombination and/or thermal activation from the triplet to the excited singlet state.

  5. Impedance spectroscopy investigation of electrophysical characteristics of the electrode-liquid crystal interface

    Science.gov (United States)

    Belyaev, B. A.; Drokin, N. A.

    2015-01-01

    The behavior of frequency dependences of the impedance of a capacitive measuring cell with a liquid crystal has been investigated in the frequency range from 10-1 to 105 Hz. A method for determining electrophysical characteristics of the liquid crystal in the bulk and at the liquid crystal-metal electrode interface has been proposed and tested for liquid crystals of the alkyl cyanobiphenyl series, which are doped with ionic surfactants. The method is based on the use of an equivalent electrical circuit, which makes it possible to approximate the impedance spectra with the required accuracy, and also on the determination of the frequency at the singular point in the impedance spectra, at which the reactive component of the electric current flowing through the liquid-crystal cell is negligible compared to the active component.

  6. The Effect of Ionic Liquids on the CaCO3 Crystal Growth

    Institute of Scientific and Technical Information of China (English)

    Zhi Guo HU; Shi Li SONG; Jian Ji WANG; Lin YANG

    2004-01-01

    In this paper, the effect of ionic liquids on the CaCO3 crystal growth has been studied for the first time. The obtained CaCO3 crystals were charactered by the X-ray diffraction and scanning electron micrographs. The results showed that the control ability of ionic liquids for CaCO3 crystals growth was dependent on the counter anion very much.

  7. Tunable complete photonic band gap in anisotropic photonic crystal slabs with non-circular air holes using liquid crystals

    Science.gov (United States)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-06-01

    In this study, we analyze the tunability of complete photonic band gap of square and triangular photonic crystal slabs composed of square and hexagonal air holes in anisotropic tellurium background with SiO2 as cladding material. The non-circular holes are infiltrated with liquid crystal. Using the supercell method based on plane wave expansion, we study the variation of complete band gap by changing the optical axis orientation of liquid crystal. Our numerical results show that noticeable tunability of complete photonic band gap can be obtained in both square and triangular structures with non-circular holes.

  8. The cuttlefish Sepia officinalis (Sepiidae, Cephalopoda) constructs cuttlebone from a liquid-crystal precursor

    Science.gov (United States)

    Checa, Antonio G.; Cartwright, Julyan H. E.; Sánchez-Almazo, Isabel; Andrade, José P.; Ruiz-Raya, Francisco

    2015-06-01

    Cuttlebone, the sophisticated buoyancy device of cuttlefish, is made of extensive superposed chambers that have a complex internal arrangement of calcified pillars and organic membranes. It has not been clear how this structure is assembled. We find that the membranes result from a myriad of minor membranes initially filling the whole chamber, made of nanofibres evenly oriented within each membrane and slightly rotated with respect to those of adjacent membranes, producing a helical arrangement. We propose that the organism secretes a chitin-protein complex, which self-organizes layer-by-layer as a cholesteric liquid crystal, whereas the pillars are made by viscous fingering. The liquid crystallization mechanism permits us to homologize the elements of the cuttlebone with those of other coleoids and with the nacreous septa and the shells of nautiloids. These results challenge our view of this ultra-light natural material possessing desirable mechanical, structural and biological properties, suggesting that two self-organizing physical principles suffice to understand its formation.

  9. Accurate heat transfer measurements using thermochromic liquid crystal. Part 1: Calibration and characteristics of crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kakade, V.U. [Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY (United Kingdom); Lock, G.D. [Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY (United Kingdom)], E-mail: ensgdl@bath.ac.uk; Wilson, M.; Owen, J.M.; Mayhew, J.E. [Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY (United Kingdom)

    2009-10-15

    Encapsulated thermochromic liquid crystal (TLC) can accurately measure surface temperature in a variety of heat transfer and fluid flow experiments. Narrow-band TLC, where the colour changes over a temperature range of {approx}1 deg. C, can be used to determine surface temperature within an uncertainty of 0.1 deg. C. Wide-band TLC, typically active over 5-20 deg. C, allow the possibility of mapping surface temperature distributions. In part 1 of this two-part paper, an extensive set of calibrations for narrow-band and wide-band TLC is reported. This generic study provides insight into the importance and influence of the various factors governing the colour-temperature relationship. These governing effects include the variation in optical path, the spectrum of the illumination source, the lighting and viewing angles, the differences between cooling or heating cycles (hysteresis), the variation with the number of heating or cooling cycles (aging) and how this varies with TLC film thickness. Two narrow-band crystals are also specifically calibrated for application to experiments on a transparent disc rotating at high speed ({approx}5000 rpm). Part 2 of this paper describes how these accurately-calibrated crystals were used to measure the transient surface temperature on, and heat transfer to, a rotating disc.

  10. Accurate heat transfer measurements using thermochromic liquid crystal. Part 1: Calibration and characteristics of crystals

    International Nuclear Information System (INIS)

    Encapsulated thermochromic liquid crystal (TLC) can accurately measure surface temperature in a variety of heat transfer and fluid flow experiments. Narrow-band TLC, where the colour changes over a temperature range of ∼1 deg. C, can be used to determine surface temperature within an uncertainty of 0.1 deg. C. Wide-band TLC, typically active over 5-20 deg. C, allow the possibility of mapping surface temperature distributions. In part 1 of this two-part paper, an extensive set of calibrations for narrow-band and wide-band TLC is reported. This generic study provides insight into the importance and influence of the various factors governing the colour-temperature relationship. These governing effects include the variation in optical path, the spectrum of the illumination source, the lighting and viewing angles, the differences between cooling or heating cycles (hysteresis), the variation with the number of heating or cooling cycles (aging) and how this varies with TLC film thickness. Two narrow-band crystals are also specifically calibrated for application to experiments on a transparent disc rotating at high speed (∼5000 rpm). Part 2 of this paper describes how these accurately-calibrated crystals were used to measure the transient surface temperature on, and heat transfer to, a rotating disc.

  11. Dielectric properties and molecular motions of liquid crystal molecules in 4-(2-methylbytylphenyl 4-(4-octylphenylbenzoate liquid crystal having blue phase (CE8

    Directory of Open Access Journals (Sweden)

    Otowski W.

    2015-06-01

    Full Text Available Blue phase liquid crystals exhibit unique properties which are used in the new type of display. A blue-phase liquid crystal display was first presented commercially by Samsung in 2007. The blue-phase-three-color pixel display eliminates the need for color filters. This type of display uses blue-phase multi-component liquid crystal. Considering the one-component systems, it turns out that they are stable only in a very narrow range of temperatures between the isotropic and the chiral nematic phase (about 1 K. In 2005, a wide temperature range BP multi-component system was reported by researchers from the University of Cambridge. There are still several unsolved problems left. One of them is chemical stability and reliability. Therefore, the knowledge of molecular dynamics of blue phase liquid crystal is a prerequisite for understanding of blue-phase multi-component system. Understanding the molecular dynamics of a single component liquid-crystalline blue phase system can facilitate the solution of these problems. We present the molecular dynamics investigation of 4-(2-methylbytylphenyl 4-(4-octylphenylbenzoate (CE8, which may be a good candidate to form materials suitable for blue-phase liquid crystal displays.

  12. Biological treatment of the liquid effluents of a paper industry

    International Nuclear Information System (INIS)

    The objective of this paper is to determine the effect of the microorganisms Candida utilis and Candida tropicalis in the reduction of the chemical oxygen demand (COD) of the liquid effluents of a producing factory of paper kraft type, by means of fermentations made to pH of 5 and a 30 centigrade degrees during 6 days. The biological processing is preceded by a physicochemical process of directed acidulation to reduce pH of the effluent (liquor black) from its initial value, of approximately 13, to 5, in order to it is adapted for the growth of yeast. In this process, which forms precipitated, that is necessary to eliminate by centrifugation and filtration to facilitate the growth of the microorganisms, with is obtained one first removal of the COD of the order of 70 %. With the biological processing obtains for both yeasts a percentage of removal of 45 -50% of the COD surplus. The total removal of the COD, that is to say, obtained with the pre-cure and the fermentation it is of the order of 84% for the yeast. Additionally the possibility studied of implementing some complementary procedures to the biological processing, with a view to obtaining greater growth of yeast in the black liquor and thus obtaining additional reductions in the OCD of the same one

  13. Synthesis of rod-like bis-ester liquid crystals and their influence on photoelectric properties of liquid crystalline materials

    Institute of Scientific and Technical Information of China (English)

    Min Yan Zheng; Yong Sheng Wei; Zhong Wei An; Shan Wang

    2009-01-01

    Six novel rod-like magnetic liquid crystals have been prepared,in which trans-bicyclobexyl or trans-cyclobexylphenyl and biphenylcarboxylic acid phenyl ester mesogenic cores with n-propyl and n-pentyl substituents were terminated by 4-hydroxylTEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-l-oxy).Their structures were confirmed by elemental analysis,IR and MS.Determined by SQUID,EPR,DSC and HS-POM (heat stage polarizing optical microscope),the six compounds all have both magnetic and liquid crystalline properties; their temperature ranges of mesophase were from 16.0 to 24.8 ~C,and the magnetic liquid crystal molecules could obviously improve the response sensitivity of liquid crystal materials.

  14. Interactions of biomacromolecules with reverse hexagonal liquid crystals: drug delivery and crystallization applications.

    Science.gov (United States)

    Libster, Dima; Aserin, Abraham; Garti, Nissim

    2011-04-15

    Recently, self-assembled lyotropic liquid crystals (LLCs) of lipids and water have attracted the attention of both scientific and applied research communities, due to their remarkable structural complexity and practical potential in diverse applications. The phase behavior of mixtures of glycerol monooleate (monoolein, GMO) was particularly well studied due to the potential utilization of these systems in drug delivery systems, food products, and encapsulation and crystallization of proteins. Among the studied lyotropic mesophases, reverse hexagonal LLC (H(II)) of monoolein/water were not widely subjected to practical applications since these were stable only at elevated temperatures. Lately, we obtained stable H(II) mesophases at room temperature by incorporating triacylglycerol (TAG) molecules into the GMO/water mixtures and explored the physical properties of these structures. The present feature article summarizes recent systematic efforts in our laboratory to utilize the H(II) mesophases for solubilization, and potential release and crystallization of biomacromolecules. Such a concept was demonstrated in the case of two therapeutic peptides-cyclosporin A (CSA) and desmopressin, as well as RALA peptide, which is a model skin penetration enhancer, and eventually a larger macromolecule-lysozyme (LSZ). In the course of the study we tried to elucidate relationships between the different levels of organization of LLCs (from the microstructural level, through mesoscale, to macroscopic level) and find feasible correlations between them. Since the structural properties of the mesophase systems are a key factor in drug release applications, we investigated the effects of these guest molecules on their conformations and the way these molecules partition within the domains of the mesophases. The examined H(II) mesophases exhibited great potential as transdermal delivery vehicles for bioactive peptides, enabling tuning the release properties according to their chemical

  15. Design and Synthesis of Novel Discotic Liquid Crystals

    Science.gov (United States)

    Kayal, Himadri Sekhar

    Columnar mesophases of discotic liquid crystals (DLCs) have attracted much attention as organic semiconductors and have been tested as active materials in light-emitting diodes, photovoltaic solar cells, and field-effect transistors. However, devices based on DLCs have shown lower performance than devices based on polymeric and small molecule glass semiconductors, despite their superior charge conducting and advantages self-organizing properties. Most DLCs also require relatively complex processing conditions for the preparation of electronic devices, which is another significant disadvantage. Consequently, new types of DLCs are sought-after to overcome these limitations and described in this thesis are new types of discotic materials and their synthesis. Chapters 2 and 3 describe star-shaped discotic molecules for donor-acceptor columnar structures and as novel flexible core discotic molecules. Presented are the first examples of star-shaped heptamers of donor and acceptor discotic molecules which have six hexaalkoxy triphenylene ligands and a hexaazatriphenylene hexacarboxylate core or a hexaazatriphenylene hexaamide core. The hexaazatriphenylene cores were chosen because of their electron deficient character while the hexaalkoxy triphenylenes are known to be electron rich. Envisioned is the formation of super-columns in which the heptamers stack on top of each other and generate a material with electron acceptor and electron donor channels separated by aliphatic chains. This is an important difference to previously reported donor-acceptor star-shaped structures that were connected via conjugated linkers and do not form separate columnar stacks. Star-shaped DLCs based on small aromatic groups linked together by short flexible spacers may represent a novel type of discotic core structure that does not require peripheral flexible chains. Softening of the core by the spacer group is expected to sufficiently lower melting points and not interfere with the columnar

  16. Phase separations in mixtures of a liquid crystal and a nanocolloidal particle

    Science.gov (United States)

    Matsuyama, Akihiko

    2009-11-01

    We present a mean field theory to describe phase separations in mixtures of a liquid crystal and a nanocolloidal particle. By taking into account a nematic, a smectic A ordering of the liquid crystal, and a crystalline ordering of the nanoparticle, we calculate the phase diagrams on the temperature-concentration plane. We predict various phase separations, such as a smectic A-crystal phase separation and a smectic A-isotropic-crystal triple point, etc., depending on the interactions between the liquid crystal and the colloidal surface. Inside binodal curves, we find new unstable and metastable regions, which are important in the phase ordering dynamics. We also find a crystalline ordering of the nanoparticles dispersed in a smectic A phase and a nematic phase. The cooperative phenomena between liquid-crystalline ordering and crystalline ordering induce a variety of phase diagrams.

  17. Novel polymer as liquid crystal alignment material for plastic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mahilny, U V; Stankevich, A I; Muravsky, A A [Physical Department of Belarusian State University, Nezavisimosti Ave. 4, 220030 Minsk (Belarus); Murauski, A A, E-mail: mogilny@bsu.b [Center for Display Research, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2009-04-07

    Implementation of the roll-to-roll (R2R) process and printable organic electronics realizes the cost reduction potential of liquid crystal displays (LCDs) on plastic substrates. These innovative technologies put a strong limitation on the chemistry and temperature treatment of the LC alignment material applied at the solid-liquid interface inside the LCD. Alignment material is the last uniform layer deposited on each of the substrates before assembling and sealing of the whole display sandwich. Deposition from an aggressive solvent, vacuum deposition or a high baking temperature can not only destroy the complex composite structure of the electronics but can also affect the material properties of the substrate. We developed a new type of polymer alignment material, B-15, which can be deposited from a non-aggressive solvent (ethyl/butyl acetate) on top of the wide range of organic layers (including UV-curable materials and TAC films of plastic polarizer) without barrier layers for chemical protection. B-15 is suitable for the R2R process for only short-time treatment operations: 5 min baking at 90 {sup 0}C is sufficient to remove the residual solvent and hard baking is not required. First, the rubbing process produces an alignment direction on the surface with the azimuthal anchoring energy over 10{sup -4} J m{sup -2}. Next, non-polarized light exposure with a 254 nm Hg line induces photopolymerization, which also shifts the absorption peak far below the 300 nm wavelength. Thus B-15 is a highly photostable alignment material possessing null absorption in both the UV-A and the VIS ranges.

  18. Miniature Compressive Ultra-spectral Imaging System Utilizing a Single Liquid Crystal Phase Retarder

    Science.gov (United States)

    August, Isaac; Oiknine, Yaniv; Abuleil, Marwan; Abdulhalim, Ibrahim; Stern, Adrian

    2016-03-01

    Spectroscopic imaging has been proved to be an effective tool for many applications in a variety of fields, such as biology, medicine, agriculture, remote sensing and industrial process inspection. However, due to the demand for high spectral and spatial resolution it became extremely challenging to design and implement such systems in a miniaturized and cost effective manner. Using a Compressive Sensing (CS) setup based on a single variable Liquid Crystal (LC) retarder and a sensor array, we present an innovative Miniature Ultra-Spectral Imaging (MUSI) system. The LC retarder acts as a compact wide band spectral modulator. Within the framework of CS, a sequence of spectrally modulated images is used to recover ultra-spectral image cubes. Using the presented compressive MUSI system, we demonstrate the reconstruction of gigapixel spatio-spectral image cubes from spectral scanning shots numbering an order of magnitude less than would be required using conventional systems.

  19. Room temperature supramolecular columnar liquid crystals formed by hydrogen bonding of isoquinoline derivatives

    Science.gov (United States)

    Hyup Lee, Jun; Lee, Seung Jun; Jho, Jae Young

    2014-07-01

    We report new self-assembled discotic liquid crystals exhibiting columnar mesophases at room temperature, which are constructed by intermolecular hydrogen bonding between the core of 1,3,5-trihydroxybenzene or 1,3,5-cyclohexanetricarboxylic acid and the peripheral molecules of isoquinoline derivatives. The mesomorphic properties of supramolecular liquid crystals were investigated by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction studies. The self-assembled liquid crystals exhibited rectangular columnar phases (Colro) with an ordered stacking structure of the mesogens in a column at room temperature, regardless of the type of the core molecule, due probably to the close-packed aromatic rings around a core molecule and the angular structure in three arms of the discotic mesogen. These room temperature columnar phases are rare examples for the discotic liquid crystals, and our findings in the present study provide a new way to prepare low melting columnar liquid crystalline materials for molecular electronics.

  20. Liquid crystal phases of two-dimensional dipolar gases and Berezinskii-Kosterlitz-Thouless melting.

    Science.gov (United States)

    Wu, Zhigang; Block, Jens K; Bruun, Georg M

    2016-01-01

    Liquid crystals are phases of matter intermediate between crystals and liquids. Whereas classical liquid crystals have been known for a long time and are used in electro-optical displays, much less is known about their quantum counterparts. There is growing evidence that quantum liquid crystals play a central role in many electron systems including high temperature superconductors, but a quantitative understanding is lacking due to disorder and other complications. Here, we analyse the quantum phase diagram of a two-dimensional dipolar gas, which exhibits stripe, nematic and supersolid phases. We calculate the stiffness constants determining the stability of the nematic and stripe phases, and the melting of the stripes set by the proliferation of topological defects is analysed microscopically. Our results for the critical temperatures of these phases demonstrate that a controlled study of the interplay between quantum liquid and superfluid phases is within experimental reach for the first time, using dipolar gases. PMID:26750156

  1. A switchable circular polarizer based on zenithal bistable liquid crystal gratings

    Science.gov (United States)

    Zografopoulos, Dimitrios C.; Isić, Goran; Kriezis, Emmanouil E.; Beccherelli, Romeo

    2016-05-01

    A switchable circular polarizer for infrared telecom wavelengths based on zenithal bistable liquid crystal gratings is designed and investigated by employing the finite-element method for the study of full-wave light propagation and a tensorial formulation for the liquid crystal orientation. The handedness of the output circular polarization can be selected by switching between the two stable states of the liquid-crystal grating. Analysis of the spectral dependence and the tolerance of the polarizer’s performance with respect to deviations from the optimized geometry reveals the robustness of its polarizing properties, which stems from the non-resonant nature of its operation.

  2. Quadrupolar Effect on Two Layered Thin Film Antiferroelectric Smectic Liquid Crystal

    International Nuclear Information System (INIS)

    Within the framework of the discrete Landau phenomenological model, the free energy of an antiferroelectric smectic liquid crystal is analyzed. This model considers the interactions between the liquid crystal molecules within the nearest and the next nearest layers. Electrostatic quadrupolar interaction up to the nearest layers is included. This quadrupolar term, bqξ???i·ξ???i+12 is positive, thus favouring a perpendicular orientation in the adjacent layer respectively. We show how quadrupolar interaction can affects the planar regions of the phase diagram of a two layered thin antiferroelectric smectic liquid crystal film.

  3. A Novel Microwave Tunable Band-Pass Filter Integrated Power Divider Based on Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Yupeng Liu

    2015-01-01

    Full Text Available This paper proposes a novel microwave continuous adjustable band-pass filter integrated power divider based on nematic liquid crystals (LCs. The proposed power divider uses liquid crystal (LC as the dielectric material. It can realize phase shift by changing the dielectric anisotropy, when biasing the high anisotropy nematic liquid crystal. It is mainly used in microwave frequencies. It has a large number of advantages compared to conventional filter integrated power divider, such as low loss, multifunction integration, continuous adjustable, miniaturization, low processing costs, low operating voltage, high phase shift, and convenient manufacture. Therefore, it has shown great potential for application.

  4. Surface effects on photopolymerization induced anisotropic phase separation in liquid crystal and polymer composites

    International Nuclear Information System (INIS)

    The surface effects on the anisotropic phase separation in photopolymerization induced phase separation of liquid crystal and polymer composites have been studied. It was found that the surface interaction between the substrate and the prepolymer and/or liquid crystal plays a crucial role in anisotropic phase separation. A theoretical model is suggested to describe the surface effects by adapting a phenomenological free energy approach. The formation of polymer layer in the presence of surface effects can be understood as competition between entropic flow and surface directed flow of polymer and liquid crystal

  5. Temperature measurement using thermosensitive liquid crystal. 2. Speeding up of measurement

    International Nuclear Information System (INIS)

    The present study describes the development of a thermometer to rapidly determine temperature from the color of thermosensitive liquid crystal using photodiodes. The output of photodiodes was calculated from the spectral characteristics of liquid crystal and the spectral sensitivity of photodiodes. In the experiment, reflected light on liquid crystal was measured in the steady state by two kinds (DC∼50 kHz and DC∼100 kHz) of avalanche photodiodes (APD) which have different spectral sensitivity. The ratio of each APD output was correlated with temperature. The speeding up of temperature measurement was realized by connecting this system to an oscillograph. (author)

  6. Strongly coupled dusty plasmas: crystals, liquids, clusters and waves

    International Nuclear Information System (INIS)

    The dusty plasma is a system that consists of many strongly-charged fine dust particles suspended in a plasma background. The slow dynamics and strong coupling due to the large mass and charges lead to the formation of highly-ordered dust crystal structures suspended in the plasma background, which can be directly observed. The dusty plasma forms a link to the area of condensed matter physics for the study of many interesting microscopic phenomena from order to disorder. In this paper, we introduce the special properties of this system from the viewpoint of conventional plasma physics, then we briefly review past works on the structure and dynamical behaviour from the highly-ordered state, through the melting and liquid states with associated vortex-type excitation and anomalous diffusion, to the state with self-organized macroscopic dust waves after losing microscopic order. The first observation of strongly-coupled dust Coulomb clusters with small numbers of particles from a few to a few hundred, which resemble classical atoms, is also demonstrated. (author)

  7. Modelling of switching in ferroelectric liquid crystal devices

    CERN Document Server

    McCrea, S

    1996-01-01

    phases in two dimensions is adapted to model this, and combined with the continuum equations to give a single dynamic equation relating the domain area to the charge (for an isolated cell) or to the voltage. Empirical relationships are found for the switching times which show two regimes separated by a distinct threshold. A finite difference model is developed to simulate the dynamics of reorientation in one and two dimensions. The model takes into account much of the known structural complexity, for example finite surface and chevron layer interactions, and the alignment layers. It also uses many physical and material parameters. A novel active matrix drive scheme is proposed which is designed as a result of including conductivity in the model. The model in two dimensions is used to simulate, again, growth of switched domains giving a remarkable agreement with experimental results. Smectic C* liquid crystals are now used in many applications such as flat panel displays and laser printer print heads. They are...

  8. An Adaptive Algorithm of Local dimming for Liquid Crystal Displays

    Directory of Open Access Journals (Sweden)

    Huaxia Wu

    2012-11-01

    Full Text Available The local dimming backlight technique enables liquid crystal display to present images with high contrast ratio and low power consumption. Considering that it is more important to make sure a high quality of the displayed image when reducing the power consumption, therefore, in this paper the new algorithm chooses RPSNR (the peak signal-to-noise ratio =30 as the lowest standard to guarantee the quality of image. RPSNR =30 could provide a value that the maximum distortion of the image can be accepted, then, we substitute the maximum gray level of each region into the formula to judge whether satisfy the flow chart. If the value do not meet the condition, we decrease it one by one until find the right value. Finally, we take the luminance of the right value as backlight luminance.   Meanwhile, a method is also proposed in this paper to simplify the calculation time. Successive searches will be made on the basis of the n (ranging from 0.1 to 1 times of the maximum luminance, and stop when RPSNR>=30. However, in order to guarantee the quality of the image, the 0.7 times of the maximum luminance is used as the minimum backlight luminance. In the end, we only choose 0.7, 0.8 and 0.9 times of the maximum luminance as backlight luminance.

  9. Modification of Urushiol Derivatives by Liquid Crystal Epoxy Resin

    Directory of Open Access Journals (Sweden)

    Gongwen Tang

    2015-01-01

    Full Text Available Urushiol derivatives have vast potentials for using as coating materials. However, the cured coatings are quite brittle, limiting their applications. In this study, urushiol-furfural (UFUR was chosen as an example of urushiol derivatives and a liquid crystal (LC epoxy resin, tetramethylbiphenyl diglycidyl ether (TMBPDE, was for the first time utilized to modify UFUR. Fourier transform infrared spectroscopy and solid-state 13C nuclear magnetic resonance showed the reactions between TMBPDE and UFUR after the UFUR/TMBPDE composite resin was cured. Differential scanning calorimetry analysis showed that the Tg significantly increased after the addition of TMBPDE. Thermogravimetry analysis indicated that the cured UFUR/TMBPDE composite resin exhibited increasing thermodecomposition temperature as the TMBPDE concentration increased, indicating its great potential for high temperature applications. Moreover, the presence of TMBPDE enhanced the toughness of UFUR as observed by impact test and reflected in the morphologies observed from SEM images of fracture surfaces. It would also be novel and effective to modify urushiol derivatives by the LC polymer.

  10. Liquid crystal based biosensors for bile acid detection

    Science.gov (United States)

    He, Sihui; Liang, Wenlang; Tanner, Colleen; Fang, Jiyu; Wu, Shin-Tson

    2013-03-01

    The concentration level of bile acids is a useful indicator for early diagnosis of liver diseases. The prevalent measurement method in detecting bile acids is the chromatography coupled with mass spectrometry, which is precise yet expensive. Here we present a biosensor platform based on liquid crystal (LC) films for the detection of cholic acid (CA). This platform has the advantage of low cost, label-free, solution phase detection and simple analysis. In this platform, LC film of 4-Cyano-4'-pentylbiphenyl (5CB) was hosted by a copper grid supported with a polyimide-coated glass substrate. By immersing into sodium dodecyl sulfate (SDS) solution, the LC film was coated with SDS which induced a homeotropic anchoring of 5CB. Addition of CA introduced competitive adsorption between CA and SDS at the interface, triggering a transition from homeotropic to homogeneous anchoring. The detection limit can be tuned by changing the pH value of the solution from 12uM to 170uM.

  11. Polarization converting textures of nematic liquid crystal in glass cavities

    Science.gov (United States)

    Wang, Xiahui; Xu, Miao; Ren, Hongwen

    2014-01-01

    When a nematic liquid crystal (LC) is filled in a glass cavity, the LC molecules present azimuthal orientations in the cavity. If the surface of the cavity is coated with a homeotropic polyimide, then the LC molecules exhibit radial orientations. By treating the LC on one side of the cavity with homogeneous alignment, the former orientations change to a twisted-azimuthal texture, while the latter orientations change to a twisted-radial texture. Both textures are verified experimentally, and they can convert a linearly polarization light to an azimuthal and/or radial polarization light, depending on the polarization direction of the incident light. In contrast to previous approaches, various LC textures can be easily formed in a cavity, and the fabrication procedure is simple. Since the LC texture is confined in a cavity, an array pattern of the texture can be obtained, if the employed substrate has multiple cavities. A LC with twisted-azimuthal and/or twisted-radial textures in a cavity array has potential applications in phase modulation, polarization compensating, sharp focus, and material processing.

  12. Anomalous swimming behavior of bacteria in nematic liquid crystals

    Science.gov (United States)

    Sokolov, Andrey; Zhou, Shuang; Lavrentovich, Oleg; Aranson, Igor

    2015-03-01

    Flagellated bacteria stop swimming in isotropic media of viscosity higher than 0.06kgm-1s-1. However, Bacillus Subtilis slows down by only about 30% in a nematic chromonic liquid crystal (CLC, 14wt% DSCG in water), where the anisotropic viscosity can be as high as 6kgm-1s-1. The bacteria velocity (Vb) is linear with the flagella rotation frequency. The phase velocity of the flagella Vf ~ 2Vb in LC, as compared to Vf ~ 10Vb in water. The flow generated by the bacteria is localized along the bacterial body axis, decaying slowly over tens of micrometers along, but rapidly over a few micrometers across this axis. The concentrated flow grants the bacteria new ability to carry cargo particles in LC, ability not seen in their habitat isotropic media. We attribute these anomalous features to the anisotropy of viscosity of the CLC, namely, the viscosities of splay and twist is hundreds times higher than that of bend deformation, which provides extra boost of swimming efficiency and enables the bacteria swim at considerable speed in a viscous medium. Our findings can potentially lead to applications such as particle transportation in microfluidic devices. A.S and I.A are supported by the US DOE, Office of Science, BES, Materials Science and Engineering Division. S.Z. and O.D.L are supported by NSF DMR 1104850, DMS-1434185.

  13. On the theory and simulation of confined liquid crystals

    CERN Document Server

    Andrienko, D

    2001-01-01

    cylindrical symmetry of the core is broken and two defects of strength +1/2 may be resolved. We use molecular dynamics to study the ordering of a nematic liquid crystal around a spherical particle or droplet. We observe three defect structures for different particle sizes: a quadrupolar one with a ring defect surrounding the particle in the equatorial plane; a dipolar one with a satellite defect at the north or south pole; and a transitional, non-equatorial, ring defect. By studying density and order-parameter maps, we are able to examine behavior near the particle surface, and in the disclination core region, where the elastic theory is inapplicable. We present the results of molecular dynamics simulations of the topological defects that appear around an elongated colloidal particle. We also study the force and the torque on the particle suspended in the bulk of the nematic mesophase and modification of this torque when the particle is close to the cell substrate. In this thesis, we investigate several aspec...

  14. On a non-isothermal model for nematic liquid crystals

    International Nuclear Information System (INIS)

    A model describing the evolution of a liquid crystal substance in the nematic phase is investigated in terms of three basic state variables: the absolute temperature thetav, the velocity field u and the director field d, representing preferred orientation of molecules in a neighbourhood of any point of a reference domain. The time evolution of the velocity field is governed by the incompressible Navier–Stokes system, with a non-isotropic stress tensor depending on the gradients of the velocity and of the director field d, where the transport (viscosity) coefficients vary with temperature. The dynamics of d is described by means of a parabolic equation of Ginzburg–Landau type, with a suitable penalization term to relax the constraint |d| = 1. The system is supplemented by a heat equation, where the heat flux is given by a variant of Fourier's law, depending also on the director field d. The proposed model is shown to be compatible with first and second laws of thermodynamics, and the existence of global-in-time weak solutions for the resulting PDE system is established, without any essential restriction on the size of the data

  15. Dielectric Properties of Nematic Liquid Crystal Modified with Diamond Nanoparticles

    International Nuclear Information System (INIS)

    In the present study, the influence of diamond nanoparticles (DNPs) on dielectric properties of nematic liquid crystal (LC) E7 from Merck has been considered. It is established that the insertion of DNPs leads to an increase in the dielectric constant ε' as well as to a significant change in the electric conductivity σ of the LC. The growth of ε' with the concentration of DNPs, CDNP, is mainly caused by a contribution of the DNP permittivity to the effective permittivity of the composite. The character of the σ(CDNP) curves depends on the ionic purity of LC E7: for the samples based on pure E7, an increase of the electric conductivity with the concentration of DNPs is detected, whereas the reverse trend is observed for the samples containing impure E7. This behavior is attributed to the competitive adsorption and desorption of ions on/from the surface of DNPs and the ion transfer along the percolation network of these particles.

  16. Molecular simulation of chevrons in confined smectic liquid crystals

    Science.gov (United States)

    Webster, Richard E.; Mottram, Nigel J.; Cleaver, Douglas J.

    2003-08-01

    Chevron structures adopted by confined smectic liquid crystals are investigated via molecular dynamics simulations of the Gay-Berne model. The chevrons are formed by quenching nematic films confined between aligning planar substrates whose easy axes have opposing azimuthal components. When the substrates are perfectly smooth, the chevron formed migrates rapidly towards one of the confining walls to yield a tilted layer structure. However, when substrate roughness is included, by introducing a small-amplitude modulation to the particle-substrate interaction well depth, a symmetric chevron is formed which remains stable over sufficiently long run times for detailed structural information, such as the relevant order parameters and director orientation, to be determined. For both smooth and rough boundaries, the smectic order parameter remains nonzero across the entire chevron, implying that layer identity is maintained across the chevron tip. Also, when the surface-stabilized chevron does eventually revert to a tilted layer structure, it does so via surface slippage, such that layer integrity is maintained throughout the chevron to tilted layer relaxation process.

  17. On the critical behaviour of two-dimensional liquid crystals

    Directory of Open Access Journals (Sweden)

    A.l. Fariñas-Sánchez

    2010-01-01

    Full Text Available The Lebwohl-Lasher (LL model is the traditional model used to describe the nematic-isotropic transition of real liquid crystals. In this paper, we develop a numerical study of the temperature behaviour and of finite-size scaling of the two-dimensional (2D LL-model. We discuss two possible scenarios. In the first one, the 2D LL-model presents a phase transition similar to the topological transition appearing in the 2D XY-model. In the second one, the 2D LL-model does not exhibit any critical transition, but its low temperature behaviour is rather characterized by a crossover from a disordered phase to an ordered phase at zero temperature. We realize and discuss various comparisons with the 2D XY-model and the 2D Heisenberg model. Having added finite-size scaling behaviour of the order parameter and conformal mapping of order parameter profile to previous studies, we analyze the critical scaling of the probability distribution function, hyperscaling relations and stiffness order parameter and conclude that the second scenario (no critical transition is the most plausible.

  18. High Chromaticity Aluminum Plasmonic Pixels for Active Liquid Crystal Displays.

    Science.gov (United States)

    Olson, Jana; Manjavacas, Alejandro; Basu, Tiyash; Huang, Da; Schlather, Andrea E; Zheng, Bob; Halas, Naomi J; Nordlander, Peter; Link, Stephan

    2016-01-26

    Chromatic devices such as flat panel displays could, in principle, be substantially improved by incorporating aluminum plasmonic nanostructures instead of conventional chromophores that are susceptible to photobleaching. In nanostructure form, aluminum is capable of producing colors that span the visible region of the spectrum while contributing exceptional robustness, low cost, and streamlined manufacturability compatible with semiconductor manufacturing technology. However, individual aluminum nanostructures alone lack the vivid chromaticity of currently available chromophores because of the strong damping of the aluminum plasmon resonance in the visible region of the spectrum. In recent work, we showed that pixels formed by periodic arrays of Al nanostructures yield far more vivid coloration than the individual nanostructures. This progress was achieved by exploiting far-field diffractive coupling, which significantly suppresses the scattering response on the long-wavelength side of plasmonic pixel resonances. In the present work, we show that by utilizing another collective coupling effect, Fano interference, it is possible to substantially narrow the short-wavelength side of the pixel spectral response. Together, these two complementary effects provide unprecedented control of plasmonic pixel spectral line shape, resulting in aluminum pixels with far more vivid, monochromatic coloration across the entire RGB color gamut than previously attainable. We further demonstrate that pixels designed in this manner can be used directly as switchable elements in liquid crystal displays and determine the minimum and optimal numbers of nanorods required in an array to achieve good color quality and intensity. PMID:26639191

  19. Chiralization and ferroelectric state induction in nanostructured liquid crystals

    Science.gov (United States)

    Katranchev, B.; Petrov, M.; Rafailov, P. M.; Todorov, N.

    2016-02-01

    The liquid crystals (LC), due to their naturally high bulk ordering, strong birefringence and easy electrooptical driving, serve as matrix in the nanocomposites doped with non-mesogenic or mesogenic nanoparticles. The nanocomposite's structural units exhibit very complex molecular form indicating the strength and the intermolecular interaction between the matrix and dopant's molecules. Hydrogen bonds are of particular significance for the formation of the nanocomposite structural units, since the symmetry of the LC nanocomposite could be controlled and controllably decreased due to the acceptor-donor interaction between the dimeric matrix and the dopants. As a result, the LC nanocomposite can reach the lowest symmetry, known as triclinic - C1. Using the LC p,n-alkyloxybensoic acids (nOBA) in form of hydrogen-bonded dimers as matrix and non-mesogenics - single walls carbon nanotubes (SWCNT), perfluorooctanoic acid (PFOA), 4-hydrooxypiridin (HOPY) or mesogen - cholesteryl benzoate (ChB) as dopants and choosing optimal concentrations (where the typical LC state was preserved), we obtained nanocomopsites 7OBA/SWCNT, 7OBA/PFOA, 9OBA/HOPY and 8OBA/ChB. We indicate two forms of ferroelectricity in the studied nanocomposites: developable ferroelectricity, characteristic for the 9OBA/HOPY, 7OBA/PFOA compounds and developed ferroelectricity characteristic for 8OBA/SWCNT, 8OBA/ChB.

  20. Rheological properties of a reentrant nematic liquid crystal.

    Science.gov (United States)

    Ananthaiah, J; Rajeswari, M; Sastry, V S S; Dabrowski, R; Dhara, Surajit

    2012-07-01

    We report experimental studies on small angle light scattering (SALS), and rheodielectric and electrorheological properties of a binary mixture of octyloxy cyanobiphenyl and hexyloxy cyanobiphenyl liquid crystals. The mixture exhibits nematic (N) to smectic-A (SmA) phase transitions, and then again to a reentrant nematic (N(R)) phase transition. Rapid shear thinning in the quenched samples in the low shear rate region in the N and SmA phases observed from SALS experiments is attributed to the realignment of the director within the domains. The domains are elongated along the shear direction at higher shear rates. The temperature variation of the effective viscosity and static dielectric constant reveals the changes in the director orientation across N-SmA-N(R) phase transitions. At a steady shear rate the effective viscosity increases with the electric field in all the phases and saturates at much higher fields. It also exhibits two anomalous peaks across N-SmA-N(R) phase transitions beyond a particular field. The shear modulus of the SmA phase in an intermediate field is significantly larger than that measured at both low and high fields. This enhanced viscoelasticity of the SmA phase is argued to originate from the increased dislocation density. PMID:23005440

  1. Rheological properties of a reentrant nematic liquid crystal

    Science.gov (United States)

    Ananthaiah, J.; Rajeswari, M.; Sastry, V. S. S.; Dabrowski, R.; Dhara, Surajit

    2012-07-01

    We report experimental studies on small angle light scattering (SALS), and rheodielectric and electrorheological properties of a binary mixture of octyloxy cyanobiphenyl and hexyloxy cyanobiphenyl liquid crystals. The mixture exhibits nematic (N) to smectic-A (SmA) phase transitions, and then again to a reentrant nematic (NR) phase transition. Rapid shear thinning in the quenched samples in the low shear rate region in the N and SmA phases observed from SALS experiments is attributed to the realignment of the director within the domains. The domains are elongated along the shear direction at higher shear rates. The temperature variation of the effective viscosity and static dielectric constant reveals the changes in the director orientation across N-SmA-NR phase transitions. At a steady shear rate the effective viscosity increases with the electric field in all the phases and saturates at much higher fields. It also exhibits two anomalous peaks across N-SmA-NR phase transitions beyond a particular field. The shear modulus of the SmA phase in an intermediate field is significantly larger than that measured at both low and high fields. This enhanced viscoelasticity of the SmA phase is argued to originate from the increased dislocation density.

  2. Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

    Energy Technology Data Exchange (ETDEWEB)

    Awwal, A; Bauman, B; Gavel, D; Olivier, S; Jones, S; Hardy, J L; Barnes, T; Werner, J S

    2003-02-05

    Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.

  3. Treating amblyopia with liquid crystal glasses: a pilot study.

    Science.gov (United States)

    Spierer, Abraham; Raz, Judith; Benezra, Omry; Herzog, Rafi; Cohen, Evelyne; Karshai, Ilana; Benezra, David

    2010-07-01

    PURPOSE. To evaluate the use of liquid crystal glasses (LCG) for the treatment of amblyopia caused by refractive errors, strabismus, or both. METHODS. In this noncomparative, prospective, interventional case series, 28 children (age range, 4-7.8 years) with monocular amblyopia participated, of which 24 completed the study. In the LCG, the occluding and nonoccluding phases of the flicker were electronically set in all patients at a fixed rate. The rate was set so that accumulated occlusion was 5 hours during 8 hours' weartime. Occlusion was applied only to the good eye. All 24 children were followed up regularly for 9 months. Best corrected VA for distance and near, fixation patterns, and binocular function were measured. VA for distance was measured with the Snellen chart and for near with the Rossano/Weiss chart. RESULTS. Mean VA for distance at the end of the study (after 9 months) was 0.59 (SD, 0.16) compared with 0.27 (SD, 0.09) at the beginning (P compliance was defined as wearing the LCG for at least 8 hours per day.) Stereopsis at the end of treatment was good (better than 60 sec arc) in 21% of the children compared with 8% at the beginning. No serious adverse events were recorded. CONCLUSIONS. The use of LCG in patients with amblyopia yielded an improvement in near and distance VA and in stereopsis. Treatment was well accepted by children and parents. PMID:20164454

  4. A liquid-crystal-based DNA biosensor for pathogen detection

    Science.gov (United States)

    Khan, Mashooq; Khan, Abdur Rahim; Shin, Jae-Ho; Park, Soo-Young

    2016-03-01

    A liquid-crystal (LC)-filled transmission electron microscopy (TEM) grid cell coated with the cationic surfactant dodecyltrimethylammonium bromide (DTAB), to which a single-stranded deoxyribonucleic acid probe (ssDNAprobe) was adsorbed at the LC/aqueous interface (TEMDTAB/DNA), was applied for the highly specific detection of target DNA molecules. The DTAB-coated E7 (used LC mixture) in the TEM grid (TEMDTAB) exhibited a homeotropic orientation, and changed to a planar orientation upon adsorption of the ssDNAprobe. The TEMDTAB/DNA was then exposed to complementary (target) ssDNA, which resulted in a planar-to-homeotropic configurational change of E7 that could be observed through a polarized optical microscope under crossed polarizers. The optimum adsorption density (2 μM) of ssDNAprobe enabled the detection of ≥0.05 nM complementary ssDNA. This TEMDTAB/DNA biosensor could differentiate complementary ssDNA from mismatched ssDNA as well as double-stranded DNA. It also successfully detected the genomic DNAs of the bacterium Erwinia carotovora and the fungi Rhazictonia solani. Owe to the high specificity, sensitivity, and label-free detection, this biosensor may broaden the applications of LC-based biosensors to pathogen detection.

  5. Feedback control of flow alignment in sheared liquid crystals

    Science.gov (United States)

    Strehober, David A.; Schöll, Eckehard; Klapp, Sabine H. L.

    2013-12-01

    Based on a continuum theory, we investigate the manipulation of the nonequilibrium behavior of a sheared liquid crystal via closed-loop feedback control. Our goal is to stabilize a specific dynamical state, that is, the stationary "flow alignment," under conditions where the uncontrolled system displays oscillatory director dynamics with in-plane symmetry. To this end we employ time-delayed feedback control (TDFC), where the equation of motion for the ith component qi(t) of the order parameter tensor is supplemented by a control term involving the difference qi(t)-qi(t-τ). In this diagonal scheme, τ is the delay time. We demonstrate that the TDFC method successfully stabilizes flow alignment for suitable values of the control strength K and τ; these values are determined by solving an exact eigenvalue equation. Moreover, our results show that only small values of K are needed when the system is sheared from an isotropic equilibrium state, contrary to the case where the equilibrium state is nematic.

  6. Hydrodynamics of Inclusions in Freely Suspended Liquid Crystal Films

    Science.gov (United States)

    Qi, Zhiyuan

    Hydrodynamic interaction of pairs of circular inclusions in two-dimensional (2D), fluid smectic membranes suspended in air has been studied systematically. By analyzing their Brownian motion, it is found that the radial mutual mobilities of identical inclusions are independent of their size but that the angular coupling becomes strongly size-dependent when their radius exceeds a characteristic hydrodynamic length. These observations are described well for arbitrary inclusion separations by a model that generalizes the Levine/MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. Beyond that, 2D flow fields generated by a rigid, oscillating post inserted in the film have been measured by analyzing the motion of tracer particles and provide a detailed understanding of the hydrodynamic behavior in the film/gas system. The Brownian diffusion of micron-scale inclusions in freely suspended smectic A liquid crystal films a few nanometers thick and several millimeters in diameter depends strongly on the air surrounding the film. Near atmospheric pressure, the three-dimensionally coupled film/gas system is well described by Hughes/Pailthorpe/White hydrodynamic theory but at lower pressure, the diffusion coefficient increases substantially, tending in high vacuum toward the two-dimensional limit where it is determined by film size. In the absence of air, the films are found to be a nearly ideal physical realization of a two-dimensional, incompressible Newtonian fluid.

  7. High Thermal and Electrical Tunability of Negative Dielectric Liquid Crystal Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Wei, Lei; Scolari, Lara; Weirich, Johannes;

    2008-01-01

    We infiltrate photonic crystal fibers with negative dielectric liquid crystals. 400nm bandgap shift is obtained in the range 22ºC-80ºC and 119nm shift of the long-wavelength bandgap edge is achieved by applying a voltage of 200V.......We infiltrate photonic crystal fibers with negative dielectric liquid crystals. 400nm bandgap shift is obtained in the range 22ºC-80ºC and 119nm shift of the long-wavelength bandgap edge is achieved by applying a voltage of 200V....

  8. Thermally Driven Photonic Actuator Based on Silica Opal Photonic Crystal with Liquid Crystal Elastomer.

    Science.gov (United States)

    Xing, Huihui; Li, Jun; Shi, Yang; Guo, Jinbao; Wei, Jie

    2016-04-13

    We have developed a novel thermoresponsive photonic actuator based on three-dimensional SiO2 opal photonic crystals (PCs) together with liquid crystal elastomers (LCEs). In the process of fabrication of such a photonic actuator, the LCE precursor is infiltrated into the SiO2 opal PC followed by UV light-induced photopolymerization, thereby forming the SiO2 opal PC/LCE composite film with a bilayer structure. We find that this bilayer composite film simultaneously exhibits actuation behavior as well as the photonic band gap (PBG) response to external temperature variation. When the SiO2 opal PC/LCE composite film is heated, it exhibits a considerable bending deformation, and its PBG shifts to a shorter wavelength at the same time. In addition, this actuation is quite fast, reversible, and highly repeatable. The thermoresponsive behavior of the SiO2 opal PC/LCE composite films mainly derives from the thermal-driven change of nematic order of the LCE layer which leads to the asymmetric shrinkage/expansion of the bilayer structure. These results will be of interest in designing optical actuator systems for environment-temperature detection. PMID:26996608

  9. Some problems of the statistical theory of polymeric lyotropic liquid crystals

    International Nuclear Information System (INIS)

    In this article we consider some topics of the statistical physics of liquid-crystalline phase in the solutions of stiff chain macromolecules. Among these topics are: the problem of the phase diagram for the liquid-crystalline transition in the solutions of completely stiff macromolecules (rigid rods); conditions of formation of the liquid-crystalline phase in the solutions of semiflexible macromolecules; possibility of the intramolecular liquid-crystalline ordering in semiflexible macromolecules; structure of intramolecular liquid crystals and dependence of the properties of the liquid-crystalline phase on the microstructure of the polymer chain. (author)

  10. Tunable Fabry-Pérot filter based on one-dimensional photonic crystals with liquid crystal components

    Science.gov (United States)

    Cos, J.; Ferre-Borrull, J.; Pallares, J.; Marsal, L. F.

    2009-03-01

    A theoretical study of a tunable Fabry-Pérot multilayer structure composed of alternating layers of silicon and liquid crystal is presented and analyzed. The structure possesses two resonant frequencies within the stop band with tunable wavelengths and transmission properties. Tuning is achieved by allowing different orientations of the liquid crystal optical axes within the cavity and within the mirrors, while keeping the optical axes parallel to the layers. Applying the transfer matrix method for thin layers of anisotropic materials we demonstrate that the resonant wavelengths depend on the difference between the liquid crystal optical axis orientations. Besides, we are able to obtain a complete characterization of the structure in the form of its Jones matrix. From this, we propose an optical two-channel equalizer for applications around 1.55 μm that allows tuning the two resonant wavelengths and their relative amplitude levels.

  11. Rebirth of Liquid Crystals for Sensoric Applications: Environmental and Gas Sensors

    Directory of Open Access Journals (Sweden)

    P. V. Shibaev

    2015-01-01

    Full Text Available Films and droplets of liquid crystals may soon become an essential part of sensitive environmental sensors and detectors of volatile organic compounds (VOCs in the air. In this paper a short overview of recent progress in the area of sensors based on liquid crystals is presented, along with the studies of low molar mass liquid crystals as gas sensors. The detection of VOCs in the air may rely on each of the following effects sequentially observed one after the other: (i slight changes in orientation and order parameter of liquid crystal, (ii formation of bubbles on the top of the liquid crystalline droplet, and (iii complete isotropisation of the liquid crystal. These three stages can be easily monitored by a photo camera and/or optical microscopy. Detection limits corresponding to the first stage are typically lower by a factor of at least 3–6 than detection limits corresponding to isotropisation. The qualitative model taking into account the reorientation of liquid crystals is presented to account for the observed changes.

  12. Thermal Analysis, Mechanical and Rheological Behaviour of Melt Manufactured Polyethylene/Liquid Crystal Polymer Blends

    Directory of Open Access Journals (Sweden)

    Ilze ELKSNITE

    2011-07-01

    Full Text Available Modification of properties of conventional thermoplastics with thermotropic liquid crystal polymers, from one hand, allows decrease their viscosities, substantially facilitating processing conditions, and, from another hand, allows increase their exploitation properties. Orientation of the labile structure of liquid crystal polymer in extrusion or injection moulding causes specific reinforcement (so-called self-reinforcement to occur in the blends containing liquid crystal polymer. Up to now the effect of self-reinforcement is mostly investigated in the blends, containing considerable amount of liquid crystal polymer. In this research the effect of minor amounts of liquid crystalline co-polyester modifier on the properties of polyethylene is investigated. Various compositions of laboratory synthesized hydroxybenzoic acid /polyethylene terephtalate copolymer containing polyethylene composites have been manufactured by thermoplastic blending. It has been observed that 1 modulus of elasticity, yield strength and ultimate strength increase with raising the content of liquid crystalline modifier; 2 void content in the investigated polyethylene/liquid crystal copolymer composites is not greater that 1 %; 3 addition of liquid crystalline co-polyester modifier improves arrangement of PE crystalline phase.http://dx.doi.org/10.5755/j01.ms.17.2.483

  13. Liquid Crystals: Alignment and Graphene-Assisted Decoration of Lyotropic Chromonic Liquid Crystals Containing DNA Origami Nanostructures (Small 12/2016).

    Science.gov (United States)

    Martens, Kevin; Funck, Timon; Kempter, Susanne; Roller, Eva-Maria; Liedl, Tim; Blaschke, Benno M; Knecht, Peter; Garrido, José Antonio; Zhang, Bingru; Kitzerow, Heinz

    2016-03-01

    On page 1658, H. Kitzerow and co-workers show that stable dispersion of the nanostructures in a liquid crystal and uniform alignment of the resulting composite are possible. DNA origami nanostructures decorated with gold nanoparticles (inset: TEM image) are dispersed in a uniformly aligned liquid crystal (background: image observed by polarizing microscopy). The unusual optical properties of such plasmonic nanostructures - for example a large circular dichroism in the case of the nanohelix - are expected to be enhanced if the nanostructures are uniformly aligned. PMID:27000497

  14. Spectroscopic and morphological investigation of conjugated photopolymerisable quinquethiophene liquid crystals

    KAUST Repository

    McGlashon, Andrew J.

    2012-09-01

    3′-methyl-(5,5′′-bis[3-ethyl-3-(6-phenyl-hexyloxymethyl) -oxetane])-2,2′:5′,2′′-terthiophene (5T(Me)Ox) is a solution processable small molecule semiconductor displaying smectic-C and nematic liquid crystal phases. The pendant oxetane group can be polymerized in situ in the presence of a suitable photoacid at concentrations ≥1% by weight. Spin-coated films of pure 5T(Me)Ox and 5T(Me)Ox doped with the soluble photoacid were characterized by absorption and photoluminescent spectroscopy. Thick pristine films showed absorption and emission from a crystalline phase. Thin monolayer (<5 nm) films, as well as thicker photoacid doped films, instead showed absorption from an H-aggregate phase and emission from an excimer. Optical microscopy showed a significant change in film structure upon addition of the photoacid; large and well-orientated crystals being replaced by much smaller domains which appear to vary in thickness. Grazing Incidence Wide Angle X-Ray Scattering (GIWAXS) was used to characterize the packing and orientation of molecules in the crystalline and doped samples. The results are consistent with the photoacid doped samples forming layers of H-aggregate phase monolayer sheets parallel to the substrate where the photoacid inhibits the transition into the three-dimensionally ordered crystalline phase. Field-effect transistors and light emitting diodes were constructed incorporating 5T(Me)Ox as the active layer. Pure 5T(Me)Ox field-effect transistors showed good, p-type device characteristics, but the morphological changes upon doping result in a loss of transistor action. In the diodes, curing through melting and exposure to UV light followed by photoacid removal resulted in an increase in current density but a decrease in light emission. These results indicate that the presence of the photoacid (≥1% by weight) can have a dramatic effect on the structure, morphology and device performance of ordered, photopatternable materials for organic

  15. Derivation of a three-dimensional phase-field-crystal model for liquid crystals from density functional theory

    OpenAIRE

    Wittkowski, Raphael; Löwen, Hartmut; Brand, Helmut R.

    2010-01-01

    Using a generalized order parameter gradient expansion within density functional theory, we derive a phase-field-crystal model for liquid crystals composed by apolar particles in three spatial dimensions. Both the translational density and the orientational direction and ordering are included as order parameters. Different terms involving gradients in the order parameters in the resulting free energy functional are compared to the macroscopic Ginzburg-Landau approach as well as to the hydrody...

  16. Carbon/Liquid Crystal Polymer Prepreg for Cryogenic and High-Temp Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — KaZaK Composites proposes to develop a pultrusion process to produce carbon fiber / liquid crystal polymer (LCP) prepreg, a first for this category of materials and...

  17. Electrically tunable refractive index in the dark conglomerate phase of a bent-core liquid crystal

    Science.gov (United States)

    Nagaraj, M.; Görtz, V.; Goodby, J. W.; Gleeson, H. F.

    2014-01-01

    Here we report an electrically tunable refractive index observed in an isotropic liquid crystal phase known as the dark conglomerate (DC) phase. This unusual change in the refractive index which has not been reported before in the DC phase of other bent-core liquid crystals occurs because of a series of electric-field-driven transformations that take place in the DC phase of the studied bent-core liquid crystal. These transformations give rise to a decrease in the refractive index of the system, when an electric field is applied across the device, and no change in the birefringence is seen during such behavior. The electro-optic phenomenon is described in detail and the possibility of exploiting this for a number of liquid crystal based device applications is discussed.

  18. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    Science.gov (United States)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm‑2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm‑2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  19. Orientational fluctuation study in nematic liquid crystals by high speed micrograph

    Science.gov (United States)

    Yoon, Beom-Jin; Park, Min Sang; Park, Jung O.; Srinivasarao, Mohan

    2009-03-01

    The orientational fluctuations in uniaxial and biaxial nematic liquid crystals were investigated with a polarized microscope and a high speed TV camera. Liquid crystals usually have fluctuations with respect to their director, even when the molecular axes tend to be aligned to each other. These fluctuations are sufficiently slow and large, have long wave length and increase with temperature. Herein, we describe our study on fluctuation dynamics by direct observations in real space, while it has been typically done by the photon scattering in reciprocal space. The twinkling of liquid crystals due to orientational fluctuations was observed with a high speed camera up to 500 frames/sec. The time correlation function of the intensity was computed via 2D spatial Fourier transform of each image and then the relaxation frequency was estimated from it. The elastic constant to the viscosity ratio was computed from the relaxation frequency. This approach provides facile route to analyze fluctuation dynamics in liquid crystals.

  20. Controlling the volatility of the written optical state in electrochromic DNA liquid crystals

    Science.gov (United States)

    Liu, Kai; Varghese, Justin; Gerasimov, Jennifer Y.; Polyakov, Alexey O.; Shuai, Min; Su, Juanjuan; Chen, Dong; Zajaczkowski, Wojciech; Marcozzi, Alessio; Pisula, Wojciech; Noheda, Beatriz; Palstra, Thomas T. M.; Clark, Noel A.; Herrmann, Andreas

    2016-05-01

    Liquid crystals are widely used in displays for portable electronic information display. To broaden their scope for other applications like smart windows and tags, new material properties such as polarizer-free operation and tunable memory of a written state become important. Here, we describe an anhydrous nanoDNA-surfactant thermotropic liquid crystal system, which exhibits distinctive electrically controlled optical absorption, and temperature-dependent memory. In the liquid crystal isotropic phase, electric field-induced colouration and bleaching have a switching time of seconds. Upon transition to the smectic liquid crystal phase, optical memory of the written state is observed for many hours without applied voltage. The reorientation of the DNA-surfactant lamellar layers plays an important role in preventing colour decay. Thereby, the volatility of optoelectronic state can be controlled simply by changing the phase of the material. This research may pave the way for developing a new generation of DNA-based, phase-modulated, photoelectronic devices.

  1. Effect of polymer structures on electro-optical properties of polymer stabilized liquid crystal films

    Institute of Scientific and Technical Information of China (English)

    Shoulian WANG; Jie HE; Yu ZENG; Bin YAN; Yinghan WANG

    2008-01-01

    The polymer stabilized liquid crystal (PSLC) film is a relatively novel electro-optical material,which is generally obtained by dissolving a small amount of a bifunctional photoreactive monomer in a low molecular mass liquid crystal.In this paper,the PSLC films were prepared with photoreactive biphenyl methacrylate monomers by photopolymerization induced phase sepa-ration.The effects of liquid crystal concentration,curing time,monomer structures and alignment layer on the elec-tro-optical-properties of PSLC films were investigated.The results show that the transmittance in the OFF state (TOFF) increased with the liquid crystal concentration,but the driving voltage decreased.TOFF was also influenced by the curing time.Furthermore,when polyimide was used as alignment layer,the films prepared from the bifunctional monomer shows a higher TOFF,while those from the single functional monomer exhibited a deformed electro-optical curve due to the unsteady polymer net-works.

  2. Alignment of liquid crystal on a polyimide surface exposed to an Ar ion beam

    International Nuclear Information System (INIS)

    In this paper properties of nematic liquid crystals aligned on polyimide surfaces exposed to a low-energy Ar ion beam are investigated. We studied how the pretilt angle of a liquid crystal cell is affected by ion-beam conditions, such as the energy of the incident ions, the angle of incidence, and the exposure time. X-ray photoelectron spectroscopy data indicate that ion-beam exposure changes the chemical bonding states of the polyimide surface, which may be one of the main causes of anisotropic liquid crystal alignment. We also found that twisted-nematic cells fabricated by the ion-beam alignment method have the voltage holding time enough for application to thin-film-transistor liquid crystal displays

  3. Poly(esterimide) bearing azobenzene units as photoaligning layer for liquid crystals

    Science.gov (United States)

    Węgłowski, Rafał; Piecek, Wiktor; Kozanecka-Szmigiel, Anna; Konieczkowska, Jolanta; Schab-Balcerzak, Ewa

    2015-11-01

    The custom synthesized azobenzene side-chain poly(esterimide) was used as an aligning material for nematic liquid crystal molecules. The anisotropy of the poly(esterimide) layer was generated by a linearly polarized UV light, as a consequence of multiple trans-cis-trans isomerization cycles. The photoalignment effect was studied by assembling a twisted nematic cell with a proper liquid crystal mixture and geometry to fulfill Mauguin's limit. The polarizing microscope pictures of the fabricated cells confirmed the twisted arrangement of liquid crystal molecules. The results of electro-optic measurements indicated a stronger anchoring of the liquid crystal molecules by photoaligned poly(esterimide) than that obtained in the case of a rubbed polyimide.

  4. Doped ionic liquid crystals as effective weakly alignment media for polar solutes

    Science.gov (United States)

    Di Pietro, Maria Enrica; Celebre, Giorgio; De Luca, Giuseppina

    2016-06-01

    The ionic liquid crystal 1-dodecyl-3-methylimidazolium tetrafluoroborate slightly doped with water is presented as a promising NMR alignment medium for the measurement of residual dipolar couplings for polar molecules dissolved therein.

  5. Coaxial electrospinning of liquid crystal-containing poly(vinylpyrrolidone microfibres

    Directory of Open Access Journals (Sweden)

    Eva Enz

    2009-10-01

    Full Text Available With the relatively new technique of coaxial electrospinning, composite fibres of poly(vinylpyrrolidone with the liquid crystal 4-cyano-4′-octylbiphenyl in its smectic phase as core material could be produced. The encapsulation leads to remarkable confinement effects on the liquid crystal, inducing changes in its phase sequence. We conducted a series of experiments to determine the effect of varying the relative flow rates of inner and outer fluid as well as of the applied voltage during electrospinning on these composite fibres. From X-ray diffraction patterns of oriented fibres we could also establish the orientation of the liquid crystal molecules to be parallel to the fibre axis, a result unexpected when considering the viscosity anisotropy of the liquid crystal kept in its smectic phase during electrospinning.

  6. Versatile alignment layer method for new types of liquid crystal photonic devices

    International Nuclear Information System (INIS)

    Liquid crystal photonic devices are becoming increasingly popular. These devices often present a challenge when it comes to creating a robust alignment layer in pre-assembled cells. In this paper, we describe a method of infusing a dye into a microcavity to produce an effective photo-definable alignment layer. However, previous research on such alignment layers has shown that they have limited stability, particularly against subsequent light exposure. As such, we further describe a method of utilizing a pre-polymer, infused into the microcavity along with the liquid crystal, to provide photostability. We demonstrate that the polymer layer, formed under ultraviolet irradiation of liquid crystal cells, has been effectively localized to a thin region near the substrate surface and provides a significant improvement in the photostability of the liquid crystal alignment. This versatile alignment layer method, capable of being utilized in devices from the described microcavities to displays, offers significant promise for new photonics applications

  7. Versatile alignment layer method for new types of liquid crystal photonic devices

    Energy Technology Data Exchange (ETDEWEB)

    Finnemeyer, V.; Bryant, D.; Lu, L.; Bos, P. [Liquid Crystal Institute, Kent State University, Kent, Ohio 44242 (United States); Reich, R.; Clark, H.; Berry, S.; Bozler, C. [MIT Lincoln Laboratory, 244 Wood St., Lexington, Massachusetts 02420 (United States); Yaroshchuk, O. [Institute of Physics, NAS of Ukraine, 44 Prospect Nauky, Kyiv 03680 (Ukraine)

    2015-07-21

    Liquid crystal photonic devices are becoming increasingly popular. These devices often present a challenge when it comes to creating a robust alignment layer in pre-assembled cells. In this paper, we describe a method of infusing a dye into a microcavity to produce an effective photo-definable alignment layer. However, previous research on such alignment layers has shown that they have limited stability, particularly against subsequent light exposure. As such, we further describe a method of utilizing a pre-polymer, infused into the microcavity along with the liquid crystal, to provide photostability. We demonstrate that the polymer layer, formed under ultraviolet irradiation of liquid crystal cells, has been effectively localized to a thin region near the substrate surface and provides a significant improvement in the photostability of the liquid crystal alignment. This versatile alignment layer method, capable of being utilized in devices from the described microcavities to displays, offers significant promise for new photonics applications.

  8. An integrated nematic liquid crystal in-fiber modulator derivates from capillary optical fiber

    Science.gov (United States)

    Guo, Xiaohui; Yang, Xinghua; Li, Song; Liu, Zhihai; Hu, Minggang; Qu, Bin; Yuan, Libo

    2016-05-01

    A novel liquid crystal integrated modulation-depth-adjustable in-fiber modulator is proposed. The liquid crystal is encapsulated in a specially designed capillary optical fiber with tubular structure. The experimental results show that the liquid crystal under the electric field can influence the light intensity in the tubular core of the fiber. The light at 632.8 nm in the circular waveguide can be modulated by only 2.71×10-2 nL of the liquid crystals under electric field. The wide range of modulation-depth from 23% to 50% can be obtained by adjusting the strength of the external electric field. In addition, the modulator shows good stability and repeatability. This work has great potentials in integrated in-fiber optical devices such as tunable modulators, optical switches and electric field sensors.

  9. Asymptotic Behavior of Solutions to the Liquid Crystals System in $\\mathbb{R}^3$

    CERN Document Server

    Dai, Mimi; Schonbek, Maria E

    2011-01-01

    In this paper we study the large time behavior of solutions to a nematic liquid crystals system in the whole space $\\mathbb{R}^3$. The fluid under consideration has constant density and small initial data.

  10. On Regularity Criteria for the Two-Dimensional Generalized Liquid Crystal Model

    Directory of Open Access Journals (Sweden)

    Yanan Wang

    2014-01-01

    Full Text Available We establish the regularity criteria for the two-dimensional generalized liquid crystal model. It turns out that the global existence results satisfy our regularity criteria naturally.

  11. 77 FR 3793 - Certain Liquid Crystal Display Devices, Including Monitors, Televisions, and Modules, and...

    Science.gov (United States)

    2012-01-25

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Liquid Crystal Display Devices, Including Monitors, Televisions, and Modules, and Components Thereof; Request for Statements on the Public Interest AGENCY: U.S. International Trade...

  12. Hydrodynamics of defects in nematic liquid crystal films

    International Nuclear Information System (INIS)

    In this thesis I propose a new theory to deal with the presence of a macroscopic density of defects or disclinations in two-dimensional systems of uniaxial nematic liquid crystal. The static part of the Abelian-Higgs model is the basis for a gauge covariant form of the Frank free energy for distortions in nematics, where the gauge field models the screening due to the presence of the defects. Certain results for vortices in the Abelian-Higgs model are reformulated for use in my theory. The model suggests disclinations with an isotropic core region. The covariant Frank free energy is used to derive a new form of the Ericksen-Leslie equations describing the hydrodynamics off nematics. These equations are set up according to the concept of thermodynamic fluxes and forces. Detailed analytic results are derived for the case where the dynamics is due to director reorientations, but no liquid flow. The hydrodynamic equations are reduced to dynamic equations for disclination points assuming a quasi-static motion in moduli space. The static form of the disclinations is based on solutions in the Bogomol'nyi limit, their quasi-static motion is induced through a deviation from this limit. The resulting equations are valid for a configuration containing disclinations with winding numbers of the same sign. These general equations require a, specific ansatz to yield further results. I consider two regimes, for defects close together and far apart from one another. A set of disclinations with winding numbers of the same sign which are close to one another, i.e. with overlapping cores, can result from disintegration of a larger disclination, and they repel one another. The results for this case predict how the disintegration could occur. The interaction of disclinations, with winding numbers of the same sign, which are far apart from one another is repulsive and decreases exponentially with the distances between them. Two such disclinations move on a straight line where their

  13. Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

    Directory of Open Access Journals (Sweden)

    Piero Morales

    2010-05-01

    Full Text Available Thin films of the discotic liquid crystal hexapentyloxytriphenylene (HAT5, prepared from solution via casting or spin-coating, were investigated by atomic force microscopy and polarizing optical microscopy, revealing large-scale ordered structures substantially different from those typically observed in standard samples of the same material. Thin and very long fibrils of planar-aligned liquid crystal were found, possibly formed as a result of an intermediate lyotropic nematic state arising during the solvent evaporation process. Moreover, in sufficiently thin films the crystallization seems to be suppressed, extending the uniform order of the liquid crystal phase down to room temperature. This should be compared to the bulk situation, where the same material crystallizes into a polymorphic structure at 68 °C.

  14. All-optical switching of diffraction gratings infiltrated with dye-doped liquid crystals

    Science.gov (United States)

    Lucchetta, D. E.; Vita, F.; Simoni, F.

    2010-12-01

    We report the realization and the characterization of an all-optical switching device based on a transmission grating recorded in a polymeric substrate infiltrated with a methyl red-doped liquid crystal. The properties of this highly nonlinear mixture are exploited to modulate the diffraction of the grating by a pump beam when a static electric field is applied. The behavior of the device is in agreement with the existing model for methyl red-doped liquid crystals.

  15. CARS polarized microscopy of three-dimensional director structures in liquid crystals

    CERN Document Server

    Kachynski, A V; Prasad, P N; Smalyukh, I I

    2007-01-01

    We demonstrate three-dimensional vibrational imaging of director structures in liquid crystals using coherent anti-Stokes Raman scattering (CARS) polarized microscopy. Spatial mapping of the structures is based on sensitivity of a polarized CARS signal to orientation of anisotropic molecules in liquid crystals. As an example, we study structures in a smectic material and demonstrate that single-scan CARS and two-photon fluorescence images of molecular orientation patterns are consistent with each other and with the structure model.

  16. Modeling and experimental verification of infusion speed of liquids in photonic crystal fibers

    DEFF Research Database (Denmark)

    Sørensen, Thorkild; Noordegraaf, Danny; Nielsen, Kristian;

    A theoretical method for predicting infusion time of liquids in microcapillaries is formulated. Through a microscopical, a fluorescent, and, finally, through a reflectometric measurement method, the model is successfully verified in real photonic crystal fibers.......A theoretical method for predicting infusion time of liquids in microcapillaries is formulated. Through a microscopical, a fluorescent, and, finally, through a reflectometric measurement method, the model is successfully verified in real photonic crystal fibers....

  17. Transient Current Behaviour of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) Liquid Crystal Polymers

    Science.gov (United States)

    Yarramaneni, Sridharbabu; Sharma, Anu; Quamara, J. K.

    2011-07-01

    Transient current behaviour of pristine Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) Liquid crystal polymer which is a copolymer of poly ethylene terephthalate and poly p-hydroxybenzoic acid referred as PET/x.PHB polymer liquid crystals have been studied at different biasing electric fields ranging from 13 kV/cm to 104.3 kV/cm and at temperatures 120° C and 250° C for molar ratio x =0.8.

  18. Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

    OpenAIRE

    Piero Morales; Jan Lagerwall; Paolo Vacca; Sabine Laschat; Giusy Scalia

    2010-01-01

    Thin films of the discotic liquid crystal hexapentyloxytriphenylene (HAT5), prepared from solution via casting or spin-coating, were investigated by atomic force microscopy and polarizing optical microscopy, revealing large-scale ordered structures substantially different from those typically observed in standard samples of the same material. Thin and very long fibrils of planar-aligned liquid crystal were found, possibly formed as a result of an intermediate lyotropic nematic state arising d...

  19. Rheological study of structural transitions in triblock copolymers in a liquid crystal solvent

    OpenAIRE

    Kempe, Michael D.; Verduzco, Rafael; Scruggs, Neal R.; Kornfield, Julia A.

    2006-01-01

    Rheological properties of triblock copolymers dissolved in a nematic liquid crystal (LC) solvent demonstrate that their microphase separated structure is heavily influenced by changes in LC order. Nematic gels were created by swelling a well-defined, high molecular weight ABA block copolymer with the small-molecule nematic LC solvent 4-pentyl-4-cyanobiphenyl (5CB). The B midblock is a side-group liquid crystal polymer (SGLCP) designed to be soluble in 5CB and the A endblocks are polystyrene, ...

  20. 100 GHz electrically tunable planar Bragg gratings via liquid crystal overlay

    OpenAIRE

    Adikan, F.R.Mahamd; J.C.Gates; Snow, B.D.; Dyadyusha, A.; Major, H.E.; Gawith, C.B.E.; Kaczmarek, M.; P.G.R.Smith

    2007-01-01

    We demonstrate 114GHz electrically tunable liquid crystal Bragg gratings using 170Vpp voltage. The devices were made using direct UV grating writing and use evanescent coupling into an electrically tuned nematic liquid crystal. Reconfigurable integrated optical devices are essential in today's dense and complex telecommunication meshes. A commonly employed component on the silica platform fulfilling the above role is a planar Bragg grating. The ability to tune the reflection peak of these gra...