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Sample records for 5cb liquid crystal

  1. Photoluminescent Properties of Composites Based on the Liquid Crystal 5CB with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Bezrodna, T. V.; Klishevich, G. V.; Nesprava, V. V.; Melnyk, V. I.; Roshchin, A. N.; Skryshevskyi, Yu. A.

    2017-01-01

    We have studied the influence of inorganic particles on the photoluminescent properties of the nematic liquid crystal 5CB in composites based on carbon nanotubes (CNTs) and hybrid nanoparticles consisting of carbon nanotubes and platelets of the organically modified mineral montmorillonite (MMT). We show that the photoluminescence (PL) of 5CB + CNT composites is characterized by excimer emission of the 5CB molecules. Adding carbon nanotubes to the liquid crystal medium leads to a considerable decrease in the photoluminescence intensity, but has practically no effect on the bulk structural alignment in the organic matrix. Hybrid CNT-MMT particles form a uniform coagulation network in the composite with 5CB and significantly disrupt the nematic structure of the liquid crystal. Bent conformations of the 5CB molecules appear which are typical of the liquid crystal monomers. The presence of the indicated 5CB conformers in the system and also the weaker interaction between the liquid crystal and the inorganic filler explain the increase in the photoluminescence intensity for the composite 5CB + CNT-MMT compared with the emission characteristics for the original liquid crystal.

  2. Electric field-induced optical second harmonic generation in nematic liquid crystal 5CB

    NASA Astrophysics Data System (ADS)

    Torgova, S. I.; Shigorin, V. D.; Maslyanitsyn, I. A.; Todorova, L.; Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.

    2014-12-01

    Electric field-induced second harmonic generation (EFISH) was studied for the liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) (a nematic phase material at room temperature). The intensity of coherent SHG from 5CB cells upon DC electric field was measured for various initial orientations of the liquid crystal. The dependence of the SHG intensity on the pump beam incidence angle was obtained in transmission geometry using sample rotation method. The experimental results (the registered light intensity in the output SHG interference patterns) were theoretically modelled and analyzed.

  3. Regular structures in 5CB liquid crystals under the joint action of ac and dc voltages

    NASA Astrophysics Data System (ADS)

    Aguirre, Luis E.; Anoardo, Esteban; Éber, Nándor; Buka, Ágnes

    2012-04-01

    A nematic liquid crystal with high, positive dielectric anisotropy (5CB) has been studied under the influence of the combined action of a dc and an ac electric field. Broad frequency, voltage, and cell thickness ranges were considered. Pattern morphologies were identified; the thresholds and critical wave numbers were measured and analyzed as a function of frequency, dc-to-ac voltage ratio, and thickness. The current-voltage characteristics were simultaneously detected.

  4. Phase Diagram and Dynamics of the Liquid Crystal Isopentylcyanobiphenyl (5*CB)

    DTIC Science & Technology

    2011-05-03

    hf) are plotted versus reciprocal T in Figure 9, for the 0.1 MPa isobar and as a function of P for the four isotherms in Figure 10. The VFTH equation...CB. Themetastable cholesteric phase could be attained by an isobaric decrease of temperature or an isothermal increase of pressure. In the available...glass, cholesteric, and crystalline), and we show that the phase boundaries differ from previous reports, reflecting the slow crystallization kinetics of

  5. Confinement of 5CB Between Lyotropic Bilayers

    NASA Astrophysics Data System (ADS)

    Dolbashian, Cory; Mahmood, Rizwan; Bellini, Tommaso; Clark, Noel

    2013-03-01

    We report phase behavior of mixtures of 5CB (4-Cyano-4'-Pentyl-1, 1'-biphenyl), a calamitic thermotropic liquid crystal, with mixtures of the lyotropic double tailed cationic surfactant DDAB (diodecyldimethylammonium-bromide) and water. These mixtures had a fixed ratio of DDAB to water (75% / 25%) and 5CB concentrations ranging from 10% to 85%. Our preliminary phase diagram suggests transition from isotropic to lamellar phase having higher birefringence at higher DDAB concentration. We have also observed low vale of birefringence at lower DDAB concentration suggesting swelling of bilayers.

  6. Optical biosensor based on liquid crystal droplets for detection of cholic acid

    NASA Astrophysics Data System (ADS)

    Niu, Xiaofang; Luo, Dan; Chen, Rui; Wang, Fei; Sun, Xiaowei; Dai, Haitao

    2016-12-01

    A highly sensitive cholic acid biosensor based on 4-cyano-4‧-penthlbiphenyl (5CB) Liquid crystal droplets in phosphate buffer saline solution was reported. A radial-to-bipolar transition of 5CB droplet would be triggered during competitive reaction of CA at the sodium dodecyl sulfate surfactant-laden 5CB droplet surface. Our liquid crystal droplet sensor is a low-cost, simple and fast method for CA detection. The detection limit (5 μM) of our method is 2.4 times lower than previously report by using liquid crystal film to detection of CA.

  7. Charge transfer reactions in nematic liquid crystals

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R. |; Galili, T.; Levanon, H.

    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.

  8. Liquid Crystals

    NASA Technical Reports Server (NTRS)

    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.

  9. Optically responsive liquid crystal microfibers for display and nondisplay applications

    NASA Astrophysics Data System (ADS)

    Buyuktanir, Ebru A.; West, John L.; Frey, Margaret W.

    2011-03-01

    We demonstrate the fabrication and characterization of optically-tunable and stimuli-responsive electrospun microfibers endowed with liquid crystal (LC) functionality. The highly flexible LC microfibers are electrospun from a solution of 4- pentyl-4'-cyanobiphenyl (5CB) and polylactic acid (PLA) in chloroform/acetone solvent. In the electrospinning process, the low molecular weight 5CB phase-separates and self-assembles to form a planarly aligned nematic core within a PLA shell. Most importantly, the orientation of LC domains and, therefore, the optical properties of the 5CB/PLA fibers can be tuned by application of an external electric field. These properties of LC fibers may, in turn, be utilized to fabricate a variety of photonic textiles, and ultimately may introduce an entirely new manufacturing process where weaving will reach well beyond the roll-to-roll manufacturing envisioned for the currently emerging flexible displays printed on flexible plastic substrates.

  10. Liquid Crystal Devices.

    ERIC Educational Resources Information Center

    Bradshaw, Madeline J.

    1983-01-01

    The nature of liquid crystals and several important liquid crystal devices are described. Ideas for practical experiments to illustrate the properties of liquid crystals and their operation in devices are also described. (Author/JN)

  11. Liquid Crystal Inquiries.

    ERIC Educational Resources Information Center

    Marroum, Renata-Maria

    1996-01-01

    Discusses the properties and classification of liquid crystals. Presents a simple experiment that illustrates the structure of liquid crystals and the differences between the various phases liquid crystals can assume. (JRH)

  12. Understanding Atomic-Scale Behavior of Liquid Crystals at Aqueous Interfaces.

    PubMed

    Ramezani-Dakhel, Hadi; Sadati, Monirosadat; Rahimi, Mohammad; Ramirez-Hernandez, Abelardo; Roux, Benoît; de Pablo, Juan J

    2017-01-10

    The ordered environment presented by liquid crystals at interfaces enables a range of novel functionalities that is only now beginning to be exploited in applications ranging from light focusing devices to biosensors. One key feature of liquid crystals is that molecular events occurring at an interface propagate over large distances through the bulk. In spite of their importance, our fundamental understanding of liquid crystal-water and liquid crystal-air interfaces remains limited. In this work, we present results from large-scale atomistic molecular dynamics simulations on the organization of the nematic and isotropic phases of the nitrile-containing mesogenic molecule 4-cyano-4'-pentylbiphenyl (5CB) in the vicinity of vacuum and aqueous interfaces. Hybrid boundary conditions are imposed by confining 5CB films between vacuum and an aqueous medium to examine how those two types of interfaces influence the specific structural arrangement and ordering of 5CB. Consistent with experiments, our results indicate that 5CB exhibits homeotropic anchoring at the vacuum interface, and planar alignment at aqueous interfaces. Two-dimensional molecular dynamics potential of mean force calculations and average polarization densities show that the polar nitrile group of 5CB remains hydrated near the aqueous interface, where it modulates the orientation of water molecules. Estimates of the anchoring strength reveal an oscillatory decay and a semilinear decay with distance from the interface in vacuum and water, respectively.

  13. Effect of MWCNTs on the electro-optic properties of 5CB LC cells during the Freedericksz Transition

    NASA Astrophysics Data System (ADS)

    Eakle, Matthew; Georgiev, Georgi; Atherton, Timothy; Cebe, Peggy

    2014-03-01

    Multi-walled carbon nanotubes (MWCNTs) affect the electro-optic properties of liquid crystals, but the mechanisms of interaction between the two remain not well understood. To address this, we are investigating the effect of alternating electric fields on the optical properties and Freedericksz Transition of 5CB liquid crystal with different concentrations of MWCNTs. 5CB cells with ITO electrodes were made using spin-coated PVA for sample alignment and MylarTM spacer films to control the thickness, which ranged from 12 to 23 microns. Transmission optical ellipsometry was used to measure the optical retardance (phase delay) and uniaxial director angle of 5CB liquid crystals as the peak voltage of a high-frequency (1 kHz - 1 MHz) AC electric field was varied from 0 to 10 V. For constant frequency, the Freedericksz Transition was noted by a sharp decrease in retardance from an initial plateau, which gradually decreased toward zero as the voltage increased. With increasing frequency, the decay broadened and the Freedericksz Transition occurred at higher voltage. Numerical simulations of CNT-facilitated switching are also presented. Research was funded by the National Science Foundation, Polymers Program of the Division of Materials Research, through DMR-12061010.

  14. Rotation of a liquid crystal by the Casimir torque

    NASA Astrophysics Data System (ADS)

    Somers, David A. T.; Munday, Jeremy N.

    2015-03-01

    We present a calculation of the Casimir torque acting on a liquid crystal near a birefringent crystal. In this system, a liquid crystal bulk is uniformly aligned at one surface and is twisted at the other surface by a birefringent crystal, e.g., barium titanate. The liquid crystal is separated from the solid crystal by an isotropic, transparent material such as SiO2. By varying the thickness of the deposited layer, we can observe the effect of retardation on the torque (which differentiates it from the close-range van der Waals torque). We find that a barium titanate slab would cause 5CB (4 -cyano -4 '-pentylbiphenyl) liquid crystal to rotate by 10∘ through its bulk when separated by 35 nm of SiO2. The optical technique for measuring this twist is also outlined.

  15. Electrical Freedericksz transitions in nematic liquid crystals containing ferroelectric nanoparticles

    NASA Astrophysics Data System (ADS)

    Cîrtoaje, Cristina; Petrescu, Emil; Stoian, Victor

    2015-03-01

    A new theoretical approach was elaborated to explain the contradictions reported in many papers about the electric threshold for Freedericksz transition in nematic liquid crystal (NLC) with ferroparticles additives. The free energy density of the mixture was estimated and the contributions of the interaction energy of NLC molecules with ferroparticles surface were calculated. Experimental results for 5CB-BaTiO3 mixture are given.

  16. Ultrabroadband terahertz spectroscopy of a liquid crystal.

    PubMed

    Vieweg, N; Fischer, B M; Reuter, M; Kula, P; Dabrowski, R; Celik, M A; Frenking, G; Koch, M; Jepsen, P U

    2012-12-17

    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 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 show that the spectra are dominated by multiple strong spectral features mainly at frequencies above 4 THz, originating from intramolecular vibrational modes of the weakly LC molecules.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  19. Fabrication of liquid crystal based sensor for detection of hydrazine vapours

    NASA Astrophysics Data System (ADS)

    Nandi, Rajib; Singh, Sachin Kumar; Singh, Hemant Kumar; Singh, Bachcha; Singh, Ranjan K.

    2014-10-01

    A novel liquid crystal (LC) based sensor to detect trace level amount of hydrazine vapour has been developed. The LC 4‧-pentyl-4-biphenylcarbonitrile (5CB) doped with 0.5 wt% 4-decyloxy benzaldehyde (DBA) shows dark to bright optical texture upon exposure of hydrazine vapours as revealed by polarizing optical microscopy under crossed polarizers. The hydrazine interacts with the doped DBA and form diimine compound which disrupt the orientation of aligned 5CB. The interaction between DBA and hydrazine has been also studied by Raman spectroscopy.

  20. The effect of CdSe/ZnS quantum dots on the rotational viscosity and charge carrier concentration of a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Shcherbinin, D. P.; Konshina, E. A.; Solodkov, D. E.

    2015-08-01

    The addition of CdSe/ZnS quantum dots (QDs) with a core diameter of 3.5 nm at a concentration of 10 wt % leads to a 2.5-fold increase in the dynamic rotational viscosity of a 5CB nematic liquid crystal (NLC). A comparison of the diffusion currents in NLC cells filled with pure 5CB and a suspension with QDs shows evidence of an increase in the concentration of charge carriers in the latter case.

  1. Liquid Crystal Optofluidics

    SciTech Connect

    Vasdekis, Andreas E.; Cuennet, J. G.; Psaltis, D.

    2012-10-11

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  2. Liquid crystal optofluidics

    NASA Astrophysics Data System (ADS)

    Vasdekis, A. E.; Cuennet, J. G.; Psaltis, D.

    2012-10-01

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  3. Wave propagation and acoustic band gaps of two-dimensional liquid crystal/solid phononic crystals

    NASA Astrophysics Data System (ADS)

    Oltulu, Oral; Mamedov, Amirullah M.; Ozbay, Ekmel

    2017-01-01

    The vast majority of acoustic wave propagation in phononic band studies has been usually carried out by scattering inclusions embedded in a viscoelastic medium, such as air or water. In this study, we present calculated band structure results for the two-dimensional square array geometry of a solid cylindrical scatterer surrounded by a liquid crystal (LC) matrix. Liquid crystals provide a unique combination of liquid-like and crystal-like properties as well as anisotropic properties. The purpose of using LC material is to take advantage of longitudinal acoustic waves propagating parallel (||) and perpendicular (⊥) to the nematic liquid crystal (NLC) director n. The compound used in this study was a room temperature NLC, called 5CB (4-pentyl-4'-cyanobiphenyl). The acoustic band structure of a two-dimensional phononic crystal containing a 5CB NLC and lithium tantalate was investigated by the plane wave expansion method. The theoretical results show that the solid/LC system can be tuned in a favorable configuration for adjusting or shifting acoustic band gaps.

  4. Liquid Crystal Airborne Display

    DTIC Science & Technology

    1977-08-01

    81/2X 11- 10 -9 .8 display using a large advertising alphanimeric ( TCI ) has been added to the front of the optical box used in the F-4 aircraft for HUD...properties over a wide range of tempera - tures, including normal room temperature. What are Liquid Crystals? Liquid crystals have been classified in three...natic fanctions and to present data needed for the semi- automatic and manual control of system functions. Existing aircraft using CRT display

  5. Langmuir Films of Flexible Polymers Transferred to Aqueous/Liquid Crystal Interfaces Induce Uniform Azimuthal Alignment of the Liquid Crystal

    PubMed Central

    Kinsinger, Michael I.; Buck, Maren E.; Meli, Maria-Victoria; Abbott, Nicholas L.; Lynn, David M.

    2009-01-01

    We reported recently that amphiphilic polymers can be assembled at interfaces created between aqueous phases and thermotropic liquid crystals (LCs) in ways that (i) couple the organization of the polymer to the order of the LC and (ii) respond to changes in the properties of aqueous phases that can be characterized as changes in the optical appearance of the LC. This investigation sought to characterize the behavior of aqueous-LC interfaces decorated with uniaxially compressed thin films of polymers transferred by Langmuir-Schaefer (LS) transfer. Here, we report physicochemical characterization of interfaces created between aqueous phases and the thermotropic LC 4-cyano-4’-pentylbiphenyl (5CB) decorated with Langmuir films of a novel amphiphilic polymer (polymer 1), synthesized by the addition of hydrophobic and hydrophilic side chains to poly(2-vinyl-4,4’-dimethylazlactone). Initial characterization of this system resulted in the unexpected observation of uniform azimuthal alignment of 5CB after LS transfer of the polymer films to aqueous-5CB interfaces. This paper describes characterization of Langmuir films of polymer 1 hosted at aqueous-5CB interfaces as well as the results of our investigations into the origins of the uniform ordering of the LC observed upon LS transfer. Our results, when combined, support the conclusion that uniform azimuthal alignment of 5CB is the result of long-range ordering of polymer chains in the Langmuir films (in a preferred direction orthogonal to the direction of compression) that is generated during uniaxial compression of the films prior to LS transfer. Although past studies of Langmuir films of polymers at aqueous-air interfaces have demonstrated that in-plane alignment of polymer backbones can be induced by uniaxial compression, these past reports have generally made use of polymers with rigid backbones. One important outcome of this current study is thus the observation of anisotropy and long-range order in Langmuir films

  6. Peculiarities of electro-optic properties of the ferroelectric particles-liquid crystal colloids

    NASA Astrophysics Data System (ADS)

    Ibragimov, T. D.; Imamaliyev, A. R.; Bayramov, G. M.

    2016-04-01

    Influence of ferroelectric barium titanate particles on electro-optic properties of the liquid crystal (LC) 4-cyano-4'-pentylbiphenyl (5CB) with positive dielectric anisotropy and the LC mixture (H37) consisting of 4-methoxybezylidene-4'-butylaniline and 4-ethoxybezylidene-4'-butylaniline with negative dielectric anisotropy was investigated. It was shown that a presence of particles (1 wt%) in 5CB and H37 decreased the clearing temperature from 35.2 °C to 32.4°C and from 61.2°C to 60.1°C, respectively. The threshold voltage of the Freedericksz effect became 0.3 V for the BaTiO3-5CB colloid while the beginning of this effect for the pure 5CB was observed at 2.1 V. The threshold voltage of the Freedericksz effect increased from 2.8 V to up 3.1 V at additive of particles in H37. A rise time of the BaTiO3-5CB colloid improved while a decay time worsened in comparison with the pure 5CB at all applied voltages. The inverse trends were observed for the H37 matrix, namely, a rise time worsened and a decay time improved. Among other things, the pecularities of Williams' domain formation (WDF) were also investigated in the colloid based on the H37 matrix. It was established that the WDF voltage decreased, a rise time increased and a decay time decreased in comparison with the pure H37. Experimental results are explained by appearance of local electric fields near the polarized ferroelectric particles at application of external electric field and an existence of the additional obstacles (particles) for movement of ions.

  7. Polymerizable ionic liquid crystals.

    PubMed

    Jazkewitsch, Olga; Ritter, Helmut

    2009-09-17

    Polymerizable vinylimidazolium ionic liquids (ILs) that contain mesogenic coumarin and biphenyl units, respectively, have been synthesized. The N-alkylation of N-vinylimidazole with bromoalkylated mesogenic units 7-(6-bromohexyloxy)coumarin (1) and 4,4'-bis(6-bromohexyloxy)biphenyl (2) was then carried out. The thermal behavior of the obtained ILs 3 and 4 was investigated by differential scanning calorimetry and polarizing optical microscopy. These measurements showed that the attached mesogenic units induce the self-assembly of ILs and, therefore, the occurrence of liquid crystalline phases. Subsequently, the ionic liquid crystals (ILCs) 3 and 4 were polymerized by a free-radical mechanism.

  8. Ferroelectric liquid crystal display

    NASA Technical Reports Server (NTRS)

    York, Paul K. (Inventor)

    1977-01-01

    A ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of X and Y address lines and to accurately define desired capacitances. The spoiler layers comprise low dielectric constant layers which space electrodes from the ferroelectric at crossover points where capacitance is not needed for device operation.

  9. Liquid crystals in tribology.

    PubMed

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-09-18

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Specific detection of avidin-biotin binding using liquid crystal droplets.

    PubMed

    Khan, Mashooq; Park, Soo-Young

    2015-03-01

    Poly(acrylicacid-b-4-cynobiphenyl-4'-undecylacrylate) (PAA-b-LCP)-functionalized 4-cyano-4'-pentylbiphenyl (5CB) droplets were made by using microfluidic technique. The PAA chains on the 5CB droplets, were biotinylated, and used to specifically detect avidin-biotin binding at the 5CB/aqueous interface. The avidin-biotin binding was characterized by the configurational change (from radial to bipolar) of the 5CB droplets, as observed through a polarized optical microscope. The maximum biotinylation was obtained by injecting a >100 μg/mL biotin aqueous solution, which enabled a limit of detection of 0.5 μg/mL avidin. This droplet biosensor could specifically detect avidin against other proteins such as bovine serum albumin, lysozyme, hemoglobin, and chymotrypsinogen solutions. Avidin detection with 5CBPAA-biotin droplets having high sensitivity, specificity, and stability demonstrates new applications of the functionalized liquid crystal droplets that can detect specific proteins or other analytes through a ligand/receptor model.

  12. Low-temperature phase transformations in 4-cyano-4‧-pentyl-biphenyl (5CB) filled by multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lebovka, N.; Melnyk, V.; Mamunya, Ye.; Klishevich, G.; Goncharuk, A.; Pivovarova, N.

    2013-08-01

    The effects of multiwalled carbon nanotubes (NTs) on low-temperature phase transformations in 5CB were studied by means of differential scanning calorimetry (DSC), low-temperature photoluminescence and measurements of electrical conductivity. The concentration of NTs was varied within 0-1 wt% The experimental data, obtained for pure 5CB by DSC and measurements of photoluminescence in the heating mode, evidenced the presence of two crystallization processes at T≈229 K and T≈262 K, which correspond to C1a→C1b, and C1b→C2 phase transformations. Increase of temperature T from 10 K tо 229 K provoked the red shift of photoluminescence spectral band that was explained by flattening of 5CB molecule conformation. Moreover, the photoluminescence data allow to conclude that crystallization at T≈229 K results in conformation transition to non-planar 5CB structure characteristic to ideal crystal. The non-planar conformations were dominating in nematic phase, i.e., at T>297 K. Electrical conductivity data for 5CB-NT composites revealed supplementary anomaly inside the stable crystalline phase C2, identified earlier in the temperature range 229-296.8 K. It can reflect the influence of phase transformation of 5CB in interfacial layers on the transport of charge carriers between NTs.

  13. Nematic liquid crystal bridges

    NASA Astrophysics Data System (ADS)

    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.

  14. Pyrrolidinium ionic liquid crystals.

    PubMed

    Goossens, Karel; Lava, Kathleen; Nockemann, Peter; Van Hecke, Kristof; Van Meervelt, Luc; Driesen, Kris; Görller-Walrand, Christiane; Binnemans, Koen; Cardinaels, Thomas

    2009-01-01

    N-alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2- thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group C(n)H(2n+1) was varied from eight to twenty carbon atoms (n = 8, 10-20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X-ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self-assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium-containing mesogens, luminescence can be induced by dissolving them in an ionic liquid matrix. The europium-containing compound shows intense red photoluminescence with high colour purity.

  15. Liquid Crystals in Tribology

    PubMed Central

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-01-01

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered. PMID:19865534

  16. Folate ligand anchored liquid crystal microdroplets emulsion for in vitro detection of KB cancer cells.

    PubMed

    Yoon, Seong H; Gupta, Kailash C; Borah, Jyoti S; Park, Soo-Young; Kim, Young-Kyoo; Lee, Joon-Hyung; Kang, Inn-Kyu

    2014-09-09

    A KB cancer cell-selective, liquid crystal microdroplets emulsion is prepared using folic acid-conjugated block copolymers (PS-b-PAA-FA) and sodium dodecyl sulfate (SDS) as a mediator to induce configurational transitions in 4-cyano-4'-pentylbiphenyl (5CB) liquid crystal microdroplets emulsion. The prepared liquid crystal microdroplets emulsion has shown a configurational transition from radial to bipolar on interacting with KB cancer cells, but no transition from radial to bipolar configuration is observed when liquid crystal microdroplets emulsion was allowed to interact with other normal cells such as fibroblast and osteoblast. The KB cancer cell selectivity of liquid crystal microdroplets emulsion has been considered due to the presence of KB cancer cell folate receptor-specific ligand (FA) at the surface of liquid crystal microdroplets, which allowed liquid crystal microdroplets to interact specifically with KB cancer cells. The ligand-receptor interactions have been considered responsible for triggering the configurational transitions from radial to bipolar in liquid crystal microdroplets emulsion. Thus, folate ligand anchored liquid crystal microdroplets emulsion has shown a potential to be used for in vitro detection of KB cancer cells in the early stage of tumor development.

  17. Liquid crystal based biosensors for bile acid detection

    NASA Astrophysics Data System (ADS)

    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.

  18. Adaptive liquid crystal iris

    NASA Astrophysics Data System (ADS)

    Zhou, Zuowei; Ren, Hongwen; Nah, Changwoon

    2014-09-01

    We report an adaptive iris using a twisted nematic liquid crystal (TNLC) and a hole-patterned electrode. When an external voltage is applied to the TNLC, the directors of the LC near the edge of the hole are unwound first. Increasing the voltage can continuously unwind the LC toward the center. When the TNLC is sandwiched between two polarizers, it exhibits an iris-like character. Either a normal mode or a reverse mode can be obtained depending on the orientations of the transmission axes of the two polarizers. In contrast to liquid irises, the aperture of the LC iris can be closed completely. Moreover, it has the advantages of large variability of the aperture diameter, good stability, and low power consumption. Applications of the device for controlling the laser energy and correcting optical aberration are foreseeable.

  19. Extreme Nonlinear Optics With Liquid Crystals

    DTIC Science & Technology

    2006-10-31

    Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic crystals,” Mol. Cryst. Liq. Cryst. 446: 233...Mallouk, “ Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic crystals,” Mol. Cryst. Liq. Cryst...Williams, B. Lewis and T. Mallouk, “Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic

  20. Predicting the Conditions for Homeotropic Anchoring of Liquid Crystals at a Soft Surface. 4-n-Pentyl-4'-cyanobiphenyl on Alkylsilane Self-Assembled Monolayers.

    PubMed

    Roscioni, Otello Maria; Muccioli, Luca; Zannoni, Claudio

    2017-04-05

    We have studied, using atomistic molecular dynamics simulations, the alignment of the nematic liquid-crystal 4-n-pentyl-4'-cyanobiphenyl (5CB) on self-assembled monolayers (SAMs) formed from octadecyl- and/or hexyltrichlorosilane (OTS and HTS) attached to glassy silica. We find a planar alignment on OTS at full coverage and an intermediate situation at partial OTS coverage because of the penetration of 5CB molecules into the monolayer, which also removes the tilt of the OTS SAM. Binary mixtures of HTS and OTS SAMs instead induce homeotropic (i.e., perpendicular) alignment. A comparison with the existing experimental literature is provided.

  1. Dynamics of a director reorientation and optical response of polymer films filled with a liquid crystal under strong electric field

    NASA Astrophysics Data System (ADS)

    Pasechnik, S. V.; Shmeleva, D. V.; Chopik, A. P.; Vakulenko, A. A.; Zakharov, A. V.

    2016-08-01

    The dynamics of the director reorientation in nematic liquid crystals (NLC) confined by cylindrical cavities of porous polymeric films under strong electric field E with has been investigated theoretically. The main attention was paid to the specific mode of field application characterized by abrupt changes of the applied voltage's polarity. In experiments with porous films filled with a liquid crystal 5CB such mode resulted in appearance of strong peak -like decreasing of an optical transparence of the films. Two mechanisms of such unusual response based on assumption of electrically induced motion of ions and overall motion of a liquid were considered and applied to explain experimental results.

  2. Liquid crystals for photonic applications

    NASA Astrophysics Data System (ADS)

    Miniewicz, A.; Gniewek, A.; Parka, J.

    2003-01-01

    In this paper we describe application of liquid crystals in optical imaging and processing. Electrically and optically addressed liquid crystal spatial light modulators are key elements in real-time holographic devices. Their implementation for beam steering and hologram formation is briefly discussed. The Joint Fourier transform optical correlator for pattern recognition is presented as well as the use of liquid crystals for the adaptive optics purposes is discussed.

  3. Fluorescence enhancement of dye-doped liquid crystal by dye-induced alignment effect

    NASA Astrophysics Data System (ADS)

    Shim, Taekyu; Kim, Sunghyun; Kim, Doseok; Oh-e, Masahito

    2011-09-01

    We investigated fluorescence from hemicyanine dye molecules in a liquid crystal (4,4'-n-pentylcyanobiphenyl) (5CB) medium at different temperatures. The fluorescence decay lifetime decreased monotonically irrespective of the thermodynamic phases of the host medium as the temperature was increased. This behavior is due to an intramolecular motion of the dye promoted with the decrease in the viscosity of the medium facilitating a nonradiative decay of the excited dye molecules. By contrast, fluorescence intensity from the dyes in the nematic phase was about 3 times stronger than that in the crystalline or isotropic phase. This fluorescence enhancement in the nematic phase was found to be due to an anisotropic alignment of the dye molecules following the anisotropic alignment of the host liquid crystal medium along the pump-beam polarization direction. This light-induced liquid crystal molecular alignment was markedly enhanced by the guest dyes preferentially excited along the pump-beam polarization direction. The orientational order parameter of the dyes in the liquid-crystalline phase deduced from fluorescence anisotropy measurement was similar to the known order parameter of the liquid crystalline 5CB.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Quick measurement of electrorheological effect for small amounts of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Tadokoro, Chiharu; Hosomi, Yuki; Nakano, Ken

    2015-08-01

    A quick measurement method of effective viscosity, employing damped oscillation between two parallel plates, was proposed to examine the electrorheological (ER) effect for small amounts of nematic liquid crystal (LC). To demonstrate the validity of the method, the viscosity measurements were conducted for ordinary liquids [polyalphaolefins (PAOs)] and a nematic LC [4-pentyl-4‧-cyanobiphenyl (5CB)] by using a newly developed apparatus that embodied the measurement principle. The viscosity measurements for PAOs showed that when the film thickness is in the submillimeter range (e.g. 0.2 mm), this method provides reliable values of the effective viscosity. The viscosity measurement for 5CB showed that this method evaluates the ER effect with a few dozen cubic millimeters of the sample (e.g. 16 mm3) under the application of a voltage (e.g. 0 to 300 V). It was confirmed that the effective viscosities of 5CB measured at various conditions were scaled to a single master curve as a function of the applied voltage, effective velocity and film thickness.

  6. Voxelated liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    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.

  7. Modeling liquid crystal polymeric devices

    NASA Astrophysics Data System (ADS)

    Gimenez Pinto, Vianney Karina

    The main focus of this work is the theoretical and numerical study of materials that combine liquid crystal and polymer. Liquid crystal elastomers are polymeric materials that exhibit both the ordered properties of the liquid crystals and the elastic properties of rubbers. Changing the order of the liquid crystal molecules within the polymer network can induce shape change. These materials are very valuable for applications such as actuators, sensors, artificial muscles, haptic displays, etc. In this work we apply finite element elastodynamics simulations to study the temperature induced shape deformation in nematic elastomers with complex director microstructure. In another topic, we propose a novel numerical method to model the director dynamics and microstructural evolution of three dimensional nematic and cholesteric liquid crystals. Numerical studies presented in this work are in agreement with experimental observations and provide insight into the design of application devices.

  8. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    NASA Astrophysics Data System (ADS)

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-08-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25-60 oC) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB.

  9. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    PubMed Central

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 oC) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  10. Dichroic Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * DICHROIC DYES * Chemical Structure * Chemical and Photochemical Stability * THEORETICAL MODELLING * DEFECTS CAUSED BY PROLONGED LIGHT IRRADIATION * CHEMICAL STRUCTURE AND PHOTOSTABILITY * OTHER PARAMETERS AFFECTING PHOTOSTABILITY * CELL PREPARATION * DICHROIC PARAMETERS AND THEIR MEASUREMENTS * Order Parameter and Dichroic Ratio Of Dyes * Absorbance, Order Parameter and Dichroic Ratio Measurements * IMPACT OF DYE STRUCTURE AND LIQUID CRYSTAL HOST ON PHYSICAL PROPERTIES OF A DICHROIC MIXTURE * Order Parameter and Dichroic Ratio * EFFECT OF LENGTH OF DICHROIC DYES ON THE ORDER PARAMETER * EFFECT OF THE BREADTH OF DYE ON THE ORDER PARAMETER * EFFECT OF THE HOST ON THE ORDER PARAMETER * TEMPERATURE VARIATION OF THE ORDER PARAMETER OF DYES IN A LIQUID CRYSTAL HOST * IMPACT OF DYE CONCENTRATION ON THE ORDER PARAMETER * Temperature Range * Viscosity * Dielectric Constant and Anisotropy * Refractive Indices and Birefringence * solubility43,153-156 * Absorption Wavelength and Auxochromic Groups * Molecular Engineering of Dichroic Dyes * OPTICAL, ELECTRO-OPTICAL AND LIFE PARAMETERS * Colour And CIE Colour space120,160-166 * CIE 1931 COLOUR SPACE * CIE 1976 CHROMATICITY DIAGRAM * CIE UNIFORM COLOUR SPACES & COLOUR DIFFERENCE FORMULAE120,160-166 * Electro-Optical Parameters120 * LUMINANCE * CONTRAST AND CONTRAST RATIO * SWITCHING SPEED * Life Parameters and Failure Modes * DICHROIC MIXTURE FORMULATION * Monochrome Mixture * Black Mixture * ACHROMATIC BLACK MIXTURE FOR HEILMEIER DISPLAYS * Effect of Illuminant on Display Colour * Colour of the Field-On State * Effect of Dye Linewidth * Optimum Centroid Wavelengths * Effect of Dye Concentration * Mixture Formulation Using More Than Three Dyes * ACHROMATIC MIXTURE FOR WHITE-TAYLOR TYPE DISPLAYS * HEILMEIER DISPLAYS * Theoretical Modelling * Threshold Characteristic * Effects of Dye Concentration on Electro-optical Parameters * Effect of Cholesteric Doping * Effect of Alignment

  11. Defects in liquid crystal nematic shells

    NASA Astrophysics Data System (ADS)

    Fernandez-Nieves, A.; Utada, A. S.; Vitelli, V.; Link, D. R.; Nelson, D. R.; Weitz, D. A.

    2006-03-01

    We generate water/liquid crystal (LC)/water double emulsions via recent micro-capillary fluidic devices [A. S. Utada, et.al. Science 308, 537 (2005)]. The resultant objects are stabilized against coalescence by using surfactants or adequate polymers; these also fix the boundary conditions for the director field n. We use 4-pentyl-4-cyanobiphenyl (5CB) and impose tangential boundary conditions at both water/LC interfaces by having polyvinyl alcohol (PVA) dispersed in the inner and outer water phases. We confirm recent predictions [D. R. Nelson, NanoLetters 2, 1125 (2002)] and find that four strength s=+1/2 defects are present; this is in contrast to the two s=+1 defect bipolar configuration observed for bulk spheres [A. Fernandez-Nieves, et.al. Phys. Rev. Lett. 92, 105503 (2004)]. However, these defects do not lie in the vertices of a tetrahedron but are pushed towards each other until certain equilibration distance is reached. In addition to the four defect shells, we observe shells with two s=+1 defects and even with three defects, a s=+1 and two s=+1/2. We argue these configurations arise from nematic bulk distortions that become important as the shell thickness increases. Finally, by adding a different surfactant, sodium dodecyl sulphate (SDS), to the outer phase, we can change the director boundary conditions at the outermost interface from parallel to homeotropic, to induce coalescing of the two pair of defects in the four defect shell configuration to yield two defect bipolar shells.

  12. Pressure sensor using liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

  13. Shape-responsive actuator from a single layer of a liquid-crystal polymer.

    PubMed

    Kamal, Tahseen; Park, Soo-young

    2014-10-22

    Actuation of various shape changes, including bending, helical twisting, and reversible hinging, has been achieved from a single-layer sheet of poly(1,4-di(4-(3-acryloyloxypropyloxy)benzoyloxy)-2-methylbenzene) [poly(RM257)]. This actuator was developed through photopolymerization of a reactive liquid-crystal (LC) monomer (RM257) mixed with 4-pentyl-4'-cyanobiphenyl (5CB, nematic LC at room temperature) in a planar polyimide-coated LC cell. The UV beam perpendicular to one side of the LC cell produced an asymmetric phase separation between the poly(RM257) network and 5CB that resulted in an asymmetric porous structure along the thickness direction when the 5CB was extracted, in which the UV-exposed surface was pore-free and compact while the opposite surface was highly porous. As a result of this structure, the dry and curled poly(RM257) film exhibits actuation behavior when placed in acetone because of a difference in swelling between the two morphologically different sides, the film UV-exposed and nonexposed sides. The actuation of a three-dimensional tetrahedron (pyramidal) structure is also demonstrated for the first time by using a simple photopatterning technique to selectively control its asymmetric morphology at specific locations.

  14. Transferability of coarse-grained force field for nCB liquid crystal systems.

    PubMed

    Zhang, Jianguo; Guo, Hongxia

    2014-05-01

    In this paper, the transferability of the coarse-grained (CG) force field originally developed for the liquid crystal (LC) molecule 5CB ( Zhang et al. J. Phys. Chem. B 2012 , 116 , 2075 - 2089 ) was investigated by its homologues 6CB and 8CB molecules. Note that, to construct the 5CB CG force field, we combined the structure-based and thermodynamic quantities-based methods and at the same time attempted to use several fragment molecular systems to derive the CG nonbonded interaction parameters. The resultant 5CB CG force field exhibits a good transferability to some extent. For example, not only the experimental densities, the local packing of atom groups, and the antiparallel arrangements of nearest neighboring molecules, but also the unique LC mesophases as well as the nematic-isotropic phase transition temperatures of 6CB and 8CB were reproduced. Meanwhile, the limitations of this 5CB CG force field were also observed, such as the phase transition from nematic to smectic was postponed to the lower temperature and the resulting smectic phase structure is single-layer-like instead of partially interdigitated bilayer-like as observed in underlying atomistic model. Apparently, more attention should be paid when applying a CG force field to the state point which is quite different from which the force field is explicitly parametrized for. The origin of the above limitations can be potentially traced back to the inherent simplifications and some approximations often adopted in the creation process of CG force field, for example, choosing symmetric CG potentials which do not explicitly include electrostatic interactions and are parametrized by reproducing the target properties of the specific nematic 5CB phase at 300 K and 1 atm, as well as using soft nonbonded potential and excluding torsion barriers. Moreover, although by construction this CG force field could inevitably incorporate both thermodynamic and local structural information on the nematic 5CB phase, the

  15. Influence of Specific Anions on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    PubMed Central

    Carlton, Rebecca J.; Ma, C. Derek; Gupta, Jugal K.; Abbott, Nicholas L.

    2012-01-01

    We report that specific anions (of sodium salts) added to aqueous phases at molar concentrations can trigger rapid, orientational ordering transitions in water-immiscible, thermotropic liquid crystals (LCs; e.g., nematic phase of 4′-pentyl-4-cyanobiphenyl, 5CB) contacting the aqueous phases. Anions classified as chaotropic, specifically iodide, perchlorate and thiocyanate, cause 5CB to undergo continuous, concentration-dependent transitions from planar to homeotropic (perpendicular) orientations at LC-aqueous interfaces within 20 s of addition of the anions. In contrast, anions classified as relatively more kosmotropic in nature (fluoride, sulfate, phosphate, acetate, chloride, nitrate, bromide, and chlorate) do not perturb the LC orientation from that observed without added salts (i.e., planar orientation). Surface pressure-area isotherms of Langmuir films of 5CB supported on aqueous salt solutions reveal ion-specific effects ranking in a manner similar to the LC ordering transitions. Specifically, chaotropic salts stabilized monolayers of 5CB to higher surface pressures and areal densities (12.6 mN/m at 27 Å2/molec. for NaClO4) and thus smaller molecular tilt angles (30° from the surface normal for NaClO4) than kosmotropic salts (5.0 mN/m at 38 Å2/molec. with a corresponding tilt angle of 53° for NaCl). These results and others reported herein suggest that anion-specific interactions with 5CB monolayers lead to bulk LC ordering transitions. Support for the proposition that these ion-specific interactions involve the nitrile group was obtained by using a second LC with nitrile groups (E7; ion-specific effects similar to 5CB were observed) and a third LC with fluorine-substituted aromatic groups (TL205; weak dipole and no ion-specific effects were measured). Finally, we also establish that anion-induced orientational transitions in micrometer-thick LC films involve a change in the easy axis of the LC. Overall, these results provide new insights into ionic

  16. Liquid Crystals for Nondestructive Evaluation

    DTIC Science & Technology

    1978-09-01

    Temperatures TI > T2 > - > TS defects was possible using the liquid crystal. are the Average TemperatursI Thes Resptivegi. Kapfer , Burns, Salvo, and Doyle...Means of Liquid Crystals,’ J. 38 .1; .1 of Sound and Vibration, Vol. 36, No. 3, pp. 407- 65. V.C. Kapfer , D.J. Bums, C.J. Salvo, and E.A. 15, Oct. 1974

  17. Adaptive Liquid Crystal Windows

    SciTech Connect

    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

  18. Liquid Crystals for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    O'Neill, Mary; Kelly, Stephen M.

    As discussed in Chaps. 2 (10.1007/978-90-481-2873-0_2), 3 (10.1007/978-90-481-2873-3), 5 (10.1007/978-90-481-2873-5) and 6 (10.1007/978-90-481-2873-6), columnar, smectic and, more recently, nematic liquid crystals are widely recognized as very promising charge-transporting organic semiconductors due to their ability to spontaneously self-assemble into highly ordered domains in uniform thin films over large areas. This and their broad absorption spectra make them suitable as active materials for organic photovoltaic devices. In this chapter, we discuss the use of liquid crystals in such devices. Firstly, we examine the principle of power generation via the photovoltaic effect in organic materials and the various device configurations that can optimise efficiency. Then we discuss photovoltaic devices incorporating columnar liquid crystals combined with electron accepting materials based on either perylene or fullerene. The use of nematic and sanditic liquid crystals in photovoltaics is investigated as well as a novel solar cell concentrator incorporating liquid crystals. Finally, we analyse the benefits and limitations of liquid-crystal-based photovoltaics in the context of the state-of-the-art for organics photovoltaics.

  19. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Transient Reorientation of a Doped Liquid Crystal System under a Short Laser Pulse

    NASA Astrophysics Data System (ADS)

    Li, Tao; Xiang, Ying; Liu, Yi-Kun; Wang, Jian; Yang, Shun-Lin

    2009-08-01

    The transient optical nonlinearity of a nematic liquid crystal doped with azo-dye DR19 is examined. The optical reorientation threshold of a 25-μm-thick planar-aligned sample of 5CB using a 50 ns pulse duration 532 nm YAG laser pulse is observed to decrease from 800 mJ/mm2 to 0.6 mJ/mm2 after the addition of 1 vol% azo dopant, a reduction of three orders of magnitude. When using a laser pulse duration of 10 ns, no such effect is observed. Experimental results indicate that the azo dopant molecules undergo photoisomerization from trans-isomer to cis-isomer under exposure to light, and this conformation change reorients the 5CB molecules via intermolecular coupling between guest and host. This guest-host coupling also affects the azo photoisomerization process.

  20. Computer Modeling of Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Hashim, Rauzah

    This chapter outlines the methodologies and models which are commonly used in the simulation of liquid crystals. The approach in the simulation of liquid crystals has always been to understand the nature of the phase and to relate this to fundamental molecular features such as geometry and intermolecular forces, before important properties related to certain applications are elucidated. Hence, preceding the description of the main "molecular-based" models for liquid crystals, a general but brief outline of the nature of liquid crystals and their historical development is given. Three main model classes, namely the coarse-grained single-site lattice and Gay-Berne models and the full atomistic model will be described here where for each a brief review will be given followed by assessment of its application in describing the phase phenomena with an emphasis on understanding the molecular organization in liquid crystal phases and the prediction of their bulk properties. Variants and hybrid models derived from these classes and their applications are given.

  1. Carbon nanotubes as liquid crystals.

    PubMed

    Zhang, Shanju; Kumar, Satish

    2008-09-01

    Carbon nanotubes are the best of known materials with a combination of excellent mechanical, electronic, and thermal properties. To fully exploit individual nanotube properties for various applications, the grand challenge is to fabricate macroscopic ordered nanotube assemblies. Liquid-crystalline behavior of the nanotubes provides a unique opportunity toward reaching this challenge. In this Review, the recent developments in this area are critically reviewed by discussing the strategies for fabricating liquid-crystalline phases, addressing the solution properties of liquid-crystalline suspensions, and exploiting the practical techniques of liquid-crystal routes to prepare macroscopic nanotube fibers and films.

  2. Shape evolution of a single liquid-crystal droplet immersed in an isotropic matrix under transient and steady flow.

    PubMed

    Wu, Youjun; Yu, Wei; Zhou, Chixing; Xu, Yuanze

    2007-04-01

    The morphology evolution of immiscible polymer-liquid crystal systems is quite different from flexible polymer-polymer mixtures due to the anisotropic properties of liquid crystals. The deformation and retraction of a single low molar mass liquid crystal 4'-pentyl-4-biphenylcarbonitrile (5CB) droplet and 4'-octyl-4-biphenylcarbonitrile (8CB) dispersed in polydimethyl-siloxane under two-dimensional linear flow was investigated by a computer-controlled four-roll mill, which is equipped with an optical microscope and a digital camera. The deformation parameter and orientation angle during deformation versus capillary number was obtained and compared with calculations using the Maffettone-Minale (MM) model and the Yu-Zhou liquid-crystal (YZ-LC) model. The MM model can describe the behavior of a Newtonian droplet in another Newtonian matrix whereas the YZ-LC model can describe the behavior of a LC droplet in a Newtonian matrix. The results showed that the deformation and rotation of a LC droplet is more difficult than viscoelastic droplets, possibly because of the resistance of the nematic elastic energy induced by the nematic mesogens deformation and orientation under flow field. Furthermore, the different behavior between flow-aligning 5CB and flow-tumbling 8CB droplets and the influence of droplet size of LC on deformation and retraction were discussed by experiment and calculation; the results reveal that the different size LC droplets show different evolution curves.

  3. Enantioselective separations using chiral supported liquid crystalline membranes.

    PubMed

    Han, Sangil; Rabie, Feras; Marand, Eva; Martin, Stephen M

    2012-07-01

    Porous and nonporous supported liquid crystalline membranes were produced by impregnating porous cellulose nitrate supports with cholesteric liquid crystal (LC) materials consisting of 4-cyano-4'-pentylbiphenyl (5CB) mixed with a cholesterol-based dopant (cholesteryl oleyl carbonate [COC], cholesteryl nonanoate [CN], or cholesteryl chloride [CC]). The membranes exhibit selectivity for R-phenylglycine and R-1-phenylethanol because of increased interactions between the S enantiomers and the left-handed cholesteric phase. The selectivity of both phenylglycine and 1-phenylethanol in 5CB/CN membranes decreases with effective pore diameter while the permeabilities increase, as expected. Phenylglycine, which is insoluble in the LC phase, exhibits no transport in the nonporous (completely filled) membranes; however, 1-phenylethanol, which is soluble in the LC phase, exhibits transport but negligible enantioselectivity. The enantioselectivity for 1-phenylethanol was higher (1.20 in 5CB/COC and 5CB/CN membranes) and the permeability was lower in the cholesteric phase than in the isotropic phase. Enantioselectivity was also higher in the 5CB/COC cholesteric phase than in the nematic phase of undoped 5CB (1.03). Enantioselectivity in the cholesteric phase of 5CB doped with CC (1.1), a dopant lacking hydrogen bonding groups, was lower than in the 5CB/COC phases. Finally, enantioselectivity increases with the dopant concentration up to a plateau value at approximately 17 mol%.

  4. Liquid crystal thermometry during anaesthesia.

    PubMed

    Lacoumenta, S; Hall, G M

    1984-01-01

    The use of cutaneous liquid crystal thermometry (EZ Temp) as an estimate of core temperature during routine surgery was investigated in 20 patients. Seventeen per cent of the recordings made with the EZ Temp were more than 1 degree C different from oesophageal temperature. There was a poor correlation between EZ Temp values and both oesophageal and aural temperatures (r = 0.54 for both sites). We conclude that liquid crystal thermometry of the forehead is not sufficiently accurate to be used as an indicator of core temperature during routine surgery.

  5. Liquid crystal Fresnel lens display

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Qian; Abhishek Kumar, Srivastava; Alwin Tam, Ming-Wai; Zheng, Zhi-Gang; Shen, Dong; Vladimir, Chigrinov G.; Kwok, Hoi-Sing

    2016-09-01

    A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter. Project supported by Partner State Key Laboratory on Advanced Displays and Optoelectronics Technologies HKUST, China, the National Natural Science Foundation of China (Grant Nos. 61435008 and 61575063), and the Fundamental Research Funds for the Central Universities, China (Grant No. WM1514036).

  6. A liquid crystal adaptive lens

    NASA Technical Reports Server (NTRS)

    Kowel, S. T.; Cleverly, D.

    1981-01-01

    Creation of an electronically controlled liquid crystal lens for use as a focusing mechanism in a multi-element lens system or as an adaptive optical element is analyzed. Varying the index of refraction is shown to be equivalent to the shaping of a solid refracting material. Basic characteristics of liquid crystals, essential for the creation of a lens, are reviewed. The required variation of index of refraction is provided by choosing appropriate electrode voltages. The configuration required for any incoming polarization is given and its theoretical performance in terms of modulation transfer function derived.

  7. Ionic Liquid Crystals: Versatile Materials.

    PubMed

    Goossens, Karel; Lava, Kathleen; Bielawski, Christopher W; Binnemans, Koen

    2016-04-27

    This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

  8. Nematic liquid crystals on sinusoidal channels: the zigzag instability

    NASA Astrophysics Data System (ADS)

    Silvestre, Nuno M.; Romero-Enrique, Jose M.; Telo da Gama, Margarida M.

    2017-01-01

    Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau-de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear.

  9. Nematic liquid crystals on sinusoidal channels: the zigzag instability.

    PubMed

    Silvestre, Nuno M; Romero-Enrique, Jose M; Telo da Gama, Margarida M

    2017-01-11

    Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau-de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear.

  10. Liquid-Crystal Optical Correlator

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang

    1989-01-01

    Optical correlator uses commercially-available liquid-crystal television (LCTV) screen as spatial light modulator. Correlations with this device done at video frame rates, making such operations as bar-code recognition possible at reasonable cost. With further development, such correlator useful in automation, robotic vision, and optical image processing.

  11. Experiments with Cholesteric Liquid Crystals

    ERIC Educational Resources Information Center

    Fergason, James L.

    1970-01-01

    Describes laboratory experiments designed to demonstrate (1) the properties of cholesteric liquid crystals, (2) thermal mapping, (3) thermal diffusivity, (4) adiabatic expansion of rubber, and (5) measurement of radiated energy by a point source. Contains all of the information on materials and apparatus needed to perform the experiments.…

  12. Copper sulfate: Liquid or crystals?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two separate experiments were conducted to evaluate copper toxicity to channel catfish and free-swimming Ichthyophthirius multifiliis or Ich (the stage of Ich that can be treated); the compounds we used were CuSO4 crystals and a non-chelated liquid CuSO4 product. In 96 hr tests conducted in aquaria...

  13. Orthoconic liquid crystals--a case study.

    PubMed

    Lagerwall, Sven T

    2014-06-01

    Since the early investigations on liquid crystals it was realized how the confining surfaces often determine the textures and even properties of the material. This influence is particularly complex and important for chiral materials. When we come to chiral smectics the surfaces may have dramatic effects. These are illustrated on the ferroelectric liquid crystals; they then again increase in importance for the antiferroelectric liquid crystals where the most recent example is given by the orthoconic liquid crystals.

  14. Liquid crystal polyester thermosets

    DOEpatents

    Benicewicz, Brian C.; Hoyt, Andrea E.

    1992-01-01

    The present invention provides (1) curable liquid crystalline polyester monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 where R.sup.1 and R.sup.2 are radicals selected from the group consisting of maleimide, substituted maleimide, nadimide, substituted naimide, ethynyl, and (C(R.sup.3).sub.2).sub.2 where R.sup.3 is hydrogen with the proviso that the two carbon atoms of (C(R.sup.3).sub.2).sub.2 are bound on the aromatic ring of A.sup.1 or A.sup.3 to adjacent carbon atoms, A.sup.1 and A.sup.3 are 1,4-phenylene and the same where said group contains one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro lower alkyl, e.g., methyl, ethyl, or propyl, alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl, e.g., trifluoromethyl, pentafluoroethyl and the like, A.sup.2 is selected from the group consisting of 1,4-phenylene, 4,4'-biphenyl, 2,6-naphthylene and the same where said groups contain one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, and B.sup.1 and B.sup.2 are selected from the group consisting of --C(O)--O-- and --O--C(O)--, (2) thermoset liquid crystalline polyester compositions comprised of heat-cured segments derived from monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 as described above, (3) curable blends of at least two of the polyester monomers and (4) processes of preparing the curable liquid crystalline polyester monomers.

  15. Liquid Crystals: The Phase of the Future.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate; And Others

    1992-01-01

    Liquid crystal displays are currently utilized to convey information via graphic displays. Presents experiments and explanations that employ the concept of liquid crystals to learn concepts related to the various states of matter, electric and magnetic forces, refraction of light, and optics. Discusses applications of liquid crystal technology.…

  16. Anchoring Orientation of Nematic and Smectic A Liquid Crystals on PTFE Treated Plates

    NASA Astrophysics Data System (ADS)

    Hubert, Pascal; Dreyfus, Hanna; Guillon, Daniel; Galerne, Yves

    1995-09-01

    The anchoring orientation of different liquid crystals in contact with poly(tetrafluoroethylene) (PTFE) treated surfaces is determined by means of optical interferometry. The anchoring is found to be planar for all the compounds tested, MBBA, 2OO6, 5CB and 7BPI, consisting of polar and non-polar molecules, in the nematic or smectic A phase. This result is consistent with the non-polar nature of PTFE, which is only sensitive to London-like interactions. L'orientation de l'ancrage de différents cristaux liquides sur des surfaces de poly(tétrafluoroéthylène) (téflon) est mesurée par interférométrie optique. Un ancrage planaire est trouvé pour tous les composés essayés MBBA, 2OO6, 5CB et 7BPI, que les molécules soient polaires ou non polaires, en phase nématique ou smectique A. Ce résultat est cohérent avec la nature non-polaire du téflon qui n'est sensible qu'à l'interaction de London.

  17. Quantification of photoinduced order increase in liquid crystals with naphthopyran guests

    NASA Astrophysics Data System (ADS)

    Rumi, Mariacristina; Cazzell, Seth A.; Kosa, Tamas; Sukhomlinova, Ludmila; Taheri, Bahman; White, Timothy J.; Bunning, Timothy J.

    2016-03-01

    Photoinduced order-increasing phase transitions can occur in dye-liquid crystal mixtures when the photoproduct of the excitation of the dye molecules is more compatible with the liquid crystalline medium than the initial dye species. A detailed investigation of the photoinduced changes of the phase behavior and optical properties of mixtures of liquid crystals with naphthopyran guests upon exposure to light at 365 nm is presented here. In these guest-host systems, the nematic-to-isotropic phase transition temperature is increased upon irradiation. We show that the nematic range can be extended up to 2.9 °C by illumination in 5CB (4 -n -pentyl-4'-cyanobiphenyl) liquid crystal mixtures. The order parameter is significantly increased by illumination at all temperatures within the nematic range and the changes are larger at higher concentrations of the guests. In particular, the illuminated guest-host mixtures exhibit order parameters close to those of the neat liquid crystal host at the same temperature relative to the clearing point. An improved understanding of the photophysical processes taking place at the molecular level in these material systems can inform the design of photoresponsive materials and enhance their potential utility in optical or photonic devices.

  18. Function Spaces for Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Bedford, Stephen

    2016-02-01

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

  19. Swimming bacteria in liquid crystal

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Dynamics of swimming bacteria can be very complex due to the interaction between the bacteria and the fluid, especially when the suspending fluid is non-Newtonian. Placement of swimming bacteria in lyotropic liquid crystal produces a new class of active materials by combining features of two seemingly incompatible constituents: self-propelled live bacteria and ordered liquid crystals. Here we present fundamentally new phenomena caused by the coupling between direction of bacterial swimming, bacteria-triggered flows and director orientations. Locomotion of bacteria may locally reduce the degree of order in liquid crystal or even trigger nematic-isotropic phase transition. Microscopic flows generated by bacterial flagella disturb director orientation. Emerged birefringence patterns allow direct optical observation and quantitative characterization of flagella dynamics. At high concentration of bacteria we observed the emergence of self-organized periodic texture caused by bacteria swimming. Our work sheds new light on self-organization in hybrid bio-mechanical systems and can lead to valuable biomedical applications. Was supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under the Contract No. DE AC02-06CH11357.

  20. Free energy perturbation method for measuring elastic constants of liquid crystals

    NASA Astrophysics Data System (ADS)

    Joshi, Abhijeet

    There is considerable interest in designing liquid crystals capable of yielding specific morphological responses in confined environments, including capillaries and droplets. The morphology of a liquid crystal is largely dictated by the elastic constants, which are difficult to measure and are only available for a handful of substances. In this work, a first-principles based method is proposed to calculate the Frank elastic constants of nematic liquid crystals directly from atomistic models. These include the standard splay, twist and bend deformations, and the often-ignored but important saddle-splay constant. The proposed method is validated using a well-studied Gay-Berne(3,5,2,1) model; we examine the effects of temperature and system size on the elastic constants in the nematic and smectic phases. We find that our measurements of splay, twist, and bend elastic constants are consistent with previous estimates for the nematic phase. We further outline the implementation of our approach for the saddle-splay elastic constant, and find it to have a value at the limits of the Ericksen inequalities. We then proceed to report results for the elastic constants commonly known liquid crystals namely 4-pentyl-4'-cynobiphenyl (5CB) using atomistic model, and show that the values predicted by our approach are consistent with a subset of the available but limited experimental literature.

  1. Nanostructuring lyotropic chromonic liquid crystals

    NASA Astrophysics Data System (ADS)

    Schneider, Tod L.

    Lyotropic Chromonic Liquid Crystals (LCLCs) are an interesting and little known family of liquid crystals. Although materials such as Disodium Cromoglycate have been studied in depth for their phase behavior for use as antiasthmatic drugs, practical applications had yet to emerge. The focus of this work was to provide new applications for LCLC materials. The three most important results are: the uniform alignment of dried LCLC films, a new type of Langmuir Blodgett molecular monolayer or stack of molecular monolayers with long-range in-plane orientational order, and the use of LCLCs as an amplifying medium of antibody-antigen binding for the purpose of biodetection. To uniformly align LCLC materials, a diblock copolymer additive was used to reduce or eliminate tiger-stripe defects in the films. Uniformly aligned LCLC films can be useful as polarizing, compensating, or alignment layers in liquid crystal displays. In-plane oriented molecular monolayers were created using the method electrostatic self assembled monolayers and allowed for interesting experiments such as imaging individual LCLC aggregates via Atomic Force Microscopy (AFM). Controlling the in-plane long-range ordering one monolayer at a time allows for the creation of novel integrated optical systems. Finally, LCLCs are biocompatible and can be used to detect specific antibody-antigen binding events through the formation of immune complexes. Once the immune complex becomes larger than a critical size (determined by the elastic and surface properties of the LCLC-immune complex), the LCLC becomes distorted around the complex and can be optically detected.

  2. Dielectric and electro-optic measurements of nematic liquid crystals doped with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Peterson, Matthew; Georgiev, Georgi; Atherton, Timothy; Cebe, Peggy

    We studied the effects of carbon nanotubes (CNTs) on the dielectric and electro-optic properties of nematic 5CB liquid crystals (LCs). Samples containing 0.01%, 0.10% and 1.00% CNTs by weight were prepared. Anti- parallel rubbed cells with a nominal thickness of 10 μm were prepared using indium tin oxide coated glass cells and a polyimide alignment layer. The capacitance and dissipation factor were measured using an Agilent 4284A precision LCR meter. From these measurements, the complex dielectric permittivity was determined as a function of frequency. Analysis of the low frequency regime (f <1000 Hz) indicates that 5CB samples containing CNTs have a higher conductance than neat samples. The Fréedericksz transition critical voltage was noted by a sharp increase in capacitance after an initial plateau. Numerical simulations of CNT-facilitated switching show that polarization induced on the nanotubes from capacitive effects can significantly reduce the critical voltage in DC electric fields, in agreement with experimental results. Measurements of the critical voltage over a range of frequencies will also be presented. Research was supported by the National Science Foundation, DMR1206010.

  3. Surface anchoring structure of a liquid crystal monolayer studied via dual polarization interferometry

    NASA Astrophysics Data System (ADS)

    Tan, Osbert; Cross, Graham H.

    2009-02-01

    The self-organization of liquid crystal molecules of 4- n -pentyl- 4' -cyanobiphenyl (5CB) forming an oriented monolayer by condensation from the vapor phase onto a silicon oxynitride surface has been observed using the evanescent wave dual slab waveguide dual polarization mode interferometry (DPI) technique. Two distinct stages to the layer formation are observed: After the formation of a layer of molecules lying prone on the surface, further condensation begins to densify the layer and produces a gradual mutual alignment of the molecules until the fully condensed, fully aligned monolayer is reached. At this limit the full coverage 5CB monolayer on this surface and at a temperature of 25°C , is found to be anchored with an average molecular axis polar angle of 56±1° and with a measured thickness of 16.6±0.5Å . These results are in reasonable agreement with the molecular dimensions provided by molecular models. The apparent precision and accuracy of these results resolves some wide disparity between earlier studies of such systems. Previous difficulties in determining optogeometrical properties of such ultrathin birefringent films using ellipsometry or in the need for complex modeling of the film layer structure using x-ray reflectivity are overcome in this instance. We provide a technique for analyzing the dual polarization data from DPI such that the bulk refractive index values, when known, can be used to determine the orientation and thickness of a layer that is on the nanometer or subnanometer scale.

  4. Spreading of Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Poulard, Christophe

    2004-11-01

    A cyanobiphenyl liquid crystal drop in the nematic phase should spread on a silicon wafer. In fact, the drop hardly spreads due to the strong antagonist anchoring on the substrate and at the free surface. In a humidity controlled box at high RH and on a hydrophilic substrate, the friction is considerably reduced and the drop spreads easily. A well defined instability develops at the contact line, with two characteristic wavelengths, associated with a modulation of the drop thickness. A theoretical analysis, made by M. Ben Amar and L. Cummings, allows to understand one of the wavelength by an elastic approach and gives a wavelength proportionnal to the local drop's thickness.

  5. Perspectives in active liquid crystals.

    PubMed

    Majumdar, Apala; Cristina, Marchetti M; Virga, Epifanio G

    2014-11-28

    Active soft matter is a young, growing field, with potential applications to a wide variety of systems. This Theme Issue explores this emerging new field by highlighting active liquid crystals. The collected contributions bridge theory to experiment, mathematical theories of passive and active nematics, spontaneous flows to defect dynamics, microscopic to continuum levels of description, spontaneous activity to biological activation. While the perspectives offered here only span a small part of this rapidly evolving field, we trust that they might provide the interested reader with a taste for this new class of non-equilibrium systems and their rich behaviour.

  6. Liquid crystals in nondestructive testing.

    PubMed

    Fergason, J L

    1968-09-01

    The cholesteric phase is associated with scattering effects that give rise to iridescent colors, the dominant wavelength being influenced by very small changes in temperature, which can be as large as 1000 A shift per degree. This unusually high temperature sensitivity has given rise to the use of the cholesteric phase as a sensitive thermometer and thermal mapping media. This paper reviews the optical effects in the cholesteric phase with some new additions that are particularly relevant to thermal mapping. An attempt has been made to give a complete picture of the cholesteric liquid crystal as applied to nondestructive testing, rather than to review the work actually being done in this field.

  7. Nanoscopic Manipulation and Imaging of Liquid Crystals

    SciTech Connect

    Rosenblatt, Charles S.

    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.

  8. Polymer Crystallization at Curved Liquid/Liquid Interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda

    Liquid/liquid interface, either flat or curved, is a unique template for studying self-assembly of a variety of nanomaterials such as nanoparticles and nanorods. The resultant monolayer films can be ordered or disordered depending on the regularity of the nanomaterials. Integration of nanoparticles into two-dimensional structure leads to intriguing collective properties of the nanoparticles. Crystallization can also be guided by liquid/liquid interface. Due to the particular shape of the interface, crystallization can happen in a different manner comparing to the normal solution crystallization. In this dissertation, liquid/liquid interface is employed to guide the crystallization of polymers, mainly focusing on using curved liquid/liquid interface. Due to the unique shape of the interface and feasibility to control the curvature, polymer crystallization can take place in different manner and lead to the formation of curved or vesicular crystals. Curved liquid/liquid interface is typically created through o/w emulsions. With the presence of surfactant, the emulsions are controlled to be stable at least for the polymer crystallization periods. The difference to normal solution crystallization is: the nuclei will diffuse to the curved interface due to the Pickering effect and guide the crystallization along the curved liquid/liquid interface. If the supercooling can be controlled to be very small, crystal growth in the bulk droplets can be avoided. The advantages of this strategy are: 1) the formation process of vesicular type crystals can be monitored by controlling the polymer supply; 2) curved crystals, bowl-like structures and enclosed capsules can be easily obtained comparing to the self-assembly method for vesicle formation; 3) the obtained vesicles will be made of polymer crystals, which will possess the extraordinary mechanical properties. Based on the nucleation type, this dissertation is divided into two parts. The first part is focused on the self

  9. Self assembled monolayer based liquid crystal biosensor for free cholesterol detection

    SciTech Connect

    Tyagi, Mukta; Agrawal, V. V.; Chandran, Achu; Joshi, Tilak; Prakash, Jai; Biradar, A. M.

    2014-04-14

    A unique cholesterol oxidase (ChOx) liquid crystal (LC) biosensor, based on the disruption of orientation in LCs, is developed for cholesterol detection. A self-assembled monolayer (SAM) of Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP) and (3-Aminopropyl)trimethoxy-silane (APTMS) is prepared on a glass plate by adsorption. The enzyme (ChOx) is immobilized on SAM surface for 12 h before utilizing the film for biosensing purpose. LC based biosensing study is conducted on SAM/ChOx/LC (5CB) cells for cholesterol concentrations ranging from 10 mg/dl to 250 mg/dl. The sensing mechanism has been verified through polarizing optical microscopy, scanning electron microscopy, and spectrometric techniques.

  10. Self assembled monolayer based liquid crystal biosensor for free cholesterol detection

    NASA Astrophysics Data System (ADS)

    Tyagi, Mukta; Chandran, Achu; Joshi, Tilak; Prakash, Jai; Agrawal, V. V.; Biradar, A. M.

    2014-04-01

    A unique cholesterol oxidase (ChOx) liquid crystal (LC) biosensor, based on the disruption of orientation in LCs, is developed for cholesterol detection. A self-assembled monolayer (SAM) of Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP) and (3-Aminopropyl)trimethoxy-silane (APTMS) is prepared on a glass plate by adsorption. The enzyme (ChOx) is immobilized on SAM surface for 12 h before utilizing the film for biosensing purpose. LC based biosensing study is conducted on SAM/ChOx/LC (5CB) cells for cholesterol concentrations ranging from 10 mg/dl to 250 mg/dl. The sensing mechanism has been verified through polarizing optical microscopy, scanning electron microscopy, and spectrometric techniques.

  11. Electric method for studying reorientation dynamics of the nematic liquid crystal director

    NASA Astrophysics Data System (ADS)

    Shcherbinin, D. P.; Vakulin, D. A.; Konshina, E. A.

    2016-07-01

    A method has been proposed for studying the reorientation dynamics of the nematic liquid crystal (NLC) director using the results of measurements of the electric response of an LC cell. The simulation of the time dependences of the current in an LC cell with a homogeneous orientation is carried out upon variation of the applied voltage, the initial tilt angle of the director, dielectric anisotropy, and the elasticity coefficient, as well as the dynamic viscosity, density, and ion mobility in the NLC. A comparison of the experimental and computational curves of the electric response for NLC 5CB shows their good agreement. The method makes it possible to monitor the steady-state current, the density, and the ion mobility in NLCs.

  12. Maxwell-Wagner-Sillars effects on the thermal-transport properties of polymer-dispersed liquid crystals.

    PubMed

    Kuriakose, M; Longuemart, S; Depriester, M; Delenclos, S; Sahraoui, A Hadj

    2014-02-01

    We present the depolarization field effects (Maxwell-Wagner-Sillars effect) for the thermal transport properties of polymer dispersed liquid crystal composites under a frequency-dependent electric field. The experiments were conducted on polystyrene/4-Cyano-4'-pentylbiphenyl (PS/5CB) PDLCs of 73 vol.% and 85 vol.% liquid crystal (LC) concentrations. A self-consistent field approximation model is used to deduce the electrical properties of polymer and LC materials as well as the threshold electric field. Electric field-varying (at constant frequency) experiments were also conducted to calculate the interfacial thermal resistance between the LC droplets and polymer matrix as well as to find the elastic constant of LCs in droplet form.

  13. Demonstrations with a Liquid Crystal Shutter

    ERIC Educational Resources Information Center

    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…

  14. Liquid crystal-templated conducting organic polymers

    DOEpatents

    Stupp, Samuel I.; Hulvat, James F.

    2004-01-20

    A method of preparing a conductive polymeric film, includes providing a liquid crystal phase comprising a plurality of hydrophobic cores, the phase on a substrate, introducing a hydrophobic component to the phase, the component a conductive polymer precursor, and applying an electric potential across the liquid crystal phase, the potential sufficient to polymerize the said precursor.

  15. Liquid Crystals in Education--The Basics

    ERIC Educational Resources Information Center

    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…

  16. Liquid-Crystal Point-Diffraction Interferometer

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.

    1996-01-01

    Liquid-crystal point-diffraction interferometer (LCPDI) invented to combine flexible control of liquid-crystal phase-shifts with robustness of point-diffraction interferometers. Produces interferograms indicative of shapes of wavefronts of laser beams having passed through or reflected from objects of interest. Interferograms combined in computers to produce phase maps describing wavefronts.

  17. Liquid crystal tunable metamaterial absorber.

    PubMed

    Shrekenhamer, David; Chen, Wen-Chen; Padilla, Willie J

    2013-04-26

    We present an experimental demonstration of electronically tunable metamaterial 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% at 2.62 THz, as well as tune the resonant absorption over 4% 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 fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.

  18. Chemical and biological sensing using liquid crystals

    PubMed Central

    Carlton, Rebecca J.; Hunter, Jacob T.; Miller, Daniel S.; Abbasi, Reza; Mushenheim, Peter C.; Tan, Lie Na; Abbott, Nicholas L.

    2014-01-01

    The liquid crystalline state of matter arises from orientation-dependent, non-covalent interaction between molecules within condensed phases. Because the balance of intermolecular forces that underlies formation of liquid crystals is delicate, this state of matter can, in general, be easily perturbed by external stimuli (such as an electric field in a display). In this review, we present an overview of recent efforts that have focused on exploiting the responsiveness of liquid crystals as the basis of chemical and biological sensors. In this application of liquid crystals, the challenge is to design liquid crystalline systems that undergo changes in organization when perturbed by targeted chemical and biological species of interest. The approaches described below revolve around the design of interfaces that selectively bind targeted species, thus leading to surface-driven changes in the organization of the liquid crystals. Because liquid crystals possess anisotropic optical and dielectric properties, a range of different methods can be used to read out the changes in organization of liquid crystals that are caused by targeted chemical and biological species. This review focuses on principles for liquid crystal-based sensors that provide an optical output. PMID:24795857

  19. Liquid crystal device and method thereof

    DOEpatents

    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.

  20. Phototropic liquid crystals comprising one component

    NASA Astrophysics Data System (ADS)

    Sobolewska, Anna; Zawada, Joanna; Bartkiewicz, Stanislaw; Galewski, Zbigniew

    2013-09-01

    Phototropic liquid crystals (PtLC), in which the phase transition can be controlled by the light, are a new class of liquid crystal materials possessing number of potential applications, especially in photonic devices. So far a significant majority of PtLC materials has been realized by the doping a classical liquid crystal with a photochromic dye. Here we report PtLCs comprising a single compound. Liquid-crystalline and photochromic properties have been accomplished in alkylo-alkoxy derivatives of azobenzene. Such compounds show a rich polymorphism which can be controlled by the light. The phenomenon of the photochemical phase transition has been investigated by means of holographic grating recording.

  1. Nanotube networks in liquid crystals

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Lagerwall, Jan Peter F.; Scalia, Giusy

    2016-03-01

    Liquid crystals (LCs) are very attractive hosts for the organization of anisotropic nanoparticles such as carbon nanotubes (CNTs) because of the macroscopic organization resulting in properties of nanoparticles manifest at a macroscopic scale. Different types of LCs have demonstrated the ability to organize nanotubes, showing the generality of the approach, i.e., that the liquid crystallinity per se is the driving factor for the organization. Compared to standard nanotube composites (e.g. with disordered polymer hosts) the introduction of carbon nanotubes into an LC allows not only the transfer of the outstanding CNT properties to the macroscopic phase, providing strength and conductivity, but these properties also become anisotropic, following the transfer of the orientational order from the LC to the CNTs. The LC molecular structure plays an important even if ancillary role since it enters in the surface interactions, fulfilling a mediating action between the particle and the bulk of the LC. Isolated nanotubes can be obtained by optimized dispersions at lower concentrations and this process requires the use or development of tailored strategies like using solvents or even another LC for pre-dispersing CNTs. Aggregates or networks can be observed in poor dispersions and at higher nanoparticle concentrations. In those, due to surface interactions, the LC behaviour can be strongly affected with changes in phase sequences or transition temperatures and the effect is expected to be more pronounced as the concentration of nanotubes increases. We present preliminary investigations and observations on nanotube - LC systems based on a smectic LC host.

  2. Liquid crystals for organic transistors (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hanna, Jun-ichi; Iino, Hiroaki

    2016-09-01

    Liquid crystals are a new type of organic semiconductors exhibiting molecular orientation in self-organizing manner, and have high potential for device applications. In fact, various device applications have been proposed so far, including photosensors, solar cells, light emitting diodes, field effect transistors, and so on.. However, device performance in those fabricated with liquid crystals is less than those of devices fabricated with conventional materials in spite of unique features of liquid crystals. Here we discuss how we can utilize the liquid crystallinity in organic transistors and how we can overcome conventional non-liquid crystalline organic transistor materials. Then, we demonstrate high performance organic transistors fabricated with a smectic E liquid crystal of Ph-BTBT-10, which show high mobility of over 10cm2/Vs and high thermal durability of over 200oC in OFETs fabricated with its spin-coated polycrystalline thin films.

  3. Investigation of the Effect of Yttrium Oxide Nanoparticles Doped with Cerium and Neodymium on Electro-Optics of Liquid Crystal Polymer Composites

    NASA Astrophysics Data System (ADS)

    Zharkova, G. M.; Osipov, V. V.; Platonov, V. V.; Podkin, A. V.; Strel'tsov, S. A.

    2016-12-01

    Morphology and properties of liquid crystal polymer composites doped with inorganic nanoparticles are described. These composites comprised nematic liquid crystal 5CB, polyvinyl acetate, and nanoparticles of oxides (Y2O3, CeO2:Y2O3, and Nd2O3:Y2O3). Nanopowders were synthesized by the laser method of vaporization of a solid target under CO2-laser or fiber ytterbium laser irradiation. The effect of oxides on the electro-optical properties of the composites and times of response to an electrical pulse is investigated. It is shown that incorporation of CeO2:Y2O3 nanopowder in liquid crystal polymer composites affects the decrease of the control field and the increase of light transmission in an electric field stronger than incorporation of Nd2O3:Y2O3 nanoparticles.

  4. Bistable liquid crystal device fabricated via microscale liquid crystal alignment

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Toyoshima, Wataru; Nose, Toshiaki

    2016-10-01

    Bistable liquid crystal (LC) molecular orientation properties in micropatterned LC cells were investigated experimentally and theoretically. When an LC cell was heated to the phase-transition temperature and then cooled, an LC orientation with ±π/2-twist domains (±π/2-twist mode) was obtained. Furthermore, a different LC orientation with ±π-twist domains (±π-twist mode) was observed when a 10-V potential was applied across a sample LC cell. Both orientation states were stably retained over a long period. Herein, cross-sectional LC orientation models in the ±π/2- and ±π-twist modes are proposed to explain the generation and behavior of two different disclination lines. The total energies within one period in the ±π/2- and ±π-twist modes (F±π/2 and F±π, respectively) were estimated theoretically. These energies were found to depend on the LC layer thickness and to cross over at a certain thickness; this indicates that F±π is equal to F±π/2 at this equilibrium thickness. The best temporal stability is likely attained at this equilibrium thickness. We demonstrated a bistable color-switching device by combining a full-wave plate and crossed polarizers. When these optical components were configured properly, stable bistable switching between two colors was achieved.

  5. Temperature sensing with thermochromic liquid crystals

    NASA Astrophysics Data System (ADS)

    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.

  6. A swing driven by liquid crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng

    Angular momentum in liquid crystals exists as flow, director reorientation, etc. However, it is hard to observe and measure angular momentum in liquid crystals by a direct mechanical approach. Torsion pendulum is a general tool to measure angular momentum by torque balance. Our torsion pendulum can harvest the angular momentum in liquid crystals to make it observable. The oscillation of the pendulum keeps increasing by constructively adding a small angular momentum of liquid crystals each period at the resonant frequency of the pendulum. Its similar to a swing driven by a force at its resonant frequency. For the torsion pendulum, a cage made of two aluminum discs, in which a liquid crystal cell is placed, is suspended between two thin tungsten wires. A gold mirror, which is a part of the optical lever system, is attached on one tungsten wire. As first demonstration, we fabricate a circular hybrid liquid crystal cell, which can induce concentric backflows to generate angular momentum. The alignment on the planar substrate is concentric and tangential. Due to the coupling between director rotation and flow, the induced backflow goes around the cell when we add electrical pulses between top and bottom substrates. The oscillation is observed by a position sensitive detector and analyzed on the basis of Eriksen-Leslie theory. With vacuum condition and synchronous driving system, the oscillation signal is improved. We demonstrate that this torsion pendulum can sensitively detect the angular momentum in liquid crystals.

  7. Stimuli-responsive photoluminescent liquid crystals.

    PubMed

    Yamane, Shogo; Tanabe, Kana; Sagara, Yoshimitsu; Kato, Takashi

    2012-01-01

    We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(p-phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex.

  8. Liquid Crystal Research Shows Deformation By Drying

    NASA Technical Reports Server (NTRS)

    2003-01-01

    These images, from David Weitz's liquid crystal research, show ordered uniform sized droplets (upper left) before they are dried from their solution. After the droplets are dried (upper right), they are viewed with crossed polarizers that show the deformation caused by drying, a process that orients the bipolar structure of the liquid crystal within the droplets. When an electric field is applied to the dried droplets (lower left), and then increased (lower right), the liquid crystal within the droplets switches its alignment, thereby reducing the amount of light that can be scattered by the droplets when a beam is shone through them.

  9. Photorefractive effect in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Sasaki, Takeo; Naka, Yumiko

    2014-03-01

    In this paper, we review recent progress of research on the photorefractive effect of ferroelectric liquid crystals. The photorefractive effect is a phenomenon that forms a dynamic hologram in a material. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon is applicable to a wide range of devices related to diffraction optics including 3D displays, optical amplification, optical tomography, novelty filters, and phase conjugate wave generators. Ferroelectric liquid crystals are considered as a candidate for practical photorefractive materials. A refractive index grating formation time of 8-10 ms and a large gain coefficient are easily obtained in photorefractive ferroelectric liquid crystals.

  10. Nanoparticles in discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep

    The self-assembly of disc-shaped molecules creates discotic liquid crystals (DLCs). These nanomaterials of the sizes ranging from 2-6 nm are emerging as a new class of organic semiconducting materials. The unique geometry of columnar mesophases formed by discotic molecules is of great importance to study the one-dimensional charge and energy migration in organized systems. A number of applications of DLCs, such as, one-dimensional conductor, photoconductor, photovoltaic solar cells, light emitting diodes and gas sensors have been reported. The conductivity along the columns in columnar mesophases has been observed to be several orders of magnitude greater than in perpendicular direction and, therefore, DLCs are described as molecular wires. On the other hand, the fields of nanostructured materials, such as gold nanoparticles, quantum dots, carbon nanotubes and graphene, have received tremendous development in the past decade due to their technological and fundamental interest. Recently the hybridization of DLCs with various metallic and semiconducting nanoparticles has been realized to alter and improve their properties. These nanocomposites are not only of basic science interest but also lead to novel materials for many device applications. This article provides an overview on the development in the field of newly immersed discotic nanoscience. After a brief introduction of DLCs, the article will cover the inclusion of various zero-, one- and two-dimensional nanoparticles in DLCs. Finally, an outlook into the future of this newly emerging intriguing field of discotic nanoscience research will be provided.

  11. Tactoids of chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Palacio-Betancur, Viviana; Villada-Gil, Stiven; Zhou, Ye; Armas-Pérez, Julio C.; de Pablo, Juan José; Hernández-Ortiz, Juan Pablo

    The phase diagram of chiral liquid crystals confined in ellipsoids is obtained, by following a theoretically informed Monte Carlo relaxation of the tensor alignment field Q. The free energy of the system is described by a functional in the framework of the Landau-de Gennes formalism. This study also includes the effect of anchoring strength, curvature, and chirality of the system. In the low chirality region of the phase diagram we found the twist bipolar (BS) phase and some cholesteric phases such as the radial spherical structure (RSS), twist cylinder (TC) and double twist cylinder (DTC) whose axis of rotation is not necessarily aligned with the major axis of the geometry. For high chirality scenarios, the disclination lines are twisted or bent near the surface preventing the formation of symmetric networks of defects, although an hexagonal pattern is formed on the surface which might serve as open sites for collocation of colloids. By analyzing the free energies of isochoric systems, prolate geometries tend to be more favorable for high chirality and low anchoring conditions. Universidad Nacional de Colombia Ph.D. grant and COLCIENCIAS under the Contract No. 110-165-843-748. CONACYT for Postdoctoral Fellowships Nos. 186166 and 203840.

  12. Liquid crystal television spatial light modulators

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-01-01

    The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.

  13. Liquid crystal on subwavelength metal gratings

    SciTech Connect

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-14

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  14. Rapid leak detection with liquid crystals

    NASA Technical Reports Server (NTRS)

    Heisman, R. M.; Iceland, W. F.; Ruppe, E. P.

    1978-01-01

    Small leaks in vacuum lines are detected by applying liquid-crystal coating, warming suspected area, and observing color change due to differential cooling by leak jet. Technique is used on inside or outside walls of vacuum-jacketed lines.

  15. Thermal Conductivity and Liquid Crystal Thermometers.

    ERIC Educational Resources Information Center

    Edge, R. D., Ed.

    1993-01-01

    Describes using stock liquid crystal postcards as inexpensive classroom thermometers. Also suggests using these postcards as a good visual temperature indicator for classroom demonstrations such as temperature gradients. One such activity is provided. (MVL)

  16. Formation of a crystal nucleus from liquid

    PubMed Central

    Kawasaki, Takeshi; Tanaka, Hajime

    2010-01-01

    Crystallization is one of the most fundamental nonequilibrium phenomena universal to a variety of materials. It has so far been assumed that a supercooled liquid is in a “homogeneous disordered state” before crystallization. Contrary to this common belief, we reveal that a supercooled colloidal liquid is actually not homogeneous, but has transient medium-range structural order. We find that nucleation preferentially takes place in regions of high structural order via wetting effects, which reduce the crystal–liquid interfacial energy significantly and thus promotes crystal nucleation. This novel scenario provides a clue to solving a long-standing mystery concerning a large discrepancy between the rigorous numerical estimation of the nucleation rate on the basis of the classical nucleation theory and the experimentally observed ones. Our finding may shed light not only on the mechanism of crystal nucleation, but also on the fundamental nature of a supercooled liquid state. PMID:20663951

  17. Liquid crystal interfaces: Experiments, simulations and biosensors

    NASA Astrophysics Data System (ADS)

    Popov, Piotr

    Interfacial phenomena are ubiquitous and extremely important in various aspects of biological and industrial processes. For example, many liquid crystal applications start by alignment with a surface. The underlying mechanisms of the molecular organization of liquid crystals at an interface are still under intensive study and continue to be important to the display industry in order to develop better and/or new display technology. My dissertation research has been devoted to studying how complex liquid crystals can be guided to organize at an interface, and to using my findings to develop practical applications. Specifically, I have been working on developing biosensors using liquid-crystal/surfactant/lipid/protein interactions as well as the alignment of low-symmetry liquid crystals for potential new display and optomechanical applications. The biotechnology industry needs better ways of sensing biomaterials and identifying various nanoscale events at biological interfaces and in aqueous solutions. Sensors in which the recognition material is a liquid crystal naturally connects the existing knowledge and experience of the display and biotechnology industries together with surface and soft matter sciences. This dissertation thus mainly focuses on the delicate phenomena that happen at liquid interfaces. In the introduction, I start by defining the interface and discuss its structure and the relevant interfacial forces. I then introduce the general characteristics of biosensors and, in particular, describe the design of biosensors that employ liquid crystal/aqueous solution interfaces. I further describe the basic properties of liquid crystal materials that are relevant for liquid crystal-based biosensing applications. In CHAPTER 2, I describe the simulation methods and experimental techniques used in this dissertation. In CHAPTER 3 and CHAPTER 4, I present my computer simulation work. CHAPTER 3 presents insight of how liquid crystal molecules are aligned by

  18. Optofluidics based on liquid crystal microflows

    NASA Astrophysics Data System (ADS)

    Vasdekis, A. E.; Cuennet, J. G.; De Sio, L.; Psaltis, D.

    2011-10-01

    By replacing common buffers with anisotropic liquids in microfluidics, an enhanced range of optofluidic functionalities is enabled. Such an anisotropic liquid is nematic liquid crystals (NLC), which exhibits optical properties that can be tuned by optical, electrical or mechanical fields, such as flow. We demonstrate an optofluidic modulator based on direct flow of nematic liquid crystals in microfluidic channels. We discuss this optofluidic paradigm both under steady state conditions, and under flow. Rapid pulsatile flows are detrimental towards more compact and ultra-fast devices. These were enabled via peristaltic pumps, demonstrating liquid crystal modulators operating above the limit of 3 kHz. We discuss the latter results, but also assess the feasibility of performing ultra-fast optics and additional functionalities for on- and off-chip imaging.

  19. Vacuum pyrolysis characteristics and kinetic analysis of liquid crystal from scrap liquid crystal display panels.

    PubMed

    Chen, Ya; Zhang, Lingen; Xu, Zhenming

    2017-04-05

    Recycling of waste liquid crystal display (LCD) panels is an urgent task with the rapid expanding LCD market. However, as important composition of LCD panels, the treatment of liquid crystal is seldom concerned for its low concentration. In present study, a stripping product enriched liquid crystal and indium is gained by mechanical stripping process, in which liquid crystal is enriched from 0.3wt.% to 53wt.% and indium is enriched from 0.02wt.% to 7.95wt.%. For the stripping product, liquid crystal should be removed before indium recovery because (a) liquid crystal will hinder indium recycling; (b) liquid crystal is hazardous waste. Hence, an effective and green approach by vacuum pyrolysis is proposed to treat liquid crystal in the stripping product. The results are summarized as: (i) From the perspective of apparent activation energy, the advantages of vacuum pyrolysis is expounded according to kinetic analysis. (ii) 89.10wt.% of liquid crystal is converted and the content of indium in residue reaches 14.18wt.% under 773K, 15min and system pressure of 20Pa. This study provides reliable information for further industrial application and an essential pretreatment for the next step of indium recycling.

  20. Liquid crystal optical fibers for sensing applications

    NASA Astrophysics Data System (ADS)

    Choudhury, P. K.

    2013-09-01

    Propagation characteristics of optical fibers are greatly dependent on materials, which the guides are comprised of. Varieties of materials have been developed and investigated for their usage in fabricating optical fibers for specific applications. Within the context, a liquid crystal medium is both inhomogeneous and optically anisotropic, and fibers made of such mediums are greatly useful. Also, liquid crystals exhibit strong electro-optic behavior, which allows alternation in their optical properties under the influence of external electric fields. These features make liquid crystal fibers greatly important for optical applications. The present communication is aimed at providing a glimpse of the efficacy of liquid crystals and/or fibers made of liquid crystals, followed by the analytical investigation of wave propagation through such guides. The sustainment of modes is explored in these fibers under varying fiber dimensions, and the novelty is discussed. The case of tapered liquid crystal fibers is also briefly discussed highlighting the usefulness. Control on the dispersion characteristics of such fibers may be imposed by making the guide even more complex; the possibility of devising such options is also touched upon.

  1. Molecular Models of Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    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.

  2. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 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. Semiconductor liquid crystal composition and methods for making the same

    DOEpatents

    Alivisatos, A. Paul; Li, Liang-shi

    2005-04-26

    Semiconductor liquid crystal compositions and methods for making such compositions are disclosed. One embodiment of the invention is directed to a liquid crystal composition including a solvent and semiconductor particles in the solvent. The solvent and the semiconductor particles are in an effective amount in the liquid crystal composition to form a liquid crystal phase.

  4. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 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)....

  5. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 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)....

  6. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 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)....

  7. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2010 CFR

    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)....

  8. Electro-osmosis in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    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.

  9. Atomic force microscopy on liquid crystals

    NASA Astrophysics Data System (ADS)

    Bahr, Christian; Schulz, Benjamin

    This chapter provides an introduction to the atomic force microscopy (AFM) on thermotropic liquid crystals. We first give a general introduction to the technique of AFM and then describe the special requirements that have to be met for the imaging of liquid-crystalline surfaces. We also discuss the relation between the quality or reliability of the imaging results and various parameters of the scanning conditions. We briey review the existing work on AFM on liquid crystals and finally describe applications beyond the imaging, such as molecular force spectroscopy or manipulation of surface structures.

  10. Electro-osmosis in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. 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. 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 exhibit electro-osmotic flows along the "guiding rails" imposed by the spatially varying director.

  11. Solid microparticles in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Muševič, Igor

    A brief historic overview of colloidal experiments in the 1990's is given in the introduction. These experiments have later inspired research on nematic colloids, after the technique of laser tweezers manipulation of particles was introduced to this field. Basic topological properties of colloidal inclusions in the nematic liquid crystals are discussed and the nematic-mediated forces between dipolar and quadrupolar colloidal particles in bulk nematic are explained. Structural and topological properties of 2D and 3D colloidal crystals and superstructures made of colloidal particles of different size and symmetry in bulk nematic liquid crystal are described. Laser-tweezer manipulation and rewiring of topological defect loops around colloidal particles is introduced. This results in the colloidal entanglement, as well as knotting and linking of defect loops of the order parameter field. Shape and size-dependent colloidal interactions in the nematic liquid crystals are reviewed. The chapter concludes with the discussion of bulk chiral nematic and blue phase colloids.

  12. Liquid nitrogen dewar for protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Gaseous Nitrogen Dewar apparatus developed by Dr. Alex McPherson of the University of California, Irvine for use aboard Mir and the International Space Station allows large quantities of protein samples to be crystallized in orbit. The specimens are contained either in plastic tubing (heat-sealed at each end). Biological samples are prepared with a precipitating agent in either a batch or liquid-liquid diffusion configuration. The samples are then flash-frozen in liquid nitrogen before crystallization can start. On orbit, the Dewar is placed in a quiet area of the station and the nitrogen slowly boils off (it is taken up by the environmental control system), allowing the proteins to thaw to begin crystallization. The Dewar is returned to Earth after one to four months on orbit, depending on Shuttle flight opportunities. The tubes then are analyzed for crystal presence and quality

  13. Liquid crystal quantitative temperature measurement technique

    NASA Astrophysics Data System (ADS)

    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.

  14. Key Developments in Ionic Liquid Crystals.

    PubMed

    Alvarez Fernandez, Alexandra; Kouwer, Paul H J

    2016-05-16

    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?

  15. Key Developments in Ionic Liquid Crystals

    PubMed Central

    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

  16. Field-cycling NMR relaxometry of a liquid crystal above TNI in mesoscopic confinement

    NASA Astrophysics Data System (ADS)

    Sebastião, P. J.; Sousa, D.; Ribeiro, A. C.; Vilfan, M.; Lahajnar, G.; Seliger, J.; Žumer, S.

    2005-12-01

    We measured the proton spin-lattice relaxation times in the isotropic phase of liquid crystal 4'-n-pentyl-4-cyanobiphenyl (5CB) confined into porous glass (CPG) with the average pore diameter ˜72nm . The analysis of T1-1 frequency dispersions, spanning over four decades, shows that the main relaxation mechanism induced by the ordered surface layer are molecular reorientations mediated by translational displacements (RMTD). The RMTD contribution to T1-1 is proportional to the inverse square root of Larmor frequency, a consequence of the equipartition of diffusion modes along the surface. Low and high frequency cutoffs of the RMTD mechanism clearly reveal that the surface alignment of liquid crystal is random planar with the size of uniformly oriented patches ˜5nm , depending on the treatment of the CPG matrix. According to the size of the uniformly oriented patches varies also the thickness of the ordered surface layer and its temperature behavior. The surface-induced order parameter is found to be temperature independent and determined by the local short range surface interactions.

  17. Onset of Thermal Convection in a Homeotropically Aligned Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Thomas, Leif N.; Ahlers, Guenter; Bajaj, Kapil M. S.

    1996-11-01

    For a homeotropically aligned nematic liquid crystal in a vertical magnetic field and heated from below, it was predicted^1 that the bifurcation from conduction to convection is a subcritical Hopf bifurcation. Using 4-n-pentyl-4'-cyanobiphenyl (5CB) at a mean temperature of 25.6^oC in a cylindrical cell of aspect ratio (radius/height) Γ=10.6, we observed travelling and standing waves during the transient from conduction to convection. We measured the Hopf frequency ω c and the critical wavenumber kc at different vertical magnetic field strengths in the range 8 alt h ≡ H/ HF alt 17 (HF = 20.1 Gauss is the Fréedericksz field). Over this field range, our results for ωc agree within their scatter of about 2% with the prediction, but our results for kc are systematically lower by about 5%. After the transients, the fully developed flow has a very slow chaotic time dependence which is unrelated to the Hopf frequency.^2 Supported by U.S. Department of Energy Grant DE-FG03-87ER13738. ^1Q. Feng, W. Decker, W. Pesch, and L. Kramer, J. Phys. France II 2, 1303 (1992). ^2G. Ahlers, in Pattern Formation in Liquid Crystals, edited by A. Buka and L. Kramer (Springer, 1996).

  18. Liquid crystal-gated-organic field-effect transistors with in-plane drain-source-gate electrode structure.

    PubMed

    Seo, Jooyeok; Nam, Sungho; Jeong, Jaehoon; Lee, Chulyeon; Kim, Hwajeong; Kim, Youngkyoo

    2015-01-14

    We report planar liquid crystal-gated-organic field-effect transistors (LC-g-OFETs) with a simple in-plane drain-source-gate electrode structure, which can be cost-effectively prepared by typical photolithography/etching processes. The LC-g-OFET devices were fabricated by forming the LC layer (4-cyano-4'-pentylbiphenyl, 5CB) on top of the channel layer (poly(3-hexylthiophene), P3HT) that was spin-coated on the patterned indium-tin oxide (ITO)-coated glass substrates. The LC-g-OFET devices showed p-type transistor characteristics, while a current saturation behavior in the output curves was achieved for the 50-150 nm-thick P3HT (channel) layers. A prospective on/off ratio (>1 × 10(3)) was obtained regardless of the P3HT thickness, whereas the resulting hole mobility (0.5-1.1 cm(2)/(V s)) at a linear regime was dependent on the P3HT thickness. The tilted ordering of 5CB at the LC-P3HT interfaces, which is induced by the gate electric field, has been proposed as a core point of working mechanism for the present LC-g-OFETs.

  19. Polymer's anchoring behavior in liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Cui, Yue

    The current dissertation mainly discusses about the polymers anchoring behavior in liquid crystal cells in two aspects: surface interaction and bulk interaction. The goal of the research is to understand the fundamental physics of anchoring strength and apply the knowledge to liquid crystal display devices. Researchers proposed two main contributors to the surface anchoring strength: the micro grooves generated by external force and the polymer chain's alignment. Both of them has experimental proofs. In the current study, explorations were made to understand the mechanisms of surface anchoring strength and easy axis of surface liquid crystal provided by rubbed polymer alignment layer. The work includes not only the variation of the alignment layer itself such as thickness(Chapter 3) and polymer side chain (Chapter 5), but also the variation of external conditions such as temperature (Chapter 4) and rubbing condition (Chapter 6). To determine the polar and azimuthal anchoring strengths, Rapini-Papoular's expression was applied. However, it was discovered that higher order terms may be required in order to fit the experimental result or theoretically predict unique anchoring behaviors (Chapter 2, Chapter 6). SEM and AFM technologies were introduced to gather the actual structures of polymer alignment layer and extrapolate the alignment of liquid crystal in a micro scale. The result shows that the anchoring strength can be adjusted by the layer thickness, side chain structure, while the easy axis direction can be adjusted by a second rubbing direction. In addition, different anchoring conditions combined with liquid crystal's elastic energy can generate quite different forms of liquid crystals (Chapter 7). In the study of bulk alignment, the main contrition from the current dissertation is applying the understanding of anchoring behavior to optimizing actual switchable devices. Conventional PDLC performance can be tuned with the knowledge of the polymer and the liquid

  20. Development of Multifunctional Ultra-Nonlinear Liquids and Liquid Crystals for Sensor Protection Applications

    DTIC Science & Technology

    2008-03-01

    13. I. C. Khoo, Yana Zhang Williams, B. Lewis and T. Mallouk, "Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed...34Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic crystals," Mol. Cryst. Liq. Cryst. 446: 233...Nonlinear nematic liquid crystals - Enhanced photorefractivity of CdSe nano-rod doped nematic liquid crystal--------------- 5 2.3 Extremely nonlinear

  1. Effects of Polymers on the Rotational Viscosities of Nematic Liquid Crystals and Dynamics of Field Alignment.

    NASA Astrophysics Data System (ADS)

    Kim, Du-Rim

    , which are normal polymer (PS, molecular weight = 2,700) in E63 and ultra-violet polymerized polymer (BAB) with BME photo-initiator in 5CB, the polymer effects for the gamma_1 were not improved contrary to the expectation. But in the case of side-chain polymer (PMA-6CB) solutions in 5CB, which are miscible in all concentrations, marked linear increase in gamma_1 is observed. This linear increase continues until 5% polymer concentration is reached. Above this concentration, overlappings of polymer chains in concentrated solutions is observed. The measurement of chi_{a } is permitted by oscillating magnetic field method. As expected, the diamagnetic anisotropy of pure liquid crystals and their polymer solutions are found to be the same.

  2. Polymer-dispersed liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-10-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

  3. Optical Properties of Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Khosla, Samriti; Lal, Suman; Tripathi, S. K.; Sood, Nitin; Singh, Darshan

    2011-12-01

    The linking of liquid crystals polymer chains together into gel network fixes their topology, and melt becomes an elastic solid. These materials are called liquid crystals elastomers. Liquid crystal elastomers possess properties of soft elasticity and spontaneous shape change. The constituent molecules of LCEs are orientationally ordered and there exist a strong coupling between the orientational order and mechanical strain. In LCEs the molecules start elongate when their component rods orient and reversibly contract when the order is lost (typically by heating). So there is a change of average molecular shape from spherical to spheroidal. These unique properties make these materials suitable for future biological applications. Various research groups have studied different properties of LCEs in which optical properties are predominant. LCE has been synthesized in our laboratory. In this paper, we report on the optical behavior of this material.

  4. Characterising laser beams with liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Dudley, Angela; Naidoo, Darryl; Forbes, Andrew

    2016-02-01

    We show how one can determine the various properties of light, from the modal content of laser beams to decoding the information stored in optical fields carrying orbital angular momentum, by performing a modal decomposition. Although the modal decomposition of light has been known for a long time, applied mostly to pattern recognition, we illustrate how this technique can be implemented with the use of liquid-crystal displays. We show experimentally how liquid crystal displays can be used to infer the intensity, phase, wavefront, Poynting vector, and orbital angular momentum density of unknown optical fields. This measurement technique makes use of a single spatial light modulator (liquid crystal display), a Fourier transforming lens and detector (CCD or photo-diode). Such a diagnostic tool is extremely relevant to the real-time analysis of solid-state and fibre laser systems as well as mode division multiplexing as an emerging technology in optical communication.

  5. Properties of the static NMR response of a confined thin nematic film of 5CB-d2 under crossed electric and magnetic fields: theory and experiments.

    PubMed

    Véron, A; Sugimura, A; Luckhurst, G R; Martins, A F

    2012-11-01

    This work describes an investigation of the static (or quasistatic) nuclear magnetic resonance (NMR) response in a nematic liquid crystal confined between two planar conducting plates and subject to a magnetic field and an electric field produced by a difference of voltage applied on the plates. Deuterium NMR spectroscopy of 4-pentyl-d(2)-4'-cyanobiphenyl (5CB-d(2)) under these conditions has revealed a voltage dependent inhomogeneous director distribution for a particular narrow range of voltages and for a fixed magnetic field (that of the spectrometer). In the ideal setup the two plates are assumed to be rigorously parallel, so that a difference of voltage applied on the plates leads to a constant electric field normal to them. When the magnetic field is parallel to the plates (orthogonal geometry) there exists a threshold value of the electric field for which the effect of both fields exactly compensate; moreover, for stronger electric field the director aligns with the electric field while for weaker electric field the director aligns with the magnetic field. If there is a lack of parallelism between the two plates, the electric field becomes inhomogeneous so that it may be larger than the threshold value in some region of the sample and smaller in the remaining part of the sample. In that case the director will adopt essentially two orientations within the sample, namely, parallel or perpendicular to the magnetic field, and the position of the frontier between the two domains depends on the voltage. This feature is clearly shown by deuterium NMR spectra that exhibit a transfer of intensity between two quadrupolar doublets with increase in the applied voltage. The coexistence of two director populations occurs for a range of voltages that depends on the degree of nonparallelism; accordingly, an estimation of this range by NMR yields an experimental estimation of the lack of parallelism. A tiny tilt of the magnetic field (nonorthogonal geometry) entrains a

  6. Hydrodynamics and Rheology of Active Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Cui, Zhenlu

    2012-02-01

    Active liquid crystals such as swimming bacteria, active gels and assemblies of motors and filaments are active complex fluids. Such systems differ from their passive counterparts in that particles absorb energy and generate motion. They are interesting from a more fundamental perspective as their dynamic phenomenons are both physically fascinating and potentially of great biological significance. In this talk, I will present a continuum model for active liquid crystals and analyze the behavior of a suspension subjected to a weak Poiseuille flow. Hydrodynamics, stability and rheology will also be discussed.

  7. Chirality and biaxiality in cholesteric liquid crystals.

    PubMed

    Dhakal, Subas; Selinger, Jonathan V

    2011-02-01

    We investigate the statistical mechanics of chirality and biaxiality in liquid crystals through a variety of theoretical approaches, including Monte Carlo simulations, lattice mean-field theory, and Landau theory. All of these calculations show that there is an important interaction between cholesteric twist and biaxial order: The twist acts as a field on the biaxial order, and conversely, the biaxial order increases the twist, that is, reduces the pitch. We model the behavior of chiral biaxial liquid crystals as a function of temperature and discuss how the predictions can be tested in experiments.

  8. Statistical foundations of liquid-crystal theory

    PubMed Central

    Seguin, Brian; Fried, Eliot

    2013-01-01

    Working on a state space determined by considering a discrete system of rigid rods, we use nonequilibrium statistical mechanics to derive macroscopic balance laws for liquid crystals. A probability function that satisfies the Liouville equation serves as the starting point for deriving each macroscopic balance. The terms appearing in the derived balances are interpreted as expected values and explicit formulas for these terms are obtained. Among the list of derived balances appear two, the tensor moment of inertia balance and the mesofluctuation balance, that are not standard in previously proposed macroscopic theories for liquid crystals but which have precedents in other theories for structured media. PMID:23554513

  9. Crystals, liquid crystals and superfluid helium on curved surfaces

    NASA Astrophysics Data System (ADS)

    Vitelli, Vincenzo

    In this thesis we study the ground state of ordered phases grown as thin layers on substrates with smooth spatially varying Gaussian curvature. The Gaussian curvature acts as a source for a one body potential of purely geometrical origin that controls the equilibrium distribution of the defects in liquid crystal layers, thin films of He4 and two dimensional crystals on a frozen curved surface. For superfluids, all defects are repelled (attracted) by regions of positive (negative) Gaussian curvature. For liquid crystals, charges between 0 and 4pi are attracted by regions of positive curvature while all other charges are repelled. As the thickness of the liquid crystal film increases, transitions between two and three dimensional defect structures are triggered in the ground state of the system. Thin spherical shells of nematic molecules with planar anchoring possess four short 12 disclination lines but, as the thickness increases, a three dimensional escaped configuration composed of two pairs of half-hedgehogs becomes energetically favorable. Finally, we examine the static and dynamical properties that distinguish two dimensional crystals constrained to lie on a curved substrate from their flat space counterparts. A generic mechanism of dislocation unbinding in the presence of varying Gaussian curvature is presented. We explore how the geometric potential affects the energetics and dynamics of dislocations and point defects such as vacancies and interstitials.

  10. The Viscoelastic Properties of Nematic Monodomains Containing Liquid Crystal Polymers.

    NASA Astrophysics Data System (ADS)

    Gu, Dongfeng

    The work presented here investigates the viscoelastic properties of nematic materials containing liquid crystal polymers (LCP). We focus on how the elastic constants and the viscosity coefficients of the mixture systems are influenced by polymer architectures. In dynamic light scattering studies of the relaxation of the director orientation fluctuations for the splay, twist, and bend deformation modes, decrease of the relaxation rates was observed when LCPs were dissolved into low molar mass nematics (LMMN). For the side-chain LCPs, the slowing down in the bend mode is comparable to or larger than those of the splay and twist modes. For main-chain LCPs, the relative changes in the relaxation rates for the twist and splay modes are about one order of magnitude larger than that for the bend mode. The results of light scattering under an electric field show that the decrease in the twist relaxation rate is due to a large increase in the twist viscosity and a minor decrease in the twist elastic constant. These changes were found to increase with decrease of the spacer length, with increase of molecular weight, and with decrease of the backbone flexibility. In Freedericksz transition measurements, the splay and bend elastic constants and the dielectric anisotropies of the nematic mixtures were determined and the values are 5~15% lower than those of the pure solvent. From the analysis of the results of Freedericksz transition and light scattering experiments, a complete set of the elastic constants and viscosity coefficients corresponding to the three director deformation modes were obtained for the LCP mixtures. The changes in the viscosity coefficients due to addition of LCPs were analysed to estimate the anisotropic shapes of the polymer backbone via a hydrodynamic model. The results suggest that an oblate backbone configuration is maintained by the side-chain LCPs and a prolate chain configuration appears for the main-chain LCPs. The rheological behavior of a side

  11. Effect of Dielectric Titanium, Yttrium, and Silicon Oxide Nanoparticles on Electro-Optical Characteristics of Polymer-Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Zhdanov, K. R.; Romanenko, A. I.; Zharkova, G. M.

    2016-01-01

    Electro-optical characteristics of composite polymer-dispersed liquid crystals doped (implanted) with inorganic SiO2, TiO2, and Y2O3 nanoparticles in strong electric fields are studied. The composites were obtained by the method of phase separation of liquid crystals (5CB) and polymer (polyvinyl acetate). It is revealed that implantation of up to 1 wt.% of nanoparticles does not noticeably affect the morphology of the composites. The implanted particles change the mismatch between the refractive indices of the polymer and the liquid crystal, and the strong particle aggregation increases the light scattering that can improve the electrooptical contrast of the composites. Changes of the dielectric permittivity with the field are correlated with the light transmittance. It is found that the yttrium and silicon oxides decrease and the titanium oxides increase the Fredericks threshold field. The titanium oxides and to a greater extent the silicon oxides decrease the dependence of the light transmittance on the changes in the dielectric permittivity.

  12. Initiatorless Photopolymerization of Liquid Crystal Monomers.

    PubMed

    Lee, Kyung Min; Ware, Taylor H; Tondiglia, Vincent P; McBride, Matthew K; Zhang, Xinpeng; Bowman, Christopher N; White, Timothy J

    2016-10-04

    Liquid crystal monomers are widely employed in industry to prepare optical compensating films as well as extend or enhance the properties of certain display modes. Because of the thermotropic nature of liquid crystalline materials, polymerization of liquid crystalline monomers (sometimes referred to as reactive mesogens) is often initiated by radical photoinitiation (photopolymerization) of (meth)acrylate functional groups. Here, we report on the initiatorless photopolymerization of commercially available liquid crystalline monomers upon exposure to 365 nm UV light. Initiatorless polymerization is employed to prepare thin films as well as polymer stabilizing networks in mixtures with low-molar-mass liquid crystals. EPR and FTIR confirm radical generation upon exposure to 365 nm light and conversion of the acrylate functional groups. A potential mechanism is proposed, informed by control experiments that indicate that the monomers undergo a type II Norrish mechanism. The initiatorless polymerization of the liquid crystalline monomers yield liquid crystalline polymer networks with mechanical properties that can be equal to those prepared with conventional radical photoinitiators. We demonstrate that initiatorless polymerization of display modes significantly increases the voltage holding ratio, which could result in a reduction in drive voltages in flat-panel televisions and hand-held devices, extending battery life and reducing power consumption.

  13. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  14. Inexpensive Electrooptic Experiments on Liquid Crystal Displays.

    ERIC Educational Resources Information Center

    Ciferno, Thomas M.; And Others

    1995-01-01

    Describes the construction and use of an electrooptic apparatus that can be incorporated into the classroom to test liquid crystal displays (LCDs) and introduce students to experiments of an applied physics nature with very practical implications. Presents experiments that give students hands-on experience with technologies of current interest to…

  15. Helmet-Mounted Liquid-Crystal Display

    NASA Technical Reports Server (NTRS)

    Smith, Steve; Plough, Alan; Clarke, Robert; Mclean, William; Fournier, Joseph; Marmolejo, Jose A.

    1991-01-01

    Helmet-mounted binocular display provides text and images for almost any wearer; does not require fitting for most users. Accommodates users from smallest interpupillary distance to largest. Two liquid-crystal display units mounted in helmet. Images generated seen from any position head can assume inside helmet. Eyes directed to position for best viewing.

  16. Fluctuation and dissipation in liquid crystal electroconvection

    NASA Astrophysics Data System (ADS)

    Goldburg, Walter I.; Goldschmidt, Yadin Y.; Kellay, Hamid

    2002-11-01

    The power dissipation P( t) was measured in a liquid crystal (MBBA) driven by an ac voltage into the chaotic electroconvective state. In that state, the power fluctuates about its mean value < P>. The quantity measured, and compared with the fluctuation theorem of Gallavotti and Cohen, is the dimensionless standard deviation of the fluctuations, σP/< P>.

  17. Infrared diagnosis using liquid crystal detectors

    NASA Technical Reports Server (NTRS)

    Hugenschmidt, M.; Vollrath, K.

    1986-01-01

    The possible uses of pulsed carbon dioxide lasers for analysis of plasmas and flows need appropriate infrared image converters. Emphasis was placed on liquid crystal detectors and their operational modes. Performance characterstics and selection criteria, such as high sensitivity, short reaction time, and high spatial resolution are discussed.

  18. Diffraction from a liquid crystal phase grating.

    PubMed

    Kashnow, R A; Bigelow, J E

    1973-10-01

    The diffraction of light by a sinusoidal perturbation of the optic axis in a nematic liquid crystal is discussed. This corresponds to experiments at the electrohydrodynamic instability thresholds. An interesting qualitative feature appears: The diffraction pattern exhibits a contribution at half of the expected spatial frequency, corresponding to nonorthogonal traversals of the thick phase grating.

  19. Liquid-Crystal Thermal-Control Panels

    NASA Technical Reports Server (NTRS)

    Dehaye, R. F.; Edge, T. M.; Feltner, W. R.

    1987-01-01

    Radiative temperature regulators have no moving parts. Conceptual temperature-regulating system proposed for spacecraft useful in automatic or remotely controlled regulation of solar heating in buildings, provided cost reduced sufficiently. System consists of liquid-crystal panels made to absorb or reflect sunlight.

  20. Randomized Grain Boundary Liquid Crystal Phase

    NASA Astrophysics Data System (ADS)

    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. Enhanced dual-frequency operation of a polymerized liquid crystal microplate by liquid crystal infiltration

    NASA Astrophysics Data System (ADS)

    Kumagai, Takayuki; Yoshida, Hiroyuki; Ozaki, Masanori

    2017-04-01

    The electric-field-induced switching behavior of a polymer microplate is investigated. A microplate fabricated with a photopolymerizable dual-frequency liquid crystal was surrounded by an unpolymerized photopolymerizable dual-frequency liquid crystal in the isotropic phase. As an electric field was applied along the plane of the microplate, the microplate switched to set its interior molecular orientation to be either parallel or perpendicular to the field, depending on the frequency. Analysis of the rotational behavior, as well as numerical calculations, showed that the surrounding unpolymerized photopolymerizable dual-frequency liquid crystal infiltrated into the microplate, which enhanced the dielectric properties of the microplate. To the best of our knowledge, this is the first report of an enhanced dual-frequency dielectric response of a polymer microplate induced by liquid crystal infiltration.

  2. Colloidal cholesteric liquid crystal in spherical confinement

    PubMed Central

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-01-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545

  3. Colloidal cholesteric liquid crystal in spherical confinement

    NASA Astrophysics Data System (ADS)

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-08-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter.

  4. Liquid Crystals for Laser Applications

    DTIC Science & Technology

    1992-07-01

    carbon black ( CB ) dopants into the films. A photoreaction between the additive and the cholesteryl groups of the liquid crystalline polymer could be...initiated above a threshold intensity of 7 x 10-9 W/gm2 (350 nm, cw, BP) or a threshold energy of 2.54 x 10-9 J/pgm 2 (1064-nm,10-ns single pulse, CB ). The...nonlinear U optics: Mesophases formed by push-pull stilbenes and diacetylenes, J. Chem. Soc., Chem. Commun., 19, 1424-1426, 1987. 276. Walba, D. M

  5. Shear-Sensitive Monomer/Polymer Liquid Crystal System

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Eftekhari, Abe; Parmar, D. S.

    1993-01-01

    Report describes preliminary investigation of new monomer/polymer liquid crystal system, thin film of shear-sensitive cholesteric monomer liquid crystal (TI 511) on Xydar (STR800) (or equivalent) liquid crystal polymer substrate. Monomer/polymer liquid crystal films applied to surfaces provide quantitative indications of shear stresses caused by winds blowing along surfaces. Effects of shear stresses reversible in new coating system. System provides quantitative data on flows in wind tunnels.

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

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 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. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 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...

  8. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 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...

  9. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2010 CFR

    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...

  10. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 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...

  11. Chem I Supplement: Liquid Crystals--The Chameleon Chemicals.

    ERIC Educational Resources Information Center

    Brown, Glenn H.

    1983-01-01

    Presents information relevant to everyday life so as to stimulate student interest in the properties of the two basic types of liquid crystals: thermotropic and lyotropic. Describes the applications of liquid crystals to electronics, biomedicine, and polymer science and appraises the future of liquid crystal research. (JM)

  12. Liquid crystals for holographic optical data storage.

    PubMed

    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.

  13. Liquid crystal assemblies in biologically inspired systems

    PubMed Central

    Safinya, Cyrus R.; Deek, Joanna; Beck, Roy; Jones, Jayna B.; Leal, Cecilia; Ewert, Kai K.; Li, Youli

    2013-01-01

    In this paper, which is part of a collection in honor of Noel Clark's remarkable career on liquid crystal and soft matter research, we present examples of biologically inspired systems, which form liquid crystal (LC) phases with their LC nature impacting biological function in cells or being important in biomedical applications. One area focuses on understanding network and bundle formation of cytoskeletal polyampholytes (filamentous-actin, microtubules, and neurofilaments). Here, we describe studies on neurofilaments (NFs), the intermediate filaments of neurons, which form open network nematic liquid crystal hydrogels in axons. Synchrotron small-angle-x-ray scattering studies of NF-protein dilution experiments and NF hydrogels subjected to osmotic stress show that neurofilament networks are stabilized by competing long-range repulsion and attractions mediated by the neurofilament's polyampholytic sidearms. The attractions are present both at very large interfilament spacings, in the weak sidearm-interpenetrating regime, and at smaller interfilament spacings, in the strong sidearm-interpenetrating regime. A second series of experiments will describe the structure and properties of cationic liposomes (CLs) complexed with nucleic acids (NAs). CL-NA complexes form liquid crystalline phases, which interact in a structure-dependent manner with cellular membranes enabling the design of complexes for efficient delivery of nucleic acid (DNA, RNA) in therapeutic applications. PMID:24558293

  14. Zeolite-like liquid crystals

    PubMed Central

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  15. Zeolite-like liquid crystals

    NASA Astrophysics Data System (ADS)

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-10-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension.

  16. Frustration of crystallisation by a liquid-crystal phase.

    PubMed

    Syme, Christopher D; Mosses, Joanna; González-Jiménez, Mario; Shebanova, Olga; Walton, Finlay; Wynne, Klaas

    2017-02-17

    Frustration of crystallisation by locally favoured structures is critically important in linking the phenomena of supercooling, glass formation, and liquid-liquid transitions. Here we show that the putative liquid-liquid transition in n-butanol is in fact caused by geometric frustration associated with an isotropic to rippled lamellar liquid-crystal transition. Liquid-crystal phases are generally regarded as being "in between" the liquid and the crystalline state. In contrast, the liquid-crystal phase in supercooled n-butanol is found to inhibit transformation to the crystal. The observed frustrated phase is a template for similar ordering in other liquids and likely to play an important role in supercooling and liquid-liquid transitions in many other molecular liquids.

  17. Carbon nanotubes dispersed in liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Ji, Yan

    Liquid crystal elastomers (LCEs), as the name indicates, unite the anisotropic order of liquid crystals and rubber elasticity of elastomers into polymer networks. One of the most notable features of LCEs is that properly aligned LCEs exhibit dramatic and reversible shape deformation (e.g. elongation-contraction) in response to various stimuli. In recent years, carbon nanotubes (CNTs) were introduced into LCEs. Besides enabling remote and spatial control of the actuation via light and electronic field, CNTs are also utilized to align mesogens as well as to improve the mechanical and electronic property of the composites. Some potential applications of CNT-LCE nanocomposites have been demonstrated. This chapter describes the preparation of CNT dispersed LCEs, new physical properties resulted from CNTs, their actuation and their proposed applications.

  18. Liquid crystal display for phase shifting

    NASA Astrophysics Data System (ADS)

    Villalobos-Mendoza, B.; Granados-Agustín, F. S.; Aguirre-Aguirre, D.; Cornejo-Rodríguez, A.

    2013-11-01

    This work arises based on the idea proposed by Millered et al. in 2004, where they show how to get in one shot interferograms with phase shift using a mask with micro-polarizers, in this work we pretend to obtain phase shift in localized areas of an interferogram using the properties of polarization and the pixelated configuration of a liquid crystal display (LCD) for testing optical surfaces. In this work we describes the process of characterization of a liquid crystal display CRL Opto and XGA2P01 model, which is introduced in one arm of a Twyman Green interferometer. Finally we show the experimental interferograms with phase shifts which are caused by different gray levels displayed in the LCD.

  19. Phototunable reflection notches of cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Hrozhyk, Uladzimir A.; Serak, Svetlana V.; Tabiryan, Nelson V.; Bunning, Timothy J.

    2008-09-01

    The reflection notch of cholesteric liquid crystals (CLCs) formed from highly photosenstive azobenzene nematic liquid crystals doped with light-insensitive, large helical twisting power chiral dopants is shown to be widely phototunable by green laser beams. The nonlinear transmission properties of these materials were studied. We have shown that the relative shift in Bragg wavelength is independent of the chiral dopant concentration and develop a predictive theory of such behavior. The theory describes the dynamics of phototuning as well. Reflection shifts greater than 150 nm were driven with low power, cw of 532 nm in these photosensitive CLCs, previously attainable only through UV pre-exposure. A nonlinear feedback mechanism was demonstrated for CLCs of left, right, and both handedness upon laser-induced blueshifting of the reflection notch from a red wavelength using a green cw laser.

  20. Angular effects on thermochromic liquid crystal thermography

    NASA Astrophysics Data System (ADS)

    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.

  1. Errors in thermochromic liquid crystal thermometry

    NASA Astrophysics Data System (ADS)

    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.

  2. Phototunable reflection notches of cholesteric liquid crystals

    SciTech Connect

    Hrozhyk, Uladzimir A.; Serak, Svetlana V.; Tabiryan, Nelson V.; Bunning, Timothy J.

    2008-09-15

    The reflection notch of cholesteric liquid crystals (CLCs) formed from highly photosenstive azobenzene nematic liquid crystals doped with light-insensitive, large helical twisting power chiral dopants is shown to be widely phototunable by green laser beams. The nonlinear transmission properties of these materials were studied. We have shown that the relative shift in Bragg wavelength is independent of the chiral dopant concentration and develop a predictive theory of such behavior. The theory describes the dynamics of phototuning as well. Reflection shifts greater than 150 nm were driven with low power, cw of 532 nm in these photosensitive CLCs, previously attainable only through UV pre-exposure. A nonlinear feedback mechanism was demonstrated for CLCs of left, right, and both handedness upon laser-induced blueshifting of the reflection notch from a red wavelength using a green cw laser.

  3. Errors in thermochromic liquid crystal thermometry

    SciTech Connect

    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 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.

  4. Nanoparticle interfacial assembly in liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Rahimi, Mohammad; Roberts, Tyler; Armas-Perez, Julio; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-03-01

    Controlled assembly of nanoparticles at liquid crystal interfaces could lead to easily manufacturable building blocks for assembly of materials with tunable mechanical, optical, and electronic properties. Past work has examined nanoparticle assembly at planar liquid crystal interfaces. In this work we show that nanoparticle assembly on curved interfaces is drastically different, and arises for conditions under which assembly is too weak to occur on planar interfaces. We also demonstrate that LC-mediated nanoparticle interactions are strong, are remarkably sensitive to surface anchoring, and lead to hexagonal arrangements that do not arise in bulk systems. All these elements form the basis for a highly tunable, predictable, and versatile platform for hierarchical materials assembly. National Science Foundation through the UW MRSEC.

  5. Electro-optical effects in porous PET films filled with liquid crystal: new possibilities for fiber optics and THZ applications.

    PubMed

    Chopik, A; Pasechnik, S; Semerenko, D; Shmeliova, D; Dubtsov, A; Srivastava, A K; Chigrinov, V

    2014-03-15

    The results of investigation of electro-optical properties of porous polyethylene terephthalate films filled with a nematic liquid crystal (5 CB) are presented. It is established that the optical response of the samples on the applied voltage drastically depends on the frequency range. At low frequencies of applied electrical field (ffc) electric field induces an overall change in the light intensity, which is typical for an electro-optical response of a liquid crystal (LC) layer in a conventional "sandwich"-like cell. The dependences of critical frequency fc, threshold voltages, and characteristic times on a pore diameter d were established. The peculiarities of electro-optical effects can be explained in the framework of the approach which connects the variations of light intensity with the corresponding changes of the effective refractive index n(eff) of a composite LC media. The unusual behavior of the electro-optical response at low frequencies is assigned to the orienting action of the specific shear flow typical for electrokinetic phenomena in polar liquids.

  6. Passive Sensor Materials Based on Liquid Crystals

    DTIC Science & Technology

    2011-03-12

    Templating Polyelectrolyte Multilayer Capsules”, Chemistry of Materials, 20(6), 2063-2065, 2008. S.S. Sridharamurthy, K. D. Cadwell, N. L. Abbott... Templating Polyelectrolyte Multilayer Capsules, filed with USPTO, 2008. Immobilization of Droplets of Liquid Crystals on Surfaces, filed with USPTO, 2009...chemical species (see above). The methodology is based on templating PEM capsules formed by the layer-by-layer (LbL) adsorption of polyelectrolytes on

  7. Nanoparticles and networks created within liquid crystals

    NASA Astrophysics Data System (ADS)

    Kang, Shin-Wong; Kundu, Sudarshan

    We report the in situ creation of growing polymer nanoparticles and resulting polymer networks formed in liquid crystals. Depending on the concentration of monomer, polymerization-induced phase separation proceeds in two distinct regimes. For a high monomer concentration with a good miscibility, phase separation is initiated through the nucleation and growth mechanism in the binodal decomposition regime and rapidly crosses over to the spinodal decomposition process, consequently resulting in interpenetrating polymer networks. For a dilute system, however, the phase separation mainly proceeds and completes in the binodal decomposition regime. The system resembles the aggregation process of colloidal particles. For a dilute system, the reaction kinetics is limited by the reaction between in situ created polymer aggregates and hence the network morphologies are greatly inuenced by the diffusion of reactive growing polymer particles. The thin polymer layers localized at the surface of substrate are frequently observed and can be comprehended by the interfacial adsorption and further cross-linking reaction of in situ created polymer aggregates at the interface. This process provides a direct perception on understanding polymer stabilized liquid crystals accomplished by the interfacial polymer layer formed by polymerization of dilute reactive monomers in liquid crystal (LC) host.

  8. Liquid crystal formation in supercoiled DNA solutions.

    PubMed Central

    Zakharova, Svetlana S; Jesse, Wim; Backendorf, Claude; van der Maarel, Johan R C

    2002-01-01

    The critical concentrations pertaining to the liquid crystal formation of pUC18 plasmid in saline solutions were obtained from (31)P nuclear magnetic resonance, polarized light microscopy, and phase equilibrium experiments. The transition is strongly first order with a broad gap between the isotropic and anisotropic phase. The critical boundaries are strongly and reversibly dependent on temperature and weakly dependent on ionic strength. With polarized light microscopy on magnetically oriented samples, the liquid crystalline phase is assigned cholesteric with a pitch on the order of 4 microm. Preliminary results show that at higher concentrations a true crystal is formed. The isotropic-cholesteric transition is interpreted with lyotropic liquid crystal theory including the effects of charge, orientation entropy, and excluded volume effects. It was found that the molecular free energy associated with the topology of the superhelix is of paramount importance in controlling the width of the phase gap. The theoretical results compare favorably with the critical boundary pertaining to the disappearance of the isotropic phase, but they fail to predict the low concentration at which the anisotropic phase first appears. PMID:12124291

  9. Nanoparticle guests in lyotropic liquid crystals

    NASA Astrophysics Data System (ADS)

    Dölle, Sarah; Park, Ji Hyun; Schymura, Stefan; Jo, Hyeran; Scalia, Giusy; Lagerwall, Jan P. F.

    In this chapter we discuss the benefits, peculiarities and main challenges related to nanoparticle templating in lyotropic liquid crystals. We first give a brief bird's-eye view of the field, discussing different nanoparticles as well as different lyotropic hosts that have been explored, but then quickly focus on the dispersion of carbon nanotubes in surfactant-based lyotropic nematic phases. We discuss in some detail how the transfer of orientational order from liquid crystal host to nanoparticle guest can be verified and which degree of ordering can be expected, as well as the importance of choosing the right surfactant and its concentration for the stability of the nanoparticle suspension. We introduce a method for dispersing nanoparticles with an absolute minimum of stabilizing surfactant, based on dispersion below the Krafft temperature, and we discuss the peculiar phenomenon of filament formation in lyotropic nematic phases with a sufficient concentration of well-dispersed carbon nanotubes. Finally, we describe how the total surfactant concentration in micellar nematics can be greatly reduced by combining cat- and anionic surfactants, and we discuss how nanotubes can help in inducing the liquid crystal phase close to the isotropic-nematic boundary.

  10. Orientational transitions in antiferromagnetic liquid crystals

    NASA Astrophysics Data System (ADS)

    Zakhlevnykh, A. N.; Petrov, D. A.

    2016-09-01

    The orientational phases in an antiferromagnetic liquid crystal (ferronematic) based on the nematic liquid crystal with the negative anisotropy of diamagnetic susceptibility are studied in the framework of the continuum theory. The ferronematic was assumed to be compensated; i.e., in zero field, impurity ferroparticles with the magnetic moments directed parallel and antiparallel to the director are equiprobably distributed in it. It is established that under the action of a magnetic field the ferronematic undergoes orientational transitions compensated (antiferromagnetic) phase-non-uniform phase-saturation (ferrimagnetic) phase. The analytical expressions for threshold fields of the transitions as functions of material parameters are obtained. It is shown that with increasing magnetic impurity segregation parameter, the threshold fields of the transitions significantly decrease. The bifurcation diagram of the ferronematic orientational phases is built in terms of the energy of anchoring of magnetic particles with the liquid-crystal matrix and magnetic field. It is established that the Freedericksz transition is the second-order phase transition, while the transition to the saturation state can be second- or first-order. In the latter case, the suspension exhibits orientational bistability. The orientational and magnetooptical properties of the ferronematic in different applied magnetic fields are studied.

  11. Polymer-dispersed liquid crystal elastomers

    PubMed Central

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-01-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations. PMID:27713478

  12. Structures of cyano-biphenyl liquid crystals

    NASA Technical Reports Server (NTRS)

    Chu, Yuan-Chao; Tsang, Tung; Rahimzadeh, E.; Yin, L.

    1989-01-01

    The structures of p-alkyl- p'-cyano- bicyclohexanes, C(n)H(2n+1) (C6H10)(C6H10) CN (n-CCH), and p-alkyl- p'-cyano- biphenyls, C(n)H(2n+1) (C6H4)(C6H4) CN (n-CBP), were studied. It is convenient to use an x ray image intensification device to search for symmetric x ray diffraction patterns. Despite the similarities in molecular structures of these compounds, very different crystal structures were found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry. In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH. Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal structures change considerably when the alkyl chain length is slightly altered. Different structures were also found in the crystalline phase of n-CBP for n = 6 to 9. For n = 7 to 9, the structures are close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n = 6 with the molecules nearly perpendicular to the c-axis.

  13. A liquid crystal-based sensor for the simple and sensitive detection of cellulase and cysteine.

    PubMed

    Wang, Yi; Hu, Qiongzheng; Tian, Tongtong; Gao, Yan'an; Yu, Li

    2016-11-01

    A liquid crystal (LC)-based sensor, which is capable of monitoring enzymatic activity at the aqueous/LC interface and detecting cellulase and cysteine (Cys), was herein reported. When functionalized with a surfactant, dodecyl β-d-glucopyranoside, the 4-cyano-4'-pentylbiphenyl (5CB) displays a dark-to-bright transition in the optical appearance for cellulase. We attribute this change to the orientational transition of LCs, as a result of enzymatic hydrolysis between cellulase and surfactant. Furthermore, by adding cellulase and Cu(2+), our surfactant-LCs system performs an interesting ability to detect Cys, even though Cys could not interact with surfactant or LC directly. Alternatively, through the strong binding between Cys and Cu(2+), cellulase was able to hydrolyze surfactant in the presence of Cu(2+), leading to the transition of LCs from dark to bright. The detection limit of the LC sensor was around 1×10(-5)mg/mL and 82.5μM for cellulase and Cys, respectively. The LC-based sensor may contribute to the development of low-cost, expedient, and label-free detection for cellulase and Cys and the design strategy may also provide a novel way for detecting multiple analytes.

  14. Influence of Simple Electrolytes on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    PubMed Central

    Carlton, Rebecca J.; Gupta, Jugal K.; Swift, Candice L.; Abbott, Nicholas L.

    2011-01-01

    We report orientational anchoring transitions at aqueous interfaces of a water-immiscible, thermotropic liquid crystal (LC; nematic phase of 4′-pentyl-4-cyanobiphenyl) that are induced by changes in pH of the aqueous solution and the addition of simple electrolytes (NaCl) to the aqueous phase. Whereas measurements of the zeta potential on the aqueous side of the interface of LC-in-water emulsions prepared with 5CB confirm pH-dependent formation of an electrical double layer extending into the aqueous phase, quantification of the orientational ordering of the LC leads to the proposition that an electrical double layer is also formed on the LC-side of the interface with an internal electric field that drives the LC anchoring transition. Further support for this conclusion is obtained from measurements of the dependence of LC ordering on pH and ionic strength, as well as a simple model based on the Poisson-Boltzmann equation from which we calculate the contribution of an electrical double layer to the orientational anchoring energy of the LC. Overall, the results presented herein provide new fundamental insights into ionic phenomena at LC-aqueous interfaces, and expand the range of solutes known to cause orientational anchoring transitions at LC-aqueous interfaces beyond previously examined amphiphilic adsorbates. PMID:22106820

  15. Touch sensors based on planar liquid crystal-gated-organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Seo, Jooyeok; Lee, Chulyeon; Han, Hyemi; Lee, Sooyong; Nam, Sungho; Kim, Hwajeong; Lee, Joon-Hyung; Park, Soo-Young; Kang, Inn-Kyu; Kim, Youngkyoo

    2014-09-01

    We report a tactile touch sensor based on a planar liquid crystal-gated-organic field-effect transistor (LC-g-OFET) structure. The LC-g-OFET touch sensors were fabricated by forming the 10 μm thick LC layer (4-cyano-4'-pentylbiphenyl - 5CB) on top of the 50 nm thick channel layer (poly(3-hexylthiophene) - P3HT) that is coated on the in-plane aligned drain/source/gate electrodes (indium-tin oxide - ITO). As an external physical stimulation to examine the tactile touch performance, a weak nitrogen flow (83.3 μl/s) was employed to stimulate the LC layer of the touch device. The LC-g-OFET device exhibited p-type transistor characteristics with a hole mobility of 1.5 cm2/Vs, but no sensing current by the nitrogen flow touch was measured at sufficiently high drain (VD) and gate (VG) voltages. However, a clear sensing current signal was detected at lower voltages, which was quite sensitive to the combination of VD and VG. The best voltage combination was VD = -0.2 V and VG = -1 V for the highest ratio of signal currents to base currents (i.e., signal-to-noise ratio). The change in the LC alignment upon the nitrogen flow touch was assigned as the mechanism for the present LC-g-OFET touch sensors.

  16. Detection of heavy-metal ions using liquid crystal droplet patterns modulated by interaction between negatively charged carboxylate and heavy-metal cations.

    PubMed

    Han, Gyeo-Re; Jang, Chang-Hyun

    2014-10-01

    Herein, we demonstrated a simple, sensitive, and rapid label-free detection method for heavy-metal (HM) ions using liquid crystal (LC) droplet patterns on a solid surface. Stearic-acid-doped LC droplet patterns were spontaneously generated on an n-octyltrichlorosilane (OTS)-treated glass substrate by evaporating a solution of the nematic LC, 4-cyano-4'-pentylbiphenyl (5CB), dissolved in heptane. The optical appearance of the droplet patterns was a dark crossed texture when in contact with air, which represents the homeotropic orientation of the LC. This was caused by the steric interaction between the LC molecules and the alkyl chains of the OTS-treated surface. The dark crossed appearance of the acid-doped LC patterns was maintained after the addition of phosphate buffered saline (PBS) solution (pH 8.1 at 25°C). The deprotonated stearic-acid molecules self-assembled through the LC/aqueous interface, thereby supporting the homeotropic anchoring of 5CB. However, the optical image of the acid-doped LC droplet patterns incubated with PBS containing HM ions appeared bright, indicating a planar orientation of 5CB at the aqueous/LC droplet interface. This dark to bright transition of the LC patterns was caused by HM ions attached to the deprotonated carboxylate moiety, followed by the sequential interruption of the self-assembly of the stearic acid at the LC/aqueous interface. The results showed that the acid-doped LC pattern system not only enabled the highly sensitive detection of HM ions at a sub-nanomolar concentration but it also facilitated rapid detection (<10 min) with simple procedures.

  17. Encapsulated liquid crystals as probes for remote thermometry.

    PubMed

    Franklin, K J; Buist, R J; den Hartog, J; McRae, G A; Spencer, D P

    1992-01-01

    A temperature probe based on the magnetic resonance properties of an encapsulated liquid crystal has been investigated. Large changes in magnetic resonance signals occur as the liquid crystal undergoes a phase transition from an anisotropic (nematic) state to the isotropic liquid. The low latent heat of such phase transitions allows for rapid phase changes during a hyperthermia treatment. Transition temperatures can be tailored by adding suitable compounds such as analogues of the liquid crystal or various solvents. Encapsulation is required to maintain the integrity of the liquid crystal, particularly for applications in vivo. Results of preliminary studies designed to demonstrate the technical feasibility of the concept are presented.

  18. Liquid-crystal blazed grating with azimuthally distributed liquid-crystal directors.

    PubMed

    Honma, Michinori; Nose, Toshiaki

    2004-09-20

    We propose a novel formation method of arbitrary phase profiles of circular light by controlling azimuthal angles of liquid-crystal directors; its principle is described theoretically. A new liquid-crystal blazed grating is demonstrated by use of the proposed method. It is revealed that the first-order diffraction efficiency reaches the maximum value (theoretically 100%, experimentally approximately 90%) at an optimum applied voltage when the phase difference between the extraordinary and ordinary rays agrees with one-half the wavelength. Furthermore, the polarization states of the diffracted light beams are analyzed by Stokes parameter measurements, and unique polarization-splitting properties are revealed.

  19. Liquid crystal-ZnO nanoparticle photovoltaics: Role of nanoparticles in ordering the liquid crystal

    SciTech Connect

    Martinez-Miranda, L. J.; Traister, Kaitlin M.; Melendez-Rodriguez, Iriselies; Salamanca-Riba, Lourdes

    2010-11-29

    We investigate the role that order plays in the transfer of charges in the ZnO nano-particle-octylcyanobiphenyl (8CB) liquid crystal system, considered for photovoltaic applications. We have changed the concentration of ZnO nanoparticles in 8CB from 1.18 to 40 wt %. Our results show an improvement in the alignment of the liquid crystal with increasing weight percentage of ZnO nanoparticles, up to a concentration of 30 wt %. In addition, the current generated by the system increases by three orders of magnitude.

  20. Perdeuterated liquid crystals for near infrared applications

    NASA Astrophysics Data System (ADS)

    Kula, P.; Bennis, N.; Marć, P.; Harmata, P.; Gacioch, K.; Morawiak, P.; Jaroszewicz, L. R.

    2016-10-01

    For majority of Liquid Crystalline compounds the absorption occurs at two spectral regions: ultraviolet UV (due to electronic excitations) and infrared IR (caused by molecular vibrations). Both cause the absorption which deteriorates electro-optical modulation abilities of LC. In the MWIR and LWIR regions, there are many fundamental molecular vibration bands. The most intense are the ones with high anharmonicity, which in the case of LCs corresponds to the Csbnd H bonds, especially present in the aliphatic chains. In the NIR region, overtone molecular vibration bands derived from IR region begin to appear. In the case of Csbnd H bond system, the first overtones are present at 1.6-1.7 μm. To reduce NIR absorptions, perdeuterated Liquid crystal has been proposed. In this paper, we report the physical and optical properties of liquid crystals based on polarimetry measurements method. We also provide a polar decomposition of experimentally measured Mueller matrix in order to determine polarization properties of the device such as depolarization and diattenuation which cannot be obtained from absorption spectra.

  1. Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals.

    PubMed

    Lee, Jin Hong; Han, Kee Sung; Lee, Je Seung; Lee, Albert S; Park, Seo Kyung; Hong, Sung Yun; Lee, Jong-Chan; Mueller, Karl T; Hong, Soon Man; Koo, Chong Min

    2016-11-01

    A novel ionic mixture of an imidazolium-based room-temperature ionic liquid containing ethylene-oxide-functionalized phosphite anions is fabricated, which, when doped with lithium salt, self-assembles into a smectic-ordered ionic liquid crystal through Coulombic interactions between the ion species. Interestingly, the smectic order in the ionic-liquid-crystal ionogel facilitates ionic transport.

  2. Liquid crystal devices for photonics applications

    NASA Astrophysics Data System (ADS)

    Chigrinov, Vladimir G.

    2007-11-01

    Liquid crystal (LC) devices for Photonics applications is a hot topic of research. Such elements begin to appear in Photonics market. Passive elements for fiber optical communication systems (DWDM components) based on LC cells can successfully compete with the other elements used for the purpose, such as micro electromechanical (MEM), thermo-optical, opto-mechanical or acousto-optical devices. Application of nematic and ferroelectric LC for high speed communication systems, producing elements that are extremely fast, stable, durable, of low loss, operable over a wide temperature range, and that require small operating voltages and extremely low power consumption. The known LC applications in fiber optics enable to produce switches, filters, attenuators, equalizers, polarization controllers, phase emulators and other fiber optical components. Good robustness due to the absence of moving parts and compatibility with VLSI technology, excellent parameters in a large photonic wavelength range, whereas the complexity of the design and the cost of the device are equivalent to regular passive matrix LC displays makes LC fiber optical devices very attractive for mass production. We have already successfully fabricated certain prototypes of the optical switches based on ferroelectric and nematic LC materials. The electrooptical modes used for the purpose included the light polarization rotation, voltage controllable diffraction and fast switching of the LC refractive index. We used the powerful software to optimize the LC modulation characteristics. Use of photo-alignment technique pioneered by us makes it possible to develop new LC fiber components. Almost all the criteria of perfect LC alignment are met in case of azo-dye layers. We have already used azo-dye materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. The prototypes of new LC efficient Photonics devices are envisaged. Controllable

  3. Imaging the oxidation effects of the Fenton reaction on phospholipids at the interface between aqueous phase and thermotropic liquid crystals.

    PubMed

    Zhang, Minmin; Jang, Chang-Hyun

    2015-08-01

    The lipid peroxidation process has attracted much attention because of the growing evidence of its involvement in the pathogenesis of age-related diseases. Herein, we report a simple, label-free method to study the oxidation of phospholipids by the Fenton reaction at the interface between an aqueous phase and immiscible liquid crystals (LCs). The different images produced by the orientation of 4-cyano-4'-pentylbiphenyl (5CB) corresponded to the presence or absence of oxidized 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DOPG). The oxidation effects of the Fenton reaction on DOPG were evaluated by monitoring the orientational response of liquid crystals upon contact with the oxidized DOPG solutions. DOPG was oxidized into chain-changed products containing hydroxy, carbonyl, or aldehyde groups, resulting in the rearrangement of the phospholipid layer. This induced the orientational transition of LCs from homeotropic to planar states; therefore, a dark to bright optical shift was observed. This shift was due to the Fenton reaction preventing DOPG to induce the orientational alignment of LCs at the aqueous/LC interface. We also used an ultraviolet spectrophotometer to confirm the effects of oxidation on phospholipids by the Fenton reaction. Using this simple method, a new approach for investigating phospholipid oxidation was established with high resolution and easy accessibility.

  4. Crystallization Response of Hydrous Granitic Liquids

    NASA Astrophysics Data System (ADS)

    London, D.; Morgan, G. B.; Evensen, J. M.

    2006-05-01

    Preconditioning of hydrous haplogranite liquid (200 MPa eutectic composition Ab38Or28Qz34) at 100° C above the liquidus temperature for 72 hr is sufficient to eliminate any vestiges of the initial structural states of vitreous or crystalline starting materials. Experimental crystallization of this composition in the presence of aqueous vapor begins by nucleation in the vapor space, following which crystal growth advances into supercooled melt. The minimum in nucleation delay (~ 200 hrs) and maximum in nucleation density and growth rate occur at liquidus undercooling (ΔT) of 200° C. Crystallization does not exceed 10% in experiments up to 600 hrs at any value of ΔT, and no crystallization occurs within 50° C of the liquidus up to 700 hrs. Though the melt composition is invariant (eutectic), and no compositional gradients are discernable by EMPA in quenched glasses, the crystallization response is sequential: at ΔT = 200° C, coarsely skeletal K-feldspar nucleates and grows first, followed by graphic to spherulitic quartz-sodic alkali feldspar intergrowths, and lastly in some experiments, monophase quartz blebs. Once formed, crystals or clusters tend not to grow larger, but rather, new centers of nucleation and growth appear. The result is a sequential history of uniform crystal texture (size and habit). At comparable ΔT, the nucleation delay decreases as the bulk composition is displaced (by choosing a composition) farther from the eutectic. At comparable ΔT, fluxes (P, F) serve to increase the nucleation delay and decrease the nucleation density but do not notably change either growth rates or crystal habits. Diffusion of alkalis through melt is rapid, such that any gradients in alkalis that should result from non-eutectic crystallization are erased in minutes or hours over distances of 5 mm and down to ΔT = 350° C, in the field of glass. These relations of undercooling (ΔT) to time (t) apply only to H2O-oversaturated systems. We do not have data for the

  5. Piperidinium, piperazinium and morpholinium ionic liquid crystals.

    PubMed

    Lava, Kathleen; Binnemans, Koen; Cardinaels, Thomas

    2009-07-16

    Piperidinium, piperazinium and morpholinium cations have been used for the design of ionic liquid crystals. These cations were combined with several types of anions, namely bromide, tetrafluoroborate, hexafluorophosphate, dodecylsulfate, bis(trifluoromethylsulfonyl)imide, dioctylsulfosuccinate, dicyclohexylsulfosuccinate, and dihexylsulfosuccinate. For the bromide salts of piperidinium containing one alkyl chain, the chain length was varied, ranging from 8 to 18 carbon atoms (n = 8, 10, 12, 14, 16, 18). The compounds show a rich mesomorphic behavior. High-ordered smectic phases (crystal smectic E and T phases), smectic A phases, and hexagonal columnar phases were observed, depending on the type of cation and anion. The morpholinium compounds with sulfosuccinate anions showed hexagonal columnar phases at room temperature and a structural model for the self-assembly of these morpholinium compounds into hexagonal columnar phases is proposed.

  6. New triazolium based ionic liquid crystals

    SciTech Connect

    Stappert, Kathrin; Unal, Derya; Mallick, Bert; Mudring, Anja-Verena

    2014-01-01

    A set of novel 1,2,3-triazolium based ionic liquid crystals was synthesized and their mesomorphic behaviour studied by DSC (differential scanning calorimetry), POM (polarizing optical microscopy) and SAXS (small angle X-ray scattering). Beside the variation of the chain length (C10, C12 and C14) at the 1,2,3-triazolium cation also the anion has been varied (Br-, I-, I3-, BF4-, SbF6-, N(CN)2-, Tf2N-) to study the influence of ion size, symmetry and H-bonding capability on the mesophase formation. Interestingly, for the 1,3-didodecyl-1,2,3-triazolium cation two totally different conformations were found in the crystal structure of the bromide (U-shaped) and the triiodide (rod shaped).

  7. Wide Angle Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Wang, Xing-Hua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John J.; Miranda, Felix A.; McManamon, Paul F.

    2004-01-01

    Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

  8. Liquid crystal temperature monitoring for microsurgery.

    PubMed

    Sudarsky, L A; Salomon, J

    1991-01-01

    Postoperative monitoring of free tissue transfers remains a problem for the microsurgeon. Liquid crystal temperature probes (LCT) are used by anesthesiologists to monitor patient core temperature and to indicate changes in temperature trends as an indicator of pending malignant hyperthermia. By placing an LCT monitor on the flap and adjacent tissue at the completion of surgery, temperature differentials can be reliably monitored. If the temperature differential exceeds 2 degrees C, the flap is re-explored. The LCT readout resembles a standard thermometer and can easily be recorded by even inexperienced personnel. LCTs are a convenient, inexpensive, and easy method to monitor both free muscle and free fasciocutaneous flaps.

  9. Liquid crystal-based hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Brodzeli, Zourab; Silvestri, Leonardo; Michie, Andrew; Chigrinov, Vladimir G.; Guo, Qi; Pozhidaev, Eugene P.; Kiselev, Alexei D.; Ladouceur, Francois

    2012-09-01

    We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications (e.g. military, counter terrorist, and customs authorities in protecting ports and harbors), offshore production facilities or coastal approaches as well as various marine applications. In this paper, we propose a new approach to underwater sonar systems using the voltage-controlled liquid crystals and simple multiplexing method. The proposed method permits measurement of sound under water at multiple points along an optical fiber using the low cost components and standard single mode fiber, without complex interferometric measurement techniques, electronics or demodulation software.

  10. Conformation and chirality in liquid crystals

    NASA Astrophysics Data System (ADS)

    West, John L.; Zhao, Lei

    2013-09-01

    High helical twisting powerchiral additives are required for an expanding variety of liquid crystal displays and devices. Molecular conformation plays a critical role in determining the helical twisting power, HTP, of chiral additives. We studied additives based on an isosorbide benzoate ester core. Molecular modeling revealed two low energy states with very different conformations for this core The ultra-violet absorption and NMR spectra show two stable isosorbide conformers These spectra reveal how the relative populations of these two conformations change with temperature and how this is related to the helical twisting power. Conformation changes can explain many of the observed anomalous responses of HPT to temperature.

  11. Stochastic rotation dynamics for nematic liquid crystals

    SciTech Connect

    Lee, Kuang-Wu Mazza, Marco G.

    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. Laser damage resistant nematic liquid crystal cell

    NASA Astrophysics Data System (ADS)

    Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Soms, L.; Marczak, J.; Nowinowski-Kruszelnicki, E.; Perkowski, P.; Kedzierski, J.; Miszczyk, E.; Olifierczuk, M.; Morawiak, P.; Mazur, R.

    2013-08-01

    There exists a problem in diagnostics of a dense plasma (so-called Thomson diagnostics). For this purpose, the plasma is illuminated by series of high energy laser pulses. Such pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along an exactly the same optical path. In this case, the energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, several independent lasers have to be used. To form optical path with λ = 1.064 μm and absolute value of the energy of laser pulse through of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell (NLCC) of type LCNP2 with switching on time τON smaller than 5 μs might be applied. High laser damage resistance of NLCC and short τON can be fulfilled by preparation of liquid crystal cells with Liquid Crystal Mixture (LCM), well tuned to twisted nematic electro-optical effect, and well tuned all optical interfaces (Air - Antireflection - Quartz Plate - Electrode - Blocking Film - Aligning Layer - LCM - Aligning Layer - Blocking Film - Electrode - Quartz Plate - Antireflection - Air). In such LCNP2 cell, the transmission is higher than 97% at λ = 1.064 μm, as it is presented by Gooch and Tarry [J. Phys. D: Appl. Phys. 8, 1575 (1975)]. The safe laser density energy is about 0.6 J/cm2 for a train of laser pulses (λ = 1.064 μm, pulse duration 10 ns FWHM, pulse repetition rate 100 pps, train duration 10 s), so the area of liquid crystal cell tolerating 3 J through it shall be as large as 5 cm2. Due to the presence of two blocking film layers between electrodes, LCNP2 can be driven by high voltages. Switching on time smaller than τON = 5 μs was obtained under 200 V switching voltage.

  13. Optical vortices from liquid crystal droplets.

    PubMed

    Brasselet, Etienne; Murazawa, Naoki; Misawa, Hiroaki; Juodkazis, Saulius

    2009-09-04

    We report on the generation of mono- and polychromatic optical phase singularities from micron-sized birefringent droplets. This is done experimentally by using liquid crystal droplets whose three dimensional architecture of the optical axis is controlled within the bulk by surfactant agents. Because of its microscopic size these optical vortex generators are optically trapped and manipulated at will, thus realizing a robust self-aligned micro-optical device for orbital angular momentum conversion. Experimental observations are supported by a simple model of optical spin-orbit coupling in uniaxial dielectrics that emphasizes the prominent role of the transverse optical anisotropy with respect to the beam propagation direction.

  14. UV sensors based on liquid crystals mixtures

    NASA Astrophysics Data System (ADS)

    Chanishvili, Andro; Petriashvili, Gia; Chilaya, Guram; Barberi, Riccardo; De Santo, Maria P.; Matranga, Mario A.; Ciuchi, F.

    2006-04-01

    The Erythemal Response Spectrum is a scientific expression that describes the sensitivity of the skin to the ultraviolet radiation. The skin sensitivity strongly depends on the UV wavelength: a long exposition to UV radiation causes erythema once a threshold dose has been exceeded. In the past years several devices have been developed in order to monitor the UV exposure, most of them are based on inorganic materials that are able to mimic the human skin behaviour under UV radiation. We present a new device based on liquid crystals technology. The sensor is based on a liquid crystalline mixture that absorbs photons at UV wavelength and emits them at a longer one. This system presents several innovative features: the absorption range of the mixture can be varied to be sensitive to different wavelengths, the luminescence intensity can be tuned, the system can be implemented on flexible devices.

  15. 1,10-Phenanthrolinium ionic liquid crystals.

    PubMed

    Cardinaels, Thomas; Lava, Kathleen; Goossens, Karel; Eliseeva, Svetlana V; Binnemans, Koen

    2011-03-01

    The 1,10-phenanthrolinium cation is introduced as a new building block for the design of ionic liquid crystals. 1,10-Phenanthroline, 5-methyl-1,10-phenanthroline, 5-chloro-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline were quaternized by reaction with 1,3-dibromopropane or 1,2-dibromoethane. The resulting cations were combined with dodecyl sulfate or dioctyl sulfosuccinate anions. The influence of both the cation and anion type on the thermal behavior was investigated. Several of the complexes exhibit mesomorphic behavior, with smectic E phases for the dodecyl sulfate salts and smectic A phases for the dioctyl sulfosuccinate salts. Structural models for the packing of the 1,10-phenanthrolinium and anionic moieties in the liquid-crystalline phases are presented. The ionic compounds show fluorescence in the solid state and in solution.

  16. Ionic liquid crystals derived from amino acids.

    PubMed

    Mansueto, Markus; Frey, Wolfgang; Laschat, Sabine

    2013-11-18

    Novel chiral amino acid derived ionic liquid crystals with amine and amide moieties as spacers between the imidazolium head group and the alkyl chain were synthesised. The key step in the synthesis utilised the relatively uncommon SO3 leaving group in a microwave-assisted reaction. The mesomorphic properties of the mesogens were determined by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction. All liquid crystalline salts exhibit a smectic A mesophase geometry with strongly interdigitated bilayer structures. An increase of the steric bulk of the stereogenic centre hindered the formation of mesophases. In case of phenylalanine-derived derivatives a mesomorphic behaviour was observed for shorter alkyl chains as compared to other amino acid derivatives indicating an additional stabilising effect by the phenyl moiety.

  17. Inorganic nanotubes and nanorods in liquid crystals

    NASA Astrophysics Data System (ADS)

    Drevenšek-Olenik, Irena

    Research efforts that focus on possible improvement of the physical properties of thermotropic liquid crystals by addition of inorganic 1D nanoparticles (inorganic nanotubes, nanorods, etc.) are reviewed. The emphasis is on modification of electro-optic switching characteristics relevant for display-related applications. In most cases the dopants generate a decrease of the threshold voltage for electrooptic switching and also a decrease of the corresponding switching times. We discuss various possible reasons for the observed effects and point out specific characteristics related to 1D nature of the dopants. We also describe investigations of inclusion of 1D nanoparticles into photo-polymerizable nematic liquid crystalline materials. Photo-polymerization in the aligned nematic phase provides a convenient way to fabricate solid polymer films with strongly anisotropic angular distribution of the nanoparticles. Investigations of structural and optical properties of some selected systems are surveyed.

  18. Tuning Fluidic Resistance via Liquid Crystal Microfluidics

    PubMed Central

    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

  19. Partially exposed polymer dispersed liquid crystals for boundary layer investigations

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Singh, Jag J.

    1992-01-01

    A new configuration termed partially exposed polymer dispersed liquid crystal in which the liquid crystal microdroplets dispersed in a rigid polymer matrix are partially entrapped on the free surface of the thin film deposited on a glass substrate is reported. Optical transmission characteristics of the partially exposed polymer dispersed liquid crystal thin film in response to an air flow induced shear stress field reveal its potential as a sensor for gas flow and boundary layer investigations.

  20. Dynamic Photonic Materials Based on Liquid Crystals (Postprint)

    DTIC Science & Technology

    2013-09-01

    AFRL-RX-WP-JA-2015-0059 DYNAMIC PHOTONIC MATERIALS BASED ON LIQUID CRYSTALS (POSTPRINT) Luciano De Sio and Cesare Umeton University...ON LIQUID CRYSTALS (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) (see back...10.1016/B978-0-444-62644-8.00001-7. 14. ABSTRACT Liquid crystals, combining optical non-linearity and self-organizing properties with fluidity, and being

  1. Tailoring liquid crystals to become fast and efficient terahertz devices

    NASA Astrophysics Data System (ADS)

    Pickwell-MacPherson, E.; Parrott, E. P. J.; Park, H.; Fan, F.; Chigrinov, V. G.

    2012-10-01

    Liquid crystals have been employed for several decades in devices such as phase shifters, Fabry-Perot filters, polarizers, phase gratings, and Bragg switches at optical frequencies. However it is only recently that such devices have been demonstrated at terahertz frequencies. This is because of several fundamental frequency dependent relationships between device properties and frequency of operation. When designing liquid crystal devices, we need to find liquid crystals with high birefringence, low viscosity and low absorption at terahertz frequencies. In this paper we will present some measurements and simulations of potentially suitable liquid crystal mixtures.

  2. Handbook of Liquid Crystals, Handbook of Liquid Crystals: Four Volume Set

    NASA Astrophysics Data System (ADS)

    Demus, Dietrich; Goodby, John W.; Gray, George W.; Spiess, Hans W.; Vill, Volkmar

    1998-06-01

    The Handbook of Liquid Crystals is a unique compendium of knowledge on all aspects of liquid crystals. In over 2000 pages the Handbook provides detailed information on the basic principles of both low- and high-molecular weight materials, as well as the synthesis, characterization, modification, and applications (such as in computer displays or as structural materials) of all types of liquid crystals. The five editors of the Handbook are internationally renowned experts from both industry and academia and have drawn together over 70 leading figures in the field as authors. The four volumes of the Handbook are designed both to be used together or as stand-alone reference sources. Some users will require the whole set, others will be best served with a selection of the volumes. Volume 1 deals with the basic physical and chemical principles of liquid crystals, including structure-property relationships, nomenclature, phase behavior, characterization methods, and general synthesis and application strategies. As such this volume provides an excellent introduction to the field and a powerful learning and teaching tool for graduate students and above. Volume 2 concentrates on low-molecular weight materials, for example those typically used in display technology. A high quality survey of the literature is provided along with full details of molecular design strategies, phase characterization and control, and applications development. This volume is therefore by far the most detailed reference source on these industrially very important materials, ideally suited for professionals in the field. Volume 3 concentrates on high-molecular weight, or polymeric, liquid crystals, some of which are found in structural applications and others occur as natural products of living systems. A high-quality literature survey is complemented by full detail of the synthesis, processing, analysis, and applications of all important materials classes. This volume is the most comprehensive

  3. Dispersive shock waves in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Smyth, Noel F.

    2016-10-01

    The propagation of coherent light with an initial step intensity profile in a nematic liquid crystal is studied using modulation theory. The propagation of light in a nematic liquid crystal is governed by a coupled system consisting of a nonlinear Schrödinger equation for the light beam and an elliptic equation for the medium response. In general, the intensity step breaks up into a dispersive shock wave, or undular bore, and an expansion fan. In the experimental parameter regime for which the nematic response is highly nonlocal, this nematic bore is found to differ substantially from the standard defocusing nonlinear Schrödinger equation structure due to the effect of the nonlocality of the nematic medium. It is found that the undular bore is of Korteweg-de Vries equation-type, consisting of bright waves, rather than of nonlinear Schrödinger equation-type, consisting of dark waves. In addition, ahead of this Korteweg-de Vries bore there can be a uniform wavetrain with a short front which brings the solution down to the initial level ahead. It is found that this uniform wavetrain does not exist if the initial jump is below a critical value. Analytical solutions for the various parts of the nematic bore are found, with emphasis on the role of the nonlocality of the nematic medium in shaping this structure. Excellent agreement between full numerical solutions of the governing nematicon equations and these analytical solutions is found.

  4. Ferroelectric Liquid Crystals In Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Holmes, Harlan K.

    1994-01-01

    The process of simultaneous optical visualization and quantitative measurement of aerodynamic boundary layer parameters requires new concepts, materials and utilization methods. Measurement of shear stress in terms of the transmitted or the reflected light intensity from an aligned ferroelectric liquid crystal (FLC) thin (approx. 1 micron) film deposited on a glass substrate has been the first step in this direction. In this paper, recent progress in utilization of FLC thin films for skin friction measurement and for studying the state of the boundary layer in a wind tunnel environment is reviewed. The switching characteristics of FLCs have been used to measure pressure from the newly devised system of partially exposed polymer dispersed ferroelectric liquid crystals (PEPDFLCs). In this configuration, a PEPDFLC thin film (approx. 10-25 microns) is sandwiched between two transparent conducting electrodes, one a rigid surface and the other a flexible sheet such as polyvinylidene fluoride or mylar. The switching characteristics of the film are a function of the pressure applied to the flexible transparent electrode and a predetermined bias voltage across the two electrodes. The results, considering the dielectrics of composite media, are discussed.

  5. Particles and curvatures in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Serra, Francesca; Luo, Yimin; Yang, Shu; Kamien, Randall D.; Stebe, Kathleen J.

    Elastic interactions in anisotropic fluids can be harnessed to direct particle interactions. A strategy to smoothly manipulate the director field in nematic liquid crystals is to vary the topography of the bounding surfaces. A rugged landscape with peaks and valleys create local deformations of the director field which can interact with particles in solution. We study this complex interaction in two different settings. The first consists of an array of shallow pores in a poly-dimethyl-siloxane (PDMS) membrane, whose curvature can be tuned either by swelling the PDMS membrane or by mechanical stretching. The second is a set of grooves with wavy walls, fabricated by photolithography, with various parameters of curvature and shapes. In this contexts we study how the motion of colloidal particles in nematic liquid crystals can be influenced by their interaction with the peaks and valleys of the bottom substrate or of the side walls. Particles with different associated topological defects (hedgehogs or Saturn rings) behave differently as they interact with the topographical features, favoring the docking on peaks or valleys. These experimental systems are also ideal to study the ``lock and key'' mechanism of particles in holes and to investigate a possible route for particle sorting.

  6. Ferromagnetic and ferroelectric nanoparticles in liquid crystals

    NASA Astrophysics Data System (ADS)

    Reznikov, Yuriy; Glushchenko, Anatoliy; Garbovskiy, Yuriy

    This chapter introduces the basic principles of physics of magnetic and ferroelectric nanoparticles suspensions in thermotropic liquid crystals (LCs). It also covers the main features of such suspensions along with the look at the challenges that researchers in the field are facing today. Special attention is paid to understanding of major physical mechanisms responsible for the inuence of nanoparticles on the properties of LCs. In the case of magnetic nanoparticles, their dipole moments are aligned by an external magnetic field that, in turn, results in a reorientation of the LC due to the surface anchoring between the nanoparticles and the LC. This mechanical coupling between the LC and the magnetic particles determines the unique sensitivity of the suspension to magnetic fields. In regard to the ferroelectric particles, their effect on LCs is due to a strong electric field by the permanent electric dipoles of the particles. This field is strong enough to change the orientational ordering of the LC surrounding the particle. In addition, the above-mentioned mechanism of the surface anchoring may also take place. The ongoing scientific and technological problems related to the suspensions are discussed. Among such problems are the stability of the suspensions, selection of the proper surfactants, formation of the particle chains, and the effect of the electric charges on the properties of the ferroelectric liquid crystal suspensions.

  7. Electrically tunable liquid crystal photonic bandgap fiber laser

    NASA Astrophysics Data System (ADS)

    Olausson, Christina B.; Scolari, Lara; Wei, Lei; Noordegraaf, Danny; Weirich, Johannes; Alkeskjold, Thomas T.; Hansen, Kim P.; Bjarklev, Anders

    2010-02-01

    We demonstrate electrical tunability of a fiber laser 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- 1065 nm by applying an electric field to the silicon assembly.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Orientational relaxation in a discotic liquid crystal.

    PubMed

    Chakrabarti, Dwaipayan; Jana, Biman; Bagchi, Biman

    2007-06-01

    We investigate orientational relaxation of a model discotic liquid crystal, consisting of disclike molecules, by molecular dynamics simulations along two isobars starting from the high temperature isotropic phase. The two isobars have been so chosen that (a) the phase sequence isotropic- (I-) nematic- (N-) columnar (C) appears upon cooling along one of them and (b) the sequence isotropic- (I-) columnar- (C) along the other. While the orientational relaxation in the isotropic phase near the I-N phase transition in system (a) shows a power law decay at short to intermediate times, such power law relaxation is not observed in the isotropic phase near the I-C phase boundary in system (b). In order to understand this difference (the existence or the absence of the power law decay), we calculated the growth of the orientational pair distribution functions (OPDFs) near the I-N phase boundary and also near the I-C phase boundary. We find that the OPDF shows a marked growth in long range correlation as the I-N phase boundary is approached in the I-N-C system (a), but such a growth is absent in the I-C system, which appears to be consistent with the result that I-N phase transition in the former is weakly first order while the I-C phase transition in the latter is not weak. As the system settles into the nematic phase, the decay of the single-particle second-rank orientational time correlation function follows a pattern that is similar to what is observed with calamitic liquid crystals and supercooled molecular liquids.

  10. Isotropization of nematic liquid crystals by TMDSC

    SciTech Connect

    Chen, Wei; Dadmun, M.; Zhang, Ge; Boller, A.; Wunderlich, B. |

    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.

  11. Hydrogen-Bonded Liquid Crystal Nanocomposites.

    PubMed

    Roohnikan, Mahdi; Toader, Violeta; Rey, Alejandro; Reven, Linda

    2016-08-23

    Nanoparticle-liquid crystal (NP-LC) composites based on hydrogen bonding were explored using a model system. The ligand shells of 3 nm diameter zirconium dioxide nanoparticles (ZrO2 NPs) were varied to control their interaction with 4-n-hexylbenzoic acid (6BA). The miscibility and effect of the NPs on the nematic order as a function of particle concentration was characterized by polarized optical microscopy (POM), fluorescence microscopy and (2)H NMR spectroscopy. Nonfunctionalized ZrO2 NPs have the lowest miscibility and strongest effect on the LC matrix due to irreversible binding of 6BA to the NPs via a strong zirconium carboxylate bond. The ZrO2 NPs were functionalized with 6-phosphonohexanoic acid (6PHA) or 4-(6-phosphonohexyloxy)benzoic acid (6BPHA) which selectively bind to the ZrO2 NP surface via the phosphonic acid groups. The miscibility was increased by controlling the concentration of the pendant CO2H groups by adding hexylphosphonic acid (HPA) to act as a spacer group. Fluorescence microscopy of lanthanide doped ZrO2 NPs showed no aggregates in the nematic phase below the NP concentration where aggregates are observed in the isotropic phase. The functionalized NPs preferably concentrate into LC defects and any remaining isotropic liquid but are still present throughout the nematic liquid at a lower concentration.

  12. Prediction of flow-aligning and tumbling in a bent-core nematic liquid crystal using measurements of orienation order parameters

    NASA Astrophysics Data System (ADS)

    Park, Min Sang; Park, Beom-Jin; Park, Jung Ok; Srinivasarao, Mohan

    2010-03-01

    The flow behavior of bent-core nematic liquid crystal (A131), which has been known to exhibit a biaxial nematic phase, is predicted by measurements of 2^nd and 4^th rank orientation order parameters. Using experimentally determined uniaxial, and , and biaxial orientation order parameters, , and from polarized micro-Raman spectroscopy, we compute the tumbling parameter, λ. The relationships between the order parameters and tumbling parameter derived by 2 different groups are used and the results are computed: a molecular theory by Archer and Larson (1995), that by Kroger and Seller (1995) for uniaxial system, and Leslie's theory for 2-director continuum. Temperature evolution of tumbling parameter shows the transition from a flow alignment regime to a tumbling instability. The results of the temperature evolution of tumbling parameter of bent-core nematic LC are compared to those of pure nematic LC (5CB) and LC mixture (E7).

  13. Quantum theory of cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Issaenko, Sergei A.

    A long standing and central problem in cholesteric liquid crystals is to relate the macroscopic pitch to the underlying microscopic interactions. These interactions are of two types which we call quantum (dispersion) and classical. Here we show that, contrary to common belief, intermolecular biaxial correlations usually play an important role for dispersion forces. To understand the microscopic picture of cholesteric liquid crystal we first analyze the effective chiral interaction between molecules arising front long-range quantum interactions between fluctuating charge moments in terms of a simple model of a chiral molecule. This model is based on the approximations that (a) the dominant excited states of a molecule form a band whose width is small compared to the average energy of excitation above the ground state and (b) biaxial orientational correlation between adjacent molecules can be neglected. We consider a system consisted of elongated molecules and, although we invoke the expansion in terms of coordinates transverse to the long axis of constituent molecules, we treat the longitudinal coordinate exactly. We identify two distinct physical limits depending on whether one or both of the interacting molecules are excited in the virtual state. The two-molecule interaction can be interpreted in terms of a superposition of pairwise interactions between individual atoms (or local chiral centers) on a chiral molecule and centers of anisotropic part of polarizability on the other molecule, while the one-molecule term involves three-body interactions between two local dipole moments of a chiral molecule and centers of anisotropic part of polarizability on the other, possibly nonchiral molecule. The numerical estimates of the pitch appeared from the above mechanism even without the Taylor expansion of the potential turns out to be considerably larger than experimental results and so it appears that the mean field treatment of these interactions can be used only in

  14. Synthesis and Physical Properties of Liquid Crystals: An Interdisciplinary Experiment

    ERIC Educational Resources Information Center

    Van Hecke, Gerald R.; Karukstis, Kerry K.; Hanhan Li; Hendargo, Hansford C.; Cosand, Andrew J.; Fox, Marja M.

    2005-01-01

    A study involves multiple chemistry and physics concepts applied to a state of matter that has biological relevance. An experiment involving the synthesis and physical properties of liquid crystals illustrates the interdisciplinary nature of liquid crystal research and the practical devices derived from such research.

  15. Slovenian Pre-Service Teachers' Conceptions about Liquid Crystals

    ERIC Educational Resources Information Center

    Pavlin, Jerneja; Vaupotic, Natasa; Glazar, Sasa A.; Cepic, Mojca; Devetak, Iztok

    2011-01-01

    A total of 448 first-year university students participated in the study at the beginning of the academic year 2009/10. A paper-pencil liquid crystal questionnaire (LCQ) comprising 20 items was used to evaluate students' general conceptions related to liquid crystals, their properties and to the state of matter in general. The results show that 2/3…

  16. Color changing plasmonic surfaces utilizing liquid crystal (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Franklin, Daniel; Wu, Shin-Tson; Chanda, Debashis

    2016-09-01

    Plasmonic structural color has recently garnered significant interest as an alternative to the organic dyes standard in print media and liquid crystal displays. These nanostructured metallic systems can produce diffraction limited images, be made polarization dependent, and exhibit resistance to color bleaching. Perhaps even more advantageous, their optical characteristics can also be tuned, post-fabrication, by altering the surrounding media's refractive index parallel to the local plasmonic fields. A common material with which to achieve this is liquid crystal. By reorienting the liquid crystal molecules through external electric fields, the optical resonances of the plasmonic filters can be dynamically controlled. Demonstrations of this phenomenon, however, have been limited to modest shifts in plasmon resonance. Here, we report a liquid crystal-plasmonic system with an enhanced tuning range through the use of a shallow array of nano-wells and high birefringent liquid crystal. The continuous metallic nanostructure maximizes the overlap between plasmonic fields and liquid crystal while also allowing full reorientation of the liquid crystal upon an applied electric field. Sweeping over structural dimensions and voltages results in a color palette for these dynamic reflective pixels that can further be exploited to create color tunable images. These advances make plasmonic-liquid crystal systems more attractive candidates for filter, display, and other tunable optical technologies.

  17. Binary Operation Of A Liquid-Crystal Light Valve

    NASA Technical Reports Server (NTRS)

    Davis, Jeffrey A.

    1990-01-01

    Conditions for operation of commercially available liquid-crystal light valve as binary spatial light modulator discovered. In mode, modulator turns on sharply and then saturates as intensity of writing beam increases. Valve comprises photoconductive layer and liquid-crystal layer separated by dielectric mirror and sandwiched between two transparent electrodes. Potential applications include enhancement of images, optical recording, and holography.

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

    NASA Technical Reports Server (NTRS)

    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.

  19. Electron paramagnetic resonance study of two smectic A liquid crystals.

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Gelerinter, E.; Fishel, D. L.

    1972-01-01

    Study of the molecular ordering in two smectic A liquid crystals using vanadyl acetylacetonate as a paramagnetic probe. The average hyperfine splitting of the spectrum in the smectic A mesophase is measured as a function of the orientation relative to the dc magnetic field of the spectrometer after alignment of the molecules of the liquid crystal.

  20. Quantum Liquid Crystal Phases in Strongly Correlated Fermionic Systems

    ERIC Educational Resources Information Center

    Sun, Kai

    2009-01-01

    This thesis is devoted to the investigation of the quantum liquid crystal phases in strongly correlated electronic systems. Such phases are characterized by their partially broken spatial symmetries and are observed in various strongly correlated systems as being summarized in Chapter 1. Although quantum liquid crystal phases often involve…

  1. Time-programmed helix inversion in phototunable liquid crystals.

    PubMed

    Asshoff, Sarah J; Iamsaard, Supitchaya; Bosco, Alessandro; Cornelissen, Jeroen J L M; Feringa, Ben L; Katsonis, Nathalie

    2013-05-14

    Doping cholesteric liquid crystals with photo-responsive molecules enables controlling the colour and polarisation of the light they reflect. However, accelerating the rate of relaxation of these photo-controllable liquid crystals remains challenging. Here we show that the relaxation rate of the cholesteric helix is fully determined by helix inversion of the molecular dopants.

  2. Fork gratings based on ferroelectric liquid crystals.

    PubMed

    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.

  3. Mueller Polarimetric Imaging System with Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Laude-Boulesteix, Blandine; de Martino, Antonello; Drévillon, Bernard; Schwartz, Laurent

    2004-05-01

    We present a new polarimetric imaging system based on liquid-crystal modulators, a spectrally filtered white-light source, and a CCD camera. The whole Mueller matrix image of the sample is measured in approximately 5 s in the transmission mode. The instrument design, together with an original and easy-to-operate calibration procedure, provides high accuracy over a wide spectral range (500-700 nm). This accuracy has been assessed by measurement of a linear polarizer at different orientations and a thick wedged quartz plate as an example of a partially depolarized retarder. Polarimetric images of a stained hepatic biopsy with significant fibrosis have been taken at several wavelengths. The optical properties of Picrosirius Red stained collagen (diattenuation, retardance, and polarizance) have been measured independently from each other between 500 and 700 nm.

  4. Statistical foundations of liquid-crystal theory

    PubMed Central

    Seguin, Brian; Fried, Eliot

    2013-01-01

    We develop a mechanical theory for systems of rod-like particles. Central to our approach is the assumption that the external power expenditure for any subsystem of rods is independent of the underlying frame of reference. This assumption is used to derive the basic balance laws for forces and torques. By considering inertial forces on par with other forces, these laws hold relative to any frame of reference, inertial or noninertial. Finally, we introduce a simple set of constitutive relations to govern the interactions between rods and find restrictions necessary and sufficient for these laws to be consistent with thermodynamics. Our framework provides a foundation for a statistical mechanical derivation of the macroscopic balance laws governing liquid crystals. PMID:23772091

  5. Clinical evaluation of liquid crystal skin thermometers.

    PubMed

    MacKenzie, R; Asbury, A J

    1994-02-01

    We have examined two types of liquid crystal thermometers (LCT) designed for clinical use: one designed to measure skin surface temperature (LCTS) and the other had its calibration shifted by 1.9 degrees C to read a "core" temperature (LCTC). In laboratory tests with LCT on a glass beaker, there were highly significant correlations between temperatures measured by thermocouples, LCTS (r = 0.99) and LCTC (r = 0.99). In five patients undergoing cooling and warming during cardiopulmonary bypass with an LCT on their forehead, next to a thermocouple, the smallest correlation coefficient was 0.92. In 7.3% of observations in patients, the LCT scale was blurred, but readable. The graph relating LCT temperature and forehead thermocouple temperature showed hysteresis between the cooling and warming phases. An additional laboratory experiment suggested that LCT might be affected by draughts; they should therefore be protected from draught in use.

  6. Dielectric Dispersion Effects in Liquid Crystals.

    NASA Astrophysics Data System (ADS)

    Lavrentovich, Oleg; Yin, Ye; Gu, Mingxia; Shiyanovskii, Sergij

    2006-03-01

    As the switching speed in practical LC devices is pushed from the currently common 10 ms to sub-millisecond levels, it is important to take into account the effects associated with the finite rate with which the electric displacement changes in the external electric field. We discuss two important general consequences of the dielectric relaxation phenomenon: (1) Non-local time relationship between the electric displacement and the electric field [1]. In a quickly changing electric field, orientation of the liquid crystal depends not only on the instantaneous value of the electric field, but also on the previous values of the field and previous orientations of the material. (2) Dielectric heating. [1] Y. Yin, S.V. Shiyanovskii, A.B. Golovin, and O. D. Lavrentovich, Phys. Rev. Lett. 95, 087801 (2005) .

  7. Fluctuation and Dissipation in Liquid Crystal Electroconvection

    NASA Astrophysics Data System (ADS)

    Goldburg, W. I.; Goldschmidt, Y. Y.

    2001-11-01

    Recently, Gallavotti and Cohen (GC) have generalized the fluctuation-dissipation theorem (FDT) to encompass systems that are in a steady state far from thermal equilibrium. We describe an experiment aimed at putting the GC theory to an experimental test [1]. The system is a liquid crystal (lc) across which an ac voltage \\cal V=√ 2V\\cos(ω t) is applied. We measure σ_P, the rms fluctuations of the power P(t) dissipated in the lc when V is large enough to generate chaotic or turbulent flow in the sample. To compare the experimental results with the GC theory, it is necessary to assign a dynamical temperature to the system by introducing a kinetic energy per quasi-particle generated by the chaotic flow. [1] W.I. Goldburg, Y. Y. Goldschmidt and Hamid Kellay, nlin.CD/0106015

  8. Planar optics with patterned chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Kobashi, Junji; Yoshida, Hiroyuki; Ozaki, Masanori

    2016-06-01

    Reflective metasurfaces based on metallic and dielectric nanoscatterers have attracted interest owing to their ability to control the phase of light. However, because such nanoscatterers require subwavelength features, the fabrication of elements that operate in the visible range is challenging. Here, we show that chiral liquid crystals with a self-organized helical structure enable metasurface-like, non-specular reflection in the visible region. The phase of light that is Bragg-reflected off the helical structure can be controlled over 0-2π depending on the spatial phase of the helical structure; thus planar elements with arbitrary reflected wavefronts can be created via orientation control. The circular polarization selectivity and external field tunability of Bragg reflection open a wide variety of potential applications for this family of functional devices, from optical isolators to wearable displays.

  9. Helical motion of chiral liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takaki; Sano, Masaki

    Artificial swimmers have been intensively studied to understand the mechanism of the locomotion and collective behaviors of cells and microorganisms. Among them, most of the artificial swimmers are designed to move along the straight path. However, in biological systems, chiral dynamics such as circular and helical motion are quite common because of the chirality of their bodies, which are made of chiral biomolecules. To understand the role of the chirality in the physics of microswimmers, we designed chiral artificial swimmers and the theoretical model for the chiral motion. We found that chiral liquid crystal droplets, when dispersed in surfactant solutions, swim in the helical path induced by the Marangoni effect. We will discuss the mechanism of the helical motion with our phenomenological model. This work is supported by Grant-in-Aid for JSPS Fellows (Grant No. 26.9814), and MEXT KAKENHI Grant No. 25103004.

  10. Lipid decorated liquid crystal pressure sensors

    NASA Astrophysics Data System (ADS)

    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. Photoinduced broadening of cholesteric liquid crystal reflectors

    NASA Astrophysics Data System (ADS)

    White, Timothy J.; Freer, Alexander S.; Tabiryan, Nelson V.; Bunning, Timothy J.

    2010-04-01

    The selective reflection of cholesteric liquid crystals (CLCs) is well-known and has been utilized in a number of dynamic optical applications. This work presents a novel approach to passively (e.g., all-optically) cue reflection notch broadening in photoresponsive CLC formulations based on high helical twisting power (HTP) bis(azo) chiral dopants. The original reflection bandwidth of approximately 100 nm is increased to as much as 1700 nm, by exposing 36 μm thick cells to UV light. The maximum attainable bandwidth is shown to be a function of cell thickness, light intensity, and strongly related to the HTP of the photoresponsive chiral dopants. An all-optical technique of simultaneous UV and green light exposure is demonstrated to trap the reflection notch at a predetermined position and bandwidth.

  12. Thermal response of cholesteric liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Nagai, Hama; Urayama, Kenji

    2015-08-01

    The effects of temperature variation on photonic properties of cholesteric liquid crystal elastomers (CLCEs) are investigated in mechanically unconstrained and constrained geometries. In the unconstrained geometry, cooling in the cholesteric state induces both a considerable shift of the selective reflection band to shorter wavelengths and a finite degree of macroscopic expansion in the two directions normal to the axis of the helical director configuration. The thermal deformation is driven by a change in orientational order of the underlying nematic structure S and the relation between the macroscopic strain and S is explained on the basis of the anisotropic Gaussian chain network model. The helical pitch varies with the film thickness in an affine manner under temperature variation. The CLCEs under the constrained geometry where thermal deformation is strictly prohibited show no shift of the reflection bands when subjected to temperature variation. This also reveals the strong correlation between the macroscopic dimensions and the pitch of the helical director configuration.

  13. Actuating materials. Voxelated liquid crystal elastomers.

    PubMed

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

    2015-02-27

    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.

  14. Band transport model for discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Lever, L. J.; Kelsall, R. W.; Bushby, R. J.

    2005-07-01

    A theoretical model is presented for charge transport in discotic liquid crystals in which a charge is delocalized over more than one lattice site. As such, charge transport is via a banded conduction process in a narrow bandwidth system and takes place over coherent lengths of a few molecules. The coherent lengths are disrupted by the geometrical disorder of the system and are treated as being terminated by quantum tunnel barriers. The transmission probabilities at these barriers have been calculated as a function of the charge carrier energy. Phononic interactions are also considered and the charge carrier scattering rates are calculated for intermolecular and intramolecular vibrations. The results of the calculations have been used to develop a Monte Carlo simulation of the charge transport model. Simulated data are presented and used to discuss the nature of the tunnel barriers required to reproduce experimental data. We find that the model successfully reproduces experimental time of flight data including temperature dependence.

  15. Chiral liquid crystals as biosensing platforms

    NASA Astrophysics Data System (ADS)

    Lee, Mon-Juan; Sung, Yu-Chien; Hsiao, Yu-Cheng; Lee, Wei

    2016-09-01

    The texture observation has long been the core technique in liquid crystal (LC)-based bioassays. Its working principle stems from the dark-to-bright texture change induced by the interruption of the initially homeotropic alignment in nematic bulks or from the radial-to-bipolar configuration transition in LC droplets in the presence of biomolecules. One of the drawbacks of this observational scheme, which requires a polarizing optical microscope, is the difficulty in quantitative analysis. In this invited paper, we report on our recent development of alternative optical biosensing techniques based on cholesteric LCs (CLCs) without the use of a polarizer. The increase in structural order in a vertically anchored CLC cell in the quasi-planar state provides a means to allow detection and quantification of the concentration of biomolecules immobilized on the interface between the mesophase and the surfactant DMOAP for LC vertical alignment.

  16. Aberration Compensation Using Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Somalingam, S.; Hain, M.; Tschudi, T.; Knittel, J.; Richter, H.

    We have developed a novel transmissive nematic liquid crystal device which is capable of compensating spherical wavefront aberration that occurs during the operation of optical pickup systems. In order to increase the storage capacity, next generation optical data storage systems beyond CD and DVD will use according to the Blu-Ray specification (BD) blue laser light and an objective lens with high numerical aperture (N.A.) of 0.85. However, such high N.A. systems have an inherent higher sensitivity on aberrations. For example spherical aberration is inversely proportional to the wavelength and grows with the fourth power of N.A. of the objective lens. In an optical pickup system there are two sources for spherical aberration: The first one is the variation of the substrate thickness due to manufacturing tolerances under mass production conditions. The second one concerns disks with multiple data-layers, which cause spherical aberration when layers are switched, as the objective lens can only be optimized for a single layer thickness. We report a method for effective compensation of spherical aberration by utilizing a novel liquid crystal device, which generates a parabolic wavefront profile. This particular shape makes the device highly tolerant against lateral movement. A sophisticated electrode design allows us to reduce the number of driving electrodes down to two by using the method of conductive ladder mashing. Further evaluation in a blue-DVD test drive has been carried out with good results. By placing the device into an optical pick-up we were able to readout a dual-layer ROM disk with a total capacity of 50 gigabytes (GB). A data-to-clock jitter of 6.9% for the 80 μm and of 8.0% for the 100 μm cover layer could be realized.

  17. Thermally switchable flexible liquid crystal devices in prepolymer-doped cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Fuh, A. Y.-G.; Li, J.-H.; Cheng, K.-T.

    2010-10-01

    This work describes an approach for fabricating thermally switchable flexible liquid crystal devices in prepolymer-doped cholesteric liquid crystals (CLCs). The roughness of the UV-cured polymer film eliminates the stability of planar CLCs, allowing the textures in the UV-cured regions to be changed from planar to focal conic. Impurities associated with doping with prepolymers cause the clearing temperature of LCs in the UV-cured regions to differ from that in the uncured regions as the prepolymers are polymerized. Therefore, the textures in these two regions can be switched by controlling the temperature. Thermally switchable flexible LC devices, such as optically addressed smart cards, light valves, and others, can be realized using this approach.

  18. Insertion of liquid crystal molecules into hydrocarbon monolayers

    SciTech Connect

    Popov, Piotr Mann, Elizabeth K.; Lacks, Daniel J.; Jákli, Antal

    2014-08-07

    Atomistic molecular dynamics simulations were carried out to investigate the molecular mechanisms of vertical surface alignment of liquid crystals. We study the insertion of nCB (4-Cyano-4{sup ′}-n-biphenyl) molecules with n = 0,…,6 into a bent-core liquid crystal monolayer that was recently found to provide good vertical alignment for liquid crystals. The results suggest a complex-free energy landscape for the liquid crystal within the layer. The preferred insertion direction of the nCB molecules (core or tail first) varies with n, which can be explained by entropic considerations. The role of the dipole moments was found to be negligible. As vertical alignment is the leading form of present day liquid crystal displays (LCD), these results will help guide improvement of the LCD technology, as well as lend insight into the more general problem of insertion of biological and other molecules into lipid and surfactant layers.

  19. The measurement of droplet temperature using thermochromic liquid crystals

    SciTech Connect

    Peterson, D.; Hu, S.H.; Richards, C.D.; Richards, R.F.

    1995-12-31

    A noninvasive technique to determine the temperature of droplets in flight is under development. The technique involves atomizing droplets of neat thermochromic liquid crystals and then inferring the droplet temperatures form the liquid crystals` color-play. Previous work has shown the feasibility of atomizing the neat liquid crystal. The present work reports results of a calibration of the temperature response of 200 to 300 micron droplets of neat liquid crystal. The calibration is accomplished by suspending droplets of the neat liquid crystal on a microthermocouple within a controlled temperature environment. The droplet is imaged using a long-distance microscope, an RGB video camera, and a frame grabber. Images of the droplet are acquired and digitized to quantify changes in RGB values (color) with temperature. The RGB information is transformed into hue, saturation, intensity (HSI) space to relate hue, H, to temperature. The temperature of the droplet is measured directly with the micro-thermocouple.

  20. Random lasing from cholesteric liquid crystal microspheres dispersed in glycerol.

    PubMed

    Li, Yong; Luo, Dan; Chen, Rui

    2016-11-01

    We demonstrate random lasing from a scattering system formed by a cholesteric liquid crystal dispersed in glycerol. Strong scattering of light is produced from the interference between the cholesteric liquid crystal microsphere and glycerol and leads to random lasing. The optical properties of random lasing, such as intensity, threshold, and the temperature effect on lasing emission are demonstrated. The random laser is distinguished from the band-edge laser generated within the cholesteric liquid crystal microspheres by analyzing the positions of the photonic band-edge of the cholesteric liquid crystal and the photoluminescence of the doped laser dye. The random laser from cholesteric liquid crystal microspheres in glycerol possesses a simple fabrication process, small volume, and low threshold, which enable it to be used in speckle-free imaging, target identification, biomedicine, document coding, and other photonic devices.

  1. Graphene chiral liquid crystals and macroscopic assembled fibres

    PubMed Central

    Xu, Zhen; Gao, Chao

    2011-01-01

    Chirality and liquid crystals are both widely expressed in nature and biology. Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals. To date, chiral liquid crystals of 2D colloids have not been explored. As a typical 2D colloid, graphene is now receiving unprecedented attention. However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method. Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations. Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance. The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles. PMID:22146390

  2. Methods of making composite optical devices employing polymer liquid crystal

    DOEpatents

    Jacobs, S.D.; Marshall, K.L.; Cerqua, K.A.

    1991-10-08

    Composite optical devices are disclosed using polymer liquid crystal materials both as optical and adhesive elements. The devices are made by assembling a heated polymer liquid crystal compound, while in a low viscosity form between optically transparent substrates. The molecules of the polymer are oriented, while in the liquid crystalline state and while above the glass transition temperature (T[sub g]) of the polymer, to provide the desired optical effects, such as polarization, and selective reflection. The liquid crystal polymer cements the substrates together to form an assembly providing the composite optical device. 7 figures.

  3. Methods of making composite optical devices employing polymer liquid crystal

    DOEpatents

    Jacobs, Stephen D.; Marshall, Kenneth L.; Cerqua, Kathleen A.

    1991-01-01

    Composite optical devices using polymer liquid crystal materials both as optical and adhesive elements. The devices are made by assembling a heated polymer liquid crystal compound, while in a low viscosity form between optically transparent substrates. The molecules of the polymer are oriented, while in the liquid crystalline state and while above the glass transition temperature (T.sub.g) of the polymer, to provide the desired optical effects, such as polarization, and selective reflection. The liquid crystal polymer cements the substrates together to form an assembly providing the composite optical device.

  4. Localized soft elasticity in liquid crystal elastomers

    PubMed Central

    Ware, Taylor H.; Biggins, John S.; Shick, Andreas F.; Warner, Mark; White, Timothy J.

    2016-01-01

    Synthetic approaches to prepare designer materials that localize deformation, by combining rigidity and compliance in a single material, have been widely sought. Bottom-up approaches, such as the self-organization of liquid crystals, offer potential advantages over top–down patterning methods such as photolithographic control of crosslink density, relating to the ease of preparation and fidelity of resolution. Here, we report on the directed self-assembly of materials with spatial and hierarchical variation in mechanical anisotropy. The highly nonlinear mechanical properties of the liquid crystalline elastomers examined here enables strain to be locally reduced >15-fold without introducing compositional variation or other heterogeneities. Each domain (⩾0.01 mm2) exhibits anisotropic nonlinear response to load based on the alignment of the molecular orientation with the loading axis. Accordingly, we design monoliths that localize deformation in uniaxial and biaxial tension, shear, bending and crack propagation, and subsequently demonstrate substrates for globally deformable yet locally stiff electronics. PMID:26902873

  5. Touch sensors based on planar liquid crystal-gated-organic field-effect transistors

    SciTech Connect

    Seo, Jooyeok; Lee, Chulyeon; Han, Hyemi; Lee, Sooyong; Nam, Sungho; Kim, Youngkyoo; Kim, Hwajeong; Lee, Joon-Hyung; Park, Soo-Young; Kang, Inn-Kyu

    2014-09-15

    We report a tactile touch sensor based on a planar liquid crystal-gated-organic field-effect transistor (LC-g-OFET) structure. The LC-g-OFET touch sensors were fabricated by forming the 10 μm thick LC layer (4-cyano-4{sup ′}-pentylbiphenyl - 5CB) on top of the 50 nm thick channel layer (poly(3-hexylthiophene) - P3HT) that is coated on the in-plane aligned drain/source/gate electrodes (indium-tin oxide - ITO). As an external physical stimulation to examine the tactile touch performance, a weak nitrogen flow (83.3 μl/s) was employed to stimulate the LC layer of the touch device. The LC-g-OFET device exhibited p-type transistor characteristics with a hole mobility of 1.5 cm{sup 2}/Vs, but no sensing current by the nitrogen flow touch was measured at sufficiently high drain (V{sub D}) and gate (V{sub G}) voltages. However, a clear sensing current signal was detected at lower voltages, which was quite sensitive to the combination of V{sub D} and V{sub G}. The best voltage combination was V{sub D} = −0.2 V and V{sub G} = −1 V for the highest ratio of signal currents to base currents (i.e., signal-to-noise ratio). The change in the LC alignment upon the nitrogen flow touch was assigned as the mechanism for the present LC-g-OFET touch sensors.

  6. Ultrahigh sensitivity in liquid-crystal-based immunodetection by surface modification of the alignment layer

    NASA Astrophysics Data System (ADS)

    Lee, Mon-Juan; Su, Hui-Wen; Sun, Shih-Hung; Lee, Wei

    2014-10-01

    Liquid crystals (LCs) can be employed in biological sensing and applied to label-free immunodetection owing to their unique birefringent, anchoring, alignment and collective properties. Like all different kinds of immunoassays, both sensitivity and specificity are universally the most important key points of concern. In this study, we developed various approaches toward ultrahigh sensitivity in LC-based immunoassays for potential clinical applications. The LC-based immunodetection technique was demonstrated with the cancer biomarker CA125, which is a mucin-like glycoprotein commonly present in the serum of patients with ovarian and other types of cancer. By using LCs with larger birefringence, such as HDN, the sensitivity of immunodetection was drastically enhanced compared to 5CB, which has a relatively lower birefringence and is commonly used in LC biosensing studies. In addition, UV modification of the monolayer of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP), which functions as the alignment layer for LCs, is suggested to increase functional groups suitable for covalent binding of biomolecules, stabilizing the immobilized anti-CA125 antibody and the immunocomplex thus formed, and contributing to the lowered detection limit. Finally, we show that it is possible to directly identify the formation of CA125 immunocomplex with HDN in a mixture of antigen and antibody without the need to eliminate unbound or unreacted biomolecules through washing, thereby creating a simplified procedure for faster LC-based immunoassay. It is evident from our results that label-free immunodetection based on birefringent LCs represents a novel biosensing technique with potentials to detect a wide range of biomolecules, providing an alternative to conventional label-based immunoassays.

  7. Defects and order in liquid crystal phases

    NASA Astrophysics Data System (ADS)

    Jain, Shilpa

    This thesis investigates the partial destruction of ordering in liquid crystalline systems due to the influence of defects and thermal fluctuations. The systems under consideration are hexagonal columnar crystals with crystalline order perpendicular to the columns, and two-dimensional smectics with order perpendicular to the layers. We first study the possibility of reentrant melting of a hexagonal columnar crystal of flexible charged polymers at high enough densities. The Lindemann criterion is employed in determining the melting point. Lattice fluctuations are calculated in the Debye model, and an analogy with the Abrikosov vortex lattice in superconductors is exploited in estimating both the elastic constants of the hexagonal lattice, and the appropriate Lindemann constant. We also discuss the unusual functional integral describing the statistical mechanics of a single polymer in an Einstein cage model using the path-integral formulation. A crossover as a function of an external field along the column axis is discussed as well. Next, we study defects in a columnar crystal in the form of vacancy/interstitial loops or strings of vacancies and interstitials bounded by column "heads" and "tails". These defect strings are oriented by the columnar lattice and can change size and shape by movement of the ends and forming kinks along the length. Hence an analysis in terms of directed living polymers is appropriate to study their size and shape distribution, volume fraction, etc. If the entropy of transverse fluctuations overcomes the string line tension in the crystalline phase, a string proliferation transition occurs, leading to a "supersolid" phase with infinitely long vacancy or interstitial strings. We estimate the wandering entropy and examine the behaviour in the transition regime. We also calculate numerically the line tension of various species of vacancies and interstitials in a triangular lattice for power-law potentials as well as for a modified Bessel

  8. Crystal Growth in Liquid-Encapsulated Float Zone

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J.; Frazier, Donald O.; Lehoczky, Sandor; Vlasse, Marcus; Facemire, Barbara

    1987-01-01

    Suitably chosen liquid encapsulant placed around melt zone in float-zone crystal-growth system performs four important functions enhancing purity and reducing strains and dislocations in final crystal. In new technique, grow dislocation-free crystals with precisely controlled composition even from materials not amenable to conventional float-zone crystal-growth method. Support provided by encapsulant make it practical to process materials of low surface tension.

  9. Liquid crystals in micron-scale droplets, shells and fibers.

    PubMed

    Urbanski, Martin; Reyes, Catherine G; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P F

    2017-04-05

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  10. Liquid crystals in micron-scale droplets, shells and fibers

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Reyes, Catherine G.; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P. F.

    2017-04-01

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  11. Microfluidic formation of pH responsive 5CB droplets decorated with PAA-b-LCP.

    PubMed

    Khan, Waliullah; Choi, Jin Ho; Kim, Gyu Man; Park, Soo-Young

    2011-10-21

    We are reporting for the first time the pH responsiveness of liquid crystal (LC) microdroplets decorated with an amphiphilic block copolymer of PAA-b-LCP. We successfully demonstrated the adsorption of block copolymer on LC droplets by fluorescence microscopy and pH response to the radial-to-bipolar orientational change of the LC droplets by changing pH from 12 to 2 through the polarized optical microscope (POM). We believe that our results may pave the way for the generation of monodisperse droplets decorated by various amphiphilic block copolymers which respond to several kinds of the external stimuli. These developments may be important for potential applications of the LC droplets in sensing and encapsulation fields.

  12. Liquid crystal bubbles forming a tunable micro-lenses array

    NASA Astrophysics Data System (ADS)

    Hamdi, R.; Petriashvili, G.; Lombardo, G.; De Santo, M. P.; Barberi, R.

    2011-10-01

    Cholesteric liquid crystals with long pitch confined in homeotropic cells can be used to generate stable but distorted and localized liquid crystal structures exhibiting spherulitic textures, known as "bubbles." As these bubbles can be induced by an external electric field with a narrow range following the confinement ratio C=d/p ≈1 (d representing cell thickness and p representing cholesteric pitch), it is possible to obtain electrically controlled micro-lenses. Here we investigated the optical and electro-optical properties of such liquid crystal bubbles for creating an array of micro-lenses with electrically tunable focal length.

  13. Positron lifetime measurements in chiral nematic liquid crystals

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Eftekhari, Abe; Parmar, Devendra S.

    1991-01-01

    Positron lifetimes in the isotropic phases of chiral nematic liquid crystal formulations and their mixtures up to the racemic level were measured. The lifetime spectra for all liquid crystal systems were analyzed into three components. Although the individual spectra in the left- and right-handed components are identical, their racemic mixtures exhibit much larger orthopositronium lifetimes; these larger lifetimes indicate the presence of larger microvoids. This result is consistent with the reportedly higher thermodynamic stability and color play range in the racemic mixtures of chiral nematic liquid crystals.

  14. Acousto-optics of liquid crystals: Yesterday, today, and tomorrow

    NASA Astrophysics Data System (ADS)

    Kapustina, O. A.

    2014-09-01

    The most important results of the recent theoretical and experimental studies in the field of acousto-optics of liquid crystals (LCs) in research lines initiated by the pioneering studies of Professor A.P. Kapustin at the Institute of Crystallography of the Russian Academy of Sciences and carried out at the Acoustic Institute of the Russian Academy of Sciences are generalized and analyzed. These lines include the study of the nature of acoustically induced supramolecular structures in nematic liquid crystals (NLCs) and cholesteric liquid crystals (CLCs) and the development of physical bases of practical LC acousto-optics, related to the detection of acoustic signals.

  15. Polarization effects in reconfigurable liquid crystal phase holograms

    NASA Astrophysics Data System (ADS)

    Komarčević, Miloš; Manolis, Ilias G.; Wilkinson, Timothy D.; Crossland, William A.

    2005-01-01

    An improved configuration for achieving true polarization insensitive reconfigurable phase holograms for optical switches using homogeneously aligned nematic liquid crystal devices is presented. Previous experimental results have been analyzed and explained using numerical modeling of the nematic liquid crystal orientation and associated optical modulation. Twisting of the liquid crystal optical axis from the optimal 45° orientation from the quarter waveplate is shown to degrade the polarization insensitive performance. The alternative direction of surface alignment perpendicular to the long pixel edge eliminates the twist of the director during switching. True polarization insensitivity is predicted with our model for this mode of operation.

  16. Numerical modeling of confined liquid crystal systems

    NASA Astrophysics Data System (ADS)

    Mkaddem, Sami

    There has been much research interest in fine structures and defects of equilibrium configurations of nematic liquid crystal droplets subject to strong homeotropic anchoring and modeled by Landau-de Gennes free-energy functionals. In particular, two configurations are the center of attention. The first one is the radial hedgehog, which has an isotropic core and a spherically symmetric structure. The second one is the ring disclination, which has a ring disclination of strength 1/2 and a cylindrically symmetric structure. In this dissertation, we undertake a detailed numerical study of the two described equilibrium configurations using the imposed symmetries to simplify the problem and utilizing a high order finite element discretization to solve it. In addition to the radial hedgehog and the ring disclination, we found a new, metastable configuration, which also is axially symmetric and consists of two isotropic points along its symmetry axis narrowly separated by a line disclination. We generate phase and bifurcation diagrams of the equilibrium configurations. We also investigate the qualitative behavior and the stability of the radial hedgehog. Using a perturbation against the radial hedgehog, we show that such configurations must become unstable at sufficiently low temperatures or in sufficiently large droplets.

  17. Light transmission loss in liquid crystal waveguides

    NASA Astrophysics Data System (ADS)

    Nowinowski-Kruszelnicki, Edward; Walczak, Andrzej; Kiezun, Aleksander; Jaroszewicz, Leszek R.

    1998-02-01

    The investigation results of the propagation loss due to light scattering in electrically induced channel in planar waveguides are presented. The channel structure was obtained by means of electric driven stripe electrode made by photolithographic process. Planar waveguiding cell has been fabricated using ITO/SiO2/polyimide-coated glass plates and LC film 20 micrometers thick. A nematic liquid crystal layer with 90 degrees-twisted nematic orientation was studied. The He-Ne light beam was endfire coupled into an input edge of a waveguide using an objective lens. The propagation loss have been evaluated from the spatial variation intensity of light scattered out perpendicularly to the waveguide surface along the light propagation direction measured with CCD camera. Loss measurements have been made in room temperature. Waveguiding channel effect has been observed above 2.5 Vrms of applied voltage with the loss of about 17 +/- 1 dB. Increased driving voltage up to 100 Vrms reduces the loss to minimum value of 12 +/- 1 dB/cm. As a result of the experiments one may conclude that transmission loss in thick nematic waveguide have bulk character caused by imperfection of molecular alignment.

  18. Latest Developments In Liquid Crystal Television Displays

    NASA Astrophysics Data System (ADS)

    Morozumi, Shinji; Oguchi, Kouichi; Ohshima, Hiroyuki

    1984-06-01

    This paper will discuss developments in liquid crystal (LC) television displays, mainly for pocket-size TV sets. There are two types of LC television displays. One is a simple multiplexing type, and the other is an active matrix type. The former type is an easier way to fabricate large and low-cost LC panels than the latter. However, it has serious drawbacks. The contrast gets lower as the duty ratio gets higher. Therefore the TV image of this type inevitably has rather low contrast and resolution. On the other hand, the active matrix type, which consists of active elements in each pixel, has several advantages in overcoming such problems. The metal oxide semiconductor transistors and the amorphous or polycrystalline Si thin-film transistors (TFTs) have possibilities in this application. A full-color LC display, which can be realized by the combina-tion of color filters and poly Si TFT arrays on a transparent substrate, was proven to have excellent color image, close to that of conventional CRTs. Here, several examples of LC television displays, including color, are shown. Some of them are already on the market, and others will be soon.

  19. Thermochromic liquid crystals in heat transfer research

    NASA Astrophysics Data System (ADS)

    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.

  20. Liquid crystal filled surface plasmon resonance thermometer.

    PubMed

    Lu, Mengdi; Zhang, Xinpu; Liang, Yuzhang; Li, Lixia; Masson, Jean-Francois; Peng, Wei

    2016-05-16

    A novel surface plasmon resonance (SPR) thermometer based on liquid crystal (LC) filled hollow fiber is demonstrated in this paper. A hollow fiber was internally coated with silver and then filled with LC. The SPR response to temperature was studied using modeling and verified experimentally. The results demonstrated that the refractive index of LC decreases with the increasing temperature and the variation can be detected by the resonance wavelength shift of the plasmon resonance. The temperature sensitivities were 4.72 nm/°C in the temperature range of 20 to 34.5 °C and 0.55 nm/°C in the temperature range of 36 to 50 °C, At the phase transition temperature between nematic and isotropic phases of the LC, the temperature sensitivity increased by one order of magnitude and a shift of more than 46 nm was observed with only a 1.5 °C temperature change. This sensor can be used for temperature monitoring and alarming, and can be extended for other physical parameter measurement.

  1. Molecular wires from discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Park, Ji Hyun; Labardi, Massimiliano; Scalia, Giusy

    2014-02-01

    Discotic liquid crystal (LC) can arrange in columnar structures along which electrical conduction occurs via π-π interaction between adjacent molecular cores. The efficiency of the conductivity is strongly dependent on the overlap of the orbitals of neighbor molecules and, in general, on the structural arrangements. The understanding of the factors that influence the organization is crucial for the optimization of the final conductive properties of the self-assembled columns. In this paper we present a study on the self-organization into molecular wires of a discotic LC using a solution based method. In particular, we focus on the effect of solvents used for preparing the LC solution. The resulting morphologies were investigated by atomic force microscopy (AFM) and optical microscopy, showing that diverse structures result from different solvents. With suitable conditions, we were able to induce very long fibers, with several tents of micrometer in length that, in turn, self-organize assuming a common orientation on a macroscopic scale.

  2. Liquid crystal polyester-carbon fiber composites

    NASA Technical Reports Server (NTRS)

    Chung, T. S.

    1984-01-01

    Liquid crystal polymers (LCP) have been developed as a thermoplastic matrix for high performance composites. A successful melt impregnation method has been developed which results in the production of continuous carbon fiber (CF) reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality. Tensile and flexural properties of LCP/CF composites are comparable to those of epoxy/CF composites. The LCP/CF composites have better impact resistance than the latter, although epoxy/CF composites possess superior compression and shear strength. The LCP/CF composites have good property retention until 200 F (67 % of room temperature value). Above 200 F, mechanical properties decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber as adequate toughness of the LCP matrix. Low mechanical property retention at high temperatures may be attributable to the low beta-transition temperature (around 80 C) of the LCP matrix material.

  3. Liquid crystal elastomer strips as soft crawlers

    NASA Astrophysics Data System (ADS)

    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.

  4. Artificial muscles based on liquid crystal elastomers.

    PubMed

    Li, Min-Hui; Keller, Patrick

    2006-10-15

    This paper presents our results on liquid crystal (LC) elastomers as artificial muscle, based on the ideas proposed by de Gennes. In the theoretical model, the material consists of a repeated series of main-chain nematic LC polymer blocks, N, and conventional rubber blocks, R, based on the lamellar phase of a triblock copolymer RNR. The motor for the contraction is the reversible macromolecular shape change of the chain, from stretched to spherical, that occurs at the nematic-to-isotropic phase transition in the main-chain nematic LC polymers. We first developed a new kind of muscle-like material based on a network of side-on nematic LC homopolymers. Side-on LC polymers were used instead of main-chain LC polymers for synthetic reasons. The first example of these materials was thermo-responsive, with a typical contraction of around 35-45% and a generated force of around 210 kPa. Subsequently, a photo-responsive material was developed, with a fast photochemically induced contraction of around 20%, triggered by UV light. We then succeeded in preparing a thermo-responsive artificial muscle, RNR, with lamellar structure, using a side-on nematic LC polymer as N block.Micrometre-sized artificial muscles were also prepared. This paper illustrates the bottom-up design of stimuli-responsive materials, in which the overall material response reflects the individual macromolecular response, using LC polymer as building block.

  5. Optically rewritable 3D liquid crystal displays.

    PubMed

    Sun, J; Srivastava, A K; Zhang, W; Wang, L; Chigrinov, V G; Kwok, H S

    2014-11-01

    Optically rewritable liquid crystal display (ORWLCD) is a concept based on the optically addressed bi-stable display that does not need any power to hold the image after being uploaded. Recently, the demand for the 3D image display has increased enormously. Several attempts have been made to achieve 3D image on the ORWLCD, but all of them involve high complexity for image processing on both hardware and software levels. In this Letter, we disclose a concept for the 3D-ORWLCD by dividing the given image in three parts with different optic axis. A quarter-wave plate is placed on the top of the ORWLCD to modify the emerging light from different domains of the image in different manner. Thereafter, Polaroid glasses can be used to visualize the 3D image. The 3D image can be refreshed, on the 3D-ORWLCD, in one-step with proper ORWLCD printer and image processing, and therefore, with easy image refreshing and good image quality, such displays can be applied for many applications viz. 3D bi-stable display, security elements, etc.

  6. Free surface dynamics of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    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.

  7. Optical defect modes in chiral liquid crystals

    SciTech Connect

    Belyakov, V. A.; Semenov, S. V.

    2011-04-15

    An analytic approach to the theory of optical defect modes in chiral liquid crystals (CLCs) is developed. The analytic study is facilitated by the choice of the problem parameters. Specifically, an isotropic layer (with the dielectric susceptibility equal to the average CLC dielectric susceptibility) sandwiched between two CLC layers is studied. The chosen model allows eliminating the polarization mixing and reducing the corresponding equations to the equations for light of diffracting polarization only. The dispersion equation relating the defect mode (DM) frequency to the isotropic layer thickness and an analytic expression for the field distribution in the DM structure are obtained and the corresponding dependences are plotted for some values of the DM structure parameters. Analytic expressions for the transmission and reflection coefficients of the DM structure (CLC-defect layer-CLC) are presented and analyzed for nonabsorbing, absorbing, and amplifying CLCs. The anomalously strong light absorption effect at the DM frequency is revealed. The limit case of infinitely thick CLC layers is considered in detail. It is shown that for distributed feedback lasing in a defect structure, adjusting the lasing frequency to the DM frequency results in a significant decrease in the lasing threshold. The DM dispersion equations are solved numerically for typical values of the relevant parameters. Our approach helps clarify the physics of the optical DMs in CLCs and completely agrees with the corresponding results of the previous numerical investigations.

  8. Mechanism of the emergence of the photo-EMF upon silicon liquid crystal-single crystal contact

    NASA Astrophysics Data System (ADS)

    Budagov, K. M.; Guseinov, A. G.; Pashaev, B. G.

    2017-03-01

    The effect light has on a silicon liquid crystal-single crystal contact at different temperatures of the surface doping of silicon, and when BaTiO3 nanoparticles are added to the composition of a liquid crystal, is studied. The mechanism of the emergence of the photo-EMF in the liquid crystal-silicon structure is explained.

  9. Optical Anisotropy and Four Possible Orientations of a Nematic Liquid Crystal on the Same Film of a Photochromic Chiral Smectic Polymer

    NASA Astrophysics Data System (ADS)

    Blinov, Lev M.; Barberi, Riccardo; Kozlovsky, Mikhail V.; Lazarev, Vladimir V.; de Santo, Maria P.

    Spin coated films of a chiral comb-like liquid crystalline copolymer containing azobenzene chromophores in its side chains are optically isotropic in their twisted smectic-like glassy state. In contact with a nematic liquid crystal (5CB, E7, MBBA) they provide a degenerate planar orientation. When irradiated by unpolarized UV light, they orient the same nematics homeotropically. Treated with linearly polarized UV light they orient nematics homogeneously with the director along the electric vector of the exciting light. After a combined irradiation first with unpolarized UV light and then with linearly polarized visible light, the films again provide a homogeneous liquid crystal orientation, this time with the director perpendicular to the visible light electric vector. The phenomena observed are related to the light induced optical anisotropy. Two main processes are responsible for the anisotropy (1) a UV light depletion of trans-isomers of the azobenzene chromophores from the chosen direction and (2) a reorientation of the chromophores by polarized visible light.

  10. Curvature oscillations and linear electro-optical effect in a surface layer of a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Blinov, L. M.; Durand, G.; Yablonsky, S. V.

    1992-05-01

    Damped curvature oscillations are excited at the surface between a nematic liquid crystal and a solid substrate, from the linear coupling of an AC electric field with the flexoelectric properties of the medium. The waves are detected by a modulation ellipsometry technique. Linear-in-field oscillations of the director in the surface nematic layer have been observed. The amplitude and characteristic response time of the oscillations are defined by visco-elastic and flexoelectric properties of the medium and the overlaping of the curvature wave with the profile of the sampling optical evanescent wave. A simple model is discussed which is in good agreement with experiments performed on a compensated MBBA mixture (with zero dielectric anisotropy) and 5CB. The anchoring energy for the nematic in contact with obliquely evaported SiO layer, as well as the sum e_1 +e_3 of the flexoelectric coefficients are measured, indicating a surface order parameter smaller than its bulk value. Des oscillations de courbure amorties sont excitées à l'interface entre un cristal liquide nématique et un substrat solide, par le couplage linéaire entre un champ électrique alternatif et la polarisation flexoélectrique du nématique. Les ondes sont détectées par une technique ellipsométrique. On observe une oscillation du directeur à la fréquence du champ. L'anplitude et le temps caractéristique de cette oscillation sont définis par les propriétés viscoélastiques et flexoélectriques du milieu, et le recouvrement de l'onde de courbure avec le profil de l'onde optique évanescente de mesure. Un modèle simple est discuté, en bon accord avec les expériences, faites sur un mélange compensé de MBBA (d'anisotropie diélectrique nulle) et sur du 5CB. L'énergie d'ancrage sur l'électrode évaporée SiO oblique, et la somme e_1 +e_3 des coefficients flexoélectriques sont mesurées, indiquant une baisse du paramètre d'ordre en surface.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    SciTech Connect

    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.

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

    SciTech Connect

    Ho, Chih-Hua; Zeng, Hao; Wiersma, Diederik S.; Cheng, Yu-Chieh; Maigyte, Lina; Trull, Jose; Cojocaru, Crina; Staliunas, Kestutis

    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.

  14. Visualization of Thin Liquid Crystal Bubbles in Microgravity

    NASA Technical Reports Server (NTRS)

    Park, C. S.; Clark, N. A.; Maclennan, J. E.; Glaser, M. A.; Tin, P.; Stannarius, R.; Hall, N.; Storck, J.; Sheehan, C.

    2015-01-01

    The Observation and Analysis of Smectic Islands in Space (OASIS) experiment exploits the unique characteristics of freely suspended liquid crystals in a microgravity environment to advance the understanding of fluid state physics.

  15. Liquid Crystal Displays: A Motivator for Some Simple Investigations.

    ERIC Educational Resources Information Center

    Selkirk, Keith

    1980-01-01

    The format of digits in liquid crystal displays (LCDs) on calculators and watches can motivate some simple investigations appropriate for school mathematics. Several sample problems or investigations are provided. (MK)

  16. Biomolecular interactions at phospholipid-decorated surfaces of liquid crystals.

    PubMed

    Brake, Jeffrey M; Daschner, Maren K; Luk, Yan-Yeung; Abbott, Nicholas L

    2003-12-19

    The spontaneous assembly of phospholipids at planar interfaces between thermotropic liquid crystals and aqueous phases gives rise to patterned orientations of the liquid crystals that reflect the spatial and temporal organization of the phospholipids. Strong and weak specific-binding events involving proteins at these interfaces drive the reorganization of the phospholipids and trigger orientational transitions in the liquid crystals. Because these interfaces are fluid, processes involving the lateral organization of proteins (such as the formation of protein- and phospholipid-rich domains) are also readily imaged by the orientational response of the liquid crystal, as are stereospecific enzymatic events. These results provide principles for label-free monitoring of aqueous streams for molecular and biomolecular species without the need for complex instrumentation.

  17. Boundary layer elasto-optic switching in ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.

    1992-01-01

    The first experimental observation of a change in the director azimuthal angle due to applied shear stress is reported in a sample configuration involving a liquid-crystal-coated top surface exposed directly to gas flow. The electrooptic response caused by the shear stress is large, fast, and reversible. These findings are relevant to the use of liquid crystals in boundary layer investigations on wind tunnel models.

  18. Colors Of Liquid Crystals Used To Measure Surface Shear Stresses

    NASA Technical Reports Server (NTRS)

    Reda, D. C.; Muratore, J. J., Jr.

    1996-01-01

    Developmental method of mapping shear stresses on aerodynamic surfaces involves observation, at multiple viewing angles, of colors of liquid-crystal surface coats illuminated by white light. Report describing method referenced in "Liquid Crystals Indicate Directions Of Surface Shear Stresses" (ARC-13379). Resulting maps of surface shear stresses contain valuable data on magnitudes and directions of skin friction forces associated with surface flows; data used to refine mathematical models of aerodynamics for research and design purposes.

  19. Low-Absorption Liquid Crystals for Infrared Beam Steering

    DTIC Science & Technology

    2014-10-17

    goals are: ri~0.2 (at-tSilri),*? (at 1 kHz), and absorption coefficient B 5/cm. 15. SUBJECT TERMS Low absorption, MWIR, chlorinated liquid crystals...spectral region of interest by deuteration, fluorination and chlorination ; 2) Employing thin cell gap by choosing a high birefringence liquid crystal...mixture. First, we synthesized several chlorinated terphenyls and made a eutectic mixture showing a low absorption window in the region of 4-5|a.m

  20. All-optical image processing with nonlinear liquid crystals

    NASA Astrophysics Data System (ADS)

    Hong, Kuan-Lun

    Liquid crystals are fascinating materials because of several advantages such as large optical birefringence, dielectric anisotropic, and easily compatible to most kinds of materials. Compared to the electro-optical properties of liquid crystals widely applied in displays and switching application, transparency through most parts of wavelengths also makes liquid crystals a better candidate for all-optical processing. The fast response time of liquid crystals resulting from multiple nonlinear effects, such as thermal and density effect can even make real-time processing realized. In addition, blue phase liquid crystals with spontaneously self-assembled three dimensional cubic structures attracted academic attention. In my dissertation, I will divide the whole contents into six parts. In Chapter 1, a brief introduction of liquid crystals is presented, including the current progress and the classification of liquid crystals. Anisotropy and laser induced director axis reorientation is presented in Chapter 2. In Chapter 3, I will solve the electrostrictive coupled equation and analyze the laser induced thermal and density effect in both static and dynamic ways. Furthermore, a dynamic simulation of laser induced density fluctuation is proposed by applying finite element method. In Chapter 4, two image processing setups are presented. One is the intensity inversion experiment in which intensity dependent phase modulation is the mechanism. The other is the wavelength conversion experiment in which I can read the invisible image with a visible probe beam. Both experiments are accompanied with simulations to realize the matching between the theories and practical experiment results. In Chapter 5, optical properties of blue phase liquid crystals will be introduced and discussed. The results of grating diffractions and thermal refractive index gradient are presented in this chapter. In addition, fiber arrays imaging and switching with BPLCs will be included in this chapter

  1. Coherent beam amplification with a photorefractive liquid crystal.

    PubMed

    Khoo, I C; Guenther, B D; Wood, M V; Chen, P; Shih, M Y

    1997-08-15

    Coherent amplification of a signal beam by a strong pump beam is observed in thin films of fullerene-doped nematic liquid crystal. Exponential gain constants as high as 2890 cm(-1) with no phase cross talk are achieved at low applied dc bias voltage and pump beam intensity. The underlying mechanism is the electro-optically induced spatially reorientation of the liquid-crystal axis and the resultant phase-shifted index grating required for two-beam coupling.

  2. Modeling of Optical Aberration Correction using a Liquid Crystal Device

    NASA Technical Reports Server (NTRS)

    Xinghua, Wang; Bin, Wang; McManamon, Paul F.; Pouch, John J.; Miranda, Felix A.

    2006-01-01

    Gruneisen (sup 1-3), has shown that small, light weight, liquid crystal based devices can correct for the optical distortion caused by an imperfect primary mirror in a telescope and has discussed the efficiency of this correction. In this paper we expand on that work and propose a semi-analytical approach for quantifying the efficiency of a liquid crystal based wavefront corrector for this application.

  3. Polarization controllable Fresnel lens using dye-doped liquid crystals.

    PubMed

    Lin, Tsung-Hsien; Huang, Yuhua; Fuh, Andy Y G; Wu, Shin-Tson

    2006-03-20

    A scattering-free, polarization controllable Fresnel zone plate lens is demonstrated using a photo-induced alignment of the dye-doped liquid crystal film. This photo-aligned liquid crystal zone plate provides orthogonal polarization states for odd and even zones. The different focus orders can be separated because of their different polarization states. The fabrication process is relatively simple and the operation voltage is less than 5 V(rms).

  4. Engineered liquid crystal anchoring energies with nanopatterned surfaces.

    PubMed

    Gear, Christopher; Diest, Kenneth; Liberman, Vladimir; Rothschild, Mordechai

    2015-01-26

    The anchoring energy of liquid crystals was shown to be tunable by surface nanopatterning of periodic lines and spaces. Both the pitch and height were varied using hydrogen silsesquioxane negative tone electron beam resist, providing for flexibility in magnitude and spatial distribution of the anchoring energy. Using twisted nematic liquid crystal cells, it was shown that this energy is tunable over an order of magnitude. These results agree with a literature model which predicts the anchoring energy of sinusoidal grooves.

  5. Surface-functionalized ionic liquid crystal-supported ionic liquid phase materials: ionic liquid crystals in mesopores.

    PubMed

    Kohler, Florian T U; Morain, Bruno; Weiss, Alexander; Laurin, Mathias; Libuda, Jörg; Wagner, Valentin; Melcher, Berthold U; Wang, Xinjiao; Meyer, Karsten; Wasserscheid, Peter

    2011-12-23

    The influence of confinement on the ionic liquid crystal (ILC) [C(18)C(1)Im][OTf] is studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ILC studied is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The temperature of the solid-to-liquid-crystalline phase transition seems mostly unaffected by the confinement, whereas the temperature of the liquid-crystalline-to-liquid phase transition is depressed for smaller pore sizes. A contact layer with a thickness in the order of 2 nm is identified. The contact layer exhibits a phase transition at a temperature 30 K lower than the solid-to-liquid-crystalline phase transition observed for the neat ILC. For applications within the "supported ionic liquid phase (SILP)" concept, the experiments show that in pores of diameter 50 nm a pore filling of α>0.4 is sufficient to reproduce the phase transitions of the neat ILC.

  6. Liquid crystal thermography and true-colour digital image processing

    NASA Astrophysics Data System (ADS)

    Stasiek, J.; Stasiek, A.; Jewartowski, M.; Collins, M. W.

    2006-06-01

    In the last decade thermochromic liquid crystals (TLC) and true-colour digital image processing have been successfully used in non-intrusive technical, industrial and biomedical studies and applications. Thin coatings of TLCs at surfaces are utilized to obtain detailed temperature distributions and heat transfer rates for steady or transient processes. Liquid crystals also can be used to make visible the temperature and velocity fields in liquids by the simple expedient of directly mixing the liquid crystal material into the liquid (water, glycerol, glycol, and silicone oils) in very small quantities to use as thermal and hydrodynamic tracers. In biomedical situations e.g., skin diseases, breast cancer, blood circulation and other medical application, TLC and image processing are successfully used as an additional non-invasive diagnostic method especially useful for screening large groups of potential patients. The history of this technique is reviewed, principal methods and tools are described and some examples are also presented.

  7. Columnar liquid crystals in cylindrical nanoconfinement.

    PubMed

    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.

  8. Liquid Crystal on Silicon Wavefront Corrector

    NASA Technical Reports Server (NTRS)

    Pouch, John; Miranda, Felix; Wang, Xinghua; Bos, Philip, J.

    2004-01-01

    A low cost, high resolution, liquid crystal on silicon, spatial light modulator has been developed for the correction of huge aberrations in an optical system where the polarization dependence and the chromatic nature are tolerated. However, the overall system performance suggests that this device is also suitable for real time correction of aberration in human eyes. This device has a resolution of 1024 x 768, and is driven by an XGA display driver. The effective stroke length of the device is 700 nm and 2000 nm for the visible and IR regions of the device, respectively. The response speeds are 50 Hz and 5 Hz, respectively, which are fast enough for real time adaptive optics for aberrations in human eyes. By modulating a wavefront of 2 pi, this device can correct for arbitrary high order wavefront aberrations since the 2-D pixel array is independently controlled by the driver. The high resolution and high accuracy of the device allow for diffraction limited correction of the tip and tilt or defocus without an additional correction loop. We have shown that for every wave of aberration, an 8 step blazed grating is required to achieve high diffraction efficiency around 80%. In light of this, up to 125 waves peak to valley of tip and tilt can be corrected if we choose the simplest aberration. Corrections of 34 waves of aberration, including high order Zernicke terms in a high magnification telescope, to diffraction limited performance (residual wavefront aberration less than 1/30 lambda at 632.8 nm) have been observed at high efficiency.

  9. Flexoelectricity of a Calamitic Liquid Crystal Elastomer Swollen with a Bent-core Liquid Crystal

    SciTech Connect

    Chambers, M.; Verduzco, R; Gleeson, J; Sprunt, S; Jakli, A

    2009-01-01

    We have measured the electric current induced by mechanical distortion of a calamitic liquid crystal elastomer (LCE) swollen with a low molecular weight bent-core nematic (BCN) liquid crystal, and have determined, for the first time, the bend flexoelectric coefficient e{sub 3} of such a BCN-LCE composite. In one method, we utilize air-pressure to induce a mechanical bend deformation and flexoelectric polarization in a BCN-LCE film, and then measure the polarization current as a function of time. An alternative technique uses a rotary-motor driven scotch yoke to periodically flex the BCN-LCE; in this case, the magnitude and phase of the induced current are recorded via a lock-in amplifier. The flexoelectric coefficient, e{sub 3}, was found to be {approx}20 nC/cm{sup 2}, and is stable in magnitude from room temperature to {approx}65 C. It is about one third the value measured in samples of the pure BCN; this fraction corresponds closely to the molar concentration of BCN in the LCE. The flexoelectric current increases linearly with the magnitude of the bend deformation and decays with frequency. These observations indicate a promising way forward towards producing very low-cost, self-standing, rugged electromechanical energy conversion devices.

  10. Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites.

    PubMed

    Kim, Hojin; Zhu, Bohan; Chen, Huiying; Adetiba, Oluwatomiyin; Agrawal, Aditya; Ajayan, Pulickel; Jacot, Jeffrey G; Verduzco, Rafael

    2016-02-06

    LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs - polysiloxane-based and epoxy-based - are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 °C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

  11. Reflective liquid crystal light valve with hybrid field effect mode

    NASA Technical Reports Server (NTRS)

    Boswell, Donald D. (Inventor); Grinberg, Jan (Inventor); Jacobson, Alexander D. (Inventor); Myer, Gary D. (Inventor)

    1977-01-01

    There is disclosed a high performance reflective mode liquid crystal light valve suitable for general image processing and projection and particularly suited for application to real-time coherent optical data processing. A preferred example of the device uses a CdS photoconductor, a CdTe light absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The non-coherent light image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the AC voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to create the bright on-state. The liquid crystal thus modulates the polarization of the coherent read-out or projection light responsively to the non-coherent image. An analyzer is used to create an intensity modulated output beam.

  12. `Guest-host' effect in liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Suchodolska, B.; Rudzki, A.; Ossowska-Chruściel, M. D.; Zalewski, S.; Chruściel, J.

    2015-01-01

    The most important goal of our research is to show the influence of the 'guest' (bent-core mesogen, 1,3-phenyldicarboxylatebis{4-[(4-octylbenzoyl)sulphanyl]phenyl} [IFOS8], banana-shaped liquid crystal [BLC]) on the 'host' (calamitic liquid crystal [CLC], (S)-(+)-1-methylheptyloxybiphenyl-(4-n-octylphenyl)thiobenzoate [MHOBS8]), on the stability and the destabilization of the antiferroelectric B2 and the ferroelectric smectic C* (SmC*) phases, and change of the temperature ranges of other phases in the binary liquid crystal mixtures. This work is focused on polymorphism of three new binary liquid crystal mixtures, exhibiting a 'guest-host' (guest liquid crystal-host liquid crystal [GH-LC]) effect. MHOBS8 has, among others, a ferroelectric SmC* phase, and IFOS8 assumes the B2 phase with antiferroelectric properties. The observed properties of the mixtures, such as variation of the phase transition temperatures, spontaneous polarization, tilt angle and switching time, are characteristic of a 'guest-host' mixture. The influence of BLC on the character of the interactions within the CLC host is discussed, with particular attention paid to electro-optical properties of the GH-LC mixtures.

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

    NASA Astrophysics Data System (ADS)

    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

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

    SciTech Connect

    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 smectic A

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

    PubMed

    Zito, Gianluigi; Pissadakis, Stavros

    2013-09-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a prepolymer/liquid crystal 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 presented here 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, and is discussed further.

  16. Do protein crystals nucleate within dense liquid clusters?

    PubMed

    Maes, Dominique; Vorontsova, Maria A; Potenza, Marco A C; Sanvito, Tiziano; Sleutel, Mike; Giglio, Marzio; Vekilov, Peter G

    2015-07-01

    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(-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 lysozyme and glucose isomerase solutions are locations for crystal nucleation.

  17. Demonstrations of Some Optical Properties of Liquid Crystals.

    ERIC Educational Resources Information Center

    Nicastro, Anthony J.

    1983-01-01

    Discusses several properties of liquid crystal displays. Includes instructions for demonstrating liquid crystalline phase, ordering of the long axes of molecules along one direction, and electro-optic effects. The latter is accomplished with the use of an overhead projector following preparation of a sandwich cell. (JN)

  18. Nano Liquid Crystal Droplet Impact on Solid Surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; de Pablo, Juan; dePablo Team

    2015-03-01

    Liquid droplet impaction on solid surfaces is an important problem with a wide range of applications in everyday life. Liquid crystals (LCs) are anisotropic liquids whose internal structure gives rise to rich optical and morphological phenomena. In this work we study the liquid crystal droplet impaction on solid surfaces by molecular dynamics simulations. We employ a widely used Gay-Berne model to describe the elongated liquid crystal molecules and their interactions. Our work shows that, in contrast to isotropic liquids, drop deformation is symmetric unless an instability kicks in, in which case a nano scale liquid crystal droplet exhibits distinct anisotropic spreading modes that do not occur in simple liquids. The drop prefers spreading along the low viscosity direction, but inertia can in some cases overcome that bias. The effects of the director field of the droplet, preferred anchoring direction and the anchoring strength of the wall are investigated. Large scale (0.1 micron) simulations are performed to connect our nano scale results to the experiments. Our studies indicate that LCs could provide an interesting alternative for development of next-generation printing inks.

  19. Liquid-filled simplified hollow-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Liu, Shengnan; Gao, Wei; Li, Hongwei; Dong, Yongkang; Zhang, Hongying

    2014-12-01

    We report on a novel type of liquid-filled simplified hollow-core photonic crystal fibers (HC-PCFs), and investigate their transmission properties with various filling liquids, including water, ethanol and FC-40. The loss and dispersion characterizations are calculated for different fiber parameters including strut thickness and core diameter. The results show that there are still low-loss windows existing for liquid-filled simplified HC-PCFs, and the low-loss windows and dispersions can be easily tailored by filling different liquids. Such liquid-filled simplified HC-PCFs open up many possibilities for nonlinear fiber optics, optical, biochemical and medical sensing.

  20. Fullerene solar cells with cholesteric liquid crystal doping

    NASA Astrophysics Data System (ADS)

    Jiang, Lulu; Jiang, Yurong; Zhang, Congcong; Chen, Zezhang; Qin, Ruiping; Ma, Heng

    2016-09-01

    This paper reports the doping effect of cholesteric liquid crystal 3β-Hydroxy-5-cholestene 3-oleate on polymer solar cells composed of the poly 3-hexyl thiophene and the fullerene derivative. With a doping ratio of 0.3 wt%, the device achieves an ideal improvement on the shunt resistor and the fill factor. Compared with the reference cell, the power conversion efficiency of the doped cell is improved 24%. The photoelectric measurement and the active layer characterization indicate that the self-assembly liquid crystal can improve the film crystallization and reduce the membrane defect. Project supported by the National Natural Science Foundation of China (Grant No. 61540016).

  1. Ice-Crystal Fallstreaks from Supercooled Liquid Water Parent Clouds

    NASA Technical Reports Server (NTRS)

    Campbell, James R.; O'C. Starr, David; Welton, Ellsworth J.; Spinhirne, James D.; Ferrare, Richard A.

    2003-01-01

    On 31 December 2001, ice-crystal fallstreaks (e.g., cirrus uncinus, or colloquially "Mare's Tails") from supercooled liquid water parent clouds were observed by ground-based lidars pointed vertically from the Atmospheric Radiation Measurement Southern Great Plains (SGP) facility near Lamont, Oklahoma. The incidence of liquid phase cloud with apparent ice-phase precipitation is investigated. Scenarios for mixed-phase particle nucleation, and fallstreak formation and sustenance are discussed. The observations are unique in the context of the historical reverence given to the commonly observed c h s uncinus fallstreak (wholly ice) versus this seemingly contradictory coincidence of liquid water begetting ice-crystal streaks.

  2. Effect of Viscosity on the Crystallization of Undercooled Liquids

    NASA Technical Reports Server (NTRS)

    2003-01-01

    There have been numerous studies of glasses indicating that low-gravity processing enhances glass formation. NASA PI s are investigating the effect of low-g processing on the nucleation and crystal growth rates. Dr. Ethridge is investigating a potential mechanism for glass crystallization involving shear thinning of liquids in 1-g. For shear thinning liquids, low-g (low convection) processing will enhance glass formation. The study of the viscosity of glass forming substances at low shear rates is important to understand these new crystallization mechanisms. The temperature dependence of the viscosity of undercooled liquids is also very important for NASA s containerless processing studies. In general, the viscosity of undercooled liquids is not known, yet knowledge of viscosity is required for crystallization calculations. Many researchers have used the Turnbull equation in error. Subsequent nucleation and crystallization calculations can be in error by many orders of magnitude. This demonstrates the requirement for better methods for interpolating and extrapolating the viscosity of undercooled liquids. This is also true for undercooled water. Since amorphous water ice is the predominant form of water in the universe, astrophysicists have modeled the crystallization of amorphous water ice with viscosity relations that may be in error by five orders-of-magnitude.

  3. Diffusion behavior in a liquid-liquid interfacial crystallization by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Kitayama, Akira; Yamanaka, Shinya; Kadota, Kazunori; Shimosaka, Atsuko; Shirakawa, Yoshiyuki; Hidaka, Jusuke

    2009-11-01

    Interfacial crystallization, such as surface crystallization in solution (solid-liquid) and liquid-liquid crystallization, gives us an asymmetric reaction field and is a technique for morphology control of crystals. In the liquid-liquid crystallization, the concentration distribution of solute ions and solvent molecules at the liquid-liquid interface directly relates to nucleation, crystal growth, and crystal morphology. Nonequilibrium molecular dynamics (MD) simulations have been performed at interfaces in NaCl solution/1-butanol and KCl solution/1-butanol system in order to clarify diffusion behavior of solute ions and solvent molecules. As simulation results, the hydrated solute ions were dehydrated with the diffusion of water from solution phase into 1-butanol phase. The different dehydration behaviors between NaCl and KCl solution can be also obtained from MD simulation results. Aggregated ions or clusters were formed by the dehydration near the solution/1-butanol interface. By comparison on the normalized number of total solute ions, the size and number of generated cluster in KCl solution/1-butanol interface are larger than those in the NaCl system. This originates in the difference hydration structures in the each solute ion.

  4. Liquid crystals based sensing platform-technological aspects.

    PubMed

    Hussain, Zakir; Qazi, Farah; Ahmed, Muhammad Imran; Usman, Adil; Riaz, Asim; Abbasi, Amna Didar

    2016-11-15

    In bulk phase, liquid crystalline molecules are organized due to non-covalent interactions and due to delicate nature of the present forces; this organization can easily be disrupted by any small external stimuli. This delicate nature of force balance in liquid crystals organization forms the basis of Liquid-crystals based sensing scheme which has been exploited by many researchers for the optical visualization and sensing of many biological interactions as well as detection of number of analytes. In this review, we present not only an overview of the state of the art in liquid crystals based sensing scheme but also highlight its limitations. The approaches described below revolve around possibilities and limitations of key components of such sensing platform including bottom substrates, alignments layers, nature and type of liquid crystals, sensing compartments, various interfaces etc. This review also highlights potential materials to not only improve performance of the sensing scheme but also to bridge the gap between science and technology of liquid crystals based sensing scheme.

  5. Novel Microstructures for Polymer-Liquid Crystal Composite Materials

    NASA Technical Reports Server (NTRS)

    Magda, Jules J.

    2004-01-01

    There are a number of interface-dominated composite materials that contain a liquid crystalline (LC) phase in intimate contact with an isotropic phase. For example, polymer- dispersed liquid crystals, used in the fabrication of windows with switchable transparency, consist of micron size LC droplets dispersed in an isotropic polymer matrix. Many other types of liquid crystal composite materials can be envisioned that might have outstanding optical properties that could be exploited in novel chemical sensors, optical switches, and computer displays. This research project was based on the premise that many of these potentially useful LC composite materials can only be fabricated under microgravity conditions where gravity driven flows are absent. In the ground-based research described below, we have focused on a new class of LC composites that we call thermotropic- lyotropic liquid crystal systems (TLLCs). TLLCs consist of nanosize droplets of water dispersed in an LC matrix, with surfactants at the interface that stabilize the structure. By varying the type of surfactant one can access almost an infinite variety of unusual LC composite microstructures. Due to the importance of the interface in these types of systems, we have also developed molecular simulation models for liquid crystals at interfaces, and made some of the first measurements of the interfacial tension between liquid crystals and water.

  6. Liquid-Crystal Thermosets, a New Generation of High-Performance Liquid-Crystal Polymers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theo; Weiser, Erik; Hou, Tan; Jensen, Brian; St. Clair, Terry

    2004-01-01

    One of the major challenges for NASA's next-generation reusable-launch-vehicle (RLV) program is the design of a cryogenic lightweight composite fuel tank. Potential matrix resin systems need to exhibit a low coefficient of thermal expansion (CTE), good mechanical strength, and excellent barrier properties at cryogenic temperatures under load. In addition, the resin system needs to be processable by a variety of non-autoclavable techniques, such as vacuum-bag curing, resin-transfer molding (RTM), vacuum-assisted resin-transfer molding (VaRTM), resin-film infusion (RFI), pultrusion, and advanced tow placement (ATP). To meet these requirements, the Advanced Materials and Processing Branch (AMPB) at NASA Langley Research Center developed a new family of wholly aromatic liquid-crystal oligomers that can be processed and thermally cross-linked while maintaining their liquid-crystal order. All the monomers were polymerized in the presence of a cross-linkable unit by use of an environmentally benign melt-condensation technique. This method does not require hazardous solvents, and the only side product is acetic acid. The final product can be obtained as a powder or granulate and has an infinite shelf life. The obtained oligomers melt into a nematic phase and do not exhibit isotropization temperatures greater than the temperatures of decomposition (Ti > T(sub dec)). Three aromatic formulations were designed and tested and included esters, ester-amides, and ester-imides. One of the major advantages of this invention, named LaRC-LCR or Langley Research Center-Liquid Crystal Resin, is the ability to control a variety of resin characteristics, such as melting temperature, viscosity, and the cross-link density of the final part. Depending on the formulation, oligomers can be prepared with melt viscosities in the range of 10-10,000 poise (100 rad/s), which can easily be melt-processed using a variety of composite-processing techniques. This capability provides NASA with custom

  7. Tuning light focusing with liquid crystal infiltrated graded index photonic crystals

    NASA Astrophysics Data System (ADS)

    Rezaei, B.; Giden, I. H.; Kurt, H.

    2017-01-01

    We perform numerical analyses of tunable graded index photonic crystals based on liquid crystals. Light manipulation with such a photonic medium is explored and a new approach for active tuning of the focal distance is proposed. The graded index photonic crystal is realized using the symmetry reduced unit element in two-dimensional photonic crystals without modifying the dielectric filling fraction or cell size dimensions. By applying an external static electric field to liquid crystals, their refractive indices and thus, the effective refractive index of the whole graded index photonic crystal will be changed. Setting the lattice constant to a=400 nm yields a tuning of 680 nm for focal point position. This property can be used for designing an electro-optic graded index photonic crystal-based flat lens with a tunable focal point. Future optical systems may have benefit from such tunable graded index lenses.

  8. Reflective and transflective liquid crystal displays

    NASA Astrophysics Data System (ADS)

    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

  9. Phase transitions in liquid crystal + aerosil gels

    NASA Astrophysics Data System (ADS)

    Ramazanoglu, Mehmet Kerim

    Liquid Crystals (LCs) are found in many different phases, the most well-known, basic ones being Isotropic (I), Nematic (N), and Smectic-A (SmA). LCs show a rich variety of phase transitions between these phases. This makes them very interesting materials in which to study the basics of phase transitions and related topics. In the low symmetry phases, LCs show both positional and directional orders. X-ray scattering is an important tool to study these phase transitions as it probes the instantaneous positional correlations in these phases. Random forces have a nontrivial effect on ordering in nature, and the problem of phase transitions in the presence of a random field is a current and not well-understood topic. It has been found that aerosils posses a quenched randomness in the mixture of LC+aerosil samples, forming a gel random network which destroys long-range order (LRO) in the SmA phase. This can be modeled as a random field problem. In the N to SmA phase transition in 4O.8 LC (butyloxybenzlidene octylaniline), orientational order (N ) is modified by a 1-D density wave describing 2-D fluid layer spacing structure (SmA). Likewise the I to Sm A phase transition in 10CB LC (decylcyanobiphenyl), a transitional ordered phase develops without going through an orientational ordered phase. To study these phase transitions with aerosil dispersion carries the opportunity to probe the effect of induced quenched random disorder on phase transitions, which are 2nd order in the first case and 1st order in the second case. A two-component line-shape analysis is developed to define the phases in all temperature ranges. It consists of the thermal and the static structure factors. The reentered nematic (RN) phase of the [6:8]OCB+aerosil gels ([6:8]OCB is a mixture of hexyloxycyanobiphenyl and octyloxcyanobiphenyl) is another interesting case in which to study the quenched random disorder effects. The weak SmA phase of [6:8]OCB+aerosil gels is followed by a RN phase at low

  10. Electronic transport in smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Shiyanovskaya, I.; Singer, K. D.; Twieg, R. J.; Sukhomlinova, L.; Gettwert, V.

    2002-04-01

    Time-of-flight measurements of transient photoconductivity have revealed bipolar electronic transport in phenylnaphthalene and biphenyl liquid crystals (LC), which exhibit several smectic mesophases. In the phenylnaphthalene LC, the hole mobility is significantly higher than the electron mobility and exhibits different temperature and phase behavior. Electron mobility in the range ~10-5 cm2/V s is temperature activated and remains continuous at the phase transitions. However, hole mobility is nearly temperature independent within the smectic phases, but is very sensitive to smectic order, 10-3 cm2/V s in the smectic-B (Sm-B) and 10-4 cm2/V s in the smectic-A (Sm-A) mesophases. The different behavior for holes and electron transport is due to differing transport mechanisms. The electron mobility is apparently controlled by rate-limiting multiple shallow trapping by impurities, but hole mobility is not. To explain the lack of temperature dependence for hole mobility within the smectic phases we consider two possible polaron transport mechanisms. The first mechanism is based on the hopping of Holstein small polarons in the nonadiabatic limit. The polaron binding energy and transfer integral values, obtained from the model fit, turned out to be sensitive to the molecular order in smectic mesophases. A second possible scenario for temperature-independent hole mobility involves the competion between two different polaron mechanisms involving so-called nearly small molecular polarons and small lattice polarons. Although the extracted transfer integrals and binding energies are reasonable and consistent with the model assumptions, the limited temperature range of the various phases makes it difficult to distinguish between any of the models. In the biphenyl LCs both electron and hole mobilities exhibit temperature activated behavior in the range of 10-5 cm2/V s without sensitivity to the molecular order. The dominating transport mechanism is considered as multiple trapping

  11. Hydrothermal decomposition of liquid crystal in subcritical water.

    PubMed

    Zhuang, Xuning; He, Wenzhi; Li, Guangming; Huang, Juwen; Lu, Shangming; Hou, Lianjiao

    2014-04-30

    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.

  12. Self-confined dynamics in supercooled liquids during crystallization

    NASA Astrophysics Data System (ADS)

    Sanz, Alejandro; Niss, Kristine; Ezquerra, Tiberio A.; Nogales, Aurora; Jimenez, Monica; Puente-Orench, Ines

    2015-03-01

    Within the temperature window limited by the equilibrium melting temperature and the liquid to glass transition temperature, some glass forming systems tend to undergo crystallization. Unlike polymeric materials, low molecular weight liquids are able to self-organize forming fully crystalline structures, in which the dynamics of the remaining disordered regions may be examined along the whole range of crystalline volume fraction when real time studies are assessed. From the point of view of the molecular mobility, dielectric spectroscopy is a unique tool for unraveling the dynamic effects during crystallization. The aim of this contribution is to show a complete picture of the crystallization process in paradigmatic glass formers like 2-propanol, ethanol and glycerol. The interrelationships between structure and dynamics during crystallization will be discussed, paying special attention to the role played by the hydrogen-bonded network across the phase transformation. Novel results on crystallization of 2-propanol studied by real time quasielastic neutron scattering measurements will also be presented.

  13. Do protein crystals nucleate within dense liquid clusters?

    SciTech Connect

    Maes, Dominique; Vorontsova, Maria A.; Potenza, Marco A. C.; Sanvito, Tiziano; Sleutel, Mike; Giglio, Marzio; Vekilov, Peter G.

    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

  14. Driving voltage properties sensitive to microscale liquid crystal orientation pattern in twisted nematic liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Takahashi, Koki; Yamaguchi, Rumiko; Nose, Toshiaki

    2016-04-01

    We investigated the micropattern-sensitive driving voltage properties of twisted nematic liquid crystal (LC) cells and found that the threshold voltage for inducing the Fréedericksz transition strongly depends on the micropatterned LC molecular orientation state. We discuss the effects of various cell parameters such as the period of the micropattern Λ, the LC layer thickness d, and the twist angle Φ on the threshold voltage. By a computer simulation of the LC molecular orientation, we found that the threshold voltage V th varies in response to the deformation factor Δ (= d 2/Λ2 + Φ2/π2) of the spatially distributed LC molecular orientation. We confirm that V\\text{th}2 is proportional to 1 - Δ from both theoretical and experimental standpoints.

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

    PubMed

    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

  16. Dynamics of Active Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    DeCamp, Stephen J.

    liquid crystal by assembling microtubule bundles into a quasi-2D film confined to a large, flat oil-water interface. Internal stresses generated by kinesin motors drive the system far from equilibrium which precludes a uniformly aligned nematic ground state through the continuous creation and annihilation of +/-1/2 motile defects. First, we demonstrate that the nematic is extensile by observing the deformation of a photobleached spot which undergoes extension along the nematic director and contraction perpendicular to the director. We map the experimentally tunable parameter, ATP concentration, to the intrinsic activity of the sample measured by the characteristic time of the contractile dynamics. Then, we characterize the flow of individual microtubules by measuring their relative velocity within the nematic and find a flow field consistent with a force dipole but where the magnitude of the extension and contraction velocity are proportional to the separation between the filaments. The extensile and contractile flow velocities can be tuned by the ATP concentration and can be as large as 6 mum/s. Then we spatially map microtubule concentration, alignment, and flow near topological defect cores. We test a theory which predicts that flows are directly proportional to the local alignment of the nematic and find our results inconsistent with that theory. Finally, we measure large scale velocity and vorticity distributions as well as vortex area distributions and find agreement with other recent theoretical predictions. Next, we turn our attention to the complex behavior of defects in the active nematic. Using defect tracking algorithms developed by Gabriel S. Redner, we measure the +/-1/2 defect velocity and lifetime distributions as well as MSD and average defect density. We find that average velocities, lifetimes, and densities are tunable by varying the ATP concentration. The MSDs reveal that motile +1/2 defects stream ballistically through the sample (up to 15 mum

  17. Supramolecular [60]fullerene liquid crystals formed by self-organized two-dimensional crystals.

    PubMed

    Zhang, Xiaoyan; Hsu, Chih-Hao; Ren, Xiangkui; Gu, Yan; Song, Bo; Sun, Hao-Jan; Yang, Shuang; Chen, Erqiang; Tu, Yingfeng; Li, Xiaohong; Yang, Xiaoming; Li, Yaowen; Zhu, Xiulin

    2015-01-02

    Fullerene-based liquid crystalline materials have both the excellent optical and electrical properties of fullerene and the self-organization and external-field-responsive properties of liquid crystals (LCs). Herein, we demonstrate a new family of thermotropic [60]fullerene supramolecular LCs with hierarchical structures. The [60]fullerene dyads undergo self-organization driven by π-π interactions to form triple-layer two-dimensional (2D) fullerene crystals sandwiched between layers of alkyl chains. The lamellar packing of 2D crystals gives rise to the formation of supramolecular LCs. This design strategy should be applicable to other molecules and lead to an enlarged family of 2D crystals and supramolecular liquid crystals.

  18. Morphology Tuning of Electrospun Liquid Crystal/Polymer Fibers.

    PubMed

    Wang, Junren; Jákli, Antal; West, John L

    2016-10-05

    This paper elucidates the means to control precisely the morphology of electrospun liquid crystal/polymer fibers formed by phase separation. The relative humidity, solution parameters (concentration, solvent), and the process parameter (feed rate) were varied systematically. We show that the morphology of the phase-separated liquid crystal can be continuously tuned from capsules to uniform fibers with systematic formation of beads-on-a-string structured fibers in the intermediate ranges. In all cases, the polymer forms a sheath around a liquid-crystal (LC) core. The width of the polymer sheath and the diameter of the LC core increase with increasing feed rates. This is similar to the results obtained by coaxial electrospinning. Because these fibers retain the responsive properties of liquid crystals and because of their large surface area, they have potential applications as thermo-, chemo-, and biosensors. Because the size and shape of the liquid-crystal domains will have a profound effect on the performance of the fibers, our ability to precisely control morphology will be crucial in developing these applications.

  19. Alignment and Stiffening of Liquid Crystal Elastomers under Dynamic Compression

    NASA Astrophysics Data System (ADS)

    Agrawal, Aditya; Patra, Prabir; Ajayan, Pulickel; Chapman, Walter; Verduzco, Rafael

    2013-03-01

    Biological tissues have the remarkable ability to remodel and repair in response to disease, injury, and mechanical stresses, a phenomenon known ``functional adaptation'' or ``remodeling''. Herein, we report similar behavior in polydomain liquid crystal elastomers. Liquid crystal elastomers dramatically increase in stiffness by up to 90 % under low-amplitude, repetitive (dynamic) compression. By studying a systematic series of materials, we demonstrate that the stiffness increase is directly influenced by the liquid crystal content of the elastomers, the presence of a nematic liquid crystal phase and the use of a dynamic as opposed to static deformation. Through a combination of rheological measurements, polarizing optical microscopy and 2-D X-ray diffraction, we demonstrate that self-stiffening arises due to rotations of the nematic director in response to dynamic compression, and show that the behavior is consistent with the theory for nematic rubber elasticity. Previous work with liquid crystal elastomers has focused primarily on `soft elastic' deformations at large strains, but our findings indicate rich behavior at previously overlooked low-strain, dynamic deformations.

  20. Theory of polymer-dispersed cholesteric liquid crystals

    SciTech Connect

    Matsuyama, Akihiko

    2013-11-07

    A mean field theory is presented to describe cholesteric phases in mixtures of a polymer and a cholesteric liquid crystal. Taking into account an anisotropic coupling between a polymer and a liquid crystal, we examine the helical pitch, twist elastic constant, and phase separations. Analytical expressions of the helical pitch of a cholesteric phase and the twist elastic constant are derived as a function of the orientational order parameters of a polymer and a liquid crystal and two intermolecular interaction parameters. We also find isotropic-cholesteric, cholesteric-cholesteric phase separations, and polymer-induced cholesteric phase on the temperature-concentration plane. We demonstrate that an anisotropic coupling between a polymer and a liquid crystal can stabilize a cholesteric phase in the mixtures. Our theory can also apply to mixtures of a nematic liquid crystal and a chiral dopant. We discuss the helical twisting power, which depends on temperature, concentration, and orientational order parameters. It is shown that our theory can qualitatively explain experimental observations.

  1. Nonlinear femtosecond pulse compression in cholesteric liquid crystals (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Liu, Yikun; Zhou, Jianying; Lin, Tsung-Hsien; Khoo, Iam-Choon

    2016-09-01

    Liquid crystals materials have the advantage of having a large nonlinear coefficient, but the response time is slow, normally up to several minisecond. This makes it is hard to apply in ultra fast optical devices. Recently, fentosecond (fs) nonlinear effect in choleteric liquid crystals is reported, nonlinear coefficient in the scale of 10-12 cm2/W is achieved. Base on this effect, in this work, fentosecond pulse compression technique in a miniature choleteric liquid crystal is demonstrated1,2. Cholesteric liquid crystals (CLC) is a kind of 1-dimensional phontonic structure with helical periodic. In a 10 μm thick CLC, femtosecond pulse with 100 fs is compressed to about 50 fs. CLC sample in planar texture with 500μm thick cell gap is further fabricated. In this sample, femtosecond pulse with 847 fs can be compressed to 286 fs. Due to the strong dispersion at the edge of photonic band gap, femtosecond pulse stretching and compensation can be achieve. In this experiment, laser pulse with duration 90 fs is stretched to above 2 picosecond in the first CLC sample and re-compressed to 120 fs in the second sample. Such technique might be applied in chirp pulse amplification. In conclusion, we report ultra fast nonlinear effect in cholesteric liquid crystals. Due to the strong dispersion and nonlinearity of CLC, femtosecond pulse manipulating devices can be achieved in the scale of micrometer.

  2. Optical Characteristics of Liquid Crystal Displays and Modulators

    NASA Astrophysics Data System (ADS)

    Lu, Kanghua

    The viewing-angle characteristics of liquid crystal displays (LCD) and the performance of liquid crystal spatial light modulators (SLM) are studied. The main contributions can be summarized as follows: (1) We have developed a new theory for LCD optics based on a generalized 2 x 2 Jones calculus. This new theory permits us to compute the transmittance of polarized light of arbitrary incident angles and wavelengths through the LCD at much higher speeds than has been possible with previous approaches. (2) We have developed a CAD software based on this theory. We used it to study the viewing-angle problem and to examine the effect of using birefringent compensation films of various types. We found that improvements can be indeed achieved. In the process we introduced a new method for display of color and viewing -angle characteristics. (3) We invented a new experimental single-step method of observing the viewing-angle characteristics based on Fourier optics. Previous methods were typically based on the use of cumbersome scanning techniques. Using our new apparatus we have verified the consistency between the experimental viewing-angle patterns and our theoretical predictions. (4) We also developed a simplified analytical model for the liquid crystal SLM, and used it to successfully interpret and improve the operation of liquid crystal light valves and liquid crystal televisions, especially when they are used as optical phase-only modulators.

  3. [Polarization-sensitive characteristics of the transmission spectra in photonic crystal with nematic liquid crystal defects].

    PubMed

    Dai, Qin; Wu, Ri-na; Yan, Bin; Zhang, Rui-liang; Wang, Peng-chong; Quan, Wei; Xu, Song-ning

    2012-05-01

    The polarization-sensitive characteristics in the transmission spectra of TiO2/SiO2 optical multilayer films of one-dimensional photonic crystal (1D PC) with nematic liquid crystal defects were investigated in the present paper. The transmission spectra measurements and simulated results show that the polarization-sensitive feature was obvious when natural light was normal incident onto the parallelly aligned nematic liquid crystal. There were peaks of the extraordinary light (TE mode) with center wavelengths 1831 and 1800 nm and the ordinary light (TM mode) with center wavelengths 1452 and 1418 nm in the photonic forbidden band, respectively. With applied voltage increasing, the peaks of the extraordinary light was blue-shifted, and coincided with the peaks of O light gradually. Their tunable ranges were about 31 and 34 nm, respectively. For the random nematic liquid crystal, polarization sensitivity was not observed. Meanwhile, an individual extraordinary light peak with center wavelength 1801 nm and an individual ordinary light peak with center wavelength 1391 nm were obtained in the photonic forbidden band, respectively. The peaks were also found blue-shifted with applied voltage increasing, and their tunable ranges were about 64 and 15 nm, respectively. The polarization insensitive photonic crystal with nematic liquid crystal defects can be achieved by random liquid crystal molecules, which make the effective refractive index of the extraordinary light equal to that of the ordinary light.

  4. Nematic-like stable glasses without equilibrium liquid crystal phases.

    PubMed

    Gómez, Jaritza; Gujral, Ankit; Huang, Chengbin; Bishop, Camille; Yu, Lian; Ediger, M D

    2017-02-07

    We report the thermal and structural properties of glasses of posaconazole, a rod-like molecule, prepared using physical vapor deposition (PVD). PVD glasses of posaconazole can show substantial molecular orientation depending upon the choice of substrate temperature, Tsubstrate, during deposition. Ellipsometry and IR measurements indicate that glasses prepared at Tsubstrate very near the glass transition temperature (Tg) are highly ordered. For these posaconazole glasses, the orientation order parameter is similar to that observed in macroscopically aligned nematic liquid crystals, indicating that the molecules are mostly parallel to one another and perpendicular to the interface. To our knowledge, these are the most anisotropic glasses ever prepared by PVD from a molecule that does not form equilibrium liquid crystal phases. These results are consistent with a previously proposed mechanism in which molecular orientation in PVD glasses is inherited from the orientation present at the free surface of the equilibrium liquid. This mechanism suggests that molecular orientation at the surface of the equilibrium liquid of posaconazole is nematic-like. Posaconazole glasses can show very high kinetic stability; the isothermal transformation of a 400 nm glass into the supercooled liquid occurs via a propagating front that originates at the free surface and requires ∼10(5) times the structural relaxation time of the liquid (τα). We also studied the kinetic stability of PVD glasses of itraconazole, which is a structurally similar molecule with equilibrium liquid crystal phases. While itraconazole glasses can be even more anisotropic than posaconazole glasses, they exhibit lower kinetic stability.

  5. Nematic-like stable glasses without equilibrium liquid crystal phases

    NASA Astrophysics Data System (ADS)

    Gómez, Jaritza; Gujral, Ankit; Huang, Chengbin; Bishop, Camille; Yu, Lian; Ediger, M. D.

    2017-02-01

    We report the thermal and structural properties of glasses of posaconazole, a rod-like molecule, prepared using physical vapor deposition (PVD). PVD glasses of posaconazole can show substantial molecular orientation depending upon the choice of substrate temperature, Tsubstrate, during deposition. Ellipsometry and IR measurements indicate that glasses prepared at Tsubstrate very near the glass transition temperature (Tg) are highly ordered. For these posaconazole glasses, the orientation order parameter is similar to that observed in macroscopically aligned nematic liquid crystals, indicating that the molecules are mostly parallel to one another and perpendicular to the interface. To our knowledge, these are the most anisotropic glasses ever prepared by PVD from a molecule that does not form equilibrium liquid crystal phases. These results are consistent with a previously proposed mechanism in which molecular orientation in PVD glasses is inherited from the orientation present at the free surface of the equilibrium liquid. This mechanism suggests that molecular orientation at the surface of the equilibrium liquid of posaconazole is nematic-like. Posaconazole glasses can show very high kinetic stability; the isothermal transformation of a 400 nm glass into the supercooled liquid occurs via a propagating front that originates at the free surface and requires ˜105 times the structural relaxation time of the liquid (τα). We also studied the kinetic stability of PVD glasses of itraconazole, which is a structurally similar molecule with equilibrium liquid crystal phases. While itraconazole glasses can be even more anisotropic than posaconazole glasses, they exhibit lower kinetic stability.

  6. Effect of curvature on cholesteric liquid crystals in toroidal geometries

    NASA Astrophysics Data System (ADS)

    Fialho, Ana R.; Bernardino, Nelson R.; Silvestre, Nuno M.; Telo da Gama, Margarida M.

    2017-01-01

    The confinement of liquid crystals inside curved geometries leads to exotic structures, with applications ranging from biosensors to optical switches and privacy windows. Here we study how curvature affects the alignment of a cholesteric liquid crystal. We model the system on the mesoscale using the Landau-de Gennes model. Our study was performed in three stages, analyzing different curved geometries from cylindrical walls and pores, to toroidal domains, in order to isolate the curvature effects. Our results show that the stresses introduced by the curvature influence the orientation of the liquid crystal molecules, and cause distortions in the natural periodicity of the cholesteric that depend on the radius of curvature, on the pitch, and on the dimensions of the system. In particular, the cholesteric layers of toroidal droplets exhibit a symmetry breaking not seen in cylindrical pores and that is driven by the additional curvature.

  7. Electrofluorochromism in π-conjugated ionic liquid crystals.

    PubMed

    Beneduci, Amerigo; Cospito, Sante; La Deda, Massimo; Veltri, Lucia; Chidichimo, Giuseppe

    2014-01-01

    Materials in which photoluminescence is modulated by redox processes are known as electrofluorochromic. Intrinsically switchable fluorophores, incorporating both redox and fluorescent moieties, could be ideal electrofluorochromic materials if they possess high fluorescence quantum yields in at least one of their redox states. Fluorescent liquid crystals with redox active centres could combine the above requirements with the advantage to work in bulk anisotropic phases. However, electrofluorochromic liquid crystals have not been reported yet because their synthesis is challenging due to aggregation-caused fluorescent quenching. Here we show the first examples of electrofluorochromic π-conjugated ionic liquid crystals based on thienoviologens. These ordered materials, combining ionic and electronic functions, are highly fluorescence in the bulk state (quantum yield>60%). Their direct electrochemical reduction leads to fast and reversible bulk electrofluorochromic response in both columnar and smectic phases allowing for fluorescence intensity modulation and colour tuning.

  8. Phase behavior and dynamics of a cholesteric liquid crystal

    SciTech Connect

    Roy, D.; Fragiadakis, D.; Roland, C. M.; Dabrowski, R.; Dziaduszek, J.; Urban, S.

    2014-02-21

    The synthesis, equation of state, phase diagram, and dielectric relaxation properties are reported for a new liquid crystal, 4{sup ′}-butyl-4-(2-methylbutoxy)azoxybenzene (4ABO5*), which exhibits a cholesteric phase at ambient temperature. The steepness of the intermolecular potential was characterized from the thermodynamic potential parameter, Γ = 4.3 ± 0.1 and the dynamic scaling exponent, γ = 3.5 ± 0.2. The difference between them is similar to that seen previously for nematic and smectic liquid crystals, with the near equivalence of Γ and γ consistent with the near constancy of the relaxation time of 4ABO5* at the cholesteric to isotropic phase transition (i.e., the clearing line). Thus, chirality does not cause deviations from the general relationship between thermodynamics and dynamics in the ordered phase of liquid crystals. The ionic conductivity of 4ABO5* shows strong coupling to the reorientational dynamics.

  9. Light-induced effects in liquid crystals: recent developments

    NASA Astrophysics Data System (ADS)

    Simoni, F.; Lucchetti, L.

    2016-09-01

    In this paper we outline that light-induced effects in liquid crystals are still able to provide scientific and technological novelty in spite of a long time investigation started more than thirty years ago. Here we review some recent achievements related to new phenomena that have been studied in the past few years. In the first part of our report we discuss optical trapping of nematic colloids whose origin relies on the elastic properties of liquid crystals rather than on the field gradient that is on the basis of conventional optical tweezing. In the second part we present some recent results obtained in studying the self-phase modulation in bent core nematic liquid crystals, pointing out a peculiar two regimes behavior.

  10. Transmission characteristics of a twisted nematic liquid-crystal layer

    NASA Technical Reports Server (NTRS)

    Grinberg, J.; Jacobson, A. D.

    1976-01-01

    An approximate analytical expression is calculated for the transmission of thin twisted nematic layers situated between a polarizer/analyzer pair. The approximation assumes that the twist angle of the nematic liquid crystal is smaller than the maximum retardation of the cell. The direction of the incident light is assumed to be parallel to the normal of the electrode. This configuration is analyzed for a general arrangement of polarizer and analyzer; the general result is evaluated for the case of the polarizer parallel and analyzer perpendicular to the liquid-crystal optical axis on the input and output electrodes, respectively. The results show that in the case of a thin twisted nematic layer the transmission depends on the thickness of the layer, on the birefringence of the liquid crystal, and on the wavelength of the light. This is a departure from the well-known independence of the transmission on these parameters for a thick twisted nematic layer.

  11. Crystal-liquid interfacial free energy via thermodynamic integration

    SciTech Connect

    Benjamin, Ronald; Horbach, Jürgen

    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.

  12. Common path point diffraction interferometer using liquid crystal phase shifting

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R. (Inventor)

    1997-01-01

    A common path point diffraction interferometer uses dyed, parallel nematic liquid crystals which surround an optically transparent microsphere. Coherent, collimated and polarized light is focused on the microsphere at a diameter larger than that of the microsphere. A portion of the focused light passes through the microsphere to form a spherical wavefront reference beam and the rest of the light is attenuated by the dyed liquid crystals to form an object beam. The two beams form an interferogram which is imaged by a lens onto an electronic array sensor and into a computer which determines the wavefront of the object beam. The computer phase shifts the interferogram by stepping up an AC voltage applied across the liquid crystals without affecting the reference beam.

  13. Relaxation Dynamics of Ferroelectric Liquid Crystals in Pulsed Electric Field

    NASA Astrophysics Data System (ADS)

    Kudreyko, A. A.; Migranov, N. G.; Migranova, D. N.

    2016-11-01

    In this contribution we report a theoretical study of relaxation processes in surface-stabilized ferroelectric liquid crystals with spontaneous polarization. The influence of pulsed electric field on the behavior of ferroelectric liquid crystal in the SmC* phase, which is placed in a thin cell with strong anchoring of SmC* molecules with the boundary substrate, is studied. In the vicinity of the substrate interface, temporal dependence of the azimuthal motion of the director induced by electric field is obtained. The response to the external distortion of ferroelectric liquid crystal confined between two microstructured substrates is the occurrence of periodic temporal formation of solitons connected with the distortion of the director field n in the sample bulk. The interplay between microstructured substrates and director distribution of the ferroelectric SmC* phase is explained by the Frenkel-Kontorova model for a chain of atoms, but adapted for the continuum problem.

  14. Profile measurement taken with liquid-crystal gratings.

    PubMed

    Kakunai, S; Sakamoto, T; Iwata, K

    1999-05-01

    Profile measurement taken with liquid-crystal gratings and a phase-shifting technique is proposed, and its effectiveness is verified by experiment. The surface profile is obtained by measurement of the phase distributions of the sinusoidal gratings deformed by an object's surface. The liquid-crystal grating gives an accurate phase shift, an arbitrary projection pitch, and a constant surface brightness compared with conventional gratings such as a laser interference fringe grating and a Ronchi grating. Therefore a flexible measuring system may be developed with it. Two gratings with different pitches are used to measure an object with large steps. A two-color projection system can be used to produce such gratings simultaneously. Locally varying reflectivity on a surface can also be compensated by adjustment of the color component of the projected grating with a liquid-crystal grating. Thus the contrast in the projected grating can be made uniform, and a good profile measurement can be accomplished.

  15. Bistable salt doped cholesteric liquid crystals light shutter

    NASA Astrophysics Data System (ADS)

    Moheghi, Alireza; Nemati, Hossein; Li, Yannian; Li, Quan; Yang, Deng-Ke

    2016-02-01

    Liquid crystals have been used to make electrically switchable light shutters (windows), but most of them are monostable: opaque in the absence of applied voltage and transparent when a voltage is applied. Here we report a bistable switchable light shutter based on cholesteric liquid crystal doped with tetrabutylammonium bromide. The salt makes it possible for the liquid crystal to have different electro-optical responses to applied voltages with different frequencies. The shutter can be either transparent or opaque in the absence of applied voltage. It can be switched from the transparent state to the opaque state by applying a low frequency (60 Hz) voltage pulse and switched back to the transparent state by applying a high frequency (2 kHz) voltage pulse. Because of the bistability, it can be used for energy-saving switchable privacy control and architectural windows.

  16. Defect topologies in chiral liquid crystals confined to mesoscopic channels

    SciTech Connect

    Schlotthauer, Sergej Skutnik, Robert A.; Stieger, Tillmann; Schoen, Martin

    2015-05-21

    We present Monte Carlo simulations in the grand canonical and canonical ensembles of a chiral liquid crystal confined to mesochannels of variable sizes and geometries. The mesochannels are taken to be quasi-infinite in one dimension but finite in the two other directions. Under thermodynamic conditions chosen and for a selected value of the chirality coupling constant, the bulk liquid crystal exhibits structural characteristics of a blue phase II. This is established through the tetrahedral symmetry of disclination lines and the characteristic simple-cubic arrangement of double-twist helices formed by the liquid-crystal molecules along all three axes of a Cartesian coordinate system. If the blue phase II is then exposed to confinement, the interplay between its helical structure, various anchoring conditions at the walls of the mesochannels, and the shape of the mesochannels gives rise to a broad variety of novel, qualitative disclination-line structures that are reported here for the first time.

  17. Conventional and nonlinear optical microscopy of liquid crystal colloids

    NASA Astrophysics Data System (ADS)

    Lee, Taewoo; Smalyukh, Ivan I.

    The fast-growing field of liquid crystal colloids requires increasingly sophisticated optical microscopy tools for experimental studies. Recent technological advances have resulted in a vast body of new imaging modalities, such as nonlinear optical microscopy techniques, that were developed to achieve high resolution while probing director structures and material composition at length scales ranging from hundreds of nanometers to oscopic. These techniques are ideally suited for experimental exploration of liquid crystal colloids. The goal of this chapter is to introduce a variety of optical microscopy techniques available to researchers in the field, starting from basic principles and finishing with a discussion of the most advanced microscopy systems. We describe traditional imaging tools, such as bright field and polarizing optical microscopy, along with state-of-the-art orientationsensitive three-dimensional imaging techniques, such as various nonlinear optical microscopies. Applications of these different imaging approaches are illustrated by providing specific examples of imaging of liquid crystal colloids and other soft matter systems.

  18. Alignment Layers for Ferro and Antiferroelectric Liquid Crystal Cells

    NASA Astrophysics Data System (ADS)

    Negi, Yuvraj Singh; Yamamoto, Norio; Suzuki, Yoshiichi; Kawamura, Ichiro; Yamada, Yuichiro; Kakimoto, Masa-aki; Imai, Yoshio

    1992-12-01

    Aromatic fluorine and nonfluorine containing polyimides, polyamide-imides and polyamides were developed and utilized as alignment layers in ferroelectric (FLC) and antiferroelectric liquid crystal (AFLC) cells. The FLC and AFLC blend (AFLCB-1) of liquid crystals used in the experiment were CS-1011 and [S(-)4-(1-methylheptyloxycarbonyl) phenyl-4-octyloxybiphenyl-4-carboxylate (MHPOBC), R(+)4-(1-trifluoromethylheptyloxy carbonyl)phenyl-4-octyloxybiphenyl-4-carboxylate (TFMHPOBC), and other homologues, [AFLCB-1], respectively. The alignment layer deposited over an ITO-coated glass electrode plate with 2 μm cell gap showed good or random alignment of liquid crystal in FLC and AFLC cells. The AFLC cells exhibited contrast ratio values greater than 10:1 depending on the molecular structure of the alignment layer. The alignment quality of FLC and AFLC cells was also compared by using different molecular structure of polymer alignment layers.

  19. Simulation of coherent backscattering of light in nematic liquid crystals

    SciTech Connect

    Aksenova, E. V. Kokorin, D. I. Romanov, V. P.

    2012-08-15

    Multiple scattering of light by the fluctuations of the director in a nematic liquid crystal (NLC) aligned by a magnetic field is considered. A peak of coherent backscattering is calculated by numerical simulation. Since the indicatrix of single scattering for a liquid crystal (LC) is known exactly, the calculations are carried out without any simplifying assumptions on the parameters of the liquid crystal. Multiple scattering is simulated as a random walk of photons in the medium. A peak of coherent backscattering in such a medium is very narrow; therefore, the so-called semianalytical method is applied. The parameters of the backscattering peak obtained by numerical simulation are compared with the available experimental data and with the results of analytical approximations. It turns out that the experimental data are in good agreement with the results of simulation. The results of numerical simulation adequately describe the anisotropy and the width of the backscattering peak.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Patterned liquid crystal order on the micro-, meso-, and nanoscale

    NASA Astrophysics Data System (ADS)

    Sousa, Matthew E.

    Liquid crystals are a unique class of material with many intriguing physical properties, which enable them for use in a variety of applications. The orientation of these anisotropic molecules can be controlled using external forces and surfaces, which ultimately enables the manipulation of their electrical, mechanical and optical properties. The overreaching theme of this thesis is the spatial patterning of these materials. Using these techniques for establishing and capturing patterned liquid crystalline order a variety of unique structures were fabricated. Lyotropic discotic liquid crystals as well as discotic mesophase pitch materials can be patterned and thermally polymerized in porous templates to produce arrays of carbon nanostructures. Alignment layers can be used in order to tune the orientation of the graphene planes of these structures such they are oriented either orthogonal or parallel to the long axis of the nanostructures. The combination of printing and alignment techniques open the exciting possibility of creating property patterns in nanostructure arrays, in which the graphene orientation varies systematically and periodically across the surface. Polymer networks within a liquid crystal host were fabricated using a holographic exposure process. Using a simple model and optical polarizing microscopy for verification, the effective thickness of the polymer planes in these structures was successfully predicted. A combination of factors, such as the low switching voltage, relatively fast response time, and polarization selectivity or non-selectivity make the reverse-mode structures attractive for many applications requiring diffractive optical elements. Polymeric liquid crystals, also known as reactive mesogens, are low molecular weight liquid crystalline monomers that can be photopolymerized in order to form well-organized, high-molecular weight structures. The molecular order and orientation of these materials can be controlled using a variety of

  2. Selective crystallization of tank supernatant liquid

    SciTech Connect

    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%.

  3. Shrink, twist, ripple and melt: Studies of frustrated liquid crystals

    NASA Astrophysics Data System (ADS)

    Fernsler, Jonathan G.

    Complex structures can arise out of a simple system with more than one competing influence on its behavior. The protypical example of this is the two-dimensional triangular lattice Ising model. The ferromagnetic model has two simple degenerate ground states of all spins up or down, but the antiferromagnetic model is a frustrated system. Its geometry does not allow satisfaction of the antiferro condition everywhere, which produces complex ordered structures with dimerization of the spins [1]. Without frustration, the complex structures and phase behavior are lost. All of the topics discussed in this thesis concern smectic liquid crystals. Liquid crystals are perhaps uniquely adept at manifesting frustrated phases. Their combination of periodicity in one or more dimensions allows ordered structures, yet their fluid nature in remaining dimensions allows creation of defects and extraordinarily complex structures in ways that a normal crystal could not tolerate. Liquid crystals contain a huge menagerie of frustrated phases and effects including the polarization modulated [2], vortex lattice [3], twist grain boundary [4], and blue [5] phases, as well as frustrated structures such as cholesteric or SmC* helix unwinding [6], defect lattices in thin films [7], and bend melted grain boundary defects [8], arising from boundary conditions and field effects. In this thesis, we study four liquid crystal systems that show unusual phase behavior or complex structures, deriving from the effects of frustration. Frustration, despite some human prejudices against the word, leaves nature all the more interesting and beautiful.

  4. Polarization Studies of Resonant Forbidden Reflections in Liquid Crystals

    SciTech Connect

    Fernandes, P.; Barois, P.; Nguyen, H. T.; Wang, S. T.; Liu, Z. Q.; McCoy, B. K.; Huang, C. C.; Pindak, R.; Caliebe, W.

    2007-11-30

    We report the results of resonant x-ray diffraction experiments performed on thick films of a biaxial liquid crystal made of achiral bent-core molecules. Polarization properties of forbidden reflections are observed as a function of the sample rotation angle {phi} about the scattering vector Q for the first time on a fluid material. The experimental data are successfully analyzed within a tensor structure factor model by taking the nonperfect alignment of the liquid crystal into account. The local structure of the B{sub 2} mesophase is hence determined to be SmC{sub S}P{sub A}.

  5. Color Gamut of Blackness in a Liquid Crystal Display

    NASA Astrophysics Data System (ADS)

    Shimomura, Teruo; Kobayashi, Shunsuke

    1985-02-01

    A guest-host mode liquid crystal display of a transmission type is investigated. Color gamut of blackness is established from an estimation experiment of color matching and is shown by the CIE 1931 chromaticity diagram and color solid. Color gamut of blackness under the influence of a light source and ambient illumination is discussed. A Munsell color ship, N-1 is used as a matching black color sample and fifty hues of liquid crystal cells are used as test sample colors. Six observers participate in the estimation experiment and measurement is done from ascending- and descending-series in the method of adjustment.

  6. Observations of dynamic stall phenomena using liquid crystal coatings

    NASA Technical Reports Server (NTRS)

    Reda, Daniel C.

    1991-01-01

    Novel, shear stress-sensitive/temperature-insensitive liquid crystal coatings have been applied to the surface of an oscillating airfoil in order to ascertain the unsteady fluid physics associated with the dynamic-stall process. Surface microtufts and laser sheet/smoke-particle flow visualization were used to compare the liquid-crystal results. Boundary-layer transition and turbulent separation locations were measured as a function of geometric angle of attack. The results obtained are compared with Eppler (1980) aerodynamic design code predictions.

  7. Simulation of weak anchoring effects on nematic liquid crystal hemispheres

    NASA Astrophysics Data System (ADS)

    Gillen, Sean; Somers, David A. T.; Munday, Jeremy N.

    The free energy of a nematic liquid crystal droplet depends on an interplay between elastic and surface interactions. When the two contributions are of similar magnitude, there exists a transition of the nematic structure of the droplet. Because the two contributions scale differently with length scales, this transition is visible as a function of the size of the droplet. We carry out numerical simulations to explore the use of this transition in measuring surface anchoring energies. This technique could help elucidate alignment forces on liquid crystals, such as those caused by rubbed surfaces, electric fields, or even the Casimir torque. Electrical and Computer Engineering.

  8. Diffractive devices based on blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Li, Yan; Huang, Shuaijia; Su, Yikai

    2016-09-01

    Blue phase liquid crystal (BPLC) has been attractive for display and photonic applications for its sub-millisecond response time, no need for surface alignment, and an optically isotropic dark state. Because of these advantages, diffractive devices based on blue phase liquid crystals have great potential for wide applications. In this work, we present several BPLC diffractive devices. The operation principles, fabrication and experimental measurements will be discussed in details for two BPLC gratings realized by holographic method and a BPLC Fresnel lens using a spatial light modulator projector. All of these devices exhibit several attractive features such as sub-millisecond response, relatively high spatial resolution and polarization-independence.

  9. Optical vortices generated by dislocations in a cholesteric liquid crystal.

    PubMed

    Voloschenko, D; Lavrentovich, O D

    2000-03-01

    We report the observation of optical vortices in a laser beam propagating through the stripe pattern of a cholesteric liquid crystal. The liquid crystal is confined in a cell with homogeneous boundary conditions and forms a diffraction phase grating. Optical vortices are produced by edge dislocations of the cholesteric grating. The vortices show up as spots of zero light intensity in the diffraction maxima. There is one spot in each +1 and -1 diffraction maximum and two spots in diffraction maxima +2 and -2.

  10. Observation of large nematic domains of discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Shinde, Abhijeet; Wang, Xuezhen; Cheng, Zhengdong

    2015-03-01

    Discotic liquid crystals are commonly found in nature in the form of clay, nacre. They are technologically important in applications such as conductive polymers, semiconductors and photovoltaics. Size and its distribution play an important role in their self-assemblies. Here we observed large nematic domains of discotic liquid crystals grown on a time scale of months. The development of such domains is observed to be faster for nanodisks that relatively smaller in size. The orientation of nanodisks is affected by gravity and inter-particle interactions which are yet to be fully understood.

  11. Observations of dynamic stall phenomena using liquid crystal coatings

    NASA Astrophysics Data System (ADS)

    Reda, Daniel C.

    1991-02-01

    Novel, shear stress-sensitive/temperature-insensitive liquid crystal coatings have been applied to the surface of an oscillating airfoil in order to ascertain the unsteady fluid physics associated with the dynamic-stall process. Surface microtufts and laser sheet/smoke-particle flow visualization were used to compare the liquid-crystal results. Boundary-layer transition and turbulent separation locations were measured as a function of geometric angle of attack. The results obtained are compared with Eppler (1980) aerodynamic design code predictions.

  12. Gradient index liquid crystal devices and method of fabrication thereof

    DOEpatents

    Lee, Jae-Cheul; Jacobs, Stephen

    1991-01-01

    Laser beam apodizers using cholesteric liquid crystals provides soft edge profile by use of two separate cholesteric liquid crystal mixtures with different selective reflection bands which in an overlap region have a gradient index where reflectivity changes as a function of position. The apodizers can be configured as a one-dimensional beam apod INTRODUCTION The U.S. government has rights in the invention under Contract No. DE-FC03-85DP40200 between the University of Rochester and the Department of Energy.

  13. Gradient index liquid crystal devices and method of fabrication thereof

    DOEpatents

    Lee, J.C.; Jacobs, S.

    1991-10-29

    Laser beam apodizers using cholesteric liquid crystals provides soft edge profile by use of two separate cholesteric liquid crystal mixtures with different selective reflection bands which in an overlap region have a gradient index where reflectivity changes as a function of position. The apodizers can be configured as a one-dimensional beam apod INTRODUCTION The U.S. government has rights in the invention under Contract No. DE-FC03-85DP40200 between the University of Rochester and the Department of Energy.

  14. Thermo - optical studies of nematic liquid crystal elastomer

    NASA Astrophysics Data System (ADS)

    Gharde, Rita A.; Mani, Santosh A.; Lal, Suman; Tripathi, S. K.; Khosla, Samriti

    2014-10-01

    The influences of structural parameter on thermo - optical properties of Nematic Liquid Crystal Elastomer (NLCE) were studied using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) Spectroscopy and Polarizing Microscopy Studies (PMS). Dielectric Measurement was also performed in addition to these measurements. The NLCE used in the present study were synthesized, has a unique coupling between anisotropic order of Liquid crystal component and elasticity of polymer network. The investigations were performed as function of temperature during heating and cooling processes. The study revealed the correlation of thermo - optical behavior of NLCE with the crosslinking agent and temperature.

  15. Small liquid-crystal display device for projection

    NASA Astrophysics Data System (ADS)

    Miyajima, Akira; Morokawa, Shigeru; Yamada, Osamu; Arai, Motonao

    1990-08-01

    In recent years, LCDs have drawn the attention of persons who present data such as sentences and patterns on the screen. This paper describes a new type of the device for projection using the LCD. CITIZEN has developed a multi-pixel, high-density and small-sized liquid crystal cell, using the Chip on Glass method. Driver ICs are directly connected to glass substrates. CITIZEN has developed a small liquid crystal display device, which is located between the light source and the lens of a conventional slide projector so that an image on the LCD is projected.

  16. Locomotion in a liquid crystal near a wall

    NASA Astrophysics Data System (ADS)

    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.

  17. Investigating the orientational order in smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    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.

  18. Schottky diode silicon liquid-crystal light valve

    NASA Astrophysics Data System (ADS)

    Sayyah, Keyvan; Efron, Uzi; Forber, Richard A.; Goodwin, Norman W.; Reif, Philip G.

    1991-06-01

    The authors report the operation of the Hughes Schottky diode-based silicon liquid crystal light valve (SLV) using readout light in the visible region. Limiting resolutions of 28 lp/mm limited by the Schottky diode periodicity, contrast ratios of >100:1, visible input light sensitivities of better than 50 (mu) W/cm2, and response times as fast as 5 ms have been measured. Both standard twisted nematic and homeotropically-aligned liquid crystal configurations have been utilized. The main parameter of this device is the leakage current of the Schottky diodes.

  19. Optical model of transient light scattering in ferroelectric liquid crystals

    SciTech Connect

    Loiko, V. A. Konkolovich, A. V.; Miskevich, A. A.

    2009-03-15

    A static optical model is developed for the effect of field-induced transient scattering on coherent light transmission through ferroelectric liquid crystals. Scattering processes are described by introducing an optically anisotropic medium containing scatterers (transient domains). The results presented in the paper are obtained for a plane parallel layer of ferroelectric liquid crystals with a planar helicoidal structure under normal illumination with a linearly polarized plane wave. An analysis is presented of the coherent transmittance of the layer in static applied electric fields.

  20. Terahertz absorption spectra and potential energy distribution of liquid crystals.

    PubMed

    Chen, Zezhang; Jiang, Yurong; Jiang, Lulu; Ma, Heng

    2016-01-15

    In this work, the terahertz (THz) absorption spectra of a set of nematic liquid crystals were studied using the density functional theories (DFT). An accurate assignment of the vibrational modes corresponding to absorption frequencies were performed using potential energy distribution (PED) in a frequency range of 0-3 THz. The impacts of different core structures on THz absorption spectra were discussed. The results indicate that scope of application must be considered in the LC-based THz device designing. This proposed work may give a useful suggestion on the design of novel liquid crystal material in THz wave.

  1. Terahertz absorption spectra and potential energy distribution of liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, Zezhang; Jiang, Yurong; Jiang, Lulu; Ma, Heng

    2016-01-01

    In this work, the terahertz (THz) absorption spectra of a set of nematic liquid crystals were studied using the density functional theories (DFT). An accurate assignment of the vibrational modes corresponding to absorption frequencies were performed using potential energy distribution (PED) in a frequency range of 0-3 THz. The impacts of different core structures on THz absorption spectra were discussed. The results indicate that scope of application must be considered in the LC-based THz device designing. This proposed work may give a useful suggestion on the design of novel liquid crystal material in THz wave.

  2. Digital Beam Deflectors Based Partly on Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Miranda, Felix A.; Kreminska, Liubov; Pishnyak, Oleg; Golovin, Andrii; Winker, Bruce K.

    2007-01-01

    A digital beam deflector based partly on liquid crystals has been demonstrated as a prototype of a class of optical beam-steering devices that contain no mechanical actuators or solid moving parts. Such beam-steering devices could be useful in a variety of applications, including free-space optical communications, switching in fiber-optic communications, general optical switching, and optical scanning. Liquid crystals are of special interest as active materials in nonmechanical beam steerers and deflectors because of their structural flexibility, low operating voltages, and the relatively low costs of fabrication of devices that contain them.

  3. Lyotropic liquid crystal directed synthesis of nanostructured materials

    PubMed Central

    Wang, Cuiqing; Chen, Dairong; Jiao, Xiuling

    2009-01-01

    This review introduces and summarizes lyotropic liquid crystal (LLC) directed syntheses of nanostructured materials consisting of porous nanostructures and zero-dimensional (0-D), one-dimensional (1-D) and two-dimensional (2-D) nanostructures. After a brief introduction to the liquid crystals, the LLCs used to prepare mesoporous materials are discussed; in particular, recent advances in controlling mesostructures are summarized. The LLC templates directing the syntheses of nanoparticles, nanorods, nanowires and nanoplates are also presented. Finally, future development in this field is discussed. PMID:27877273

  4. Bubble migration in a compacting crystal-liquid mush

    NASA Astrophysics Data System (ADS)

    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

  5. Interactions of carbon nanotubes in a nematic liquid crystal. II. Experiment

    NASA Astrophysics Data System (ADS)

    Agha, Hakam; Galerne, Yves

    2016-04-01

    Multiwall carbon nanotube (CNT) colloids with different anchoring conditions are dispersed in pentyl-cyanobiphenyl (5CB), a thermotropic liquid crystal (LC) that exhibits a room-temperature nematic phase. The experiments make use of CNTs treated for strong planar, homeotropic, or Janus anchorings. Observations with a polarizing microscope show that the CNTs placed in a uniform nematic field stabilize parallel or perpendicular to n depending on their anchoring conditions. In the presence of a splay-bend disclination line, they are first attracted toward it and ultimately, they get trapped on it. Their orientation relative to the line is then found to be parallel or perpendicular to it, again depending on the anchoring conditions. When a sufficient number of particles are deposited on a disclination line, they form a micro- or nanonecklace in the shape of a thin thread or of a bottle brush, with the CNTs being oriented parallel or perpendicular to the disclination line according to the anchoring treatment. The system exhibits a rich versatility, even if until now the weak anchorings appear to be difficult to control. In a next step, the necklaces may be glued by means of pyrrole electropolymerization. In this manner, we realize a true materialization of the disclination lines, and we obtain nanowires capable of conducting the electricity in the place of the initial disclinations that just worked as templates. The advantage of the method is that it finally provides nanowires that are automatically connected to predesignated three-dimensional (3D) electrodes. Such a 3D nanowiring could have important applications, as it could allow one to develop electronic circuits in the third dimension. They could thus help with increasing the transistor density per surface unit, although downsizing of integrated circuits will soon be limited to atomic sizes or so. In other words, the predicted limitation to Moore's law could be avoided. For the moment, the nanowires that we obtain

  6. Nanolitre-scale crystallization using acoustic liquid-transfer technology

    SciTech Connect

    Villaseñor, Armando G.; Wong, April; Shao, Ada; Garg, Ankur; Donohue, Timothy J.; Kuglstatter, Andreas; Harris, Seth F.

    2012-08-01

    Acoustic droplet ejection achieves precise, tipless, non-invasive transfer of diverse aqueous solutions, enabling nanolitre-scale crystallization trials. The rapid and scalable technique demonstrated successful crystal growth with diverse targets in drop volumes as small as 20 nl. Focused acoustic energy allows accurate and precise liquid transfer on scales from picolitre to microlitre volumes. This technology was applied in protein crystallization, successfully transferring a diverse set of proteins as well as hundreds of precipitant solutions from custom and commercial crystallization screens and achieving crystallization in drop volumes as small as 20 nl. Only higher concentrations (>50%) of 2-methyl-2, 4-pentanediol (MPD) appeared to be systematically problematic in delivery. The acoustic technology was implemented in a workflow, successfully reproducing active crystallization systems and leading to the discovery of crystallization conditions for previously uncharacterized proteins. The technology offers compelling advantages in low-nanolitre crystallization trials by providing significant reagent savings and presenting seamless scalability for those crystals that require larger volume optimization experiments using the same vapor-diffusion format.

  7. Photocontrol of fluid slugs in liquid crystal polymer microactuators

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

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

    SciTech Connect

    Ouskova, Elena; Sio, Luciano De Vergara, Rafael; Tabiryan, Nelson; White, Timothy J.; Bunning, Timothy J.

    2014-12-08

    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.

  9. Liquid Crystal Materials for Matrix Displays.

    DTIC Science & Technology

    1981-04-01

    traces of oxygen. The reaction products and mechanisms need to be established first with relatively simple mixtures, followed by studies of corrective...oxygen are involved in th* degradation mechanism is consistent with this observation. No crystal formation is observed in thin layer test cells...oxygen, and that this instability is catalyzed by glass surfaces. The general mechanism of this thermal instability needs to be determined in order to

  10. Nematic liquid crystals confined in microcapillaries for imaging phenomena at liquid-liquid interfaces.

    PubMed

    Zhong, Shenghong; Jang, Chang-Hyun

    2015-09-21

    Here, we report the development of an experimental system based on liquid crystals (LCs) confined in microcapillaries for imaging interfacial phenomena. The inner surfaces of the microcapillaries were modified with octadecyltrichlorosilane to promote an escaped-radial configuration of LCs. We checked the optical appearance of the capillary-confined LCs under a crossed polarizing microscope and determined their arrangement based on side and top views. We then placed the capillary-confined LCs in contact with non-surfactant and surfactant solutions, producing characteristic textures of two bright lines and a four-petal shape, respectively. We also evaluated the sensitivity, stability, and reusability of the system. Our imaging system was more sensitive than previously reported LC thin film systems. The textures formed in microcapillaries were stable for more than 120 h and the capillaries could be reused at least 10 times. Finally, we successfully applied our system to image the interactions of phospholipids and bivalent metal ions. In summary, we developed a simple, small, portable, sensitive, stable, and reusable experimental system that can be broadly applied to monitor liquid-liquid interfacial phenomena. These results provide valuable information for designs using confined LCs as chemoresponsive materials in optical sensors.

  11. Crystallization of Polymers at liquid/liquid interface templated by single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher

    2012-02-01

    Nanosized single-walled carbon nanotube rings were fabricated by using a Pickering emulsion-based method. By tuning a water/oil/SWNT miniemulsion system, SWNT rings with a diameter of ˜200 nm can be readily achieved. The formation mechanism is attributed to the bending force induced by the curved liquid/liquid interface. Crystallization of polyethylene homo- and copolymers using this unique SWNT rings as the nucleation agent was conducted at the curved liquid/liquid interface. Crystal structure, hybrid morphology and crystallization kinetics were systematically studied. The structure of controlled alternating patterns on SWNT rings has great potential in various applications in large-scale integrated circuits and single-electron devices.

  12. 21 CFR 884.2982 - Liquid crystal thermographic system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... breast cancer or other uses—(1) Identification. A nonelectrically powered or an AC-powered liquid crystal... for detection of breast cancer or other uses is a nonelectrically powered or an AC-powered device... screening for detection of breast cancer or other uses—(1) Identification. A nonelectrically powered or...

  13. 21 CFR 884.2982 - Liquid crystal thermographic system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... breast cancer or other uses—(1) Identification. A nonelectrically powered or an AC-powered liquid crystal... for detection of breast cancer or other uses is a nonelectrically powered or an AC-powered device... screening for detection of breast cancer or other uses—(1) Identification. A nonelectrically powered or...

  14. Thermo-elastic behaviour of liquid crystal elastomer

    NASA Astrophysics Data System (ADS)

    J, Jessy P.; Mani, Santosh A.; Amare, Jyoti R.; Gharde, Rita A.

    2015-06-01

    The effect of temperature on Liquid Crystal Elastomer was studied to understand thermo-elastic behaviour of these fantastic soft materials. The investigations were performed using Polarizing Microscopy Studies (PMS) and Differential Thermal Analysis (DTA). The relative length shows hysteresis as function of temperature. As temperature increases, the length shrinks, while it returns to original shape on cooling.

  15. Frederiks transition in ferroelectric liquid-crystal nanosuspensions

    NASA Astrophysics Data System (ADS)

    Shelestiuk, Sergii M.; Reshetnyak, Victor Yu.; Sluckin, Timothy J.

    2011-04-01

    We construct a theoretical model of the dielectric properties of a ferroelectric LC nanosuspension (FLCNS), using a generalized Maxwell-Garnett picture. The theory supposes that an FLCNS may as a first approximation be considered as a complex homogeneous dielectric ceramic, thus neglecting positional correlations of the colloidal particles. The FLCNS then consists of an anisotropic matrix with a very low concentration (<1% by volume) of impurity particles. The impurity particles possess both shape and dielectric anisotropy, as well as a permanent electric polarization and strong liquid-crystal director anchoring on the particle surface. We show that the effective dielectric properties for capacitance properties and for effective liquid-crystal free energies do not coincide. We calculate the effect of doping a liquid crystal with ferroelectric impurities on the Frederiks transition. The theory takes account of inclusion shape, dielectric susceptibility, and local field effects. We neglect the possibility of dielectric particle chaining, which appears experimentally not to occur in general. Our calculations suggest, in qualitative agreement with experiment, that doping a nematic liquid crystal with ferroelectric particles, even at very low particle concentration, can in some cases significantly decrease the electric Frederiks threshold field.

  16. Anisotropic and Electro-Optical Effects in Liquid Crystals.

    DTIC Science & Technology

    1981-08-01

    nematic-phase liquid crystals of negative dielectric anisotropy has been previously studied primarily with azoxy mixtures, such as Merck NP-V. These yellow ...of these patterns are similar to a wallpaper pattern while the ac-activated Williams domains consist of many parallel line domains. The dc-Vth

  17. Imaging Spectrometer Using a Liquid Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

    Chrien, Tomas G.; Chovit, Christopher; Miller, Peter J.

    1993-01-01

    A demonstration imaging spectrometer using a liquid crystal tunable filter (LCTF) was built and tested on a hot air balloon platform. The LCTF is a tunable polarization interference or Lyot filter. The LCTF enables a small, light weight, low power, band sequential imaging spectrometer design.

  18. Liquid Crystals Indicate Directions Of Surface Shear Stresses

    NASA Technical Reports Server (NTRS)

    Reda, Daniel C.

    1996-01-01

    Report consisting of main text of U.S. Patent 5,394,752 presents detailed information on one aspect of method of using changes in colors of liquid-crystal coatings to indicate instantaneous directions of flow-induced shear stresses (skin friction) on aerodynamic surfaces.

  19. Film-Cooling Heat-Transfer Measurements Using Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Hippensteele, Steven A.

    1997-01-01

    The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.

  20. A statistical calibration technique for thermochromic liquid crystals

    NASA Astrophysics Data System (ADS)

    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.

  1. Properties of freely suspended liquid crystal films and their applications

    NASA Astrophysics Data System (ADS)

    Yablonskii, S. V.; Bodnarchuk, V. V.; Yoshino, K.

    2016-05-01

    We report the review on the physical properties of the liquid crystal freely suspended films. The importance of the freely suspended films for the study of the fundamental problems of the self-confined systems as well as their practical implementations are demonstrated.

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

    PubMed

    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.

  3. Electrically tunable holographic polymer templated blue phase liquid crystal grating

    NASA Astrophysics Data System (ADS)

    He, Zheng-Hong; Chen, Chao-Ping; Zhu, Ji-Liang; Yuan, Ya-Chao; Li, Yan; Hu, Wei; Li, Xiao; Li, Hong-Jing; Lu, Jian-Gang; Su, Yi-Kai

    2015-06-01

    In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer templated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications. Project supported by the National Basic Research Program of China (Grant No. 2013CB328804), the National Natural Science Foundation of China (Grant No. 61307028), the Funds from the Science and Technology Commission of Shanghai Municipality (Grant Nos. 11JC1405300, 13ZR1420000, and 14ZR1422300), and the Fundamental Research Funds for the Central Universities, China (Grant No. XDJK 2011C047).

  4. Adaptive optics fundus camera using a liquid crystal phase modulator

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tatsuo; Nakazawa, Naoki; Bessho, Kenichiro; Kitaguchi, Yoshiyuki; Maeda, Naoyuki; Fujikado, Takashi; Mihashi, Toshifumi

    2008-05-01

    We have developed an adaptive optics (AO) fundus camera to obtain high resolution retinal images of eyes. We use a liquid crystal phase modulator to compensate the aberrations of the eye for better resolution and better contrast in the images. The liquid crystal phase modulator has a wider dynamic range to compensate aberrations than most mechanical deformable mirrors and its linear phase generation makes it easy to follow eye movements. The wavefront aberration was measured in real time with a sampling rate of 10 Hz and the closed loop system was operated at around 2 Hz. We developed software tools to align consecutively obtained images. From our experiments with three eyes, the aberrations of normal eyes were reduced to less than 0.1 μm (RMS) in less than three seconds by the liquid crystal phase modulator. We confirmed that this method was adequate for measuring eyes with large aberrations including keratoconic eyes. Finally, using the liquid crystal phase modulator, high resolution images of retinas could be obtained.

  5. Probing Viscoelasticity of Cholesteric Liquid Crystals in a Twisting Cell

    NASA Astrophysics Data System (ADS)

    Angelo, Joseph; Moheghi, Alireza; Diorio, Nick; Jakli, Antal

    2013-03-01

    Viscoelastic properties of liquid crystals are typically studied either using Poiseuille flow, which can be produced by a pressure gradient in a capillary tube,[2] or Couette flow, which can be generated by a shear between concentric cylinders.[3] We use a different method in which we twist the liquid crystal sandwiched between two cylindrical glass plates, one of which can rotate about its center, the other of which is fixed. When the cell is twisted, there is a force proportional to the twist angle and the twist elastic constant, and inversely proportional to the pitch and sample thickness, normal to the substrates due to the change in pitch in the cholesteric liquid crystal (CLC). Measuring this force on various CLCs with known pitch we could obtain the twist elastic constants. In addition to the equilibrium force, we observed a transient force during the rotation, which is related to the flow of the material, thus allowing us to determine the Leslie viscosity component α1, which typically cannot be assessed by other methods. We expect this apparatus to be a useful tool to study the visco-elastic properties of liquid crystals. The authors acknowledge support from NSF grant DMR-0907055.

  6. Intangible pointlike tracers for liquid-crystal-based microsensors

    SciTech Connect

    Brasselet, Etienne; Juodkazis, Saulius

    2010-12-15

    We propose an optical detection technique for liquid-crystal-based sensors that is based on polarization-resolved tracking of optical singularities and does not rely on standard observation of light-intensity changes caused by modifications of the liquid crystal orientational ordering. It uses a natural two-dimensional network of polarization singularities embedded in the transverse cross section of a probe beam that passes through a liquid crystal sample, in our case, a nematic droplet held in laser tweezers. The identification and spatial evolution of such a topological fingerprint is retrieved from subwavelength polarization-resolved imaging, and the mechanical constraint exerted on the molecular ordering by the trapping beam itself is chosen as the control parameter. By restricting our analysis to one type of point singularity, C points, which correspond to location in space where the polarization azimuth is undefined, we show that polarization singularities appear as intangible pointlike tracers for liquid-crystal-based three-dimensional microsensors. The method has a superresolution potential and can be used to visualize changes at the nanoscale.

  7. LIQUID CRYSTAL POLYMERS (LCP) USED AS A MACHINING FLUID CD

    EPA Science Inventory

    This interactive CD was produced to present the science, research activities, and beneficial environmental and machining advantages for utilizing Liquid Crystal Polymers (LCPs) as a machine fluid in the manufacturing industry.

    In 1995, the USEPA funded a project to cut flu...

  8. Liquid crystals detect voids in fiber glass laminates

    NASA Technical Reports Server (NTRS)

    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.

  9. 21 CFR 884.2982 - Liquid crystal thermographic system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... breast cancer or other uses—(1) Identification. A nonelectrically powered or an AC-powered liquid crystal... for detection of breast cancer or other uses is a nonelectrically powered or an AC-powered device... screening for detection of breast cancer or other uses—(1) Identification. A nonelectrically powered or...

  10. 21 CFR 884.2982 - Liquid crystal thermographic system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... breast cancer or other uses—(1) Identification. A nonelectrically powered or an AC-powered liquid crystal... for detection of breast cancer or other uses is a nonelectrically powered or an AC-powered device... screening for detection of breast cancer or other uses— (1) Identification. A nonelectrically powered or...

  11. 21 CFR 884.2982 - Liquid crystal thermographic system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... breast cancer or other uses—(1) Identification. A nonelectrically powered or an AC-powered liquid crystal... for detection of breast cancer or other uses is a nonelectrically powered or an AC-powered device... screening for detection of breast cancer or other uses—(1) Identification. A nonelectrically powered or...

  12. Switchable Fresnel lens using polymer-stabilized liquid crystals.

    PubMed

    Fan, Yun-Hsing; Ren, Hongwen; Wu, Shin-Tson

    2003-11-17

    A switchable Fresnel zone plate lens is demonstrated using a polymer-stabilized liquid crystal. The fabrication process is relatively simple and the device can be operated below 10 volts with fast response time. Such a device works well for a linearly polarized light.

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

    NASA Astrophysics Data System (ADS)

    Kaur, S.; Panov, V. P.; Greco, C.; Ferrarini, A.; Görtz, V.; Goodby, J. W.; Gleeson, H. F.

    2014-12-01

    We have determined experimentally the magnitude of the difference in the splay and bend flexoelectric coefficients, |e1 - e3|, of an oxadiazole bent-core liquid crystal by measuring the critical voltage for the formation of flexodomains together with their wave number. The coefficient |e1 - e3| is found to be a factor of 2-3 times higher than in most conventional calamitic nematic liquid crystals, varying from 8 pCm-1 to 20 pCm-1 across the ˜60 K—wide nematic regime. We have also calculated the individual flexoelectric coefficients e1 and e3, 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.

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

    SciTech Connect

    Kaur, S. Panov, V. P.; Gleeson, H. F.; Greco, C.; Ferrarini, A.; Görtz, V.; Goodby, J. W.

    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.

  15. Shape of impurity electronic absorption bands in nematic liquid crystal

    SciTech Connect

    Aver`yanov, E.M.

    1994-11-01

    The impurity-matrix anisotropic static intermolecular interactions, orientation-statistical properties, and electronic structure of uniaxial impurity molecules are shown to have a significant influence on spectral moments of the electronic absorption bands of impurities in the nematic liquid crystal. 14 refs., 3 figs.

  16. Thermo- and mechanico-optical effects in liquid crystals and their application in aerodynamics

    NASA Astrophysics Data System (ADS)

    Zharkova, Galina M.; Kovrizhina, Valentina N.; Petrov, Alexander P.

    2016-10-01

    Temperature and shear sensitive liquid crystals may be used for global quantitative and qualitative diagnostics of near-wall flows. The results of experimental studies of liquid crystals and relevant technologies tested at ITAM SB RAS are presented.

  17. Reflection Spectra of Distorted Cholesteric Liquid Crystal Structures in Cells with Interdigitated Electrodes (Postprint)

    DTIC Science & Technology

    2014-07-01

    adjusting the magnitude of the electric field. 15. SUBJECT TERMS liquid crystals, liquid-crystal devices, Bragg reflectors, optical properties, chiral ...160.3710) Liquid crystals; (230.3720) Liquid-crystal devices; (230.1480) Bragg reflectors; (160.4760) Optical properties; (160.1585) Chiral media...polymerizing chiral - nematic media,” Adv. Mater. 11(7), 573–578 (1999). 13. M. Rumi, V. P. Tondiglia, L. V. Natarajan, T. J. White, and T. J. Bunning

  18. Dispersive kinetics in discotic liquid crystals.

    PubMed

    Kruglova, O; Mulder, F M; Kearley, G J; Picken, S J; Stride, J A; Paraschiv, I; Zuilhof, H

    2010-11-01

    The dynamics of the discotic liquid-crystalline system, hexakis (n-hexyloxy) triphenylene (HAT6), is considered in the frame of the phenomenological model for rate processes proposed by Berlin. It describes the evolution of the system in the presence of the long-time scale correlations in the system, and we compare this with experimental quasielastic neutron scattering of the molecular assembly of HAT6 in the columnar phase. We interpret the parameters of this model in terms of nonextensive thermodynamics in which rare events in the local fast dynamics of some parts of the system control the slower dynamics of the larger molecular entity and lead to a fractional diffusion equation. The importance of these rare local events to the overall dynamics of the system is linked to the entropic index, this being obtained from the data within the model approach. Analysis of the waiting-time dependence from momentum transfer reveals a Lévy distribution of jump lengths, which allows us to construct the van Hove correlation function for discotic liquid-crystalline system.

  19. 75 FR 63856 - In the Matter of Certain Liquid Crystal Display Devices, Including Monitors, Televisions, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-18

    ... COMMISSION In the Matter of Certain Liquid Crystal Display Devices, Including Monitors, Televisions, and... sale for importation, and the sale within the United States after importation of certain liquid crystal... importation of certain liquid crystal display devices, including monitors, televisions, and modules,...

  20. 75 FR 74080 - In the Matter of Certain Liquid Crystal Display Devices, Including Monitors, Televisions, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-30

    ... COMMISSION Inv. No. 337-TA-749 In the Matter of Certain Liquid Crystal Display Devices, Including Monitors... sale within the United States after importation of certain liquid crystal display devices, including... importation of certain liquid crystal display devices, including monitors, televisions, and modules,...

  1. Polarization properties of the variable-grating-mode liquid-crystal device.

    PubMed

    Tanguay, A R; Chavel, P; Strand, T C; Wu, C S; Soffer, B H

    1984-05-01

    The principal features of the liquid-crystal molecular orientation within the variable-grating-mode liquid-crystal device have been determined as a function of the applied voltage across the cell by measurement of the polarization properties of light diffracted by the liquid-crystal birefringent phase grating.

  2. Ordering Transitions Triggered by Specific Binding of Vesicles to Protein-Decorated Interfaces of Thermotropic Liquid Crystals

    PubMed Central

    Tan, Lie Na; Orler, Victor J.; Abbott, Nicholas L.

    2012-01-01

    We report that specific binding of ligand-functionalized (biotinylated) phospholipid vesicles (diameter = 120 ± 19 nm) to a monolayer of proteins (streptavidin or anti-biotin antibody) adsorbed at an interface between an aqueous phase and an immiscible film of a thermotropic liquid crystal (LC) (nematic 4′-pentyl-4-cyanobiphenyl (5CB)) triggers a continuous orientational ordering transition (continuous change in the tilt) in the LC. Results presented in this paper indicate that, following the capture of the vesicles at the LC interface via the specific binding interaction, phospholipids are transferred from the vesicles onto the LC interface to form a monolayer, reorganizing and partially displacing proteins from the LC interface. The dynamics of this process are accelerated substantially by the specific binding event relative to a protein-decorated interface of a LC that does not bind the ligands presented by vesicles. The observation of the continuous change in the ordering of the LC, when combined with other results presented in this paper, is significant as it is consistent with the presence of sub-optical domains of proteins and phospholipids on the LC interface. An additional significant hypothesis that emerges from the work reported in this paper is that the ordering transition of the LC is strongly influenced by the bound state of the protein adsorbed on the LC interface, as evidenced by the influence on the LC of (i) “crowding” of the protein within a monolayer formed at the LC interface and (ii) aging of the proteins on the LC interface. Overall, these results demonstrate that ordering transitions in LCs can be used to provide fundamental insights into the competitive adsorption of proteins and lipids at oil-water interfaces, and that LC ordering transitions have the potential to be useful for reporting specific binding events involving vesicles and proteins. PMID:22372743

  3. Molecular alignment enhancement phenomenon of polymer formed from a liquid crystal monomer in a liquid crystal solvent

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Kawakita, Masahiro; Kikuchi, Hiroshi

    2003-03-01

    We report an abnormal alignment enhancement phenomenon of polymer molecules. The alignment order of a rigid-skeleton polymer made from a liquid crystalline monomer in a low-molecular-weight liquid crystal solvent was drastically enhanced with increasing temperature, even though the alignment order of the solution of the liquid crystal and monomer decreased. From polymer molecular alignment observations using polarizing Raman scattering microscopy, it was found that the polymer alignment order was three times greater than that of the original aligned monomer and polymer. This super alignment technique of polymer using a molecular-scaled self-assembly mechanism is applicable to the formation of electrically and/or optically functional nanopolymer wires.

  4. Toughening Thermoplastics with Thermotropic Liquid Crystal Polymers

    NASA Astrophysics Data System (ADS)

    Wiff, Donald

    1997-03-01

    Blends of thermotropic liquid crystalline and thermoplastic polymers have improvements in mechanical properties when high elongational flow provides LC needle shaped domains. This means the test sample must be a filament. Without elongational flow the LC domains are globular in shape and provide little or no mechanical property enhancement. One solution to this problem is to make the LC domains small enough so that their size approaches that of microvoids in the thermoplastic polymer system. Such an approach can potentially provide a pseudo-compatible blend. Thus if the thermoplastic matrix polymer is transparent, the nano size LC domains can provide reinforcement, modified optical properties, and still leave the bulk material transparent. This investigation focusses on the process and improvement in mechanical and fracture resistant properties.

  5. Liquid crystals from mesogens containing gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Lewandowski, Wiktor; Gorecka, Ewa

    Long-range ordered structures made of nanoparticles are perspective materials for future optical, electronic and sensing technologies. Conspicuous physicochemical features of nanoparticle aggregates originate from distant-dependent collective interactions, therefore lately a lot of attention was put to the development of assembly strategies allowing control over nanoparticle spatial distribution. In this chapter we will focus on the assembly process based on using thermotropic liquid-crystalline molecules as surface nanoparticle ligands. First, we discuss architectural parameters that inuence structure and thermal properties of the aggregates. Then, we show that this approach enables formation of assemblies with metamaterial characteristic, gives access to dynamic materials with light-, magneto- and thermo-responsive behavior and allows formation of aggregates with unique structures, which all make this strategy an attractive object of research.

  6. Dynamics of disk pairs in a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Antipova, Alena; Denniston, Colin

    2016-11-01

    We use a hybrid lattice Boltzmann method to study the behavior of sets of ferromagnetic colloidal disks in a nematic liquid crystal. When a weak rotating magnetic field acts on the system, the disks rotate following the magnetic field. This leads to a distortion in the liquid crystal that drives translational motion of the disks. If the concentration of disks is high, disks get locked together: a stable chain configuration is created, where each disk lays on the nearest neighbor. For intermediate concentrations of disks, a different behavior is observed. When disks are rotated by the magnetic field by more than 90∘ from their initial orientation, the distortion in the liquid crystal leads to a simultaneous flip of both disks. The final disk positions depends only weakly on the initial configuration. Consecutive rotations of magnetic field push disks towards an equidistant configuration. Periodicity of the systems studied and analysis of the flipping motion of a single disk imply that one can use weak rotating magnetic fields to create stable crystal structures of disks.

  7. Nanostructured liquid crystals combining ionic and electronic functions.

    PubMed

    Yazaki, Sanami; Funahashi, Masahiro; Kagimoto, Junko; Ohno, Hiroyuki; Kato, Takashi

    2010-06-09

    New molecular materials combining ionic and electronic functions have been prepared by using liquid crystals consisting of terthiophene-based mesogens and terminal imidazolium groups. These liquid crystals show thermotropic smectic A phases. Nanosegregation of the pi-conjugated mesogens and the ionic imidazolium moieties leads to the formation of layered liquid-crystalline (LC) structures consisting of 2D alternating pathways for electronic charges and ionic species. These nanostructured materials act as efficient electrochromic redox systems that exhibit coupled electrochemical reduction and oxidation in the ordered bulk states. For example, compound 1 having the terthienylphenylcyanoethylene mesogen and the imidazolium triflate moiety forms the smectic LC nanostructure. Distinct reversible electrochromic responses are observed for compound 1 without additional electrolyte solution on the application of double-potential steps between 0 and 2.5 V in the smectic A phase at 160 degrees C. In contrast, compound 2 having a tetrafluorophenylterthiophene moiety and compound 3 having a phenylterthiophene moiety exhibit irreversible cathodic reduction and reversible anodic oxidation in the smectic A phases. The use of poly(3,4-ethylenedioxythiophene)-poly(4-styrene sulfonate) (PEDOT-PSS) as an electron-accepting layer on the cathode leads to the distinct electrochromic responses for 2 and 3. These results show that new self-organized molecular redox systems can be built by nanosegregated pi-conjugated liquid crystals containing imidazolium moieties with and without electroactive thin layers on the electrodes.

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

    NASA Astrophysics Data System (ADS)

    Kühnel, M.; Fernández, J. M.; Tramonto, F.; Tejeda, G.; Moreno, E.; Kalinin, A.; Nava, M.; Galli, D. E.; Montero, S.; Grisenti, R. E.

    2015-08-01

    By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH2) or orthodeuterium (oD2) 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 pH2 and oD2 crystal growth rates, similarly to what found in our previous work on supercooled pH2-oD2 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.

  9. Liquid Crystals for Organic Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    O'Neill, Mary; Kelly, Stephen M.

    Columnar, smectic and lamellar polymeric liquid crystals are widely recognized as very promising charge-transporting organic semiconductors due to their ability to spontaneously self-assemble into highly ordered domains in uniform thin films over large areas. The transport properties of smectic and columnar liquid crystals are discussed in Chaps. 2 (10.1007/978-90-481-2873-0_2) and 3 (10.1007/978-90-481-2873-0_3). Here we examine their application to organic field-effect transistors (OFETs): after a short introduction in Sect. 9.1 we introduce the OFET configuration and show how the mobility is measured in Sect. 9.2. Section 9.3 discusses polymeric liquid crystalline semiconductors in OFETs. We review research that shows that annealing of polymers in a fluid mesophase gives a more ordered microcrystalline morphology on cooling than that kinetically determined by solution processing of the thin film. We also demonstrate the benefits of monodomain alignment and show the application of liquid crystals in light-emitting field-effect transistors. Some columnar and smectic phases are highly ordered with short intermolecular separation to give large π-π coupling. We discuss their use in OFETs in Sects. 9.4, and 9.5 respectively. Section 9.6 summarises the conclusions of the chapter.

  10. Cubic and Hexagonal Liquid Crystals as Drug Delivery Systems

    PubMed Central

    Chen, Yulin; Ma, Ping; Gui, Shuangying

    2014-01-01

    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. PMID:24995330

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

    SciTech Connect

    Kühnel, M.; Kalinin, A.; Fernández, J. M.; Tejeda, G.; Moreno, E.; Montero, S.; Tramonto, F.; Galli, D. E.; Nava, M.; Grisenti, R. E.

    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.

  12. Mixing of molecular excitation in a uniaxial liquid crystal

    SciTech Connect

    Aver`yanov, E.M.

    1995-07-01

    The influence of the mixing of molecular excitations due to local-field effects on the dielectric and spectral properties of uniaxial liquid crystals is investigated. The general properties of the spectrum of transverse optical excitations of the medium, viz, the sum rules for the oscillator strengths, frequencies, and damping constants of the dielectric function resonances, are established. The restricted applicability of the idea of a back ground polarizability (dielectric function) in the analysis of the mixing of molecular excitations is demonstrated. Mixing is taken into account in deriving new dispersion formulas for the imaginary and real parts of the dielectric tensor, which differ significantly from those used in the literature. A range of applicability has been established for the latter. Qualitative and quantitative interpretations of controversial experimental data for an extensive list of objects are given. The occurrence of mixing of dipole-active molecular vibrations, whose intensity has been found to be strongest for polyphilic objects that form nonchiral ferroelectric phases, has been demonstrated for molecular liquids and uniaxial liquid crystals from various chemical classes for the first time. The mixing of molecular excitations is considered as a possible mechanism for {open_quotes}polarization catastrophe{close_quotes} in liquid crystals having a soft mode in hthespectrum of transverse optical modes of vibration for the high-temperature phase. 53 refs., 1 fig.

  13. Liquid crystal cells and optical fibers in neural network implementation

    NASA Astrophysics Data System (ADS)

    Domanski, Andrzej W.; Buczynski, Ryszard; Sierakowski, Marek W.

    1995-08-01

    Optical binary computer may be as easy to operate as parallel system. For such configuration Boolean logic is not very convenient and therefore neural networks should be introduced. In works leading to the paper we used liquid crystal cells as a standard system of liquid crystalline layer between to conducting electrodes in 'sandwich' geometry. We have used 25 micrometers display cells filled with nematic 6CHBT working on 'twisted nematic' effect. Based on such elements a mode of a simple Hopfield network was set up. More advanced experiments were carried out on a model of neurone with supervised learning. The model consists of four laser diodes pigtailed to the multimode optical fibers with 50 micrometers core diameter. The directional couplers help to control the level of input optical power. Four liquid crystal cells allow to change the transmission level according to superivised learning requirements. All the signals were detected by one photodiode. The presented results of experiments are in excellent agreement with theoretical predictions. An additional study was done to check the possibility to build up a linear neural network with Grossberg layer, a neural network with Kohonen layer, and a counter propagation network with two layers of neurones. We have proved that such models may be set up based on simple liquid crystals cells and optical fiber networks.

  14. Colorimetric qualification of shear sensitive liquid crystal coatings

    NASA Technical Reports Server (NTRS)

    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

  15. Colorimetric qualification of shear sensitive liquid crystal coatings

    NASA Astrophysics Data System (ADS)

    Muratore, Joseph J., Jr.

    1993-08-01

    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

  16. Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 4. Synthesis of Amorphous and Side Chain Liquid Crystal AB Block Copolymers

    DTIC Science & Technology

    1992-05-01

    Metathesis Polymerization. 4. Synthesis of C N00014-89-JI542 Amorphous and Side Chain Liquid Crystal AB Block Copolym rs 6. AUTHOR(S) Zen Komiya, Coleen ...Liquid Crystal AB Block Copolymers by Zen Komiya, Coleen Pugh: and Richard R. Schrock* Submitted to Macromolecules F r fCarnegie Mellon University...Amorphous and Side Chain Liquid Crystal AB Block Copolymers by Zen Komiya, Coleen Pught, and Richard R. Schrock* Contribution from Department of Chemistry 6

  17. Crystallization of electrons on the surface of liquid helium

    NASA Astrophysics Data System (ADS)

    Grimes, C. C.; Adams, G.

    1980-08-01

    The classical, two-dimensional Coulomb system formed by a monolayer of electrons trapped on the surface of liquid helium has been observed to crystallize into a triangular lattice. Measured melting temperatures range from 0.37 to 0.65 K for areal densities of electrons from 3 × 10 8 cm -2 to 9 × 10 8 cm -2. Melting occurs at Γ = 131 ± 7 where Γ is a measure of the ratio of potential energy to kinetic energy per electron. The measured value of Γ at melting is consistent with dislocation mediated melting of a two-dimensional crystal.

  18. Crystal growth of sulfide materials from alkali polysulfide liquids

    NASA Technical Reports Server (NTRS)

    White, W. B.

    1979-01-01

    The fluids experiment system was designed for low temperature solution growth, nominally aqueous solution growth. The alkali polysulfides, compositions in the systems Na2S-S and K2S-S form liquids in the temperature range of 190 C to 400 C. These can be used as solvents for other important classes of materials such as transition metal and other sulfides which are not soluble in aqueous media. Among these materials are luminescent and electroluminescent crystals whose physical properties are sensitive functions of crystal perfection and which could, therefore, serve as test materials for perfection improvement under microgravity conditions.

  19. Smectic A and C* liquid crystal light valves

    NASA Astrophysics Data System (ADS)

    Dupont, L.; Wu, Z. Y.; Cambon, P.; de Bougrenet de La Tocnaye, J. L.

    1993-07-01

    The development of light valves for application in the domain of imaging and information display has benefited from simultaneous advances in liquid crystal materials. We will focus on recent developments involving the use of smectic A and smectic C*. Two types of light valves are described with their addressing technology. The first one is optically addressed spatial light modulator: optical information is converted into electric information through the medium of a photoconductivity material layer (amorphous silicon). The second type of valve is a VLSI chip covered with liquid crystal which can be optically addressed on each pixel and perform local electronic processing. The local switching of the liquid crystal allows the reading of the final state. Le développement des valves optiques dans le domaine de l'image et la représentation spatiale de l'information a bénéficié des progrès réalisés sur les matériaux “cristaux liquides". Nous allons étudier tout spécialement les développements récents concernant l'utilisation des phases smectiques A et C*. Deux types de valves sont décrites avec leurs modes d'adressage respectifs : le modulateur à adressage optique : l'information est envoyée par voie optique et la commutation s'effectue par la conversion du signal optique en signal électrique grâce à une couche d'un matériau photoconducteur (silicium amorphe hydrogéné). Le deuxième type de valve est un circuit VLSI recouvert de cristal liquide pouvant être adressé par voie optique et effectuant un traitement logique local de l'information reçue ; la commutation locale du cristal liquide permet alors la lecture de l'état final.

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

    SciTech Connect

    Wahle, Markus Kitzerow, Heinz-Siegfried

    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.

  1. Crystal growth in a three-phase system: Diffusion and liquid-liquid phase separation in lysozyme crystal growth

    NASA Astrophysics Data System (ADS)

    Heijna, M. C. R.; van Enckevort, W. J. P.; Vlieg, E.

    2007-07-01

    In the phase diagram of the protein hen egg-white lysozyme, a region is present in which the lysozyme solution demixes and forms two liquid phases. In situ observations by optical microscopy show that the dense liquid droplets dissolve when crystals grow in this system. During this process the demixed liquid region retracts from the crystal surface. The spatial distribution of the dense phase droplets present special boundary conditions for Fick’s second law for diffusion. In combination with the cylindrical symmetry provided by the kinetically roughened crystals, this system allows for a full numerical analysis. Using experimental data for setting the boundary conditions, a quasi-steady-state solution for the time-dependent concentration profile was shown to be valid. Comparison of kinetically rough growth in a phase separated system and in a nonseparated system shows that the growth kinetics for a three-phase system differs from a two-phase system, in that crystals grow more slowly but the duration of growth is prolonged.

  2. Crystal growth in a three-phase system: diffusion and liquid-liquid phase separation in lysozyme crystal growth.

    PubMed

    Heijna, M C R; van Enckevort, W J P; Vlieg, E

    2007-07-01

    In the phase diagram of the protein hen egg-white lysozyme, a region is present in which the lysozyme solution demixes and forms two liquid phases. In situ observations by optical microscopy show that the dense liquid droplets dissolve when crystals grow in this system. During this process the demixed liquid region retracts from the crystal surface. The spatial distribution of the dense phase droplets present special boundary conditions for Fick's second law for diffusion. In combination with the cylindrical symmetry provided by the kinetically roughened crystals, this system allows for a full numerical analysis. Using experimental data for setting the boundary conditions, a quasi-steady-state solution for the time-dependent concentration profile was shown to be valid. Comparison of kinetically rough growth in a phase separated system and in a nonseparated system shows that the growth kinetics for a three-phase system differs from a two-phase system, in that crystals grow more slowly but the duration of growth is prolonged.

  3. Mesogenic linear azobenzene polymer-stabilized nematic liquid crystals

    SciTech Connect

    Bagramyan, Arutyun; Thibault-Maheu, Olivier; Galstian, Tigran; Bessette, Andre; Zhao, Yue

    2011-03-15

    We describe the detailed study of a polymer stabilized liquid crystal compound, which was created by using a reactive (monofunctional) azobenzene mesogenic guest and a nematic liquid crystal host. The resonant interaction of light with the azobenzene segment of the guest and the mesogenic nature of the latter enable the optical alignment of host molecules and the permanent fixing of that orientation by means of UV polymerization of the guest. We use dynamic spectral, polarimetric, and scattering techniques to study the orientational ordering and interaction of the guest-host system. We show that the uniform UV polymerization of this compound results in a low scattering material system with dielectric and elastic properties that are relatively close to those of the host, while still providing the capacity for optical configuration of its morphology.

  4. Chirality Differentiation by Diffusion in Chiral Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Jiang, Jinghua; Yang, Deng-Ke

    2017-01-01

    Chirality is of great importance in the living world. It helps differentiate biochemical reactions such as those that take place during digestion. It may also help differentiate physical processes such as diffusion. Aiming to study the latter effect, we investigate the diffusion of guest chiral molecules in chiral nematic (cholesteric) liquid-crystal hosts. We discover that the diffusion dramatically depends on the handedness of the guest and host molecules and the chiral differentiation is greatly enhanced by the proper alignment of the liquid-crystal host. The diffusion of a guest chiral molecule in a chiral host with the same handedness is much faster than in a chiral host with opposite handedness. We also observe that the differentiation of chirality depends on the diffusion direction with respect to the twisting direction (helical axis). These results might be important in understanding effects of chirality on physical processes that take place in biological organisms. In addition, this effect could be utilized for enantiomer separation.

  5. Ordering Quantum Dot Clusters via Nematic Liquid Crystal Defects

    NASA Astrophysics Data System (ADS)

    Rodarte, Andrea; Pandolfi, R.; Hirst, L. S.; Ghosh, S.

    2012-11-01

    Nematic liquid crystal (LC) materials can be used to create ordered clusters of CdSe/ZnS core/shell quantum dots (QDs) from a homogeneous isotropic dispersion. At the phase transition, the ordered domains of nematic LC expel the majority of dispersed QDs into the isotropic domains. The final LC phase produces a series of QD clusters that are situated at the defect points of the liquid crystal texture. Lower concentrations of QDs are organized in a network throughout the LC matrix that originates from the LC phase transition. Inside the QD clusters the inter-particle distance enables efficient energy transfer from high energy dots to lower energy dots. Because the QD clusters form at defect sites, the location of the clusters can be preselected by seeding the LC cell with defect nucleation points.

  6. Myelin structures formed by thermotropic smectic liquid crystals.

    PubMed

    Peddireddy, Karthik; Kumar, Pramoda; Thutupalli, Shashi; Herminghaus, Stephan; Bahr, Christian

    2013-12-17

    We report on transient structures, formed by thermotropic smectic-A liquid crystals, resembling the myelin figures of lyotropic lamellar liquid crystals. The thermotropic myelin structures form during the solubilization of a smectic-A droplet in an aqueous phase containing a cationic surfactant at concentrations above the critical micelle concentration. Similar to the lyotropic myelin figures, the thermotropic myelins appear in an optical microscope as flexible tubelike structures growing at the smectic/aqueous interface. Polarizing microscopy and confocal fluorescence microscopy show that the smectic layers are parallel to the tube surface and form a cylindrically bent arrangement around a central line defect in the tube. We study the growth behavior of this new type of myelins and discuss similarities to and differences from the classical lyotropic myelin figures.

  7. Orientational order parameter measurements of discotic liquid crystal

    SciTech Connect

    Kaur, Supreet; Raina, K. K.; Kumar, S.; Pratibha, R.

    2014-04-24

    The IR dichroism technique is a convenient method which can be used to measure the molecular order parameter corresponding to the IR bands exclusively present in the disc –like molecules in discotic liquid crystal (DLC). To measure orientational order parameter, homeotropic alignment of discotic liquid crystal was attained by slow cooling of sample from isotropic phase on untreated flat CaF{sub 2} substrate. The homeotropic alignment thus achieved was found to be thermodynamically stable in the discotic mesophase. IR spectra were recorded at different temperatures for the DLC. The order parameter was calculated by comparing the spectra of discotic phase with that of the isotropic phase. Order parameter has been presented as function of temperature for different significant IR bands present in the DLC.

  8. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    SciTech Connect

    Middha, Manju Kumar, Rishi Raina, K. K.

    2014-04-24

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence.

  9. An optoelectronic connectionist machine utilizing liquid crystal spatial light modulators

    SciTech Connect

    Bigner, J.; Zhang, L.; Cotter, L.K.; Johnson, K.M.

    1988-09-01

    The significant feature of neural-like networks is their highly interconnected architectures. In principle, optical implementations of these networks have an advantage over electronics because they can exploit a third dimension for interconnecting processing elements. Experimental demonstrations of optical neurocomputers include those using planar and volume and spatial light modulators. The former has the advantage of implementing large sized networks, but with much less control over the value of individual connection weights as compared to spatial light modulator based systems. In this paper the authors present experimental results on a liquid crystal spatial light modulator (SLM) based neural-like netowrk. This optoelectronic network, as shown schematically in figure 1, uses liquid crystal SLM's for the input and connection weight matricies. The system is interfaced with a computer to provide electronic feedback and control of the individual weights.

  10. Thermodynamic properties of a liquid crystal carbosilane dendrimer

    NASA Astrophysics Data System (ADS)

    Samosudova, Ya. S.; Markin, A. V.; Smirnova, N. N.; Ogurtsov, T. G.; Boiko, N. I.; Shibaev, V. P.

    2016-11-01

    The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6-370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C p ° ( T), H°( T) - H°(0), S°( T) - S°(0), and G°( T) - H°(0) are calculated from the obtained experimental data for the region of T → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at T = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.

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

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.; Marshall, Keneth L.

    2002-01-01

    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

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

    PubMed

    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.

  13. Skin friction measurement with partially exposed polymer dispersed liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Partially exposed polymer dispersed liquid crystal thin film (10-25 microns) deposited on a flat glass substrate has been used for the first time to measure skin friction. Utilizing the shear-stress-induced director reorientation in the partially exposed liquid-crystal droplets, optical transmission under crossed polarization has been measured as a function of the air flow differential pressure. Direct measurement of the skin friction with a skin friction drag balance, under the same aerodynamic conditions, lets us correlate the skin friction with optical transmission. This provides a unique technique for the direct measurement of skin friction from the transmitted light intensity. The results are in excellent agreement with the model suggested in this paper.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Liquid crystals for unsteady surface shear stress visualization

    SciTech Connect

    Reda, D.C.

    1988-01-01

    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 10/sup 6/. Angle-of-attack forcing functions were sine waves of amplitude +- 10/degree/ about each of three mean angles of attack: 0/degree/, 10/degree/, and 20/degree/. 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. 11 refs.

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

    PubMed Central

    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

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

    SciTech Connect

    Baglama, J.; Farrell, P.A.; Reichel, L.; Ruttan, A.; Calvetti, D.

    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.

  18. Temperature and Depth Dependence of Order in Liquid Crystal Interfaces

    SciTech Connect

    Martinez-Miranda,L.; Hu, Y.

    2006-01-01

    We have studied the depth dependence and temperature behavior of the ordering of smectic-A films close to the smectic A-nematic transition, deposited on grated glass. X-ray grazing incidence geometry in reflection mode through the glass substrate was used to characterize the samples. Our results indicate the presence of a structure similar to the helical twist grain boundary phase. The structure has two maxima, one close to the glass-liquid crystal interface and another about 8 {mu}m above the surface. The structure at 8 {mu}m is the one that dominates at higher temperatures. In addition, we find that order is preserved to temperatures close to the nematic-isotropic transition temperature for the deeper gratings. We find also a dependence of the orientation of the structure with the depth of the grating and the elastic constant of the liquid crystal.

  19. Fluorinated Azobenzenes for Shape-Persistent Liquid Crystal Polymer Networks.

    PubMed

    Iamsaard, Supitchaya; Anger, Emmanuel; Aßhoff, Sarah Jane; Depauw, Alexis; Fletcher, Stephen P; Katsonis, Nathalie

    2016-08-16

    Liquid crystal polymer networks respond with an anisotropic deformation to a range of external stimuli. When doped with molecular photoswitches, these materials undergo complex shape modifications under illumination. As the deformations are reversed when irradiation stops, applications where the activated shape is required to have thermal stability have been precluded. Previous attempts to incorporate molecular switches into thermally stable photoisomers were unsuccessful at photogenerating macroscopic shapes that are retained over time. Herein, we show that to preserve photoactivated molecular deformation on the macroscopic scale, it is important not only to engineer the thermal stability of the photoswitch but also to adjust the cross-linking density in the polymer network and to optimize the molecular orientations in the material. Our strategy resulted in materials containing fluorinated azobenzenes that retain their photochemical shape for more than eight days, which constitutes the first demonstration of long-lived photomechanical deformation in liquid-crystal polymer networks.

  20. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    NASA Astrophysics Data System (ADS)

    Middha, Manju; Kumar, Rishi; Raina, K. K.

    2014-04-01

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence.

  1. Intrinsic response of polymer liquid crystals in photochemical phase transition

    SciTech Connect

    Ikeda, Tomiki; Sasaki, Takeo; Kim, Haengboo )

    1991-01-24

    Time-resolved measurements were performed on the photochemically induced isothermal phase transition of polymer liquid crystals (PLC) with mesogenic side chains of phenyl benzoate (PAPB3) and cyanobiphenyl (PACB3) under conditions wherein the photochemical reaction of the doped photoresponsive molecule (4-butyl-4-{prime}-methoxyazobenzene, BMAB) was completed within {approximately} 10 ns, and the subsequent phase transition of the matrix PLC from nematic (N) to isotropic (I) state was followed by time-resolved measurements of the birefringence of the system. Formation of a sufficient amount of the cis isomer of BMAB with a single pulse of a laser lowered the N-I phase transition temperature of the mixture, inducing the N-I phase transition of PLCs isothermally in a time range of {approximately} 200 ms. This time range is comparable to that of low molecular weight liquid crystals, indicating that suppression in mobility of mesogens in PLCs does not affect significantly the thermodynamically controlled process.

  2. Finding exact spatial soliton profiles in nematic liquid crystals.

    PubMed

    Beeckman, J; Neyts, K; Vanbrabant, P J M; James, R; Fernandez, F A

    2010-02-15

    Finding exact analytical soliton profile solutions is only possible for certain types of non-linear media. In most cases one must resort to numerical techniques to find the soliton profile. In this work we present numerical calculations of spatial soliton profiles in nematic liquid crystals. The nonlinearity is governed by the optical-field-induced liquid crystal director reorientation, which is described by a system of coupled nonlinear partial differential equations. The soliton profile is found using an iterative scheme whereby the induced waveguide and mode profiles are calculated alternatively until convergence is achieved. In this way it is also possible to find higher order solitons. The results in this work can be used to accurately design all-optical interconnections with soliton beams.

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

    DOE PAGES

    Shuai, M.; Klittnick, A.; Shen, Y.; ...

    2016-01-28

    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. We find Its zero-field magnetization produces distinctive magnetic self-interaction effects, includingmore » 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.« less

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

    SciTech Connect

    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.

    2016-01-28

    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. We find 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.

  5. Effects of electrohydrodynamic instability in smectic C liquid crystals

    NASA Astrophysics Data System (ADS)

    Denisova, O. A.; Chuvyrov, A. N.

    2013-03-01

    The effects of electrohydrodynamic instability (EHDI) in smectic C liquid crystals in an electric field are studied. The objects of study are oriented layers of para-hydroxybenzoic acid possessing a smectic phase. The observed effects are divided into three groups according to the character of the motion of molecular centers of mass and the orientation of the director and the smectic C liquid crystal layers. The instabilities of the azimuthal and Kapustin-Williams domains are experimentally found. The experimental cell consists of two glass plates with tin dioxide electrodes separated by Mylar spacers of a specified thickness. Various schemes of domain rotation are considered. The EHDI is found to depend on the layer geometry.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Liquid crystal alignment on ZnO nanostructure films

    NASA Astrophysics Data System (ADS)

    Chung, Yueh-Feng; Chen, Mu-Zhe; Yang, Sheng-Hsiung; Jeng, Shie-Chang

    2016-03-01

    The study of liquid crystal (LC) alignment is important for fundamental researches and industrial applications. The tunable pretilt angles of liquid crystal (LC) molecules aligned on the inorganic zinc oxide (ZnO) nanostructure films with controllable surface wettability are demonstrated in this work. The ZnO nanostructure films are deposited on the ITO- glass substrates by the two-steps hydrothermal process, and their wettability can be modified by annealing. Our experimental results show that the pretilt angles of LCs on ZnO nanostructure films can be successfully adjusted over a wide range from ~90° to ~0° as the surface energy on the ZnO nanostructure films changes from ~30 to ~70 mJ/m. Finally we have applied this technique to fabricate a no-bias optically-compensated bend (OCB) LCD with ZnO nanostructure films annealed at 235 °C.

  8. The Study of Hypersonic Heat Transfer by Liquid Crystals Thermography

    NASA Astrophysics Data System (ADS)

    Kovrizhina, V. N.; Kharitonov, A. M.; Petrov, A. P.; Schpack, S. I.; Zharkova, G. M.; Zvegintsev, V. I.

    2009-01-01

    The results of experimental application of the Liquid Crystal Thermography in short-duration facility AT-303 of ITAM Novosibirsk (Russia) are presented. Experiments were carried out at free stream Mach number M∞ ≍ 10.9, unit Reynolds number Re1≍2.9*106M-1, run duration 350 MC and temperature factor Tw/To ≍ 0.2 on a semi-spherically blunted cone. Polymer dispersed liquid crystals (PDLC), developed at ITAM, have been used as thermosensitive coating. Transient technique and color pattern video acquisition was realized at different framing rates. It was obtained that high temperature sensitivity of PDLC allows visualize the fine features of the temperature field on the model surface. The heat flux in comparison with semi- empirical estimation are presented and discussed too.

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

    SciTech Connect

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

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Modeling texture transitions in cholesteric liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Selinger, Robin; Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Konya, Andrew

    2012-02-01

    Cholesteric liquid crystals can be switched reversibly between planar and focal-conic textures, a property enabling their application in bistable displays, liquid crystal writing tablets, e-books, and color switching ``e-skins.'' To explore voltage-pulse induced switching in cholesteric droplets, we perform simulation studies of director dynamics in three dimensions. Electrostatics calculations are solved at each time step using an iterative relaxation method. We demonstrate that as expected, a low amplitude pulse drives the transition from planar to focal conic, while a high amplitude pulse drives the transition from focal conic back to the planar state. We use the model to explore the effects of droplet shape, aspect ratio, and anchoring conditions, with the goal of minimizing both response time and energy consumption.

  13. Substrate induced gliding for a nematic liquid crystal layer

    NASA Astrophysics Data System (ADS)

    Mema, Ensela; Cummings, Linda; Kondic, Lou

    2015-03-01

    The interaction between nematic liquid crystals (NLC) and polymer substrates is of current industrial interest, due to a desire to manufacture a new generation of flexible Liquid Crystal Displays (LCDs) for use in portable electronic devices. Polymer substrates present challenges because they can interact with the NLC, exhibiting a phenomenon known as gliding: the preferred orientation of the NLC molecules at the interface changes over timescales of minutes to hours. We present two models for gliding, inspired by the physics and chemistry of the interaction between the NLC and polymer substrate. These models, though simple, lead to non-trivial results, including loss of bistability, a finding that may have implications for display devices. Supported by NSF Grant No. DMS-1211713.

  14. Dynamic arrest of nematic liquid-crystal colloid networks

    NASA Astrophysics Data System (ADS)

    Zou, Lu; Hwang, Jeoung-Yeon; Kim, Chanjoong

    2013-10-01

    We report interesting self-assembly structures of nematic liquid-crystal colloid (NLCC) networks, which are arrested during cooling from the isotropic temperature to room temperature. The NLCC is composed of sterically stabilized colloidal particles and a nematic liquid crystal (NLC) with nematic-isotropic transition temperature (TNI) that is much higher than those of previously studied 4-Cyano-4'-pentylbiphenyl and N-(4-Methoxybenzylidene)-4-butylaniline. We find that the structure of NLCCs depends on TNI, cooling rates, and boundary conditions, varying from cellular network to hierarchical fern structures in different length scales. Our time-lapse study shows that the transition from the cellular network to the fern structure directly corresponds to the transition from a spinodal demixing to a nucleation-and-growth mechanism.

  15. Polarizer-free imaging of liquid crystal lens.

    PubMed

    Bao, Rui; Cui, Chunhui; Yu, Shuda; Mai, Huafu; Gong, Xiaoda; Ye, Mao

    2014-08-11

    An image processing method is proposed to realize polarizer-free imaging of liquid crystal lens. Images I(l) and I(nl) are captured sequentially in the lens and non-lens states of the LC lens, respectively, and are used to generate a final high contrast image. The proposal is tested by experiments. Clear and well focused images are obtained, even though no polarizer is employed in the imaging system.

  16. Liquid-Crystal Light Valve Enhances Edges In Images

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Liu, Hua-Kuang

    1991-01-01

    Experiments show liquid-crystal light valve (LCLV) exhibits operating mode in which it enhances edges in images projected on it. Operates in edge-enhancing mode (or in combination of edge-enhancing and normal modes) by suitably adjusting bias voltage and frequency. Enhancement of edges one of most important preprocessing steps in optical pattern-recognition systems. Incorporated into image-processing system to enhance edges without introducing excessive optical noise.

  17. Imaging Spectrometer With Liquid-Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

    Chrien, Thomas G.

    1996-01-01

    Imaging spectrometer constructed from charged-coupled-device video camera; liquid-crystal tunable filter (LCTF) placed in front of camera lens; and associated digital and analog control, signal-processing, and data-processing circuits. To enable operation of instrument in specific application for which designed (balloon flights in cold weather), camera and LCTF surrounded by electric heating pad. Total operating power, excluding that consumed by heating pad, 16 W. Instrument weighs 4.5 kg.

  18. Localized soft elasticity in liquid crystal elastomers (POSTPRINT)

    DTIC Science & Technology

    2016-02-23

    elastomers. J. Phys. II 1, 1253–1261 (1991). 15. Liu, D. & Broer, D. J. Liquid crystal polymer networks: preparation, properties, and applications of films...continued on page 2) 5d. PROJECT NUMBER 4348 5e. TASK NUMBER 0026 5f. WORK UNIT NUMBER X0V5 7. PERFORMING ORGANIZATION NAME(S...AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 1) AFRL/RX Wright-Patterson AFB, OH 45433 2) University of Texas at Dallas

  19. Density of States Simulations of Proteins, Liquid Crystals, and DNA

    NASA Astrophysics Data System (ADS)

    Knotts, Thomas A.; Rathore, Nitin; Kim, Evelina B.; de Pablo, Juan J.

    2003-11-01

    Three variations of the Wang-Landau density of states (WLDOS) scheme are presented: 1) combining WLDOS with parallel tempering, 2) obtaining the density of states from the configurational temperature, and 3) performing DOS simulations in an expanded ensemble. Results for the folding of small peptides (methods 1 and 2), the behavior of liquid crystals around colloidal particles (method 3), and the hybridization of DNA base pairs (method 3) are presented.

  20. Development of Ferroelectric Liquid Crystals with Enhanced Nonlinear Optical Properties.

    DTIC Science & Technology

    1994-04-24

    cyclic cores known to produce the smectic C* phase are benzene, cyclohexane, pyridine , and pyrimidine. The tails could be n -alkyl chains containing...one or more chiral centers. Locally, the molecules self-organize into smetic liquid crystal layers with the director n tilted with respect to the...manifested through a spontaneous polarization P. defined by: P = (z x n )P. The spontaneous polarization magnitude is a function of the chiral center in

  1. Novel Liquid Crystals - Polymers and Monomers - As Nonlinear Optical Materials

    DTIC Science & Technology

    1987-12-31

    and pyridine N - oxides . Results of collaborative efforts in further characterization (electrooptic, dielectric, Langmuir-Blodgett films) are described...Polymalonate Liquid Crystals for Nonlinear Optics", A. C. Griffin, A. M. Bhatti and R. S. L. Hung, Mol Cryst LiS Cryst, 155, 129 (1988). " Pyridine N - oxides ... pyridine N - oxide based side chain polymers having a push-pull pi electronic structure, (d) generation of a series of copolymers involving both an nlo

  2. Polychromatic Optical Vortex Generation from Patterned Cholesteric Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Kobashi, Junji; Yoshida, Hiroyuki; Ozaki, Masanori

    2016-06-01

    Generation of optical vortices is described in cholesteric liquid crystals with a singular point in the spatial distribution of a helix phase. The phenomenon uses the fact that a Bragg reflected light phase varies in proportion to the spatial phase of the helix, both at normal and oblique incidences. Our proposal enables high-efficiency, polychromatic generation of optical vortices without the need of a cumbersome fabrication process and fine-tuning.

  3. Low-Absorption Liquid Crystals for Infrared Beam Steering

    DTIC Science & Technology

    2015-09-30

    am2 and JE:=521.37meV. Thus, such large viscosity results in slow response time, which is not preferred in the beam steering applications ...liquid crystals for infrared laser beam steering applications . To suppress the optical loss in MW1R and LW1R, we have investigated following...pi phase change at MW1R and response time less than 4ms. To extend the potential applications into LWIR, we synthesized several chlorinated teiphenyl

  4. Mechanically tunable microlasers based on highly viscous chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Shibaev, Petr V.; Crooker, Benjamin; Manevich, Michael; Hanelt, Eckhard

    2011-12-01

    Chiral composition is designed for highly viscous lasing microemitters. The composition forms cholesteric liquid crystal and after doping with pyrromethene 597 was used as an active lasing media in stretchable aluminized silicone cavities. Optical pumping of the system led to lasing at the wavelengths defined by a degree of cavity deformation. Lasing thresholds were lower in aluminized cavity than in transparent cavity. A simple model allowing to predict the shift of lasing wavelength as a function of deformation is developed.

  5. Principles of thermal design with nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Fumeron, S.; Pereira, E.; Moraes, F.

    2014-02-01

    Highly engineered materials are arousing great interest because of their ability to manipulate heat, as described by the coordinate transformation approach. Based on recently developed analog gravity models, we present how a simple device based on nematic liquid crystals can achieve in principle either thermal concentration or expulsion. These outcomes are shown to stem from the topological properties of a disclination-like structure, induced in the nematic phase by anchoring conditions.

  6. Fast Response and Low Voltage Dual Frequency Liquid Crystals

    DTIC Science & Technology

    2014-02-24

    mixtures, 2) submillisecond-response and scattering-free polymer network liquid crystals for IR laser beam steering, and 3) low absorption loss nematic...favorable. 3.2.3 High birefringence DFLC using 3- ring NCS tolane compounds High n DFLC materials are equally favoured from fast response time and...and synthesized 3- ring NCS tolane compounds with a structure shown in Fig.1 (b). In the structure, lateral difluoro on the middle ring of the

  7. Mechanic and electromechanic effects in biaxially stretched liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Diaz-Calleja, Ricardo; Llovera-Segovia, Pedro; Riande, Evaristo; Quijano López, Alfredo

    2013-02-01

    The effect of combined electromechanic force fields in nematic side chain liquid crystal elastomers will be analyzed. A biaxially stretched plate in the x- and y-directions under an electric field applied in the perpendicular direction to the plate will be considered. A neo-Hookean model is chosen, which implies Gaussian behaviour. Results are obtained for both a soft and semisoft case showing the effect of the electric field on the rotation of the director and the free energy density function.

  8. Liquid crystal claddings for passive temperature stabilization of silicon photonics

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna N.; Khoo, Iam-Choon; Fainman, Yeshaiahu

    2014-10-01

    Silicon photonics allows for high density component integration on a single chip and it brings promise for low-loss, high-bandwidth data processing in modern computing systems. Owing to silicon's high positive thermo-optic coefficient, temperature fluctuations tend to degrade the device performance. This work explores passive thermal stabilization of silicon photonic devices using nematic liquid crystal (NLC) claddings, as they possess large negative thermo-optic coefficients in addition to low absorption at the telecommunication wavelengths.

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

    NASA Astrophysics Data System (ADS)

    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

  10. Trace element partitioning between ionic crystal and liquid

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Philpotts, J. A.; Yin, L.

    1978-01-01

    The partitioning of trace elements between ionic crystals and the melt has been correlated with lattice energy of the host. The solid-liquid partition coefficient has been expressed in terms of the difference in relative ionic radius of the trace element and the homogeneous and heterogeneous strain of the host lattice. Predictions based on this model appear to be in general agreement with data for alkali nitrates and for rare-earth elements in natural garnet phenocrysts.

  11. Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals.

    PubMed

    Scolari, Lara; Gauza, Sebastian; Xianyu, Haiqing; Zhai, Lei; Eskildsen, Lars; Alkeskjold, Thomas T; Wu, Shin-Tson; Bjarklev, Anders

    2009-03-02

    We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability of the device is achieved by varying the amplitude and the frequency of the applied external electric field. The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared.

  12. Liquid crystal thermometry for micro-fluidic applications

    NASA Astrophysics Data System (ADS)

    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.

  13. Quantum Dot Chain Assembly Mediated by Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Brereton, Peter; Basu, Rajratan; Finkenstadt, Daniel

    2015-03-01

    A small quantity of CdSe quantum dots (QDs) were dispersed in a nematic liquid crystal (LC) media and the QDs were found to exhibit self-assembled asymmetric structures, most likely QD-chains. In the nematic phase the ensemble LC +QD photoluminescence (PL) exhibits an anisotropic spectral line shape, as compared to the emission of QDs doped in the isotropic phase. This indicates a nematic mediated arrangement of the QDs. A simple model is proposed to explain the asymmetric behavior of the PL band as an effective chain of radiatively coupled emitters. The effect of the liquid crystals is to provide an entropic force that attracts dots to minimize the excluded volume. The dielectric reorientation dynamics immediately following the removal of an applied field appears as a one-step exponential decay for the LC and a two-step exponential decay with a slower process for the LC +QD system. The results suggest that anisotropic chain-like QD-assemblies are formed in the nematic platform. A related study has examined PL of ferroelectric LC doped with graphene QD [Kumar, Veeresh, et al., Liquid Crystals (2014)

  14. Nanoconfinement-induced structures in chiral liquid crystals.

    PubMed

    Melle, Michael; Theile, Madlona; Hall, Carol K; Schoen, Martin

    2013-08-28

    We employ Monte Carlo simulations in a specialized isothermal-isobaric and in the grand canonical ensemble to study structure formation in chiral liquid crystals as a function of molecular chirality. Our model potential consists of a simple Lennard-Jones potential, where the attractive contribution has been modified to represent the orientation dependence of the interaction between a pair of chiral liquid-crystal molecules. The liquid crystal is confined between a pair of planar and atomically smooth substrates onto which molecules are anchored in a hybrid fashion. Hybrid anchoring allows for the formation of helical structures in the direction perpendicular to the substrate plane without exposing the helix to spurious strains. At low chirality, we observe a cholesteric phase, which is transformed into a blue phase at higher chirality. More specifically, by studying the unit cell and the spatial arrangement of disclination lines, this blue phase can be established as blue phase II. If the distance between the confining substrates and molecular chirality are chosen properly, we see a third structure, which may be thought of as a hybrid, exhibiting mixed features of a cholesteric and a blue phase.

  15. Liquid crystal foil for the detection of breast cancer

    NASA Astrophysics Data System (ADS)

    Biernat, Michał; Trzyna, Marcin; Byszek, Agnieszka; Jaremek, Henryk

    2016-09-01

    Breast cancer is the most common malignant tumor in females around the world, representing 25.2% of all cancers in women. About 1.7 million women were diagnosed with breast cancer worldwide in 2012 with a death rate of about 522,0001,2. The most frequently used methods in breast cancer screening are imaging methods, i.e. ultrasonography and mammography. A common feature of these methods is that they inherently involve the use of expensive and advanced equipment. The development of advanced computer systems allowed for the continuation of research started already in the 1980s3 and the use of contact thermography in breast cancer screening. The physiological basis for the application of thermography in medical imaging diagnostics is the so-called dermothermal effect related to higher metabolism rate around focal neoplastic lesion. This phenomenon can occur on breast surface as localized temperature anomalies4. The device developed by Braster is composed of a detector that works on the basis of thermotropic liquid crystals, image acquisition device and a computer system for image data processing and analysis. Production of the liquid crystal detector was based on a proprietary CLCF technology (Continuous Liquid Crystal Film). In 2014 Braster started feasibility study to prove that there is a potential for artificial intelligence in early breast cancer detection using Braster's proprietary technology. The aim of this study was to develop a computer system, using a client-server architecture, to an automatic interpretation of thermographic pictures created by the Braster devices.

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

    SciTech Connect

    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.

  17. Critical Slowing of Density Fluctuations Approaching the Isotropic-Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory.

    PubMed

    Sokolowsky, Kathleen P; Bailey, Heather E; Hoffman, David J; Andersen, Hans C; Fayer, Michael D

    2016-07-21

    Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid.

  18. Structure, Hydrodynamics, and Phase Transition of Freely Suspended Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2000-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enable the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable condensed phase fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new liquid crystal physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and

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

    NASA Technical Reports Server (NTRS)

    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.

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

    PubMed

    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.