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Sample records for polymer-dispersed liquid-crystal films

  1. Formation and performance of polymer dispersed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Chan, Philip Kwok-Kiou

    Polymer dispersed liquid crystals (PDLC's) are novel composite materials consisting of micron-size liquid crystalline droplets dispersed uniformly in a solid polymer matrix. PDLC's are formed by spinodal decomposition induced by thermal quenching or polymerization. These materials have excellent magneto-optical properties, and have great potential in applications that require efficient light scattering. Present commercial applications include switchable windows for privacy control and large-scale billboards. The optical properties depend on the droplet size, shape and positional order, which are determined during the formation stage, and reorientation dynamics of the liquid crystalline molecules confined within the droplets which occurs during product use. In this thesis, new complex mathematical models that describe the formation and performance of PDLC's are successfully developed, implemented, solved and validated. The nonequilibrium thermodynamic formation model takes into account initial thermal fluctuations computed using Monte Carlo simulations and realistic arbitrary boundary conditions. The performance model is based on classical nematic liquid crystalline magneto-viscoelastic theories, and incorporates transient viscoelastic boundary conditions. The simulations are able to reproduce successfully all the experimentally observed significant dynamical and morphological features of film formation as well as all the dynamical stages observed during the use of these thin optical films. In addition, the sensitivity of the phase separating morphology to processing conditions and material parameters is elucidated. Furthermore, a new scaling method is introduced to describe the phase separation phenomena during the early and intermediate stages of spinodal decomposition induced by thermal quenching. The droplet size selection mechanism for the polymerization-induced phase separation method of forming PDLC films is identified and explained for the first time. Lastly

  2. Selective scattering polymer dispersed liquid crystal film for light enhancement of organic light emitting diode.

    PubMed

    Jiang, Jinghua; McGraw, Greg; Ma, Ruiqing; Brown, Julie; Yang, Deng-Ke

    2017-02-20

    We developed a novel light enhancing film for an organic light emitting diode (OLED) based on polymer dispersed liquid crystal (PDLC). In the film, the liquid crystal droplets are unidirectionally aligned along the film normal direction and exhibit selective scattering. The film scatters light emitted only in directions with large incident angles but not light emitted in directions with small incident angles. When the light is scattered, it changes propagation direction and exits the OLED. The PDLC film reduces the total internal reflection and thus can significantly increase the light efficiency of the OLED.

  3. Random lasing in dye-doped polymer dispersed liquid crystal film

    NASA Astrophysics Data System (ADS)

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

    2016-09-01

    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  4. Small-angle light scattering from polymer-dispersed liquid-crystal films

    SciTech Connect

    Loiko, V. A. Maschke, U.; Zyryanov, V. Ya.; Konkolovich, A. V.; Misckevich, A. A.

    2008-10-15

    A method is developed for modeling and computing the angular distribution of light scattered forward from a single-layer polymer-dispersed liquid-crystal (PDLC) film. The method is based on effective-medium approximation, anomalous diffraction approximation, and far-field single-scattering approximation. The angular distribution of forward-scattered light is analyzed for PDLC films with droplet size larger than the optical wavelength. The method can be used to study field-and temperature-induced phase transitions in LC droplets with cylindrical symmetry by measuring polarized scattered light intensity.

  5. Refractive indices of polymer-dispersed liquid-crystal film materials: Epoxy-based systems

    NASA Astrophysics Data System (ADS)

    Vaz, Nuno A.; Montgomery, G. Paul, Jr.

    1987-10-01

    Polymer-dispersed liquid crystal (PDLC) films are potentially useful in applications requiring electrically controllable light transmission. In these applications, both a high on-state transmittance and a strong off-state attenuation are often needed over a wide operating temperature range. These transmittance characteristics depend strongly on the refractive indices of the materials in the PDLC films. We have measured the temperature dependent refractive indices of typical PDLC film materials and the temperature dependent electro-optic transmittance of a PDLC film composed of liquid crystal microdroplets dispersed in an epoxy matrix. We show that our refractive index measurements can account for all the features in the measured transmittance characteristics and discuss several methods for controlling refractive indices to optimize electro-optic transmittance over an extended temperature range. We have also measured the room temperature refractive indices of mixtures of epoxy resins and hardeners as a function of composition. We discuss the problems associated with predicting the refractive indices of such mixtures in terms of either the volume fractions or mole fractions of the mixture components. These considerations are important in matching refractive indices of droplets and matrix materials to maximize on-state transmittance. The refractive indices of epoxy matrix materials increase monotonically with time during their chemical cure. The measured time dependence can be described by a simple model in which the concentrations of the reacting resin and hardener each decay exponentially in time with their own characteristic time constants while the concentration of the cured polymer increases. Finally, we relate the measured rates of index change with temperature to the coefficients of volume expansion of PDLC film materials; the results are used to discuss the mechanical stability of PDLC films.

  6. 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.

  7. Polarization-independent holographic gratings based on azo-dye-doped polymer-dispersed liquid-crystal films.

    PubMed

    Fuh, Andy Ying-Guey; Chen, Che-Chang; Cheng, Ko-Ting; Liu, Cheng-Kai; Chen, Wei-Ko

    2010-01-10

    We demonstrate polarization-independent holographic gratings (PIHGs) based on azo-dye-doped polymer-dispersed liquid crystal films. The PIHGs are recorded by irradiation under an intensity-modulated interference field, generated by two linearly polarized green optical beams, and by simultaneously applying a suitable AC voltage to the sample. The photoexcited azo dyes are adsorbed onto the UV-cured polymer film with their long axes parallel to the normal of the substrate. When the applied voltage is switched off, the PIHGs are generated with periodic modulation of liquid-crystal structures with transparently homeotropic and randomly scattered alignments. Additionally, the generated PIHGs can be completely switched off by an applied voltage.

  8. Sensor for monitoring the vibration of a laser beam based on holographic polymer dispersed liquid crystal films.

    PubMed

    Li, Ming Shian; Wu, Shing Trong; Fuh, Andy Ying-Guey

    2010-12-06

    A continuous multiple exposure diffraction grating (CMEDG) is fabricated holographically on polymer dispersed liquid crystal (PDLC) films using two-beam interference with multiple exposures. The grating is fabricated by exposing a PDLC film to 18 repeated exposure/non-exposure cycles with an angular step of ~10°/10° while it revolves a circle on a rotation stage. The structure of the sample thus formed is analyzed using a scanning electron microscope (SEM) and shows arc-ripples around the center. From the diffraction patterns of the formed grating obtained using a normally incident laser beam, some or all of the 18 recorded arc beams can be reconstructed, as determined by the probing location. Thus, it can be applied for use as a beam-vibration sensor for a laser.

  9. Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Gao, Hong-Yue; Liu, Pan; Zeng, Chao; Yao, Qiu-Xiang; Zheng, Zhiqiang; Liu, Jicheng; Zheng, Huadong; Yu, Ying-Jie; Zeng, Zhen-Xiang; Sun, Tao

    2016-09-01

    We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474194, 11004037, and 61101176) and the Natural Science Foundation of Shanghai, China (Grant No. 14ZR1415500).

  10. Preparation of a Thermally Light-Transmittance-Controllable Film from a Coexistent System of Polymer-Dispersed and Polymer-Stabilized Liquid Crystals.

    PubMed

    Guo, Shu-Meng; Liang, Xiao; Zhang, Cui-Hong; Chen, Mei; Shen, Chen; Zhang, Lan-Ying; Yuan, Xiao; He, Bao-Feng; Yang, Huai

    2017-01-25

    Polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC) systems are the two primary distinct systems in the field of liquid crystal (LC) technology, and they are differentiated by their unique microstructures. Here, we present a novel coexistent system of polymer-dispersed and polymer-stabilized liquid crystals (PD&SLCs), which forms a homeotropically aligned polymer network (HAPN) within the LC droplets after a microphase separation between the LC and polymer matrix and combines the advantages of both the PDLC and PSLC systems. Then, we prepare a novel thermally light-transmittance-controllable (TLTC) film from the PD&SLC system, where the transmittance can be reversibly changed through thermal control from a transparent to a light-scattering state. The film also combines the advantageous features of flexibility and a potential for large-scale manufacturing, and it shows significant promise in future applications from smart windows to temperature sensors.

  11. NIR-Vis-UV Light-Responsive Actuator Films of Polymer-Dispersed Liquid Crystal/Graphene Oxide Nanocomposites.

    PubMed

    Cheng, Zhangxiang; Wang, Tianjie; Li, Xiao; Zhang, Yihe; Yu, Haifeng

    2015-12-16

    To take full advantage of sunlight for photomechanical materials, NIR-vis-UV light-responsive actuator films of polymer-dispersed liquid crystal (PDLC)/graphene oxide (GO) nanocomposites were fabricated. The strategy is based on phase transition of LCs from nematic to isotropic phase induced by combination of photochemical and photothermal processes in the PDLC/GO nanocomposites. Upon mechanical stretching of the film, both topological shape change and mesogenic alignment occurred in the separated LC domains, enabling the film to respond to NIR-vis-UV light. The homodispersed GO flakes act as photoabsorbent and nanoscale heat source to transfer NIR or VIS light into thermal energy, heating the film and photothermally inducing phase transition of LC microdomains. By utilizing photochemical phase transition of LCs upon UV-light irradiation, one azobenzene dye was incorporated into the LC domains, endowing the nanocomposite films with UV-responsive property. Moreover, the light-responsive behaviors can be well-controlled by adjusting the elongation ratio upon mechanical treatment. The NIR-vis-UV light-responsive PDLC/GO nanocomposite films exhibit excellent properties of easy fabrication, low-cost, and good film-forming and mechanical features, promising their numerous applications in the field of soft actuators and optomechanical systems driven directly by sunlight.

  12. 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.

  13. Dynamical studies of gratings formed in polymer-dispersed liquid crystal films doped with a guest-host dye

    PubMed

    Fuh; Tsai; Lee; Fan

    2000-09-01

    This study investigated the dynamic behavior of the first-order diffraction efficiency of gratings formed in polymer-dispersed liquid crystal (PDLC) films doped with a guest-host dye. PDLC films were fabricated using various LC-polymer mixing ratios, and written with various powers. Experimental results indicated that several peaks appeared in the curve of the first-order diffraction efficiency versus time. According to the light scattering study, we believe that the first peak was due to the superposition of density and absorption gratings. The density grating was associated with the spatially varied molecular weight of polymer molecules across the sample, and the absorption grating resulted from the spatially varied density of free electrons. The other peaks were caused by the superposition of the absorption and phase gratings. The phase grating was generated by the formation of a periodic structure of polymer-rich and LC-rich regions in the sample. This study also proposes a model to explain these experimental results. Moreover, the theory derived from this model correlates well with the experimental results, allowing us to determine the amplitude of the final grating.

  14. 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

  15. Electro-optical behavior of polymer dispersed blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Kemiklioglu, E.; Chien, L.-C.

    2015-03-01

    We have investigated a new form of polymer dispersed liquid crystals (PDLC) electro-optical films comprised of blue phase liquid crystal and polymer prepared by the solvent evaporation method. In this method, polymer dispersed blue phase (PDBP) films, which were laminated between two indium-tin-oxidecoated conductive substrates, demonstrated two switching modes between light scattering and transparent states in response to an applied electric field across the film. The electro-optical properties of PDBP liquid crystals can be altered by changing the concentrations of liquid crystal and polymer. The compositions, film preparations, physical and morphological behaviors, and electro-optical properties of PDBP films are described.

  16. 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.

  17. Physical studies of holographically-formed polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Bowley, Christopher Chadwick

    2000-12-01

    Switchable gratings formed holographically in polymer dispersed liquid crystals are new soft-matter composite materials that show potential for numerous electro-optic device applications. Still in their infancy, the fundamental understanding of the factors dictating the electro-optic performance of these materials remains limited, and the challenges facing this technology are significant. Here, a detailed description of the formation, characterization, and evaluation of holographically- formed polymer dispersed liquid crystals (H-PDLCs) is given. Characterization methods used include visible reflection spectroscopy, electro-optic measurements, polarizing optical microscopy and scanning electron microscopy. All-optical methods are used to study the in situ holographic formation of gratings. Significant materials-based advances are reported. Drive- voltage improvements, through surfactant doping, are discussed. Also, increases in grating diffraction efficiency through the use of oligomer blends are observed. A phenomenological diffusion model and morphological studies suggest this is the result of a spatial composition modulation in the resulting polymer matrix. This discovery has important implications for future ``tailored'' H-PDLC materials sets. New techniques enhancing the optical properties of H- PDLCs are presented. Multiplexing methods allow the formation of multiple gratings in a single film. Emulsion prepolymers yielding `dual-domain' H-PDLCs are also discussed. An overview of potential H-PDLC applications, particularly as reflective flat panel displays, is presented. The performance issues and challenges associated with each application are discussed. Finally, new passive and opto-mechanical H-PDLC applications are mentioned, and directions for future work suggested.

  18. Broadband Wavelength Spanning Holographic Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Rai, Kashma; Shriyan, Sameet; Fontecchio, Adam

    2008-03-01

    Broadened interaction wavelength of holographic polymer dispersed liquid crystals (HPDLCs) have extensive applications in beam steering for instrument clusters, hyperspectral imaging, wavelength filtering and construction of lightweight optics. A novel simultaneous time and spatial multiplexing formation configuration is proposed here, to increase narrow wavelength reflecting notch to broad range wavelength spanning device. HPDLC films have electro-optic controllability by applying field. No moving parts, light weight, small footprint compared to prisms and lenses, high color purity make the broadband wavelength HPDLCs desirable for the above applications. Varying the incident laser beam exposure angles using motorized rotating stage, during formation is the key step here for their formation in a single medium. The fabricated broadband wavelength sensitive HPDLCs are characterized for the uniformity of the reflected peak and electro optic response. Their output wavefront is analyzed using wavefront analysis technique.

  19. Ultrasound visualization using polymer dispersed liquid crystal sensors

    NASA Astrophysics Data System (ADS)

    Edwards, R. S.; Trushkevych, O.; Eriksson, T. J. R.; Ramadas, S. N.; Dixon, S.

    2017-02-01

    The acousto-optic effect in liquid crystals (LCs) has previously been exploited to build large area acoustic sensors for visualising ultrasound fields, opening up the field of acoustography. There is an opportunity to simplify this technique and open new application areas by employing polymer dispersed LC (PDLC) thin films instead of aligned LC layers. In PDLCs, the normally opaque film becomes transparent under the influence of an acoustic field (e.g. when surface acoustic waves are propagating in the material under the film). This is called acoustic clearing and is visible by eye. There is potential for producing ultrasonic sensors which can be `painted on' to a component, giving direct visualisation of the ultrasonic field without requiring scanning. We demonstrate the effect by using PDLC films to characterise a resonant mode of a flexural air-coupled transducer. Visualisation was quick, with a switching time of a few seconds. The effect shows promise for ultrasound sensing applications for transducer characterisation and NDE.

  20. Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

  1. Surface relief gratings on polymer dispersed liquid crystals by polarization holography

    SciTech Connect

    Mazzulla, A.; Pagliusi, P.; Provenzano, C.; Russo, G.; Carbone, G.; Cipparrone, G.

    2004-09-27

    We report the observation of surface relief gratings (SRGs) on polymer dispersed liquid crystal films after polarization holographic recording, demonstrating the formation of SRGs in systems without azo compounds, where photoisomerization and chromophore reorientation processes do not occur. Permanent SRGs, several hundred nanometers deep, are recorded on the surface of a polymeric material containing oriented liquid crystal droplets. The results suggest that SRG growth under uniform intensity irradiation is not exclusively related to the photoisomerization, but is a more general phenomenon which can involve different photoinduced chemical and physical mechanisms sensitive to the light polarization state. These effects contribute to the formation of anisotropic structures during the recording process.

  2. Polymer-dispersed liquid crystal devices with graphene electrodes.

    PubMed

    Chung, Seok-Hwan; Noh, Hee Yeon

    2015-12-14

    Although polymer-dispersed liquid crystal (PDLC) devices have considerable potential application in smart windows, the high material cost of the indium tin oxide (ITO) electrodes conventionally used in these devices hinders their wide usage. In this work, we explore the use of graphene electrodes as a potential substitute for ITO electrodes in PDLC devices. The fabricated PDLC devices with graphene electrodes exhibit higher contrast and faster response than PDLC devices with ITO electrodes fabricated using the same chemical formulation and polymerization process. However, they also exhibit higher operation voltage and haze, which is primarily attributed to the inherently large resistance and inhomogeneity of the large-area graphene sheets initially transferred onto the transparent substrates. PDLC devices with graphene electrodes are robust under standard operating conditions and also have the advantage of flexibility and stretchability, unlike PDLCs with ITO electrodes.

  3. Interference forming of transmission by polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  5. Switchable Solar Window Devices Based on Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Murray, Joseph; Ma, Dakang; Munday, Jeremy

    Windows are an interesting target for photovoltaics due to the potential for large area of deployment and because glass is already a ubiquitous component of solar cell devices. Many demonstrations of solar windows in recent years have used photovoltaic devices which are semitransparent in the visible region. Much research has focused on enhancing device absorption in the UV and IR ranges as a means to circumvent the basic tradeoff between efficiency and transparency to visible light. Use of switchable solar window is a less investigated alternative approach; these windows utilize the visible spectrum but can toggle between high transparency and high efficiency as needed. We present a novel switchable solar window device based on Polymer Dispersed Liquid Crystals (PDLC). By applying an electric field to the PDLC layer, the device can be switched from an opaque, light diffusing, efficient photovoltaic cell to a clear, transparent window. In the off state (i.e. scattering state), these devices have the added benefits of increased reflectivity for reduced lighting and cooling costs and haze for privacy. Further, we demonstrate that these windows have the potential for self-powering due to the very low power required to maintain the on, or high transparency, state. Support From: University of Maryland and Maryland Nano-center and its Fablab.

  6. Ultrasound sensing using the acousto-optic effect in polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Trushkevych, O.; Eriksson, T. J. R.; Ramadas, S. N.; Dixon, S.; Edwards, R. S.

    2015-08-01

    Acousto-optic effects are demonstrated in polymer dispersed liquid crystal (PDLC) films, showing promise for applications in ultrasound sensing. The PDLC films are used to image two displacement profiles of air-coupled flexural transducers' resonant modes at 295 kHz and 730 kHz. Results are confirmed using laser vibrometry. The regions on the transducers with the largest displacements are clearly imaged by the PDLC films, with the resolution agreeing well with laser vibrometry scanning. Imaging takes significantly less time than a scanning system (switching time of a few seconds, as compared to 8 h for laser vibrometry). Heating effects are carefully monitored using thermal imaging and are found not to be the main cause of PDLC clearing.

  7. Organic holographic polymer dispersed liquid crystal distributed feedback laser from different diffraction orders

    NASA Astrophysics Data System (ADS)

    Liu, Minghuan; Liu, Yonggang; Zhang, Guiyang; Peng, Zenghui; Li, Dayu; Ma, Ji; Xuan, Li

    2016-11-01

    Holographic polymer dispersed liquid crystal (HPDLC) based distributed feedback (DFB) lasers were prepared with poly (-methoxy-5-(2‧-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) film as the active medium layer. The HPDLC grating film was fabricated via holographic induced photopolymerization. The pure film spectra of MEH-PPV and the amplified spontaneous emission (ASE) spectrum were investigated. The laser device was single-longitudinal mode operation. The tunability of the HPDLC DFB laser was achieved by selecting different grating periods. The lasing performances were also characterized and compared from different diffraction orders. The lasing threshold increased with the diffraction order and the third order laser possessed the largest conversion efficiency in this device. The experimental results were in good agreement with the theoretical calculations.

  8. Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

  9. Pattern Polymerization-Induced Phase Separation in a Polymer-Dispersed Liquid Crystal System

    NASA Astrophysics Data System (ADS)

    Kyu, Thein

    2002-03-01

    Liquid crystal (LC)/polymer composite films have gained attention increasingly due to their applications in flat panel displays and shutters. Photopolymerization is a preferred method to produce LC/polymer composite films from mixtures of reactive monomers and LCs. On the basis of the combined Flory-Huggins free energy for isotropic mixing and Maier-Saupe free energy for nematic ordering along with the elastic free energy of the network, phase diagrams have been established by solving self-consistently. A theoretical simulation has been modeled by incorporating the kinetics of crosslinking reaction into the time-dependent Ginzburg-Landau (TDGL-model C) equations to elucidate the emergence of nematic domains during photopolymerization induced phase separation in electrically switchable holographic polymer-dispersed liquid crystals (H-PDLC). The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid crystal droplets alternating periodically with polymer network-rich layers. Furthermore, we recognized the potential for producing electrically tunable microlens from PDLC systems through pattern-photopolymerization-induced phase separation by means of the interference of two horizontal waves and two vertical waves. Our simulation revealed that the emerged LC microlens are of the order of a few hundred nanometers. These LC microlens are not only uniformed in size, but also form in regular arrays, reminiscence of the compound eyes found in flies, ants, and wasps. Supported by ALCOM, NSF DMR 99-03519, and OBR.

  10. 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.

  11. Impedance of Polymer-Dispersed Liquid Crystals with Carbon Nanofibers in Weak Electric Fields

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    Impedance of polymer-dispersed liquid crystals modified by carbon nanofibers is studied in fields lower than the threshold field of the director reorientation of a liquid crystal. It is shown that the real and imaginary parts of the impedance obey to the relationship (Zre - X0)2 + (Zim - Y0)2 = R 0 2 , where X0, Y0, and R0 are the fitting parameters depending on the frequency of the exciting electric field.

  12. Dynamics of polymer-dispersed cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kitzerow, H.-S.; Rand, J.; Crooker, P. P.

    1992-02-01

    We have studied the electrooptic properties of droplets of cholesteric liquid crystal dispersed in a polymer. Application of AC electric fields to the droplets leads to a conversion of the droplet from a nonreflecting to a selectively reflecting appearance. When the field is suddenly switched on, the switching times are found to decrease strongly with increasing field strength, with increasing temperature and with decreasing drop size. For the switching off process, both switching times and microscopic textures indicate that two different relaxation processes can occur, depending on the applied voltage and on the drop size. Nous avons étudié les propriétés électro-optiques des cristaux liquides cholestériques dispersés dans un matériau polymère. L'application d'un champ électrique fait apparaître une forte réflection de Bragg. La vitesse d'apparition de cette réflection augmente avec l'amplitude du champ électrique, avec la température et avec la diminution du diamètre des gouttelettes. L'interruption du champ électrique cause deux réactions très différentes, dépendant du voltage et du diamètre des gouttes.

  13. Optical reconfiguration by anisotropic diffraction in holographic polymer-dispersed liquid crystal memory.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru

    2012-07-20

    Holographic polymer dispersed liquid crystal (HPDLC) memory is fabricated by a photoinduced phase separation comprised of polymer and liquid crystal (LC) phases using laser light interference exposures. The anisotropic diffraction induced by the alignment of LC in the periodic structure of the HPDLC memory is applied to reconstruct the configuration contexts for the optically reconfigurable gate arrays. Optical reconfiguration for various circuits under parallel programmability is implemented by switching the polarization state of incident light on the HPDLC memory using a spatial light modulator.

  14. Holographically formed, acoustically switchable gratings based on polymer-dispersed liquid crystals.

    PubMed

    Liu, Yan Jun; Lu, Mengqian; Ding, Xiaoyun; Leong, Eunice S P; Lin, Sz-Chin Steven; Shi, Jinjie; Teng, Jing Hua; Wang, Lin; Bunning, Timothy J; Huang, Tony Jun

    2013-08-01

    We report holographic polymer-dispersed liquid crystal (H-PDLC) gratings driven by surface acoustic waves (SAWs). Our experiments show that upon applying SAWs, the H-PDLC grating exhibited switchable properties: The diffraction of the H-PDLC grating decreased, whereas the transmission increased. This acoustically switchable behavior is due to the acoustic streaming-induced realignment of liquid crystals as well as absorption-resulted thermal diffusion. Such SAW-driven H-PDLC gratings are potentially useful in many photonic applications, such as optical switches, spatial light modulators, and switchable add/drop filters.

  15. Electrically Tunable Distributed Feedback Laser Emission from Scaffolding Morphologic Holographic Polymer Dispersed Liquid Crystal Grating

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Diao, Zhihui; Yao, Lishuang; Cao, Zhaoliang; Liu, Yonggang; Ma, Ji; Xuan, Li

    2013-02-01

    Electrically tunable distributed feedback (DFB) laser emission from a dye-doped holographic polymer dispersed liquid crystal (HPDLC) transmission grating is demonstrated. The homogenously aligned liquid crystal (LC) in this polymer scaffolding morphologic grating enables a large refractive index (RI) change for the TM wave under applied electric field, which in turn leads to a red-shift of 8 nm in the output laser emission. The tuning behavior of the DFB laser is well explained on the basis of DFB waveguide theory and amount of phase-separated LCs.

  16. Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.

  17. Effect of dopant nanoparticles on reorientation process in polymer-dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Zobov, K. V.; Zharkova, G. M.; Syzrantsev, V. V.

    2016-01-01

    The analysis of the experimental data of the nanoscale powders application for doping polymer-dispersed liquid crystals (PDLC) was represented in this work. A model based on the separation of the liquid crystals reorientation process on the surface mode and the volume mode was proposed and tested. In the research the wide-spread model mixture PDLC were used. But alumina nanoparticles were the distinctive ones obtained by electron beam evaporation. The proposed model allowed to conclude that the nanoparticles localization at the surface of the droplets (as in the Pickering emulsion) lead to the variation of the connection force between the liquid crystals and the polymer. The effect of nanoparticles resulted in an acceleration of the reorientation process near the surface when the control field is turned on and in a deceleration when it is turned off. The effect for the different size particles was confirmed.

  18. Thermo-driven light controller by using thermal modulation of diffraction wavelength in holographic polymer dispersed liquid crystal grating

    NASA Astrophysics Data System (ADS)

    Ogiwara, Akifumi; Kakiuchida, Hiroshi

    2014-02-01

    A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated based on a photo-induced phase separation technique by laser interferometric exposure. The diffraction wavelength of HPDLC gratings formed by different LC composites and grating structures was experimentally investigated by spectroscopic measurements as a function of temperature at around 30 °C. The HPDLC gratings composed of nematic LC having low nematic to isotropic temperature (TNI) and film thickness of 25 μm showed the switch of diffraction wavelength between visible and infrared lights by the change of temperature. The optical characteristics achieved in HPDLC gratings are expected to be applicable for the basis of diffractive type of thermodriven light controller which can supply visibility constantly for solar-ray control windows.

  19. Gas flow-field induced director alignment in polymer dispersed liquid crystal microdroplets deposited on a glass substrate

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on glass substrates by the processes of polymerization and solvent evaporation induced phase separation. The electron and the optical polarization microscopies of the films reveal that PDLC microdroplets formed during the process of phase separation near the top surface of the film remain exposed and respond to shear stress due to air or gas flow on the surface. Optical response of the film to an air flow-induced shear stress input on the free surface has been measured. Director orientation in the droplets changes with the applied shear stress leading to time varying transmitted light intensity. Director dynamics of the droplet for an applied step shear stress has been discussed from free energy considerations. Results on the measurement of light transmission as a function of the gas flow parameter unambiguously demonstrate the potential of these systems for use as boundary layer and gas flow sensors.

  20. Theory and characteristics of holographic polymer dispersed liquid crystal transmission grating with scaffolding morphology.

    PubMed

    Huang, Wenbin; Liu, Yonggang; Diao, Zhihui; Yang, Chengliang; Yao, Lishuang; Ma, Ji; Xuan, Li

    2012-06-20

    We have performed a detailed characterization of the optical properties of a holographic polymer dispersed liquid crystal (LC) transmission grating with polymer scaffolding morphology, which was fabricated with conventional high-functionality acrylate monomer under low curing intensity. Temporal evolution of the grating formation was investigated, and the amount of phase-separated LC was determined by birefringence investigation. A grating model combined with anisotropic coupled-wave theory yielded good agreement with experimental data without any fitting parameter. The results in this study demonstrate the non droplet scaffolding morphology grating is characterized by a high degree of phase separation (70%), high anisotropy, low scattering loss (<6%), and high diffraction efficiency (95%).

  1. A novel approach for normalizing the photoreflectance spectrum by using polymer-dispersed liquid crystal.

    PubMed

    Liao, Y F; Chang, C C; Wang, D P; Tseng, B H; Liao, Y D; Lin, C H

    2012-10-01

    This study developed a novel type of normalization procedure for modulation reflectance spectroscopy experiments to obtain the relative change in the reflectance spectrum, ΔR/R. This technique uses a polymer-dispersed liquid crystal to ensure that the dc component of the signal from the detector remained constant by varying the intensity of the light striking the sample. This method is particularly useful for photoreflectance measurement, which may encounter background problems because of scattered pump light and/or photoluminescence. It does not require a change in the gain of the detector or the use of a variable neutral density filter mounted on a servo-motor.

  2. A novel approach for normalizing the photoreflectance spectrum by using polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Liao, Y. F.; Chang, C. C.; Wang, D. P.; Tseng, B. H.; Liao, Y. D.; Lin, C. H.

    2012-10-01

    This study developed a novel type of normalization procedure for modulation reflectance spectroscopy experiments to obtain the relative change in the reflectance spectrum, ΔR/R. This technique uses a polymer-dispersed liquid crystal to ensure that the dc component of the signal from the detector remained constant by varying the intensity of the light striking the sample. This method is particularly useful for photoreflectance measurement, which may encounter background problems because of scattered pump light and/or photoluminescence. It does not require a change in the gain of the detector or the use of a variable neutral density filter mounted on a servo-motor.

  3. Effect of liquid crystal concentration on electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses with auto-shading and auto-focusing function

    NASA Astrophysics Data System (ADS)

    Kim, Jaeyong; Han, Jeong In

    2014-05-01

    Polymer dispersed liquid crystal lenses were prepared from a mixture of prepolymer (NOA 65) and E7 liquid crystal. The mixture of polymer dispersed liquid crystal was polymerized by ultraviolet (UV) curing in the polymerization induced phase separation process. With liquid crystal concentration, electro-optical properties of polymer dispersed liquid crystal lens devices including transmittance, driving voltage, response times, contrast ratio and slope of the linear region of the transmittance-voltage were measured and optimized for smart electronic glasses. The optimum concentration for polymer dispersed liquid crystal lens was NOA 65 of 40% and E7 liquid crystal concentration of 60%. This is the first report of the use of the polymer dispersed liquid crystal lens for smart electronic glasses with auto-shading and/or auto-focusing functions.

  4. Single-mode lasing from dye-doped holographic polymer-dispersed liquid crystal transmission gratings

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Liu, Quan; Xuan, Li; Chen, Linsen

    2014-12-01

    We demonstrate single-mode laser operation in dye-doped holographic polymer-dispersed liquid crystal (HPDLC) transmission gratings. The gratings are fabricated in cells made from specifically chosen glass substrates to decrease the refractive index difference between the waveguide core layer and cladding layer. The phase separation degree of liquid crystal after holographic recording is further optimized to confine only the lowest propagation mode in the device. The mode selection mechanism is explained under the framework of the waveguide distributed feedback (DFB) theory. The wavelength of single-mode lasing can be tuned between 620 and 660 nm by varying the grating period. Our results show the HPDLC technique could provide single-mode organic DFB lasers in a tunable, simple, and large-area manner.

  5. Design and fabrication of a variable optical attenuator based on polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    She, Jun; Xu, Su; Tao, Tao; Wang, Qian

    2005-02-01

    In order to obtain a low polarization dependent loss (PDL) and a large attenuation range simultaneously, an optimal design and fabrication of a polymer-dispersed liquid crystal (PDLC) based variable optical attenuator (VOA) is presented. First, an optimal diameter of the liquid crystal droplets is determined by the anomalous diffraction approach (ADA). This optimal diameter gives maximal scattering and thus a large attenuation range is achieved with a relatively thin liquid crystal cell. Secondly, the fabrication of PDLC cell is carried out. The influence of the ultraviolet (UV) curing condition on the morphology of the LC droplets is investigated. For a given liquid crystal concentration, the optimal UV curing power is obtained after a series of statistically designed experiments. Finally, an optical configuration of the PDLC based VOA is presented. Measurements of the attenuation and the PDL are carried out with this configuration. The measured results show that the device has a typical attenuation range of 25dB. The corresponding PDL is nearly 1dB and the insertion loss is 1.8dB. The threshold voltage is 8Vrms and the saturation voltage is 40Vrms. From these measured results, one can see that the fabricated VOA based on PDLC is much more practical for optical communications as compared to the existing ones.

  6. Fabrication of Microcapsules for Dye-Doped Polymer-Dispersed Liquid Crystal-Based Smart Windows.

    PubMed

    Kim, Mingyun; Park, Kyun Joo; Seok, Seunghwan; Ok, Jong Min; Jung, Hee-Tae; Choe, Jaehoon; Kim, Do Hyun

    2015-08-19

    A dye-doped polymer-dispersed liquid crystal (PDLC) is an attractive material for application in smart windows. Smart windows using a PDLC can be operated simply and have a high contrast ratio compared to those of other devices that employed photochromic or thermochromic material. However, in conventional dye-doped PDLC methods, dye contamination can cause problems and has a limited degree of commercialization of electric smart windows. Here, we report on an approach to resolve dye-related problems by encapsulating the dye in monodispersed capsules. By encapsulation, a fabricated dye-doped PDLC had a contrast ratio of >120 at 600 nm. This fabrication method of encapsulating the dye in a core-shell structured microcapsule in a dye-doped PDLC device provides a practical platform for dye-doped PDLC-based smart windows.

  7. Electro-optical properties of low viscosity driven holographic polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Moon, K. R.; Bae, S. Y.; Kim, B. K.

    2015-04-01

    Relative diffraction efficiency (RDE), operating voltage, and response times are most important performance characteristics of holographic polymer dispersed liquid crystals (HPDLC). Two types of triallyl isocyanurate (TI) having different structures were incorporated into the conventional transmission grating of HPDLC. Premix viscosity decreased by 13-18% with up to 3% TI, beyond which it increased. TI eliminated induction period and augmented initial grating formation rate at all contents. Saturation RDE increased over 200% while threshold voltage and rise time decreased to about half and 2/3, respectively up to 3% TI, beyond which the tendencies were reversed. Among the two TIs, low viscosity monomer (TA) showed high RDE, while high miscibility monomer (TE) low characteristic voltages and short response times. It is concluded that grating formation is largely favored by low viscosity, while interface tensions and electro-optical performances by miscibility at similar viscosities.

  8. Temperature dependence of optical anisotropy of holographic polymer-dispersed liquid crystal transmission gratings.

    PubMed

    Drevensek-Olenik, I; Fally, M; Ellabban, M A

    2006-08-01

    We measured the angular dependence of the 0th, +/-1 st, and +/-2 nd optical diffraction orders from a 50 microm thick transmission grating recorded in a UV-curable holographic polymer-dispersed liquid crystal (HPDLC) made from commercially available constituents. The analysis was performed for two orthogonal polarizations of the probe beams. The emphasis was laid on the temperature dependence of the grating anisotropy. Above the nematic-isotropic phase transition, the grating is optically isotropic. At lower temperatures the grating strength for the optical polarization perpendicular to the grating vector decreases with decreasing temperature, while for orthogonal polarization it increases with decreasing temperature. As a consequence, a regime of diffraction with strongly overmodulated gratings is observed. Our investigations indicate that the anisotropy of the refractive-index modulation scales with the optical anisotropy of the liquid crystal medium forming the phase-separated domains. We further demonstrate that light scattering effects, which are profound only in the nematic phase, must not be neglected and can be taken into account via a Lorentzian line-shape broadening of the probing wave vector directions in the framework of the diffraction theory for anisotropic optical phase gratings.

  9. Electro-optical investigations of holographic-polymer-dispersed ferroelectric liquid crystals.

    PubMed

    Woltman, Scott J; Eakin, James N; Crawford, Gregory P; Zumer, Slobodan

    2007-12-01

    Uniform alignment of ferroelectric liquid-crystal domains encapsulated by a polymer binder was established through a holographic exposure process. The refractive index modulation in these thin films is modeled as a phase grating that can be electrically addressed to erase the optical diffractive properties. A phenomenological model is developed to take into account a distribution of domain sizes and an effective field that stabilizes the ferroelectric liquid-crystal domains. A diffraction model successfully predicts changes in normalized intensities for first-order diffraction with applied field. These gratings demonstrate microsecond-scale response and relaxation times for various grating pitch sizes between approximately 3 and approximately 12 microm.

  10. Topological Polymer Dispersed Liquid Crystals with Bulk Nematic Defect Lines Pinned to Handlebody Surfaces

    NASA Astrophysics Data System (ADS)

    Campbell, Michael G.; Tasinkevych, Mykola; Smalyukh, Ivan I.

    2014-05-01

    Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They are comprised of a polymer matrix with suspended spherical nematic drops and are topologically constrained to host defects of an elementary hedgehog charge per droplet, such as bulk or surface point defects or closed disclination loops. We control the genus of the closed surfaces confining such micrometer-sized nematic drops with tangential boundary conditions for molecular alignment imposed by the polymer matrix, allowing us to avoid defects or, on the contrary, to generate them in a controlled way. We show, both experimentally and through numerical modeling, that topological constraints in nematic microdrops can be satisfied by hosting topologically stable half-integer bulk defect lines anchored to opposite sides of handlebody surfaces. This enriches the interplay of topologies of closed surfaces and fields with nonpolar symmetry, yielding new unexpected configurations that cannot be realized in vector fields, having potential implications for topologically similar defects in cosmology and other fields.

  11. Development of an x-ray detector based on polymer- dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Oh, K.; Hong, J.; Kim, G.; Park, S.; Min, B.; Yang, J.; Nam, S.

    2015-02-01

    The applications of active matrix flat-panel imagers (AMFPIs) in large-area x-ray imaging systems have increased over time but are still severely limited owing to its pixel resolution, complex fabrication processes, and high cost. As a solution, x-ray light valve (XLV) technology was introduced and expected to have a better resolution and contrast ratio than those of AMFPI, owing to its micrometer level of the LC cells and signal amplification by an external light source. The twisting angle of the LC cells was changed by charge carrier signals created in a photoconductor layer against x-rays, and the diagnostic images from XLV were acquired from the transmittance of the external light source. However, there was a possibility that the photoconductor layer may be crystallized or degenerated due to the application of high temperatures for sealing the LC layer during the fabrication process. To solve such problems, polymer-dispersed liquid crystals (PDLCs), which do not need high temperature for the sealing process of the LC layer, are used in this study instead of typical LC cells. A photoconductor and PDLC are combined to develop an x-ray detector. An external light source and optical sensor are used to investigate the light transmission of the PDLC . The PDLCs used in this paper do not need polarizers and are self-adhesive. Hence, the transmittance is very high in the transparent state, which allows for a linear x-ray response and sufficient dynamic range in digital radiography.

  12. Embedded Ag mesh electrodes for polymer dispersed liquid crystal devices on flexible substrate.

    PubMed

    Liu, Yanhua; Shen, Su; Hu, Jin; Chen, Linsen

    2016-10-31

    An embedded Ag mesh transparent conductive electrode (TCE) on flexible substrate, which is suitable for polymer dispersed liquid crystal (PDLC) device, is demonstrated. With the combination of soft ultra-violet nanoimprinting lithography and scrape technique, it offers parallel processing with high resolution (10000dpi), as well as remarkable simplicity and fully controllable flexibility to tailor the transmittance and sheet resistance. While being able to achieve maximum transmittance 60% in the on state and the minimum 0.1% in the off state, the PDLC smart window displays low sheet resistance (5.58 Ω/sq.) under low driven voltage (30V) safe for human. The main advantage of adoption of PDLC as an optically scattering element lies in the fact that there needs no mechanical part for in situ tunability. An enhancement factor of 50 of the diffraction intensity is observed experimentally. The embedded Ag mesh TCE for PDLC device has an environmentally-friendly additive manufacturing process inherently. Compared to existing solutions, the fabricated sample shows superior performance in both optoelectronic and mechanic characteristics. We envision that the embedded Ag mesh TCE will enable economically widen application of PDLC devices on flexible substrate.

  13. Effect of UV intensity on the electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Jaeyong; Han, Jeong In

    2014-05-01

    Polymer dispersed liquid crystal (PDLC) lenses were made from a mixture of prepolymer (NOA 65) and E7 liquid crystal (LC). The mixture of polymer dispersed in LC was polymerized by ultraviolet (UV) irradiation in the polymerization induced phase separation process. With varying UV curing intensity in this process, the electrooptical properties of PDLC lens device such as transmittance, driving voltage, response times, contrast ratio (C/R) and slope of the linear region of the transmittance-voltage were measured and optimized for application to smart electronic glasses with auto-shading and auto-focusing functions. The optimum UV intensity for the PDLC lenses was more than 580 µW/cm2. These results were improved compared to our previously reported data[1] for the application of these PDLC lenses to smart electronic glasses with auto-shading and/or auto-focusing functions.

  14. Effect of cell gap on electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Jaeyong; Han, Jeong In

    2014-07-01

    Polymer dispersed liquid crystal (PDLC) lenses with a cell gap of 11 μm and 30 μm were made from a uniformly dispersed mixture of 40% prepolymer (NOA 65, Norland optical adhesive 65) and 60% E7 liquid crystal. PDLC's mixture between two ITO coated glasses was polymerized by UV (ultraviolet) curing in the polymerization induced phase separation (PIPS) process. Decline of cell gap is a physical approach to improve the electrooptical properties, while cooling or doping of SiO2 nanoparticles is the microstructural approach to enhance the properties, because the electric field applied to the liquid crystal molecules in LC droplets is inversely proportional to the cell gap. A smaller cell gap significantly and effectively increases the electric field applied to PDLCD devices. The driving voltages and slope for the sample with a cell gap of 11 μm and 30 μm were drastically improved. The driving voltage and the slope of the linear region of PDLC lens with narrow cell gap of 11 μm were drastically enhanced compared to those of the samples with 30 μm cell gap and the cooled and doped samples. These improvements were due to the increase of the applied electric field. However, the response time and contrast ratio were deteriorated. It seems that this deterioration was caused by the sticking or fixing of liquid crystal molecules in LC (liquid crystal) droplets by the intensive electric field applied to the PDLC device.

  15. All-optical switchable holographic Fresnel lens based on azo-dye-doped polymer-dispersed liquid crystals.

    PubMed

    Jashnsaz, Hossein; Nataj, Nahid Hosain; Mohajerani, Ezeddin; Khabbazi, Amir

    2011-08-01

    Fabrication of an all-optical switchable holographic liquid crystal (LC) Fresnel lens based on azo-dye-doped polymer-dispersed LCs is reported using a Michelson interferometer. It is found that, upon circularly polarized photoirradiation, the diffraction efficiency of the fabricated Fresnel lens was increased significantly in a reversible manner. We believe this is due to the anisotropy induced by reorientation of the LC molecules coupled with azo-dye molecule orientation due to trans-cis-trans photoisomerization, which modulates the refractive index of the LC-rich regions. We also studied the effect of azo dye on the polarization dependency of the fabricated lens.

  16. 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.

  17. 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.

  18. 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.

  19. Three-Dimensional Large Screen Display Using Polymer-Dispersed Liquid-Crystal Light Valves and a Schlieren Optical System: Proposal and Basic Experiments

    NASA Astrophysics Data System (ADS)

    Takizawa, Kuniharu

    A novel three-dimensional (3-D) projection display used with polarized eyeglasses is proposed. It consists of polymer-dispersed liquid crystal-light valves that modulate the illuminated light based on light scattering, a polarization beam splitter, and a Schlieren projection system. The features of the proposed display include a 3-D image display with a single projector, half size and half power consumption compared with a conventional 3-D projector with polarized glasses. Measured electro-optic characteristics of a polymer-dispersed liquid-crystal cell inserted between crossed polarizers suggests that the proposed display achieves small cross talk and high-extinction ratio.

  20. Electrohydrodynamic Behaviors in the Multiwalled Carbon Nanotubes Doped Optically Compensated Bend Polymer-Dispersed Nematic Liquid Crystal Cell

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ning; Wu, Jin-Jei; Ke, Hung-Lin

    2008-11-01

    We fabricated three optically compensated bend (OCB) polymer-dispersed nematic liquid crystal (PDLC) cells doped with a minute amount of multiwalled carbon nanotubes (MWCNTs) and observed the eletrohydrodynamic (EHD) behaviors of LCs in these three MWCNT-doped OCB PDLC cells at 5 or 12 V AC voltage with a frequency of 1 kHz or 60 Hz, respectively. Using the polarizing microscope, we discovered many kinds of domain patterns, including the fingerprint-like domain pattern, the uniform domain pattern, the bean-like domain pattern, the irregular big spot domain pattern, the hexagonal short period lattice domain pattern, and the rectangular period lattice domain pattern. This suggests that some domain patterns differ from the Kapustin-William's domain pattern while others were somewhat similar to the Kapustin-William's domain pattern.

  1. Multi-imaging characteristics of electrically controlled on-axis holographic polymer-dispersed liquid-crystal Fresnel lens

    NASA Astrophysics Data System (ADS)

    Wei, Xiaopeng; Zheng, Jihong; Wang, Yanan; Gao, Zheng; Sun, Lijia; Lu, Yang; Zhuang, Songlin

    2015-03-01

    This paper reports on the investigation of the electrically controlled multifocus, multi-imaging characteristics of an on-axis holographic polymer-dispersed liquid-crystal (H-PDLC) Fresnel lens. The Fresnel lens is examined within a PDLC cell through the analysis of interference fringes generated by on-axis plane and spherical waves. Experiments are conducted to investigate the multifocus and multi-imaging phenomena of the H-PDLC Fresnel lens, and a corresponding geometrical optical analysis is also provided. It is then demonstrated that the H-PDLC Fresnel lens is a plane-surface diffractive optical device which modulates the phase of incident light through a periodic change of refractive index and forms multiple symmetrical images. Its diffraction properties, which can be controlled electrically, have further potential applications in this field.

  2. Visible and near-infrared characterization and modeling of nanosized holographic-polymer-dispersed liquid crystal gratings.

    PubMed

    Vita, Francesco; Marino, Antigone; Tkachenko, Volodymyr; Abbate, Giancarlo; Lucchetta, Daniele E; Criante, Luigi; Simoni, Francesco

    2005-07-01

    We have studied the electro-optical and angular behavior of holographic-polymer-dispersed liquid crystal gratings at different wavelengths, in the visible and in the near-infrared range. As usual in these kinds of materials, a strong polarization dependent behavior was observed. Our samples showed very high diffraction efficiency for p-polarized radiation at 1.55 microm, which is very interesting for many possible applications in the telecom field. However, we also observed a very unusual behavior for visible p-polarized light and we try to suggest some explanation for that. By analyzing the angular dependence of the diffraction efficiency, we could measure the components of the permittivity modulation tensor and infer important information about the main parameters involved in the grating structure: the degree of phase separation and the anisotropy in the liquid crystal droplet distribution. In our opinion, this simple and nondestructive methodology can be very useful for studying these kinds of materials and getting information on their morphology, in view of optimizing their properties. Finally, we discuss the role of the refractive index optical dispersion in order to describe the behavior of these materials at different wavelengths. These remarks are especially important when properties in the infrared range are extrapolated from measurements in the visible.

  3. Effect of dielectric permittivity on the performance of polymer dispersed liquid crystal (PDLC) electrolyte dye-sensitized solar cells (DSSCs)

    NASA Astrophysics Data System (ADS)

    Kamarudin, Muhammad A. A.; Khan, Ammar A.; Qasim, Malik M.; Wilkinson, Timothy D.

    2016-09-01

    Dye-sensitized solar cells (DSSCs) are a type of organic solar cell often cited for their high efficiency and easy fabrication. Recent studies have shown that modification of the standard liquid electrolyte DSSC architecture by the changing one of the components or the addition of additives often results in the improvement in one of the photovoltaic parameters and hence the overall efficiency. Here we explore a dielectric liquid crystal material which is a known insulator but possesses a high degree of order and optical anisotropy. In the presence of an applied electric field, the equilibrium of positive and negative charges are displaced in opposite directions. In this work, different mixtures with different dielectric anisotropies ranging from negative, zero and positive are formulated. These mixtures are then used to prepare polymer dispersed liquid crystal (PDLC) electrolytes and subsequently DSSC devices based on these PDLC electrolytes are fabricated. The morphology of the PDLC is observed through polarizing optical microscopy (POM) and the electrical/photovoltaic characterizations are performed through current density-voltage (J-V) measurements and electrochemical impedance spectroscopy.

  4. Effects of monomer functionality on performances of scaffolding morphologic transmission gratings recorded in polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Pu, Donglin; Shen, Su; Wei, Guojun; Xuan, Li; Chen, Linsen

    2015-09-01

    The effects of monomer functionality on performances of holographic polymer dispersed liquid crystal (HPDLC) transmission gratings are systematically investigated. Acrylate monomers with an average functionality ranging from 2.0 to 5.0 are used to prepare these samples. We find scaffolding morphologic transmission gratings (characterized by a high phase separation degree, a well alignment of LCs and low scattering loss) can be obtained irrespective of the monomer functionality, although the exact optimal curing intensity varies. The temporal evolution of the grating formation is studied and the onset time of the LC phase separation decreases significantly with the increase in average monomer functionality. It is also shown that the gratings prepared from low average functionality monomers require a comparatively low switch-off electric field (~8 V μm-1) whilst suffering from mechanical fragility and long-term instability. Our results not only provide a complete understanding of scaffolding morphologic gratings in terms of the material composition effect, but also provide insight into the formation mechanisms of non-droplet morphologic HPDLC gratings.

  5. Effects of multi-context information recorded at different regions in holographic polymer-dispersed liquid crystal on optical reconfiguration

    NASA Astrophysics Data System (ADS)

    Ogiwara, Akifumi; Watanabe, Minoru

    2016-08-01

    A holographic polymer-dispersed liquid crystal (HPDLC) memory to record multi-context information for an optically reconfigurable gate array is formed by constructing a laser illumination system to implement successive laser exposures at different small regions in a glass cell filled with LC composites. The context pattern arrangements for circuit information are designed in a 3 × 3 in.2 photomask by electron beam lithography, and they are recorded as laser interference patterns at nine regions separated in an HPDLC sample by a laser interferometer composed of movable pinhole and photomask plates placed on motorized stages. The multi-context information reconstructed from the different regions in the HPDLC is written to a photodiode array in a gate-array VLSI by switching only the position of laser irradiation using the displacement of the pinhole plate under the control of a personal computer (PC). The effects of multi-context information recorded at different regions in the HPDLC on optical reconfiguration are discussed in terms of the optical system composed of ORGA VLSI and HPDLC memory. The internal structures in the HPDLC memory formed by multi-context recording are investigated by scanning electron microscopy (SEM) observation, and the configurations composed of LC and polymer phases are revealed at various regions in the HPDLC memory.

  6. Multi-wavelength sensitive holographic polymer dispersed liquid crystal grating applied within image splitter for autostereoscopic display

    NASA Astrophysics Data System (ADS)

    Zheng, Jihong; Wang, Kangni; Gao, Hui; Lu, Feiyue; Sun, Lijia; Zhuang, Songlin

    2016-09-01

    Multi-wavelength sensitive holographic polymer dispersed liquid crystal (H-PDLC) grating and its application within image splitter for autostereoscopic display are reported in this paper. Two initiator systems consisting of photoinitiator, Methylene Blue and coinitiator, p-toluenesulfonic acid as well as photoinitiator, Rose Bengal and coinitiator, Nphenylglycine are employed. We demonstrate that Bragg gratings can be formed in this syrup polymerized under three lasers simultaneously including 632.8nm from He-Ne laser, 532nm from Verdi solid state laser, and 441.6nm from He- Cd laser. The diffraction efficiency of three kinds of gratings with different exposure wavelength are 57%, 75% and 33%, respectively. The threshold driving voltages of those gratings are 2.8, 3.05, and 2.85 V/μm, respectively. We also present the results for the feasibility of this proposed H-PDLC grating applied into image splitter without color dispersion for autostereoscopic display according to experimental splitting effect.

  7. Electro-optical response of polymer-dispersed liquid crystal single layers of large nematic droplets oriented by rubbed teflon nanolayers

    NASA Astrophysics Data System (ADS)

    Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.; Marino, S.; Versace, C.; Scaramuzza, N.

    2013-02-01

    The surface orienting effect of rubbed teflon nanolayers on the morphology and electro-optical (EO) response of polymer-dispersed liquid crystal (PDLC) single layers of large nematic droplets was studied experimentally. In PDLC composites of the nematic liquid crystal (LC) E7 and NOA65 polymer, single droplets of LC with diameters as larger as 10 μm were confined in layers with a thickness of 10 μm, and the nematic director field was efficiently modified by nanostructuring teflon rubbing of the glass plates of the PDLC cell. For layered PDLCs arranged and oriented in this way, the modulated EO response by the dielectric oscillations of the nematic director exhibits a selective amplitude-frequency modulation controllable by both temperature and voltage applied, and is simply related to the LC droplet size. That may be of practical interest for PDLC-based modulators operating in the infrasound frequency range.

  8. Holographic polymer dispersed liquid crystal (HPDLC) transmission gratings formed by visible light initiated thiol-ene photopolymerization

    NASA Astrophysics Data System (ADS)

    Wofford, Jeremy M.; Natarajan, Lalgudi V.; Tondiglia, Vincent P.; Sutherland, Richard L.; Lloyd, Pamela F.; Siwecki, Stephen A.; Bunning, Timothy J.

    2006-08-01

    We report on the initial development of a visible initiator for thiol-ene photopolymerization using the 647 nm radiation from a Krypton ion laser. The photoinitiator system consists of the dye oxazine 170 perchlorate and the co-initiator benzoyl peroxide. Electron transfer occurs between the singlet excited state of the oxazine dye and benzoyl peroxide with subsequent decomposition of the peroxide yielding benzoyl oxy radicals capable of free radical initiation. We demonstrate that this photoinitiation system enables holographic patterning of HPDLC gratings as initial Bragg transmission gratings with a periodicity less than one micron using 647 nm radiation. These gratings were electrically switchable between a diffractive and transmissive state. Morphology studies using bright field transmission electron microscopy (BFTEM) indicate the phase separation of nearly spherical shaped nematic liquid crystal droplets of several hundred nanometers in diameter. This demonstration suggests that reflection gratings can be written using this photoinitiator system and 647 nm radiation which have switchable notch wavelengths approaching 2 microns.

  9. All-optically controllable distributed feedback laser in a dye-doped holographic polymer-dispersed liquid crystal grating with a photoisomerizable dye.

    PubMed

    Tong, Huai-Pei; Li, Yu-Ren; Lin, Jia-De; Lee, Chia-Rong

    2010-02-01

    This work demonstrates, for the first time, an all-optically controllable distributed feedback (DFB) laser based on a dye-doped holographic polymer-dispersed liquid crystal (DDHPDLC) grating with a photoisomerizable dye. Intensity of the lasing emission can be reduced and increased by raising the irradiation intensity of one CW circularly-polarized green beam and the irradiation time of one CW circularly-polarized red beam, respectively. The all-optical controllability of the lasing emission is owing to the green-beam-induced isothermal nematic-->isotropic and red-beam-induced isothermal isotropic-->nematic phase transitions of the LCs via trans-->cis and cis-->trans back isomerizations of the azo-dye, respectively, in the LC-droplet-rich regions of the grating. The former (latter) mechanism can reduce (increase) the index modulation and thereby the coupling strength in the DFB grating, resulting in the decay (rise) of the lasing emission. Thermal effect is excluded from possible mechanisms causing such an optical controllability of the lasing emission.

  10. 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

  11. 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.

  12. In situ prepared polymer films as alignment layers for nematic liquid crystals

    SciTech Connect

    Pires, David; Galerne, Yves

    2006-12-15

    By means of UV-visible irradiations and convenient photoinitiators, we realize the cross-linked polymerization of a triacrylate monomer in solution in a nematic liquid crystal (p-pentyl-p{sup '}-cyanobiphenyl) at low concentrations (a few wt %), i.e., under conditions opposite to the synthesis of polymer-dispersed liquid crystals. As atomic force microscope measurements show, when operating close to, but below, the percolation transition, a thin polymer layer is synthesized in situ, directly covering and coating all the substrate. These observations therefore confirm that the properties of anchoring and of alignment memory previously observed in such nematic cells effectively originate from the synthesized polymer film. According to the photoinitiator used, bulk or surface polymerizations dominate and respectively produce continuous or discontinuous films (i.e., with separate clusters). In the former case, polymer aggregates are first synthesized. They then diffuse in the volume until they meet a surface, where they definitely stick if they are large enough. An estimate of the entropy and interaction energy differences between the two states, stuck or free, shows that the aggregates stick on the substrates if their size exceeds the length of about three monomers, i.e., if they contain more than 20-30 monomers. Interestingly, these films may be used to replicate nonuniform alignment patterns that are difficult to realize otherwise. The method may be considered as an imprinting method.

  13. 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.

  14. 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.

  15. Tilted Liquid Crystal Alignment on Asymmetrically Grooved Porous Alumina Film

    NASA Astrophysics Data System (ADS)

    Maeda, Tsuyoshi; Hiroshima, Kohki

    2005-06-01

    This paper reports the achievement of tilted liquid crystal (LC) alignment on an anodic porous alumina (APA) film using microgrooves with asymmetric shapes and dozens of minute pores. The microgrooves with asymmetric shapes were formed by a rubbing technique. The minute pores were then produced by anodization. The LC pretilt angle was controlled by the shapes of the microgrooves and pores. The LC director was orientated in the same inclining direction as that of a rubbed polyimide (PI) film. The pretilt angle was in the range of 20 to 90°. This tilted LC alignment remains very stable against external forces such as thermal shock and intense light.

  16. Two-dimensional microrheology of freely suspended liquid crystal films.

    PubMed

    Eremin, A; Baumgarten, S; Harth, K; Stannarius, R; Nguyen, Z H; Goldfain, A; Park, C S; Maclennan, J E; Glaser, M A; Clark, N A

    2011-12-23

    Smectic liquid crystals form freely-suspended, fluid films of highly uniform structure and thickness, making them ideal systems for studies of hydrodynamics in two dimensions. We have measured particle mobility and shear viscosity by direct observation of the gravitational drift of silica spheres and smectic islands included in these fluid membranes. In thick films, we observe a hydrodynamic regime dominated by lateral confinement effects, with the mobility of the inclusion determined predominantly by coupling of the fluid flow to the fixed boundaries of the film. In thin films, the mobility of inclusions is governed primarily by coupling of the fluid to the surrounding air, as predicted by Saffman-Delbrück theory.

  17. Orthogonal orientation of chromonic liquid crystals by rubbed polyamide films.

    PubMed

    Mcguire, Aya; Yi, Youngwoo; Clark, Noel A

    2014-05-19

    Chromonic liquid crystals (CLCs) have drawn attention for applications to organic electronics and optical films as well as biological materials. Understanding the alignment mechanism of CLCs is important for those applications. Using a polarized transmission optical microscope, we observe the optical texture, dichroism, and birefringence of CLC films of sunset yellow (SSY) confined by polyamide (nylon) films that are rubbed with a brush. The films align with the stacks of SSY molecules oriented, surprisingly, perpendicular to the rubbing direction. We propose that this alignment is stabilized by molecular interaction between the stretched nylon chains and molecular grooves of the SSY stacks rather than elastic energy of the CLCs due to surface topography induced by the rubbing.

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

    PubMed

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

    2016-06-05

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

  19. Alignment mechanism of liquid crystal in a stretched porous polymer film

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Kuboki, Masashi; Murashige, Takeshi; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro

    2003-09-01

    This article discusses the mechanism of nematic liquid crystal alignment in stretched porous polymer films. The polymer films were formed by extreme stretching of an isotropic porous polyolefin, such that the draw ratio was 12:1. A 6-μm-thick porous film with a high porosity coefficient of 92% revealed fine string-shaped areas that exhibited optical anisotropy due to their possessing a high degree of molecular alignment. The porous film was filled with nematic liquid crystal and then the composite film was sandwiched between transparent electrodes coated onto glass substrates, without the use of conventional alignment layers. From polarizing microscopy observations it was found that the string-like polymer areas induce liquid crystal molecular alignment. The liquid crystal cells can exhibit an electrically controlled birefringence effect. This alignment technique enables us to realize three-dimensional control of liquid crystal alignment.

  20. Aligned Carbon Nanotube Thin Films from Liquid Crystal Polyelectrolyte Inks.

    PubMed

    Tune, Daniel D; Blanch, Adam J; Shearer, Cameron J; Moore, Katherine E; Pfohl, Moritz; Shapter, Joseph G; Flavel, Benjamin S

    2015-11-25

    Single walled carbon nanotube thin films are fabricated by solution shearing from high concentration sodium nanotubide polyelectrolyte inks. The solutions are produced by simple stirring of the nanotubes with elemental sodium in dimethylacetamide, and the nanotubes are thus not subject to any sonication-induced damage. At such elevated concentrations (∼4 mg mL(-1)), the solutions exist in the liquid crystal phase and during deposition this order is transferred to the films, which are well aligned in the direction of shear with a 2D nematic order parameter of ∼0.7 determined by polarized absorption measurements. Compared to similarly formed films made from superacids, the polyelectrolyte films contain smaller bundles and a much narrower distribution of bundle diameters. After p-doping with an organic oxidizer, the films exhibit a very high DC electrical to optical conductivity ratio of σ(DC)/σ(OP) ∼ 35, corresponding to a calculated DC conductivity of over 7000 S cm(-1). When very thin (T550 ∼ 96%), smooth (RMS roughness, R(q) ∼ 2.2 nm), and highly aligned films made via this new route are used as the front electrodes of carbon nanotube-silicon solar cells, the power conversion efficiency is almost an order of magnitude greater than that obtained when using the much rougher (R(q) ∼ 20-30 nm) and less conductive (peak σ(DC)/σ(OP) ∼ 2.5) films formed by common vacuum filtration of the same starting material, and having the same transmittance.

  1. Controlled Growth of Organic Semiconductor Films Using Liquid Crystal Solvents

    NASA Astrophysics Data System (ADS)

    Bufkin, Kevin; Ohlson, Brooks; Hillman, Ben; Johnson, Brad; Patrick, David

    2008-05-01

    Interest in using organic semiconductors in applications such as large area displays, photovoltaic devices, and RFID tags stems in part from their prospects for enabling significantly reduced manufacturing costs compared to traditional inorganic semiconductors. However many of the best performing prototype devices produced so far have involved expensive or time-consuming fabrication methods, such as the use of single crystals or thin films deposited under high vacuum conditions. We present a new approach for growing low molecular weight organic crystalline films at ambient conditions based on a vapor-liquid-solid growth mechanism using thermotropic nematic liquid crystal (LC) solvents. Tetracene is deposited via atmospheric-pressure sublimation onto substrates coated by a LC layer oriented using rubbed polyimide, producing films that are highly crystalline, with large grain sizes, and possessing macroscopic uniaxial orientation. This poster will describe the growth mechanism, discuss the effects of processing conditions such as LC layer thickness, substrate temperature and flux rate, and compare the results to a model of deposition-diffusion aggregation accounting for the finite thickness of the solvent layer.

  2. Controlled Growth of Organic Semiconductor Films Using Liquid Crystal Solvents

    NASA Astrophysics Data System (ADS)

    Bufkin, Kevin; Ohlson, Brooks; Hillman, Ben; Johnson, Brad; Patrick, David

    2008-03-01

    Interest in using organic semiconductors in applications such as large area displays, photovoltaic devices, and RFID tags stems in part from their prospects for enabling significantly reduced manufacturing costs compared to traditional inorganic semiconductors. However many of the best performing prototype devices produced so far have involved expensive or time-consuming fabrication methods, such as the use of single crystals or thin films deposited under high vacuum conditions. We present a new approach for growing low molecular weight organic crystalline films at ambient conditions based on a vapor-liquid-solid growth mechanism using thermotropic nematic liquid crystal (LC) solvents. Tetracene is deposited via atmospheric-pressure sublimation onto substrates coated by a LC layer oriented using rubbed polyimide, producing films that are highly crystalline, with large grain sizes, and possessing macroscopic uniaxial orientation. This poster will describe the growth mechanism, discuss the effects of processing conditions such as LC layer thickness, substrate temperature and flux rate, and compare the results to a model of diffusion limited aggregation accounting for the finite thickness of the solvent layer.

  3. Hydrodynamic interactions in freely suspended liquid crystal films

    NASA Astrophysics Data System (ADS)

    Kuriabova, Tatiana; Powers, Thomas R.; Qi, Zhiyuan; Goldfain, Aaron; Park, Cheol Soo; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.

    2016-11-01

    Hydrodynamic interactions play an important role in biological processes in cellular membranes, a large separation of length scales often allowing such membranes to be treated as continuous, two-dimensional (2D) fluids. We study experimentally and theoretically the hydrodynamic interaction of pairs of inclusions in two-dimensional, fluid smectic liquid crystal films suspended in air. Such smectic membranes are ideal systems for performing controlled experiments as they are mechanically stable, of highly uniform structure, and have well-defined, variable thickness, enabling experimental investigation of the crossover from 2D to 3D hydrodynamics. Our theoretical model generalizes the Levine-MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. We describe in detail the theoretical and computational approach previously outlined in Z. Qi et al., Phys. Rev. Lett. 113, 128304 (2014), 10.1103/PhysRevLett.113.128304 and extend the method to study the mutual mobilities of inclusions with asymmetric shapes. The model predicts well the observed mutual mobilities of pairs of circular inclusions in films and the self-mobility of a circular inclusion in the vicinity of a linear boundary.

  4. Hydrodynamic interactions in freely suspended liquid crystal films.

    PubMed

    Kuriabova, Tatiana; Powers, Thomas R; Qi, Zhiyuan; Goldfain, Aaron; Park, Cheol Soo; Glaser, Matthew A; Maclennan, Joseph E; Clark, Noel A

    2016-11-01

    Hydrodynamic interactions play an important role in biological processes in cellular membranes, a large separation of length scales often allowing such membranes to be treated as continuous, two-dimensional (2D) fluids. We study experimentally and theoretically the hydrodynamic interaction of pairs of inclusions in two-dimensional, fluid smectic liquid crystal films suspended in air. Such smectic membranes are ideal systems for performing controlled experiments as they are mechanically stable, of highly uniform structure, and have well-defined, variable thickness, enabling experimental investigation of the crossover from 2D to 3D hydrodynamics. Our theoretical model generalizes the Levine-MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. We describe in detail the theoretical and computational approach previously outlined in Z. Qi et al., Phys. Rev. Lett. 113, 128304 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.128304 and extend the method to study the mutual mobilities of inclusions with asymmetric shapes. The model predicts well the observed mutual mobilities of pairs of circular inclusions in films and the self-mobility of a circular inclusion in the vicinity of a linear boundary.

  5. The ion capturing effect of 5° SiOx alignment films in liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Huang, Yi; Bos, Philip J.; Bhowmik, Achintya

    2010-09-01

    We show that SiOx, deposited at 5° to the interior surface of a liquid crystal cell allows for a surprisingly substantial reduction in the ion concentration of liquid crystal devices. We have investigated this effect and found that this type of film, due to its surface morphology, captures ions from the liquid crystal material. Ion adsorption on 5° SiOx film obeys the Langmuir isotherm. Experimental results shown allow estimation of the ion capturing capacity of these films to be more than an order of 10 000/μm2. These types of materials are useful for new types of very low power liquid crystal devices such as e-books.

  6. Quadrupolar Effect on Two Layered Thin Film Antiferroelectric Smectic Liquid Crystal

    SciTech Connect

    Lum, Chia-Yuee; Ong, Lye-Hock; Cepic, Mojca

    2011-03-30

    Within the framework of the discrete Landau phenomenological model, the free energy of an antiferroelectric smectic liquid crystal is analyzed. This model considers the interactions between the liquid crystal molecules within the nearest and the next nearest layers. Electrostatic quadrupolar interaction up to the nearest layers is included. This quadrupolar term, b{sub q{xi}}???{sub i{center_dot}{xi}}???{sub i+1}{sup 2} is positive, thus favouring a perpendicular orientation in the adjacent layer respectively. We show how quadrupolar interaction can affects the planar regions of the phase diagram of a two layered thin antiferroelectric smectic liquid crystal film.

  7. Studies of Optical Wave Front Conjugation and Imaging Properties of Nematic Liquid Crystal Films

    DTIC Science & Technology

    1988-06-30

    processes was also demonstrated. The capability of optical four wave mixing to generate amplified reflection and self- oscillation in nematic liquid crystal...via real time optical wave mixing process was also demonstrated. The capability of optical four wave mixing to generate amplified reflection and self...the special nonlinear optical properties of liquid crystal films for optical wave front conjugation and in related four -wave mixing processes. The

  8. The electro-optical behavior of liquid crystal molecules on the surface of SiO2 inorganic thin films.

    PubMed

    Sung, Shi-Joon; Yang, Kee-Jeong; Kim, Dae-Hwan; Do, Yun Seon; Kang, Jin-Kyu; Choi, Byeong-Dae

    2009-12-01

    Inorganic thin films are well known for the liquid crystal alignment layers for LCoS application due to the higher thermal and photochemical stability of inorganic materials. The switching time of liquid crystals is the important factor for the projection application and the faster switching time is required for the high quality display. The switching behavior of liquid crystal molecules on inorganic thin films might be closely related with the surface properties of the inorganic thin films. Therefore the understanding of surface properties of the inorganic thin films is required for the enhancement of the switching time of liquid crystals of LCoS devices. In this work, we prepared the SiO2 inorganic thin films and the electro-optical behavior of liquid crystal molecules on SiO2 thin film was investigated. The sputtering condition of SiO2 thin film was closely related with the thickness and the surface morphology of SiO2 thin film. The switching time of liquid crystals with negative dielectric constant on SiO2 inorganic thin films was dominantly affected by the size of protrusion on the surface of SiO2 thin film and the surface roughness of SiO2 thin film was also related with the switching time of liquid crystals. From these results, it is possible to prepare the SiO2 inorganic thin film suitable for the liquid crystal alignment layer for VAN LC mode.

  9. 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

  10. Variable Thickness Liquid Crystal Films for High Repetition Rate Laser Applications

    NASA Astrophysics Data System (ADS)

    Poole, Patrick; Willis, Christopher; Cochran, Ginevra; Hanna, Randall; Andereck, C. David; Schumacher, Douglass

    2015-05-01

    The presentation of a clean target or target substrate at high repetition rates is of importance to a number of photoelectron spectroscopy and free electron laser applications, often in high vacuum environments. Additionally, high intensity laser facilities are approaching the 10 Hz shot rate at petawatt powers, but are currently unable to insert targets at these rates. We have developed liquid crystal films to address this need for high rep rate targets while preserving the planar geometry advantageous to many applications. The molecular ordering of liquid crystal is variable with temperature and can be manipulated to form a layered thin film. In this way temperature and volume control can be used to vary film thickness in vacuo and on-demand between 10 nm and over 10 μm. These techniques were previously applied to a single-shot ion acceleration experiment in, where target thickness critically determines the physics of the acceleration. Here we present an automatic film formation device that utilizes a linear sliding rail to form liquid crystal films within the aforementioned range at rates up to 0.1 Hz. The design ensures film formation location within 2 μm RMS, well within the Rayleigh range of even short f-number systems. Details of liquid crystal films and this target formation device will be shown as well as recent experimental data from the Scarlet laser facility at OSU. This work was supported by DARPA through a grant from AMRDEC.

  11. Heat, Light, and Videotapes: Experiments in Heat Conduction Using Liquid Crystal Film.

    ERIC Educational Resources Information Center

    Bacon, Michael E.; And Others

    1995-01-01

    Presents a range of experiments in heat conduction suitable for upper-level undergraduate laboratories that make use of heat sensitive liquid crystal film to measure temperature contours. Includes experiments mathematically described by Laplace's equation, experiments theoretically described by Poisson's equation, and experiments that involve…

  12. Complex Nanoscale-Ordered Liquid Crystal Polymer Film for High Transmittance Holographic Polarizer.

    PubMed

    Du, Tao; Fan, Fan; Tam, Alwin Ming Wai; Sun, Jiatong; Chigrinov, Vladimir G; Sing Kwok, Hoi

    2015-11-25

    A special design of a complex-ordered liquid crystal polymer film is developed into a holographic polarizer. The holographic polarizer shows over 90% transmittance, which provides a simple solution to make LEDs polarized. Furthermore, the holographic polarizer exhibits intensity and polarization maintenance properties, which could be further developed for photonics applications.

  13. Changes in adsorption and optical properties of liquid crystal langmuir films at structural phase transition

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. B.; Levshin, N. L.; Khlybov, S. V.; Yudin, S. G.

    2012-12-01

    The adsorption isotherms of water molecules, absorption spectra, and spectra of diffuse scattering and polarization of reflected light are studied for ultrathin Langmuir films prepared based on liquid crystals. A structural phase transition near 70°C is detected. Some specific features of the reflection spectra at the phase transition temperature are found. Suggestions are made regarding the nature of the phase transition.

  14. Dynamic studies of holographic gratings in dye-doped liquid-crystal films.

    PubMed

    Fuh, A Y; Liao, C C; Hsu, K C; Lu, C L; Tsai, C Y

    2001-11-15

    The dynamic behavior of a holographic grating induced in a homeotropically aligned dye-doped liquid-crystal film is investigated. In the presence of an applied dc voltage, photoexcited azo dyes induce a photorefractive grating and then diffuse and are adsorbed onto cell substrates. The reorientation of liquid crystals as a result of adsorbed dyes leads to a phase grating that is phase shifted 90 degrees from the photorefractive grating. Competition of these two gratings induces two-beam coupling of the writing beams, initially transferring energy from beam 1 to beam 2 and then, after a pause, from beam 2 to beam 1.

  15. Moderate repetition rate ultra-intense laser targets and optics using variable thickness liquid crystal films

    NASA Astrophysics Data System (ADS)

    Poole, P. L.; Willis, C.; Cochran, G. E.; Hanna, R. T.; Andereck, C. D.; Schumacher, D. W.

    2016-10-01

    Liquid crystal films are variable thickness, planar targets for ultra-intense laser matter experiments such as ion acceleration. Their target qualities also make them ideal for high-power laser optics such as plasma mirrors and waveplates. By controlling parameters of film formation, thickness can be varied on-demand from 10 nm to above 50 μm, enabling real-time optimization of laser interactions. Presented here are results using a device that draws films from a bulk liquid crystal source volume with any thickness in the aforementioned range. Films form within 2 μm of the same location each time, well within the Rayleigh range of even tight F / # systems, thus removing the necessity for realignment between shots. The repetition rate of the device exceeds 0.1 Hz for sub-100 nm films, facilitating higher repetition rate operation of modern laser facilities.

  16. Moderate repetition rate ultra-intense laser targets and optics using variable thickness liquid crystal films

    DOE PAGES

    Poole, P. L.; Willis, C.; Cochran, G. E.; ...

    2016-10-10

    Liquid crystal films are variable thickness, planar targets for ultra-intense laser matter experiments such as ion acceleration. Their target qualities also make them ideal for high-power laser optics such as plasma mirrors and waveplates. By controlling parameters of film formation, thickness can be varied on-demand from 10 nm to above 50 μm, enabling real-time optimization of laser interactions. Presented here are results using a device that draws films from a bulk liquid crystal source volume with any thickness in the aforementioned range. Films form within 2 μm of the same location each time, well within the Rayleigh range of evenmore » tight F/# systems, thus removing the necessity for realignment between shots. As a result, the repetition rate of the device exceeds 0.1 Hz for sub-100nm films, facilitating higher repetition rate operation of modern laser facilities.« less

  17. Moderate repetition rate ultra-intense laser targets and optics using variable thickness liquid crystal films

    SciTech Connect

    Poole, P. L.; Willis, C.; Cochran, G. E.; Hanna, R. T.; Andereck, C. D.; Schumacher, D. W.

    2016-10-10

    Liquid crystal films are variable thickness, planar targets for ultra-intense laser matter experiments such as ion acceleration. Their target qualities also make them ideal for high-power laser optics such as plasma mirrors and waveplates. By controlling parameters of film formation, thickness can be varied on-demand from 10 nm to above 50 μm, enabling real-time optimization of laser interactions. Presented here are results using a device that draws films from a bulk liquid crystal source volume with any thickness in the aforementioned range. Films form within 2 μm of the same location each time, well within the Rayleigh range of even tight F/# systems, thus removing the necessity for realignment between shots. As a result, the repetition rate of the device exceeds 0.1 Hz for sub-100nm films, facilitating higher repetition rate operation of modern laser facilities.

  18. New Insight into Photoalignment of Liquid Crystals on Coumarin-Containing Polymer Films

    SciTech Connect

    Kim, C.; Trajkovska, A.; Wallace, J.U.; Chen, S.H.

    2006-06-09

    Polymers containing 6- and 7-substituted coumarin moieties were prepared as photoalignment films through linearly polarized UV irradiation to a varying fluence for an investigation of liquid crystal orientation. Model coumarin monomers and dimers were also synthesized and characterized as part of a novel approach to the interpretation of liquid crystal orientation in terms of monomer conversion. The experimental results for monomer conversion as a function of fluence were used to validate the first-order kinetics with an exponentially decaying rate constant as the reaction proceeds. A kinetic model was constructed to describe the evolutions of the orientational order on the parts of the reacted and the unreacted coumarin moieties. The model was instrumental to the visualization of liquid crystal orientation on photoalignment films at the early and late stages of dimerization. Furthermore, the observed crossover in liquid crystal orientation on the polymer film comprising 7-substituted coumarin moieties was successfully interpreted by considering three factors: the relative abundance of the reacted and unreacted coumarin moieties, the degrees of their orientational order predicted by the kinetic model, and the energetics of molecular interaction.

  19. Electrical and electro-optical investigations of liquid crystal cells containing WO3 thin films

    NASA Astrophysics Data System (ADS)

    Strangi, G.; Cazzanelli, E.; Scaramuzza, N.; Versace, C.; Bartolino, R.

    2000-08-01

    An interesting application of the fast ion transport properties of tungsten trioxide is presented, when it is inserted as an electrode in nematic liquid crystal (NLC) cells. In a standard sandwichlike cell the nematic liquid crystal, confined between two transparent plane electrodes of purely electronic conductors [indium tin oxide (ITO)], undergoes a molecular reorientation under the action of an external electric field E. This electrically controlled birefringence (electro-optical switching) is proportional to E2, thus polarity insensitive [L. M. Blinov and V. G. Chigrinov, Electrooptic Effects in Liquid Crystal Materials (Springer-Verlag, New York, 1994)]. When a thin film of tungsten trioxide is deposited by magnetron sputtering onto one of the transparent ITO electrodes, and a NLC cell is assembled with such asymmetry, the electro-optical response becomes polarity sensitive [G. Strangi et al., Appl. Phys. Lett. 74, 534 (1999)]. The analysis of this response suggests the occurrence of a reverse internal electric field, associated with the ionic diffusion process of protons always present in these sputtered WO3 films [E. Cazzanelli et al., Electrochim. Acta 44, 3101 (1999)]. By using an opportune voltage waveform it is possible to evaluate such an internal field. Impedance and cyclic voltammetry measurements were carried out on these cells, comparing ``as-deposited'' and ``annealed'' tungsten trioxide electrodes. These studies confirm that an important ionic diffusion process is involved in the establishment of an internal electric field, which modifies the electro-optical response of the nematic liquid crystal cell.

  20. Surface energetics of freely suspended fluid molecular monolayer and multilayer smectic liquid crystal films

    PubMed Central

    Nguyen, Zoom Hoang; Park, Cheol Soo; Pang, Jinzhong; Clark, Noel A.

    2012-01-01

    A study of the surface energetics of the thinnest substrate-free liquid films, fluid molecular monolayer and multilayer smectic liquid crystal films suspended in air, is reported. In films having monolayer and multilayer domains, the monolayer areas contract, contrary to predictions from the van der Waals disjoining pressure of thin uniform slabs. This discrepancy is accounted for by modeling the environmental asymmetry of the surface layers in multilayer films, leading to the possibility that preferential end-for-end polar ordering of the rod shaped molecules can reduce the surface energy of multilayers relative to that of the monolayer, which is inherently symmetric. PMID:22826264

  1. Dynamics of photoinduced processes in liquid-crystal polymer films containing azo compounds

    SciTech Connect

    Simonov, A N; Larichev, A V

    1999-07-31

    The photoinduced processes in azo-compound-containing side-chain polymer films with liquid-crystal properties are examined theoretically. A model is proposed whereby it is possible to consider the dynamics of the optical response of a medium taking into account the anisotropic saturation in the angular distribution of the azo-dye isomers as well as the intermolecular interaction. The influence of the liquid-crystal ordering in the polymer is taken into account by introducing a phenomenological mean-field factor. Analytical solutions describing changes in the optical properties of a polymer film during the initial illumination stages are in good agreement with experimental data. (this issue is dedicated to the memory of s a akhmanov)

  2. Rupture mechanism of liquid crystal thin films realized by large-scale molecular simulations

    NASA Astrophysics Data System (ADS)

    Nguyen, Trung Dac; Carrillo, Jan-Michael Y.; Matheson, Michael A.; Brown, W. Michael

    2014-02-01

    The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented large-scale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. We further demonstrate that the primary driving force for rupture is closely related to the tendency of the LC mesogens to recover their local environment in the bulk state. Our study not only provides new insights into the rupture mechanism of liquid crystal films, but also sets the stage for future investigations of thin film systems using peta-scale molecular dynamics simulations.The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented large-scale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism

  3. 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

  4. Nanoparticle free polymer blends for light scattering films in liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Takei, Satoshi; Mochiduki, Kazuhide; Kubo, Naoya; Yokoyama, Yoshiyuki

    2012-06-01

    This paper reports an approach using nanoparticle free polymer blends for light scattering films in liquid crystal displays. The ability to create the regularly structured circle of approximately 200 nm diameter in the light scattering film by blending two specified polymers with carboxylic acid groups and epoxy groups was demonstrated. The developed light scattering film based on thermosetting system indicated regularly structured nanomorphology, high light scattering rates of more than 3.9% at 300-600 nm of wavelength, and fast thermal cross-linking reaction at 150 °C and 60 s in thermosetting conditions for high productivity.

  5. Polarization Raman Microscopic Study of Molecular Alignment Behavior in Liquid Crystal/Polymer Composite Films

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2005-12-01

    We clarified that the molecular alignment of aggregated polymers is partially synchronized with liquid crystal (LC) director reorientation in an LC/polymer composite film. The molecular alignment behavior in composite films with LC- and polymer-rich regions formed by photopolymerization-induced phase separation was investigated using polarization Raman spectral microscopy. Raman scattering intensity induced by aligned side chains of polymers in the LC-rich region changed with LC director reorientation when voltage was applied to the composite film. It was confirmed for the first time that polymers capable of movement are formed in the LC-rich region.

  6. Optical Switching of Nematic Liquid Crystal Film based on Localized Surface Plasmon Resonance

    NASA Astrophysics Data System (ADS)

    Quint, Makiko; Delgado, Silverio; Nuno, Zachary; Hirst, Linda; Ghosh, Sayantani

    2015-03-01

    We have demonstrated an all-optical technique to reversibly switch the spatial orientation of nematic liquid crystal molecules from homeotropic to planar in a few micron thick films. Our method leverages the highly localized electric fields that are generated in the near-field of a densely packed gold nanoparticle layer when the samples are excited by light resonant with the localized surface plasmon absorption. We present simulations and control measurements for off-resonance excitation, where the switching behavior is not observed. Using polarized microscopy and transmission measurements, we observe this switching over a temperature range starting several degrees below and up to the isotropic transition, and at on-resonance excitation power less than 10 μW. In addition, we controllably vary the in-plane directionality of the liquid crystal molecules in the planar state by altering the linear polarization of the incident excitation. This work is supported by NSF Grant No. DMR-1056860 and ECC-1227034.

  7. Biphotonic-induced reorientation inversion in azo-dye-doped liquid crystal films.

    PubMed

    Lin, Hui-Chi; Chu, Chia-Wei; Li, Ming-Shian; Fuh, Andy Ying-Guey

    2011-07-04

    The reorientation inversion of liquid crystal molecules in azo-dye-doped liquid crystal (ADDLC) films irradiated by biphotonic (green and red light) lasers is studied using the self-phase-modulation method. The results show that the induced change of refractive index (∆n) in an ADDLC cell illuminated with a fixed intensity of green light increases with the red-light intensity. Notably, the value of ∆n is initially negative, and becomes positive when the intensity of the red laser is increasing. It is due to the fact that an extra positive torque is exerted on the LCs, which is produced by cis-isomers upon absorbing red light to compensate the negative torque induced by the excitation of the green light.

  8. Polymer Wall Formation Using Liquid-Crystal/Polymer Phase Separation Induced on Patterned Polyimide Films

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2004-12-01

    We could form lattice-shaped polymer walls in a liquid crystal (LC) layer through the thermal phase separation of an LC/polystyrene solution between substrates with polyimide films etched by short-wavelength ultraviolet irradiation using a photomask. The LC wetting difference between the polyimide and substrate surfaces caused the coalescence of growing LC droplets on patterned polyimide films with the progress of phase separation. Consequently, polymer walls were formed on substrate surface areas without polyimide films. The shape of the polymer wall formed became sharp with the use of rubbed polyimide films because the nucleation of growing LC droplets concentrated on the patterned polyimide films. It is thought that the increase in the alignment order of LC molecules in the solution near the rubbed polyimide films promotes the formation of LC molecular aggregation, which becomes the growth nuclei of LC droplets.

  9. Rupture mechanism of liquid crystal thin films realized by large-scale molecular simulations

    SciTech Connect

    Nguyen, Trung D; Carrillo, Jan-Michael Y; Brown, W Michael; Matheson, Michael A

    2014-01-01

    The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented largescale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. We further demonstrate that the primary driving force for rupture is closely related to the tendency of the LC mesogens to recover their local environment in the bulk state. Our study not only provides new insights into the rupture mechanism of liquid crystal films, but also sets the stage for future investigations of thin film systems using peta-scale molecular dynamics simulations.

  10. Characterization of Liquid Crystal Layer and Cholesteric Film by Renormalized Spectroscopic Ellipsometry

    NASA Astrophysics Data System (ADS)

    Kimura, Munehiro; Kamada, Hirokazu; Onuma, Toshihiko; Akahane, Tadashi

    2009-03-01

    Renormalized transmission spectroscopic ellipsometry (RTSE) is used to evaluate the device parameters of liquid crystal display (LCD). To determine the reduced dielectric and elastic constants, threshold voltage, pretilt angle, cell gap, and surface polar anchoring energy coefficient, symmetrically oblique incidence transmission ellipsometry (SOITE) was applied to vertical-alignment (VA) LCD. It is suggested that the rubbing process on the alignment films for VA LCD does not disturb the measurement of the genuine surface polar anchoring energy coefficient. RTSE is also applicable to the determination of the total twist angle of the cholesteric film.

  11. Permanent photoalignment of liquid crystals on nanostructured chalcogenide glassy thin films

    SciTech Connect

    Gelbaor, Miri; Abdulhalim, I.; Klebanov, Matvey; Lyubin, Victor

    2011-02-14

    Photoalignment of nematic liquid crystals is obtained on the chalcogenide glassy thin film of As{sub 2}S{sub 3} using irradiation with polarized blue light. A uniform homogeneously aligned device is obtained with high contrast and strong anchoring. The device alignment quality is permanent as checked by following its functionality over a period of few months. The origin of the observed photoalignment is attributed to the photoinduced anisotropy in chalcogenide glasses. No differences between the different As{sub 2}S{sub 3} film thicknesses observed, thus supporting the proposition that some orientational order is photoinduced on the surface of the glass and responsible for the photoalignment.

  12. Transient self-interaction of light in a liquid-crystal polymer film containing azodye molecules

    SciTech Connect

    Simonov, A N

    1999-07-31

    Transient self-interaction of low-power He - Ne laser radiation (1 < 50 mW cm{sup -2} ) in a liquid-crystal polymer film containing chemically bound azodye molecules was observed experimentally. The self-interaction occurred in the region of a temperature-induced phase transition in the polymer film and was accompanied by the formation of quasi-periodic ring-shaped structures in the distribution of the transmitted light intensity. (this issue is dedicated to the memory of s a akhmanov)

  13. Transflective spatial filter based on azo-dye-doped cholesteric liquid crystal films

    SciTech Connect

    Lin, T.-H.; Fuh, Andy Y.-G.

    2005-07-04

    This work demonstrates the feasibility of exploiting the photoisomerization effect in azo-dye-doped cholesteric liquid crystal (DDCLC) films with a concomitant decline of the phase transition temperature from the cholesteric to an isotropic phase (T{sub Ch-I}) as a spatial filter. The fabrication depends on the fact that the various intensities of the diffracted orders are responsible for the various degrees of transparency associated with the photoisomerized DDCLC film. High- and low-pass images in the Fourier optical signal process can be simultaneously observed via reflected and transmitted signals, respectively. A simulation is also performed, and the results are consistent closely with experimental data.

  14. A novel digital image processing system for the transient liquid crystal technique applied for heat transfer and film cooling measurements.

    PubMed

    Vogel, G; Boelcs, A

    2001-05-01

    This paper is dedicated to the transient liquid crystal technique measurements for multiple view access by using a novel digital recording and image processing system. The transient liquid crystal technique is widely used for heat transfer investigations in turbomachinery. It has been applied in our laboratory in several test facilities such as a linear cascade for external film cooling measurements or on a ribbed squared duct for internal cooling measurements. The data analysis as well as the measurement equipment is described, with a special focus on the newly developed computerized image processing system suitable to capture the liquid crystal signal.

  15. Pyrolysis mechanism for recycle renewable resource from polarizing film of waste liquid crystal display panels.

    PubMed

    Wang, Ruixue; Xu, Zhenming

    2014-08-15

    Liquid crystal display (LCD) panels mainly consist of polarizing film, liquid crystal and glass substrates. In this study, a novel pyrolysis model and a pyrolysis mechanism to recover the reusable resource from polarizing film of waste LCD panels was proposed. Polarizing film and its major components, such as cellulose triacetate (TAC) and polyvinyl alcohol (PVA) were pyrolyzed, respectively, to model the pyrolysis process. The pyrolysis process mainly generated a large ratio of oil, a few gases and a little residue. Acetic acid was the main oil product and could be easily recycled. The pyrolysis mechanism could be summarized as follows: (i) TAC, the main component of polarizing film, was heated and generated active TAC with a low polymerization, and then decomposed into triacetyl-d-glucose. (ii) Some triacetyl-d-glucose generated triacetyl-d-mannosan and its isomers through an intramolecular dehydration, while most triacetyl-d-glucose generated the main oil product, namely acetic acid, through a six-member cyclic transition state. (iii) Meanwhile, other products formed through a series of bond cleavage, dehydration, dehydrogenation, interesterification and Diels-Alder cycloaddition. This study could contribute significantly to understanding the polarizing film pyrolysis performance and serve as guidance for the future technological parameters control of the pyrolysis process.

  16. Liquid crystal devices with continuous phase variation based on high-permittivity thin films

    NASA Astrophysics Data System (ADS)

    Willekens, Oliver; Neyts, Kristiaan; Beeckman, Jeroen

    2016-03-01

    Most liquid crystal devices use transparent conductive electrodes such as indium tin oxide (ITO) to apply a potential difference in order to achieve electro-optic switching. As an alternative, we study a device with narrow metallic electrodes in combination with dielectric layers with large dielectric permittivity. In this approach the applied voltage can be a continuous function of the lateral distance from the electrode line. Simulations for a one-dimensional beam-steering device show that the switching of the liquid crystal (LC) director depends indeed on the distance from the addressing electrodes and on the value of the relative permittivity. We show that in a device with electrodes spaced 60 µm apart, the LC director halfway between the electrodes shows a considerable reorientation, when a dielectric layer with permittivity of Epsilonr = 550 is used, whereas no reorientation is observed for the uncoated reference sample at the same voltage. An added advantage is that the proposed configuration only contains dielectric materials, without resistive losses, which means that almost no heat is dissipated. This indicates that this technology could be used in low-power LC devices. The results show that using dielectric thin films with high relative permittivity in liquid crystal devices could form a cost-efficient and low-power alternative to many LC technologies where a gradient electric field is desirable.

  17. Stability of a free-standing liquid-crystal film: The measurement of the interaction between the film surfaces

    SciTech Connect

    Dolganov, P. V.; Nguyen, H. T.; Joly, G.; Kats, E. I. Dolganov, V. K.; Cluzeau, P.

    2007-10-15

    The interaction energy of the surfaces of a free-standing liquid-crystal film has been determined. The measurements are performed in a smectic phase below the melting temperature of a bulk sample T{sub C}, in the temperature range of structural instability of thin films at T > T{sub C}, and in a quasi-smectic phase at T > T{sub C}. Two modes of smectic-layer motion in the film are detected: they lead to film thinning at T > T{sub C} and film thickening at a low temperature. The measurement results are discussed in terms of recent theoretical concepts.

  18. Acoustic streaming in two-dimensional freely suspended smectic liquid crystal films

    NASA Astrophysics Data System (ADS)

    Yablonskii, S. V.; Kurbatov, N. M.; Parfenyev, V. M.

    2017-01-01

    We study horizontal streaming excited by means of a low-frequency and low-intensity acoustic wave in 2D freely suspended films of thermotropic smectic liquid crystals. Acoustic pressure induces fast periodic transverse oscillations of the film, which produce in-plane stationary couples of vortices slowly rotating in opposite directions owing to hydrodynamic nonlinearity. The parameters of the vortices are measured using a new method, based on tracking solidlike disk-shaped islands. The horizontal motion occurs only when the amplitude of the acoustic pressure exceeds the threshold value, which can be explained by Bingham-like behavior of the smectic film. The measurements above threshold are in good agreement with existing theoretical predictions. We demonstrate experimentally that in-plane flow is well controlled by changing the acoustic pressure, excitation frequency, and geometry of the film. The observations open the way to using the phenomenon in nondisplay applications.

  19. Liquid crystal films as on-demand, variable thickness (50–5000 nm) targets for intense lasers

    SciTech Connect

    Poole, P. L. Andereck, C. D.; Schumacher, D. W.; Daskalova, R. L.; Feister, S.; George, K. M.; Willis, C.; Akli, K. U.; Chowdhury, E. A.

    2014-06-15

    We have developed a new type of target for intense laser-matter experiments that offers significant advantages over those currently in use. The targets consist of a liquid crystal film freely suspended within a metal frame. They can be formed rapidly on-demand with thicknesses ranging from nanometers to micrometers, where the particular value is determined by the liquid crystal temperature and initial volume as well as by the frame geometry. The liquid crystal used for this work, 8CB (4′-octyl-4-cyanobiphenyl), has a vapor pressure below 10{sup −6} Torr, so films made at atmospheric pressure maintain their initial thickness after pumping to high vacuum. Additionally, the volume per film is such that each target costs significantly less than one cent to produce. The mechanism of film formation and relevant physics of liquid crystals are described, as well as ion acceleration data from the first shots on liquid crystal film targets at the Ohio State University Scarlet laser facility.

  20. Utilizing liquid crystal phases to obtain highly ordered thin films for organic electronics

    NASA Astrophysics Data System (ADS)

    Springer, Mike T.

    Organic electronic materials offer several advantages when compared to inorganic materials, but they suffer from low charge carrier mobility. Two major factors hindering effective charge transport in organic materials are: 1) effective wavefunction overlap in organic crystals and 2) the domain morphology of thin films. Charge transport in organic materials occurs via a hopping mechanism along the conjugated pi system. Often, rigid, aromatic organic materials crystallize in a herringbone, edge-to-face orientation, limiting pi-pi stacking and decreasing charge carrier mobility. Face-to-face orientation of aromatic rings decreases intermolecular pi-pi distances and increases wavefunction overlap. Control of the crystal structure can be achieved to some extent by tuning structural features of the molecule, like increasing the ratio of carbon atoms to hydrogen atoms in the aromatic rings; this is often achieved by introducing heteroatoms like sulfur and oxygen into the aromatic ring structure. Thin films of organic materials often contain many unaligned domains; this is caused by rapid crystallization. Control of the domain morphology of thin films has been shown to increase charge carrier mobility by 6 orders of magnitude for thin films of the same material. Liquid crystal phases allow a slow process of crystallization, whereby the molecules in a thin film can be slowly aligned into a monodomain before crystallization. The crystal-smectic phases, like smectic E, are particularly attractive for this strategy due to their high degree of intermolecular order. This project describes the synthesis and characterization of organic semiconductors designed to exhibit short pi-pi distances and highly ordered crystal-smectic phases to obtain thin films with high charge carrier mobility. The n,2-OBTTT series contains 15 newly designed and synthesized mesogens. The liquid crystal and solid crystal structures of these mesogens are examined and deposition conditions are optimized for

  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. Stabilization of nematic liquid crystal dispersions with acrylamide copolymers and their electrooptical properties

    NASA Astrophysics Data System (ADS)

    Park, Soo-Jin; Seo, Min-Kang; Han, Mijeong; Lee, Jae-Rock

    2003-01-01

    This study reports the observation of electrooptical properties in polymer-dispersed liquid crystal films during the formation of a copolymerization of hydrophilic acrylamide with hydrophobic monomers (styrene and methyl methacrylate). According to the interfacial tension and coalescence time measurements, it is proposed that the presence of hydrophobic moieties onto nematic liquid crystal (NLC) droplet surface leads to a steric stabilization of the dispersion, due to increasing interfacial tension of NLC, decreasing NLC droplet size, and finally reducing anchoring effect between NLC and polymeric wall.

  3. Observation of two regions of selective light reflection from a thin film of a cholesteric liquid crystal

    SciTech Connect

    Alaverdyan, R B; Dadalyan, T K; Chilingaryan, Yurii S

    2013-05-31

    Two regions of selective light reflection (in the short- and long- wavelength parts of the visible spectrum) from a thin film of a cholesteric liquid crystal (CLC), consisting of the mixture of two CLCs with opposite chirality and a nematic liquid crystal, are experimentally found for the first time. The spectral position of the reflection regions and the separation between them varies depending on the CLC composition and the temperature. The long-wavelength region of reflection corresponds to the region of Bragg reflection from the CLC helix, while the short-wavelength region is probably due to the defects in the structure of the CLC film. (letters)

  4. Photomechanical bending mechanics of polydomain azobenzene liquid crystal polymer network films

    SciTech Connect

    Cheng Liang; Torres, Yanira; Oates, William S.; Lee, Kyung Min; McClung, Amber J.; Baur, Jeffery; White, Timothy J.

    2012-07-01

    Glassy, polydomain azobenzene liquid crystal polymer networks (azo-LCNs) have been synthesized, characterized, and modeled to understand composition dependence on large amplitude, bidirectional bending, and twisting deformation upon irradiation with linearly polarized blue-green (440-514 nm) light. These materials exhibit interesting properties for adaptive structure applications in which the shape of the photoresponsive material can be rapidly reconfigured with light. The basis for the photomechanical output observed in these materials is absorption of actinic light by azobenzene, which upon photoisomerization dictates an internal stress within the local polymer network. The photoinduced evolution of the underlying liquid crystal microstructure is manifested as macroscopic deformation of the glassy polymer film. Accordingly, this work examines the polarization-controlled bidirectional bending of highly concentrated azo-LCN materials and correlates the macroscopic output (observed as bending) to measured blocked stresses upon irradiation with blue-green light of varying polarization. The resulting photomechanical output is highly dependent on the concentration of crosslinked azobenzene mesogens employed in the formulation. Experiments that quantify photomechanical bending and photogenerated stress are compared to a large deformation photomechanical shell model to quantify the effect of polarized light interactions with the material during static and dynamic polarized light induced deformation. The model comparisons illustrate differences in internal photostrain and deformation rates as a function of composition and external mechanical constraints.

  5. 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.

  6. Wrinkling of a thin film on a nematic liquid-crystal elastomer

    NASA Astrophysics Data System (ADS)

    Soni, Harsh; Pelcovits, Robert A.; Powers, Thomas R.

    2016-07-01

    Wrinkles commonly develop in a thin film deposited on a soft elastomer substrate when the film is subject to compression. Motivated by recent experiments [Agrawal et al., Soft Matter 8, 7138 (2012)], 10.1039/c2sm25734c that show how wrinkle morphology can be controlled by using a nematic elastomer substrate, we develop the theory of small-amplitude wrinkles of an isotropic film atop a nematic elastomer. The directors of the nematic elastomer are initially uniform. For uniaxial compression of the film along the direction perpendicular to the elastomer directors, the system behaves as a compressed film on an isotropic substrate. When the uniaxial compression is along the direction of nematic order, we find that the soft elasticity characteristic of liquid-crystal elastomers leads to a critical stress for wrinkling which is very small compared to the case of an isotropic substrate. We also determine the wavelength of the wrinkles at the critical stress and show how the critical stress and wavelength depend on substrate depth and the anisotropy of the polymer chains in the nematic elastomer.

  7. Optically switchable and axially symmetric half-wave plate based on photoaligned liquid crystal films

    NASA Astrophysics Data System (ADS)

    Lin, C.-C.; Huang, T.-C.; Chu, C.-C.; Hsiao, Vincent K. S.

    2016-07-01

    We demonstrate an optically switchable half-wave plate (HWP) composed of a photoaligned and axially symmetric liquid crystal (ASLC) film containing two azobenzene derivatives, methyl red (MR) and 4-butyl-4‧-methoxyazobenzene (BMAB). MR is responsible for photoalignment, and BMAB is used for optical tuning and switching the state of polarization (SOP) of probe beam (633 nm He-Ne laser) passing through the MR/BMAB doped ASLC film. The photoaligned ASLC film is first fabricated using a line-shaped laser beam (532 nm) exposure applied on a rotating LC sample. The fabricated ASLC film can passively change the linearly polarized light. Under UV light exposure, the formation of cis-BMAB (bend-like shape) within the film disrupts the LC molecules, switches the LC orientation, and further changes the SOP of the probe beam. Under laser irradiation (532 nm), the formation of trans-BMAB (rod-like shape) reverts the LC orientation back and simultaneously generates cis-MR, helping anchor the LC in the previously photoaligned orientation. The photoaligned MR/BMAB-doped LC HWP can change the linear SOP under alternating UV and visible light exposure.

  8. Wrinkling of a thin film on a nematic liquid-crystal elastomer.

    PubMed

    Soni, Harsh; Pelcovits, Robert A; Powers, Thomas R

    2016-07-01

    Wrinkles commonly develop in a thin film deposited on a soft elastomer substrate when the film is subject to compression. Motivated by recent experiments [Agrawal et al., Soft Matter 8, 7138 (2012)]1744-683X10.1039/c2sm25734c that show how wrinkle morphology can be controlled by using a nematic elastomer substrate, we develop the theory of small-amplitude wrinkles of an isotropic film atop a nematic elastomer. The directors of the nematic elastomer are initially uniform. For uniaxial compression of the film along the direction perpendicular to the elastomer directors, the system behaves as a compressed film on an isotropic substrate. When the uniaxial compression is along the direction of nematic order, we find that the soft elasticity characteristic of liquid-crystal elastomers leads to a critical stress for wrinkling which is very small compared to the case of an isotropic substrate. We also determine the wavelength of the wrinkles at the critical stress and show how the critical stress and wavelength depend on substrate depth and the anisotropy of the polymer chains in the nematic elastomer.

  9. Merged vector gratings recorded in a photocrosslinkable polymer liquid crystal film for polarimetry

    SciTech Connect

    Sasaki, Tomoyuki Wada, Takumi; Noda, Kohei; Ono, Hiroshi; Kawatsuki, Nobuhiro

    2014-01-14

    A merged vector grating, which is holographically fabricated in an anisotropic medium by irradiation with interference light with intensity modulation and polarization modulation, was designed to detect the polarization of light. The merged vector grating is recorded by the interference of two elliptically polarized beams with equal intensities, parallel azimuths, equal ellipticities, and different directions of rotation. We clarified theoretically that the Stokes parameters of the incident light beam are described by the diffraction efficiency of the merged vector grating. Also, to apply this property to formation of a polarimeter without any moving parts or mechanisms, two merged vector gratings with different grating vectors were recorded in a photocrosslinkable polymer liquid crystal film by angle-multiplexed holography. By investigation of the diffraction properties of the gratings obtained, we demonstrated the applicability of the merged vector gratings for use in polarimetry.

  10. Spatially resolved lasers using a glassy cholesteric liquid crystal film with lateral pitch gradient

    NASA Astrophysics Data System (ADS)

    Wei, Simon K. H.; Chen, Shaw H.

    2011-03-01

    To fabricate spatially resolved glassy cholesteric liquid crystal (CLC) lasers, a lateral pitch gradient was introduced by thermally activated diffusion across the interface of two films comprising nematic and cholesteric oligofluorene doped with a red-emitting oligifluorene. The formation of spatially resolved Grandjean-Cano bands was accountable by strong surface anchoring at substrates and the qualitative chiral concentration profile. Across each band there was a common stop band, and a set of bands produced multiple lasing peaks across the spectral range determined by light-emitter's fluorescence spectrum. The resultant lasing thresholds, 6.6-7.6 mJ/cm2, and slope efficiencies, 0.2%-1.5%, are superior to those reported to date for gradient-pitch CLC lasers.

  11. The ergonomics approach for thin film transistor-liquid crystal display manufacturing process.

    PubMed

    Lu, Chih-Wei; Yao, Chia-Chun; Kuo, Chein-Wen

    2012-01-01

    The thin film transistor-liquid crystal display (TFT-LCD) has been used all over the world. Although the manufacture process of TFT-LCD was highly automated, employees are hired to do manual job in module assembly process. The operators may have high risk of musculoskeletal disorders because of the long work hours and the repetitive activities in an unfitted work station. The tools of this study were questionnaire, checklist and to evaluate the work place design. The result shows that the participants reported high musculoskeletal disorder symptoms in shoulder (59.8%), neck (49.5%), wrist (39.5%), and upper back (30.6%). And, to reduce the ergonomic risk factors, revising the height of the work benches, chairs and redesigning the truck to decrease the chance of unsuitable positions were recommended and to reduce other ergonomics hazards and seta good human machine interface and appropriate job design.

  12. Interference patterns of scattering light induced by orientational fluctuations in an electric-field-biased nematic liquid-crystal film.

    PubMed

    Shen, Y; Chen, S H; Hsu, C H; Lai, Y

    1998-06-15

    A new light-scattering phenomenon from a planar aligned nematic liquid-crystal film is observed and studied. This new phenomenon exhibits ring patterns in the orthogonal polarization. A simple model based on optical interference has been developed, and its predictions agree well with experimental observation.

  13. Vacuum filtration based formation of liquid crystal films of semiconducting carbon nanotubes and high performance transistor devices

    NASA Astrophysics Data System (ADS)

    King, Benjamin; Panchapakesan, Balaji

    2014-05-01

    In this paper, we report ultra-thin liquid crystal films of semiconducting carbon nanotubes using a simple vacuum filtration process. Vacuum filtration of nanotubes in aqueous surfactant solution formed nematic domains on the filter membrane surface and exhibited local ordering. A 2D fast Fourier transform was used to calculate the order parameters from scanning electron microscopy images. The order parameter was observed to be sensitive to the filtration time demonstrating different regions of transformation namely nucleation of nematic domains, nanotube accumulation and large domain growth.Transmittance versus sheet resistance measurements of such films resulted in optical to dc conductivity of σ opt/σ dc = 9.01 indicative of purely semiconducting nanotube liquid crystal network.Thin films of nanotube liquid crystals with order parameters ranging from S = 0.1-0.5 were patterned into conducting channels of transistor devices which showed high I on/I off ratios from 10-19 800 and electron mobility values μ e = 0.3-78.8 cm2 (V-s)-1, hole mobility values μ h = 0.4-287 cm2 (V-s)-1. High I on/I off ratios were observed at low order parameters and film mass. A Schottky barrier transistor model is consistent with the observed transistor characteristics. Electron and hole mobilities were seen to increase with order parameters and carbon nanotube mass fractions. A fundamental tradeoff between decreasing on/off ratio and increasing mobility with increasing nanotube film mass and order parameter is therefore concluded. Increase in order parameters of nanotubes liquid crystals improved the electronic transport properties as witnessed by the increase in σ dc/σ opt values on macroscopic films and high mobilities in microscopic transistors. Liquid crystal networks of semiconducting nanotubes as demonstrated here are simple to fabricate, transparent, scalable and could find wide ranging device applications.

  14. Characterization of rhenium oxide films and their application to liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Cazzanelli, E.; Castriota, M.; Marino, S.; Scaramuzza, N.; Purans, J.; Kuzmin, A.; Kalendarev, R.; Mariotto, G.; Das, G.

    2009-06-01

    Rhenium trioxide exhibits high electronic conductivity, while its open cubic crystal structure allows an appreciable hydrogen intercalation, generating disordered solid phases, with protonic conductivity. Rhenium oxide thin films have been obtained by thermal evaporation of ReO3 powders on different substrates, maintained at different temperatures, and also by reactive magnetron sputtering of a Re metallic target. A comparative investigation has been carried out on these films, by using micro-Raman spectroscopy and x-ray diffraction. Two basic types of solid phases appear to grow in the films: a red metallic HxReO3 compound, with distorted perovskite structures, like in the bulk material, and ordered HReO4 crystals based on tetrahedral perrhenate ions. Because of its conduction properties, the electrical and electro-optical behaviors of ReO3 films deposited on standard indium tin oxide/glass substrate have been tested inside asymmetric nematic liquid crystal cells, showing an appreciable capability of rectification of their electro-optical response, in similar way to tungsten trioxide.

  15. Ion capturing/ion releasing films and nanoparticles in liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Garbovskiy, Yuriy

    2017-01-01

    Nanoparticles dispersed in liquid crystals can change the concentration of mobile ions through the adsorption/desorption process. In the majority of the reported cases, the effects of nanoparticles on the electrical properties of liquid crystals are analysed, neglecting the interactions of ions with substrates. In this paper, the combined effect of nanoparticles and substrates on the concentration of ions in liquid crystals is discussed. Depending on the ionic purity of substrates and nanoparticles, the ion capturing/ion releasing regimes can be achieved. In addition, the concentration of mobile ions in liquid crystal nanocolloids also depends on the cell thickness.

  16. Orientations of Chromonic Liquid Crystals by Imprinted or Rubbed Polymer Films

    NASA Astrophysics Data System (ADS)

    Yi, Youngwoo; McGuire, Aya; Clark, Noel

    2014-03-01

    A variety of novel alignment effects of chromonic liquid crystal phases of sunset yellow (SSY)/water, disodium cromoglycate (DSCG)/water, and their mixtures by thiol-ene polymer films topographically imprinted with linear channels are observed using polarizing optical microscopy. Nematic DSCG and SSY at low concentration and their nematic mixtures orient with the long axes of stacked chromonic aggregates on average parallel to the channels, that is, with the molecular planes normal to the channel axis. On the contrary, nematic SSY in contact with the rubbed polyimide films orients with the long axes on average in-plane perpendicular to the rubbing direction, arguably, due to a tongue-groove interaction between SSY and the stretched PI chains. Furthermore, multi-stable alignments are observed in SSY solutions of sufficiently high concentration, including preferential in-plane orientation of the long axes of the aggregates parallel to, perpendicular to, and 45° rotated from the channels. This work was supported by NSF grant DMR 1207606, NSF MRSEC grant DMR 0820579, and NSF Research Experience for Undergraduate programs.

  17. Self-organized arrays of dislocations in thin smectic liquid crystal films.

    PubMed

    Coursault, Delphine; Zappone, Bruno; Coati, Alessandro; Boulaoued, Athmane; Pelliser, Laurent; Limagne, Denis; Boudet, Nathalie; Ibrahim, Bicher Haj; de Martino, Antonello; Alba, Michel; Goldmann, Michel; Garreau, Yves; Gallas, Bruno; Lacaze, Emmanuelle

    2016-01-21

    Combining optical microscopy, synchrotron X-ray diffraction and ellipsometry, we studied the internal structure of linear defect domains (oily streaks) in films of a smectic liquid crystal 8CB with thicknesses in the range of 100-300 nm. These films are confined between air and a rubbed PVA polymer substrate which imposes hybrid anchoring conditions (normal and unidirectional planar, respectively). We show how the presence or absence of dislocations controls the structure of highly deformed thin smectic films. Each domain contains smectic layers curved in the shape of flattened hemicylinders to satisfy both anchoring conditions, together with grain boundaries whose size and shape are controlled by the presence of dislocation lines. A flat grain boundary normal to the interface connects neighboring hemicylinders, while a rotating grain boundary (RGB) is located near the axis of curvature of the cylinders. The RGB shape appears such that dislocation lines are concentrated at its summit close to the air interface. The smectic layers reach the polymer substrate via a transition region where the smectic layer orientation satisfies the planar anchoring conditions over the entire polymer substrate and whose thickness does not depend on that of the film. The strength of planar anchoring appears to be high, larger than 10(-2) mJ m(-2), compensating for the high energy cost of creating an additional 2D defect between a horizontal smectic layer and perpendicular ones of the transition region. This 2D defect may be melted, in order to avoid the creation of a transition region structure composed of a large number of dislocations. As a result, linear defect domains can be considered as arrays of oriented defects, straight dislocations of various Burger vectors, whose location is now known, and 2D nematic defects. The possibility of easy variation between the present structure with a moderate amount of dislocations and a structure with a large number of dislocations is also

  18. 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.

  19. The utilization of thin film transistor liquid crystal display waste glass as a pozzolanic material.

    PubMed

    Lin, K L; Huang, Wu-Jang; Shie, J L; Lee, T C; Wang, K S; Lee, C H

    2009-04-30

    This investigation elucidates the pozzolanic behavior of waste glass blended cement (WGBC) paste used in thin film transistor liquid crystal displays (TFT-LCD). X-ray diffraction (XRD) results demonstrate that the TFT-LCD waste glass was entirely non-crystalline. The leaching concentrations of the clay and TFT-LCD waste glass all met the current regulatory thresholds of the Taiwan EPA. The pozzolanic strength activity indices of TFT-LCD waste glass at 28 days and 56 days were 89% and 92%, respectively. Accordingly, this material can be regarded as a good pozzolanic material. The amount of TFT-LCD waste glass that is mixed into WGBC pastes affects the strength of the pastes. The strength of the paste clearly declined as the amount of TFT-LCD waste glass increased. XRD patterns indicated that the major difference was the presence of hydrates of calcium silicate (CSH, 2 theta=32.1 degrees), aluminate and aluminosilicate, which was present in WGBC pastes. Portland cement may have increased the alkalinity of the solution and induced the decomposition of the glass phase network. WGBC pastes that contained 40% TFT-LCD waste glass have markedly lower gel/space ratios and exhibit less degree of hydration than ordinary Portland cement (OPC) pastes. The most satisfactory characteristics of the strength were observed when the mixing ratio of the TFT-LCD waste glass was 10%.

  20. Liquid crystal photoalignment on As2S3 chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Sheremet, N. V.; Sharpnack, L.; Gelbaor-Kirzhner, M.; Agra-Kooijman, D. M.; Chaudhary, A.; Kumar, T. A.; Klebanov, M.; Abdulhalim, I.; Kumar, S.; Reznikov, Yu A.

    2017-02-01

    Recent studies of photoalignment of liquid crystals (LCs) on chalcogenide surfaces have a rich variety of mechanisms responsible for the photoalignment on these materials. Both chalcogenide surface-mediated and LC bulk-mediated photoalignment were observed. We report on investigation toward understanding the origin of the chalcogenide surface-mediated photoalignment. The contributions of light-induced optical and surface morphological anisotropy of the chalcogenide surface were studied. Light-induced optical anisotropy in the film was observed by polarization interferometry and the surface anisotropy was measured by high-resolution x-ray reflectivity. The data reveals the lack of a strong anisotropy in the surfaces’ morphology after irradiation with polarized blue light. At the same time, an evident correlation between the anchoring energy and the quality of the photoalignment was observed. This allows us to conclude that the photoalignment of LCs on chalcogenide surfaces is mainly determined by a light-induced anisotropic distribution of the glass structural elements in the bulk and on the chalcogenide surface.

  1. Automated optical inspection of liquid crystal display anisotropic conductive film bonding

    NASA Astrophysics Data System (ADS)

    Ni, Guangming; Du, Xiaohui; Liu, Lin; Zhang, Jing; Liu, Juanxiu; Liu, Yong

    2016-10-01

    Anisotropic conductive film (ACF) bonding is widely used in the liquid crystal display (LCD) industry. It implements circuit connection between screens and flexible printed circuits or integrated circuits. Conductive microspheres in ACF are key factors that influence LCD quality, because the conductive microspheres' quantity and shape deformation rate affect the interconnection resistance. Although this issue has been studied extensively by prior work, quick and accurate methods to inspect the quality of ACF bonding are still missing in the actual production process. We propose a method to inspect ACF bonding effectively by using automated optical inspection. The method has three steps. The first step is that it acquires images of the detection zones using a differential interference contrast (DIC) imaging system. The second step is that it identifies the conductive microspheres and their shape deformation rate using quantitative analysis of the characteristics of the DIC images. The final step is that it inspects ACF bonding using a back propagation trained neural network. The result shows that the miss rate is lower than 0.1%, and the false inspection rate is lower than 0.05%.

  2. Direct induction of molecular alignment in liquid crystal polymer network film by photopolymerization

    NASA Astrophysics Data System (ADS)

    Hisano, K.; Aizawa, M.; Ishizu, M.; Kurata, Y.; Shishido, A.

    2016-09-01

    Liquid crystal (LC) is the promising material for the fabrication of high-performance soft, flexible devices. The fascinating and useful properties arise from their cooperative effect that inherently allows the macroscopic integration and control of molecular alignment through various external stimuli. To date, light-matter interaction is the most attractive stimuli and researchers developed photoalignment through photochemical or photophysical reactions triggered by linearly polarized light. Here we show the new choice based on molecular diffusion by photopolymerization. We found that photopolymerization of a LC monomer and a crosslinker through a photomask enables to direct molecular alignment in the resultant LC polymer network film. The key generating the molecular alignment is molecular diffusion due to the difference of chemical potentials between irradiated and unirradiated regions. This concept is applicable to various shapes of photomask and two-dimensional molecular alignments can be fabricated depending on the spatial design of photomask. By virtue of the inherent versatility of molecular diffusion in materials, the process would shed light on the fabrication of various high-performance flexible materials with molecular alignment having controlled patterns.

  3. Photoalignment of a Nematic Liquid Crystal Fluid and Glassy-Nematic Oligofluorenes on Coumarin-Containing Polymer Films

    SciTech Connect

    Trajkovska, A.; Kim, C.; Marshall, K.L.; Mourey, T.H.; Chen, S.H.

    2007-03-19

    The orientations of both a nematic liquid crystal fluid and a series of monodisperse glassy-nematic oligofluorenes were investigated on photoalignment films comprising a polymethacrylate backbone with 7-benzoyloxycoumarin pendants. Both classes of liquid crystalline material were found to undergo a transition from a parallel to a perpindicular orientation with reference to the polarization axis of UV-irradiation at a sufficiently high extent of dimerization.

  4. 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.

  5. Recycling acetic acid from polarizing film of waste liquid crystal display panels by sub/supercritical water treatments.

    PubMed

    Wang, Ruixue; Chen, Ya; Xu, Zhenming

    2015-05-19

    Waste liquid crystal display (LCD) panels mainly contain inorganic materials (glass substrate) and organic materials (polarizing film and liquid crystal). The organic materials should be removed first since containing polarizing film and liquid crystal is to the disadvantage of the indium recycling process. In the present study, an efficient and environmentally friendly process to obtain acetic acid from waste LCD panels by sub/supercritical water treatments is investigated. Furthermore, a well-founded reaction mechanism is proposed. Several highlights of this study are summarized as follows: (i) 99.77% of organic matters are removed, which means the present technology is quite efficient to recycle the organic matters; (ii) a yield of 78.23% acetic acid, a quite important fossil energy based chemical product is obtained, which can reduce the consumption of fossil energy for producing acetic acid; (iii) supercritical water acts as an ideal solvent, a requisite reactant as well as an efficient acid-base catalyst, and this is quite significant in accordance with the "Principles of Green Chemistry". In a word, the organic matters of waste LCD panels are recycled without environmental pollution. Meanwhile, this study provides new opportunities for alternating fossil-based chemical products for sustainable development, converting "waste" into "fossil-based chemicals".

  6. Effects of nanoparticle doping on the phase transitional behaviour of ferroelectric liquid crystal Langmuir-Blodgett composite films

    NASA Astrophysics Data System (ADS)

    Kaur, Ramneek; Raina, K. K.

    2015-12-01

    Langmuir-Blodgett films of ferroelectric liquid crystals (FLCs) doped with a low concentration of functionalized Al: ZnO (AZO) nanoparticles were prepared and characterized. Pressure-area isotherms show that the nanoparticles as well as FLC composite systems have the capability to form stable monolayers at the air-water interface. The molecular interaction between nanoparticles and FLC molecules increased during barrier compression, which resulted in increased surface pressure. We observed various phases in isotherms with increasing concentration of nanoparticles in the FLC matrix. An X-ray diffraction profile at a low angle confirmed that FLCs retain their layer structure at a low concentration doping of AZO nanoparticles in the FLC matrix. Atomic force microscopy images indicate that low wt% composites are uniformly deposited without disturbing the translation behaviour of SmC* liquid crystals.

  7. 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.

  8. Microfludic Sensing Devices Employing In Situ-Formed Liquid Crystal Thin Film for Detection of Biochemical Interactions1†

    PubMed Central

    Liu, Ye; Cheng, Daming; Lin, I-Hsin; Abbott, Nicholas L.; Jiang, Hongrui

    2012-01-01

    Although biochemical sensing using liquid crystals (LC) has been demonstrated, relatively little attention has been paid towards the fabrication of in situ-formed LC sensing devices. Herein, we demonstrate a highly reproducible method to create uniform LC thin film on treated substrates, as needed, for LC sensing. We use shear forces generated by the laminar flow of aqueous liquid within a microfluidic channel to create LC thin films stabilized within microfabricated structures. The orientational response of the LC thin films to targeted analytes in aqueous phases was transduced and amplified by the optical birefringence of the LC thin films. The biochemical sensing capability of our sensing devices was demonstrated through experiments employing two chemical systems: dodecyl trimethylammonium bromide (DTAB) dissolved in an aqueous solution, and the hydrolysis of phospholipids by the enzyme phospholipase A2 (PLA2). PMID:22842797

  9. Effects of thermomechanical properties of polarizer components on light leakage in thin-film transistor liquid-crystal displays

    NASA Astrophysics Data System (ADS)

    Lin, Taiy-In; Chen, Alexander; Chen, Shou-I.; Leu, Jihperng

    2015-07-01

    In this paper, we present static thermal analysis of stress and strain on a thin-film transistor liquid-crystal display (TFT-LCD) panel and their correlation with light leakage phenomena under high-temperature durability test. Three-dimensional (3D) finite element analysis (FEA) is coupled with experimental parameters of key components of the TFT-LCD panel for the analysis. A strong correlation exists between light leakage and retardation difference induced by stress on triacetyl cellulose (TAC) films. Moreover, shrinkage in stretched poly(vinyl alcohol) (PVA) film and modulus of the adhesive layer are key factors affecting stress distribution and displacement of polarizer stack. An increase in Young’s modulus (E) of the adhesive layer effectively reduces polarizer shrinkage and light leakage at the center of the panel. A TAC film with lower Young’s modulus and/or coefficient of thermal expansion (CTE) is also an effective solution.

  10. Morphology of SiO2 films as a key factor in alignment of liquid crystals with negative dielectric anisotropy

    PubMed Central

    Marino, Antigone; Otón, Eva; Bennis, Noureddine; Otón, Josè Manuel

    2016-01-01

    Control of liquid crystal (LC) orientation using a proper SiO2 alignment layer is essential for the optimization of vertically aligned nematic (VAN) displays. With this aim, we studied the optical anisotropy of thin SiO2 films by generalized ellipsometry as a function of deposition angle. The columnar SiO2 structure orientation measured by a noninvasive ellipsometry technique is reported for the first time, and its morphology influence on the LC alignment is demonstrated for large deposition angles. PMID:28144524

  11. Effects of Saponification Rate on Electrooptical Properties and Morphology of Poly(vinyl alcohol)/Liquid Crystal Composite Films

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Kawatsuki, Nobuhiro

    1995-03-01

    The relationship between the saponification rate of poly(vinyl alcohol) (PVA), and the electrooptical properties and morphology of the PVA/liquid crystal (LC) composite films was investigated. Light transmission clazing and the LC droplet size were varied by changing the saponification rate or the blend ratio of two kinds of PVA with different saponification rates because the refractive index and surface tension could be controlled by the saponification rate of PVA. The threshold voltage decreased with increasing saponification rate though the extrapolation length was decreased. It was suggested that the electrooptical properties were strongly dependent on the droplet size.

  12. Morphology of SiO2 films as a key factor in alignment of liquid crystals with negative dielectric anisotropy.

    PubMed

    Tkachenko, Volodymyr; Marino, Antigone; Otón, Eva; Bennis, Noureddine; Otón, Josè Manuel

    2016-01-01

    Control of liquid crystal (LC) orientation using a proper SiO2 alignment layer is essential for the optimization of vertically aligned nematic (VAN) displays. With this aim, we studied the optical anisotropy of thin SiO2 films by generalized ellipsometry as a function of deposition angle. The columnar SiO2 structure orientation measured by a noninvasive ellipsometry technique is reported for the first time, and its morphology influence on the LC alignment is demonstrated for large deposition angles.

  13. A low-power all-optical bistable device based on a liquid crystal layer embedded in thin gold films

    NASA Astrophysics Data System (ADS)

    Takase, Yuki; Tien Thanh, Pham; Fujimura, Ryushi; Kajikawa, Kotaro

    2014-04-01

    An all-optical bistable (AOB) resonator device composed of a 430-nm-thick liquid crystal (LC) layer embedded in two thin gold films (MLM) is reported in this paper. This device allows the use of the incident illumination at normal incidence, whereas the previous AOB devices based on twisted nematic (TN)-LC function only for illumination at oblique incidence. The fastest switching time was measured to be 1.8 ms, which is significantly faster than that of TN-LC. Because the MLM device operates free from electronic circuits, it is promising for two-dimensional optical data processing, random access optical memories, and spatial light modulators.

  14. Optical monitoring of anchoring change in vertically aligned thin liquid crystal film for chemical and biological sensor.

    PubMed

    Zou, Yang; Namkung, Jun; Lin, Yongbin; Lindquist, Robert

    2010-04-01

    A significant advance in sensitivity of liquid-crystal (LC)-based chemical and biological sensors can be achieved by actively monitoring anchoring energy change. We simulate the deformation of a LC director with different anchoring energies using the finite element method and the optical properties of the LC film using the finite-difference time-domain method. Polarizing micrographs are collected and compared with simulated textures. Measurement of optical transmission is used to monitor the anchoring change. Experimental and simulation results both demonstrate the optical method can effectively monitor the surface anchoring change due to the presence of targeted analytes.

  15. Development of Liquid Crystal Display Panel Integrated with Drivers Using Amorphous In-Ga-Zn-Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Takeshi Osada,; Kengo Akimoto,; Takehisa Sato,; Masataka Ikeda,; Masashi Tsubuku,; Junichiro Sakata,; Jun Koyama,; Tadashi Serikawa,; Shunpei Yamazaki,

    2010-03-01

    We designed, prototyped, and evaluated a liquid crystal panel integrated with a gate driver and a source driver using amorphous In-Ga-Zn-oxide thin film transistors (TFTs). Using bottom-gate bottom-contact (BGBC) thin film transistors, superior characteristics could be obtained. We obtained TFT characteristics with little variation even when the thickness of the gate insulator (GI) film was reduced owing to etching of source/drain (S/D) wiring, which is a typical process for the BGBC TFT. Moreover, a favorable ON-state current was obtained even when an In-Ga-Zn-oxide layer was formed over the S/D electrode. Since the upper portion of the In-Ga-Zn-oxide layer is not etched, the BGBC structure is predicted to be effective in thinning the In-Ga-Zn-oxide layer in the future. Upon evaluation, we found that the prototyped liquid crystal panel integrated with the gate and source drivers using the TFTs with improved characteristics had stable drive.

  16. Liquid-crystal-anchoring transitions at surfaces created by polymerization-induced phase separation

    NASA Astrophysics Data System (ADS)

    Amundson, Karl R.; Srinivasarao, Mohan

    1998-08-01

    A surface anchoring transition of a nematic at polymer surfaces created by polymerization-induced phase separation is presented. This transition is unusual in that it occurs far from bulk nematic phase transitions and it is tunable across nearly the entire nematic temperature range by modification of the polymer side group. Anchoring behavior is qualitatively understood by considerating enthalpic and entropic contributions to surface energy. Interesting behavior of some polymer-dispersed liquid-crystal films is explained, and observations provide a pathway to control properties.

  17. Unsteady High Turbulence Effects on Turbine Blade Film Cooling Heat Transfer Performance Using a Transient Liquid Crystal Technique

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Ekkad, S. V.; Du, H.; Teng, S.

    2000-01-01

    Unsteady wake effect, with and without trailing edge ejection, on detailed heat transfer coefficient and film cooling effectiveness distributions is presented for a downstream film-cooled gas turbine blade. Tests were performed on a five-blade linear cascade at an exit Reynolds number of 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.4 to 1.2; air and CO2 were used as coolants to simulate different density ratios. Surface heat transfer and film effectiveness distributions were obtained using a transient liquid crystal technique; coolant temperature profiles were determined with a cold wire technique. Results show that Nusselt numbers for a film cooled blade are much higher compared to a blade without film injection. Unsteady wake slightly enhances Nusselt numbers but significantly reduces film effectiveness versus no wake cases. Nusselt numbers increase only slic,htly but film cooling, effectiveness increases significantly with increasing, blowing ratio. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher 0 effectiveness at lower blowing ratios (M = 0.8). Trailing edge ejection generally has more effect on film effectiveness than on the heat transfer, typically reducing film effectiveness and enhancing heat transfer. Similar data is also presented for a film cooled cylindrical leading edge model.

  18. Photoinduced changes of surface order in coumarin side-chain polymer films used for liquid crystal photoalignment

    SciTech Connect

    Bergmann, G.; Jackson, P.O.; Hogg, J.H.C.; Stirner, T.; O'Neill, M.; Duffy, W.L.; Kelly, S.M.; Clark, G.F.

    2005-08-08

    Specular x-ray reflectivity probes morphological changes in a crosslinkable coumarin photoalignment polymer film resulting from ultraviolet irradiation. An ordered surface layer with density oscillations compatible with planar side-chain alignment is obtained before irradiation. The ordering is enhanced in the early stages of crosslinking. This is attributed to the photoinduced increase of mobility of the side-chains resulting from the creation of free volume by the crosslinking process. The expansion of the thin film confirms that free volume is created. The surface ordering decreases with prolonged ultraviolet irradiation because of increased material viscosity resulting from a high crosslinked density. The implications of surface ordering on liquid crystal photoalignment are discussed.

  19. Blazed vector grating liquid crystal cells with photocrosslinkable polymeric alignment films fabricated by one-step polarizer rotation method

    NASA Astrophysics Data System (ADS)

    Kawai, Kotaro; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2014-12-01

    Blazed vector grating liquid crystal (LC) cells, in which the directors of low-molar-mass LCs are antisymmetrically distributed, were fabricated by one-step exposure of an empty glass cell inner-coated with a photocrosslinkable polymer LC (PCLC) to UV light. By adopting a LC cell structure, twisted nematic (TN) and homogeneous (HOMO) alignments were obtained in the blazed vector grating LC cells. Moreover, the diffraction efficiency of the blazed vector grating LC cells was greatly improved by increasing the thickness of the device in comparison with that of a blazed vector grating with a thin film structure obtained in our previous study. In addition, the diffraction efficiency and polarization states of ±1st-order diffracted beams from the resultant blazed vector grating LC cells were controlled by designing a blazed pattern in the alignment films, and these diffraction properties were well explained on the basis of Jones calculus and the elastic continuum theory of nematic LCs.

  20. Electrically switchable liquid crystal Fresnel lens using UV-modified alignment film.

    PubMed

    Jeng, Shie-Chang; Hwang, Shug-June; Horng, Jing-Shyang; Lin, Kuo-Ren

    2010-12-06

    A simple method to make a switchable liquid crystal (LC) Fresnel lens with high diffraction efficiency and a low driving voltage was proposed based on the photo-induced surface modification of the vertical alignment layer. UV illumination alters the pretilt angle of alignment layers, a Fresnel zone-distribution hybrid alignment in the homeotropic LC cell can be straightforwardly achieved through UV exposure, yielding a concentric structure of the Fresnel phase LC lens. A remarkable diffraction efficiency of ~31.4%, close to the measured diffraction efficiency of the used Fresnel-zone-plate mask of 32%, was detected using a linearly polarized incident beam.

  1. Comparative study of acoustic relaxation time of cholesteric liquid crystal and mixtures

    NASA Astrophysics Data System (ADS)

    Bhave, Manisha G.; Gharde, Rita; Radha, S.

    2016-09-01

    The present study focuses on the relaxation processes in Cholesteric Liquid Crystal and mixtures. We have dispersed two different monomers in CLC to form Polymer dispersed liquid crystals (PDCLCs). PDLC films have a remarkable electro-optical behavior since they can be switched from highly light scattering state (OFF) to transparent state (ON) simply by application of an electric field. We have also doped ferroelectric nano - powder (NP) in CLC. The phase transitions occurred at temperatures lower than those exhibited by the mesogenic component before doping. The viscosity, ultrasonic velocity and density show variation with change in the material as well as temperature. The acoustic relaxation time and ultrasonic attenuation decrease with increase in temperature for CLC and CLC+NP. The parameters of PDCLC2 in comparison with PDCLC1 are more linear in isotropic and anisotropic regions. For PDCLC2 the values reach maximum value at the Cholesteric-isotropic transition.

  2. 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.

  3. 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)

  4. 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)

  5. Conducting glasses recovered from thin film transistor liquid crystal display wastes for dye-sensitized solar cell cathodes.

    PubMed

    Chen, C-C; Chang, F-C; Peng, C Y; Wang, H Paul

    2015-01-01

    Transparent conductive glasses such as thin film transistor (TFT) array and colour filter glasses were recovered from the TFT-liquid crystal display panel wastes by dismantling and sonic cleaning. Noble metals (i.e. platinum (Pt)) and indium tin oxide (ITO) are generally used in the cathode of a dye-sensitized solar cell (DSSC). To reduce the DSSC cost, Pt was replaced with nano nickel-encapsulated carbon-shell (Ni@C) nanoparticles, which were prepared by carbonization of Ni²⁺-β-cyclodextrin at 673 K for 2 h. The recovered conductive glasses were used in the DSSC electrodes in the substitution of relatively expensive ITO. Interestingly, the efficiency of the DSSC having the Ni@C-coated cathode is as high as 2.54%. Moreover, the cost of the DSSC using the recovered materials can be reduced by at least 24%.

  6. A biosensor of high-density lipoprotein of human serum on a liquid crystal and polymer composite film

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chang, Kai-Han; Chu, Wei-Lin; Tsou, Yu-Shih; Wu, Li-Ching; Li, Chien-Feng

    2013-10-01

    A biosensor for the concentration of high-density lipoprotein (HDL) in human serum on a liquid crystal and polymer composite film (LCPCF) is demonstrated. The sensing mechanism is based on a polar-polar interaction between orientation of LC directors and HDL in human serum. The concentration of polar HDL in human serum affects the orientations of LC directors at the interface between LCPCF and the human serum. In addition, the surface free energy of LCPCF changes with the applied voltage due to the electrically tunable orientations of LC directors anchored among the polymer grains of LCPCF. As a result, the droplet motion of human serum on LCPCF under applied voltages can sense the concentration of HDL in human serum.

  7. Multifunctional Optical Thin Films Fabricated by the Photopolymerization of Uniaxially Oriented Lyotropic Liquid Crystal Monomers for Electro-Optical Devices

    PubMed Central

    Im, Pureun; Choi, Yu-Jin; Yoon, Won-Jin; Kang, Dong-Gue; Park, Minwook; Kim, Dae-Yoon; Lee, Cheul-Ro; Yang, Seungbin; Lee, Ji-Hoon; Jeong, Kwang-Un

    2016-01-01

    A multifunctional optical thin film (MOTF) is fabricated by coating the newly synthesized perylene-based reactive mesogen (PBRM) and stabilized by the subsequent photopolymerization. Based on the spectroscopic results combined with morphological observations, it is found that nematic liquid crystal (NLC) is aligned parallel to the molecular long axis of PBRM not only due to the long-range physical anchoring effect but also due to the short-range molecular physical interactions between alignment layer and NLC molecules. From the electro-optical properties of LC test cells fabricated with the PBRM MOTF, it is clearly demonstrated that the PBRM MOTF can work as the planar LC alignment layer as well as the in-cell coatable polarizer. The coatable PBRM MOTF from lyotropic chromonic reactive mesogens can pave a new way for the flexible optoelectronic devices. PMID:27812042

  8. Photopolymerization-Induced Phase Separation Process of Thin Composite Films of Liquid Crystal and Polymer Fiber Networks

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Ikehata, Seiichiro; Sato, Fumio

    2003-11-01

    It was clarified that a thin composite film of a liquid crystal (LC) and polymer fiber networks can be obtained through two phase separation processes: spinodal decomposition, and nucleation and growth. The phase separation phenomenon was observed using a polarizing microscope under ultraviolet irradiation. Results showed that spinodal decomposition initially occurred in the LC/polymer solution under photopolymerization of a monomer. The polymer fibers were then grown on a surface of solid materials (such as substrates and spacer particles) by the nucleation and growth process in the polymer-rich solution induced by the spinodal decomposition. It was found that the spatially noncyclic morphology of the polymer fibers dispersed in the LC was obtained by the intervention of the nucleation and growth process after the spinodal decomposition process.

  9. Multifunctional Optical Thin Films Fabricated by the Photopolymerization of Uniaxially Oriented Lyotropic Liquid Crystal Monomers for Electro-Optical Devices

    NASA Astrophysics Data System (ADS)

    Im, Pureun; Choi, Yu-Jin; Yoon, Won-Jin; Kang, Dong-Gue; Park, Minwook; Kim, Dae-Yoon; Lee, Cheul-Ro; Yang, Seungbin; Lee, Ji-Hoon; Jeong, Kwang-Un

    2016-11-01

    A multifunctional optical thin film (MOTF) is fabricated by coating the newly synthesized perylene-based reactive mesogen (PBRM) and stabilized by the subsequent photopolymerization. Based on the spectroscopic results combined with morphological observations, it is found that nematic liquid crystal (NLC) is aligned parallel to the molecular long axis of PBRM not only due to the long-range physical anchoring effect but also due to the short-range molecular physical interactions between alignment layer and NLC molecules. From the electro-optical properties of LC test cells fabricated with the PBRM MOTF, it is clearly demonstrated that the PBRM MOTF can work as the planar LC alignment layer as well as the in-cell coatable polarizer. The coatable PBRM MOTF from lyotropic chromonic reactive mesogens can pave a new way for the flexible optoelectronic devices.

  10. A High-Retardation Polymer Film for Viewing Liquid Crystal Displays through Polarized Sunglasses without Chromaticity Change in the Image

    NASA Astrophysics Data System (ADS)

    Kobayashi, Daisuke; Tagaya, Akihiro; Koike, Yasuhiro

    2011-04-01

    We describe a high-retardation polymer film (HRPF) that enables liquid crystal displays (LCDs) to be viewed through polarized sunglasses at all rotation angles without any chromaticity changes in the image. We investigated the relationship between retardation and polymer interference color after developing a program that simulates the interference colors of polymers taking into consideration the polymer birefringence dispersion and LCD emission light spectrum. As a result, we confirmed that the retardation value required for our HRPF made of polyethylene terephthalate and applied to an LCD with white LED backlight was not less than 7832 nm. We also confirmed that the image quality was not degraded by attaching the HRPF to the LCD, and chromaticity change in the image observed through HRPF and polarized sunglasses was negligible compared to the LCD image.

  11. Electro- and photo-controllable spatial filter based on a liquid crystal film with a photoconductive layer

    NASA Astrophysics Data System (ADS)

    Huang, S.-Y.; Wung, T.-C.; Fuh, A. Y.-G.; Yeh, H.-C.; Huang, C.-Y.; Ma, C.-M.; Huang, S.-C.; Mo, T.-S.; Lee, C.-R.

    2009-12-01

    This work presents an electro- and photo-controllable spatial filter that is based on a liquid crystal (LC) film with a photoconductive layer. The controllable spatial filter can be formed because of the controllability of the photoelectro-induced screen effect of the space charge in the LC cell. An applied dc voltage or incident pumped intensity can be controlled to enable different spatial distributions of the diffraction pattern of the target object to be selected for filtering by the LC cell, such that various reconstructed images can be obtained. A simulation using Fourier analysis is developed, and its results agree closely with experimental results. Additionally, the LC spatial filter has the extra advantage of controllable low or high filtering functions: they are controlled by switching the configuration between normally black and normally white modes.

  12. Development of a new kind of switchable holographic grating made of liquid-crystal films separated by slices of polymeric material.

    PubMed

    Caputo, Roberto; De Sio, Luciano; Veltri, Alessandro; Umeton, Cesare; Sukhov, Andrey V

    2004-06-01

    We present a new kind of UV-cured holographic grating that consists of polymer slices alternated with pure nematic films. By preventing the appearance of the nematic phase during the curing process, it is possible to avoid the formation of liquid-crystal droplets and obtain a sharp and uniform morphology, which reduces scattering losses and increases diffraction efficiency.

  13. Surface-Controlled Orientational Transitions in Elastically Strained Films of Liquid Crystal That Are Triggered by Vapors of Toluene.

    PubMed

    Bedolla Pantoja, Marco A; Abbott, Nicholas L

    2016-05-25

    We report the fabrication of chemically patterned microwells that enable the rapid and facile preparation (by spin coating and patterned dewetting) of thin films of liquid crystals (LCs) that have precise thicknesses (0.7-30 μm), are supported on chemically defined substrates, and have free upper surfaces. We use these microwells to prepare elastically strained nematic LC films supported on silica glass, gold, or polystyrene substrates and thereby characterize the response of the strained LC films to vapors of toluene. We report that low concentrations of toluene vapor (<500 ppm) can partition into the LC to lower the anchoring energy of the LC on these substrates, thus allowing the elastic energy of the strained LC film to drive the LC films through an orientational transition. The central role of the toluene-induced change in surface anchoring energy is supported by additional experiments in which the response of the nematic LC to changes in film thickness and substrate identity are quantified. A simple thermodynamic model captures these trends and yielded estimates of anchoring energies (8-22 μJ/m(2)). Significantly, the orientational transitions observed in these strained LC thin films occur at concentrations of toluene vapor that are almost 1 order of magnitude below those which lead to bulk phase transitions, and they are not triggered by exposure to water vapor. Overall, these results hint at principles for the design of responsive LC-based materials that can be triggered by concentrations of aromatic, volatile organic compounds that are relevant to human health.

  14. 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.

  15. Optical-to-optical interface device. [consisting of two transparent electrodes on glass substrates that enclose thin film photoconductor and thin layer of nematic liquid crystal

    NASA Technical Reports Server (NTRS)

    Jacobson, A. D.

    1973-01-01

    Studies were conducted on the performance of a photoactivated dc liquid crystal light valve. The dc light valve is a thin film device that consists of two transparent electrodes, deposited on glass substrates, that enclose a thin film photoconductor (cadmium sulfide) and a thin layer of a nematic liquid crystal that operates in the dynamic scattering mode. The work was directed toward application of the light valve to high resolution non-coherent light to coherent light image conversion. The goal of these studies was to improve the performance and quality of the already existing dc light valve device and to evaluate quantitatively the properties and performance of the device as they relate to the coherent optical data processing application. As a result of these efforts, device sensitivity was improved by a factor of ten, device resolution was improved by a factor of three, device lifetime was improved by two-orders of magnitude, undesirable secondary liquid crystal scattering effects were eliminated, the scattering characteristics of the liquid crystal were thoroughly documented, the cosmetic quality of the devices was dramatically improved, and the performance of the device was fully documented.

  16. Effect of Ion Trapping Films on the Electrooptic Characteristics of Polymer-Stabilized Ferroelectric Liquid Crystal Display Exhibiting V-Shaped Switching

    NASA Astrophysics Data System (ADS)

    Furuichi, Keiji; Xu, Jun; Inoue, Masaru; Furuta, Hirokazu; Yoshida, Nobuaki; Tounai, Atsushi; Tanaka, Yoshiki; Mochizuki, Akihiro; Kobayashi, Shunsuke

    2003-07-01

    Ion trapping films TOP-COAT TA606B20 are installed beneath the polyimide alignment films, which are coated over the ITO electrode films, in a polymer-stabilized ferroelectric liquid crystal display exhibiting V-shaped switching. The ion trapping films are shown to play the following two roles: one is to remove zigzag-defects owing to their planarizing function and the other is to remove mobile ions. The latter effect gives rise to the reduction of the operational voltage and an increase of the voltage holding ratio owing to the removal of the depolarization field.

  17. Transitions between paraelectric and ferroelectric phases of bent-core smectic liquid crystals in the bulk and in thin freely suspended films

    NASA Astrophysics Data System (ADS)

    Eremin, Alexey; Floegel, Martin; Kornek, Ulrike; Stern, Stephan; Stannarius, Ralf; Nádasi, Hajnalka; Weissflog, Wolfgang; Zhu, Chenhui; Shen, Yongqiang; Park, Cheol Soo; Maclennan, Joseph; Clark, Noel

    2012-11-01

    We report on the contrasting phase behavior of a bent-core liquid crystal with a large opening angle between the mesogenic units in the bulk and in freely suspended films. Second-harmonic generation experiments and direct observation of director inversion walls in films in an applied electric field reveal that the nonpolar smectic C phase observed in bulk samples becomes a ferroelectric “banana” phase in films, showing that a mesogen with a small steric moment can give a phase with polar order in freely suspended films even when the corresponding bulk phase is paraelectric.

  18. Erasable thin-film optical diode based on a photoresponsive liquid crystal polymer

    NASA Astrophysics Data System (ADS)

    Zhang, Xinping; Zhang, Jian; Sun, Yujian; Yang, Huai; Yu, Haifeng

    2014-03-01

    We report a thin-film optical diode written into thin films of a liquid-crystalline polymer (LCP), which is based on the photoinduced LC-to-isotropic phase transition of LCPs. The interference pattern between a collimated and a focused UV laser beam is imprinted as chirped volume-phase gratings in photoresponsive LCP films and no further processing steps like development or liftoff are required for the fabrication. The resultant thin-film device not only possesses the fundamental functions of an optical lens for laser beam focusing, but also shows diode effects with the focusing/defocusing function dependent on the direction of light incidence and orientation of the device. Furthermore, this photonic thin-film lens exhibits a spatially tunable spectroscopic response, revealing a unique physics of secondary excitations of resonance modes of the single-layer LCP waveguide grating structures. This reveals the mechanisms for the focusing/defocusing of laser beams by chirped grating structures. Erasability and reconstructibility of the photoresponsive LCPs guarantee rewritability of the thin-film diode lens.We report a thin-film optical diode written into thin films of a liquid-crystalline polymer (LCP), which is based on the photoinduced LC-to-isotropic phase transition of LCPs. The interference pattern between a collimated and a focused UV laser beam is imprinted as chirped volume-phase gratings in photoresponsive LCP films and no further processing steps like development or liftoff are required for the fabrication. The resultant thin-film device not only possesses the fundamental functions of an optical lens for laser beam focusing, but also shows diode effects with the focusing/defocusing function dependent on the direction of light incidence and orientation of the device. Furthermore, this photonic thin-film lens exhibits a spatially tunable spectroscopic response, revealing a unique physics of secondary excitations of resonance modes of the single-layer LCP

  19. Quantitative Assessment of Coumarin-Containing Polymer Film's Capability for Photoalignment of Liquid Crystals

    SciTech Connect

    Kim, C.; Wallace, J.U.; Trajkovska, A.; Ou, J.J.; Chen, S.H.

    2007-12-12

    The photoalignment of a nematic fluid, E-7, and a glassy-nematic oligofluorene, F(MB)5, was investigated on films of Polymers 1 and 2 in the parallel regime. Polarized absorption spectroscopy and computational chemistry were employed to characterize coumarin monomer's and dimer's molar extinction coefficients and to locate absorption dipoles as parallel to their long molecular axes. Moreover, their orientational order parameters, S_m and S_d, were experimentally determined as functions of the extent of dimerization. Higher S_d and Y_d, coumarin dimer's mole fraction, were achieved in films of Polymer 1 than in Polymer 2 because of the greater coumarin mobility of the former. The ability of a coumarin-containing photoalignment film to orient a spin-cast F(MB)5 film was found to improve with increasing Y_d S_d to an extent comparable to that of a rubbed polyimide film. Because of the relatively short lengths of its constituent molecules, E-7 was oriented equally well on both polymer films regardless of the Y_d S_d values.

  20. Erasable thin-film optical diode based on a photoresponsive liquid crystal polymer.

    PubMed

    Zhang, Xinping; Zhang, Jian; Sun, Yujian; Yang, Huai; Yu, Haifeng

    2014-04-07

    We report a thin-film optical diode written into thin films of a liquid-crystalline polymer (LCP), which is based on the photoinduced LC-to-isotropic phase transition of LCPs. The interference pattern between a collimated and a focused UV laser beam is imprinted as chirped volume-phase gratings in photoresponsive LCP films and no further processing steps like development or liftoff are required for the fabrication. The resultant thin-film device not only possesses the fundamental functions of an optical lens for laser beam focusing, but also shows diode effects with the focusing/defocusing function dependent on the direction of light incidence and orientation of the device. Furthermore, this photonic thin-film lens exhibits a spatially tunable spectroscopic response, revealing a unique physics of secondary excitations of resonance modes of the single-layer LCP waveguide grating structures. This reveals the mechanisms for the focusing/defocusing of laser beams by chirped grating structures. Erasability and reconstructibility of the photoresponsive LCPs guarantee rewritability of the thin-film diode lens.

  1. 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.

  2. Dichroic Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    * Effect of Thickness * Impact of Order Parameter * Impact of the Host * Impact of Polarizer * Colour Applications * Multiplexing * QUARTER WAVE PLATE DICHROIC DISPLAYS * Operational Principle and Display Configuration11-13 * Electro-Optical Performance * DYE-DOPED TN DISPLAYS * Threshold Characteristic, Contrast Ratio and Switching Speed * PHASE CHANGE EFFECT DICHROIC LCDs * Theoretical Background * Threshold Characteristic and Molecular Orientation * MOLECULAR ORIENTATION DURING FIELD-INDUCED PHASE TRANSITION WITH HOMOGENEOUS WALL ALIGNMENT * MOLECULAR ORIENTATION DURING FIELD-INDUCED PHASE TRANSITION WITH HOMEOTROPIC WALL ALIGNMENT * Contrast Ratio, Transmission, Brightness and Switching Speed3,7,10,198-214 * Memory or Reminiscent Contrast * Electro-optical Performance vs. Temperature * Multiplexing Phase Change Dichroic LCDs * DOUBLE CELL DICHROIC LCDs3,9,14-17,232-234 * Double Cell Nematic Dichroic LCD3,8,9,14,15,233 * Double Cell One Pitch Cholesteric LCD16,17 * Double Cell Phase Change Dichroic LCD214,232 * POSITIVE MODE DICHROIC LCDS3,8,9 * Positive Mode Heilmeier Cells3,8,9,43,77,78,235-238 * USING PLEOCHROIC DYES3,8,9,43,235-238 * USING NEGATIVE DICHROIC DYES3,8,9,63,77,78156 * DUAL FREQUENCY ADDRESSED DICHROIC DISPLAYS75,238 * Positive Mode Dichroic LCDs Using λ/4 Plate * Positive Mode Double Cell Dichroic LCD * Positive Mode Dichroic LCDs Using Special Electrode patterns7,8,239-241 * Positive Mode Phase Change Dichroic LCDs3,8,9,230,243-248 * Dichroic LCDs Using an Admixture of Pleochroic and Negative Dichroic Dyes78,118 * SUPERTWIST DICHROIC EFFECT (SDE) DISPLAYS21-23 * FERROELECTRIC DICHROIC LCDs24-27 * Devices Using A Single Polarizer * Devices Using No Polarizer24-27 * POLYMER DISPERSED DICHROIC LCDs28-30,252-259 * DICHROIC POLYMER LIQUID CRYSTAL DISPLAYS * Heilmeier Type Displays * Guest-Host Cell Using an Admixture Of L.C. Polymer and Low Molecular Weight Liquid Crysta As Host * Polymeric Ferroelectric Dichroic LCDs * SMECTIC A DICHROIC LCDs * Laser

  3. 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.

  4. 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.

  5. Improvement of the Response Time of Super Thin Film Transistor Liquid Crystal Displays by Using a Backlight System

    NASA Astrophysics Data System (ADS)

    Hirakata, Jun-ichi; Shingai, Akira; Ono, Kikuo; Kawabe, Kazuyoshi; Furuhashi, Tsutomu

    2003-04-01

    To enable application to full moving images, the response time of liquid crystal displays (LCDs) must be improved. In this paper, we will discuss our results of improving the response time using the blink backlight system. When the display image changes from black to white, the lamp turns on after the rise of the LCD response. On the other hand, when the display image changes from white to black, the lamp turns off before the LCD response falls. The total response time of the super thin film transistor (TFT)-LCD was improved from 25 ms to 8 ms, which corresponded to the lamp response time. Moreover, the response time was dependent on the fluorescence wavelength of the lamp material. The blue fluorescent lamp (CFL) material has the fastest response time, 2 ms. If the response time of green and red fluorescent materials can be improved similarly to the blue one, it will be possible to obtain a moving picture quality comparable to that of a cathode-ray tube.

  6. Exposure to volatile organic compounds and kidney dysfunction in thin film transistor liquid crystal display (TFT-LCD) workers.

    PubMed

    Chang, Ta-Yuan; Huang, Kuei-Hung; Liu, Chiu-Shong; Shie, Ruei-Hao; Chao, Keh-Ping; Hsu, Wen-Hsin; Bao, Bo-Ying

    2010-06-15

    Many volatile organic compounds (VOCs) are emitted during the manufacturing of thin film transistor liquid crystal displays (TFT-LCDs), exposure to some of which has been reported to be associated with kidney dysfunction, but whether such an effect exists in TFT-LCD industry workers is unknown. This cross-sectional study aimed to investigate the association between exposure to VOCs and kidney dysfunction among TFT-LCD workers. The results showed that ethanol (1811.0+/-1740.4 ppb), acetone (669.0+/-561.0 ppb), isopropyl alcohol (187.0+/-205.3 ppb) and propylene glycol monomethyl ether acetate (PGMEA) (102.9+/-102.0 ppb) were the four dominant VOCs present in the workplace. The 63 array workers studied had a risk of kidney dysfunction 3.21-fold and 3.84-fold that of 61 cell workers and 18 module workers, respectively. Workers cumulatively exposed to a total level of isopropyl alcohol, PGMEA and propylene glycol monomethyl ether> or =324 ppb-year had a significantly higher risk of kidney dysfunction (adjusted OR=3.41, 95% CI=1.14-10.17) compared with those exposed to <25 ppb-year after adjustment for potential confounding factors. These findings indicated that array workers might be the group at greatest risk of kidney dysfunction within the TFT-LCD industry, and cumulative exposure to specific VOCs might be associated with kidney dysfunction.

  7. Optical switching of nematic liquid crystal film arising from induced electric field of localized surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Quint, Makiko T.; Delgado, Silverio; Paredes, John H.; Hirst, Linda S.; Ghosh, Sayantani

    2015-08-01

    We have developed an all-optical method to control the in- and out-of-plane spatial orientation of nematic liquid crystal (NLC) molecules by leveraging the highly localized electric fields produced in the near-field regime of gold nanoparticle (AuNP) layers. A 1-2 micron thick NLC film is deposited on a close-packed drop-cast AuNP layer, excited with tunable optical sources and the transmission of white light through it analyzed using polarization optics as a function of incident light wavelength, excitation power and sample temperature. Our findings, supported by simulations using discrete-dipole approximations, establish the optical switching effect to be repeatable, reversible, spectrally-selective, operational over a broad temperature range, including room temperature, and requiring very small on-resonance excitation intensity (0.3 W/cm2). For the case of the in-plane switching we have additionally demonstrated that controlling the incident excitation polarization can continuously vary the alignment of the NLC molecules, allowing for grayscale transmission.

  8. Studies on ultrathin films of tricycloquinazoline (TCQ) based discotic liquid crystal molecules

    NASA Astrophysics Data System (ADS)

    Gupta, Raj Kumar; V, Manjuladevi; Karthik, C.; Kumar, Sandeep

    2013-03-01

    The assembly of disk-shaped molecules on surfaces has drawn considerable attention because of their unique electro-optical properties. We have studied the monolayer of the tricycloquinazoline based disk-shaped (TCQCB) molecules at air-water and air-solid interfaces. The TCQCB molecules form a stable Langmuir monolayer at the air-water interface. The monolayer exhibits gas, low density liquid (L1), and high density liquid (L2) phases. In L1 and L2 phases, the molecules prefer edge-on conformation. The atomic force microscope study on the Langmuir-Blodgett films of the molecules reveals a structural transformation. The elongated domains in the film deposited in L1 phase transformed to a compact grainy texture in the film deposited in the L2 phase.

  9. Theoretical and experimental optical studies of cholesteric liquid crystal films with thermally induced pitch gradients.

    PubMed

    Zografopoulos, Dimitrios C; Kriezis, Emmanouil E; Mitov, Michel; Binet, Corinne

    2006-06-01

    The reflection properties of cholesteric films with thermally induced pitch gradients are theoretically and experimentally studied. It is shown that the optical behavior of such films corresponds to the averaged contribution of a number of stochastic pitch variation profiles, due to the transversal and longitudinal nonuniformities that develop in the helical structure of such samples. Depending on the annealing time, both narrow-band and broadband behavior can be selectively achieved. The influence of the pitch profile gradient on the broadband reflection performance of cholesteric samples is theoretically analyzed, and a multi-slab structure for achieving optimum efficiency is proposed.

  10. Thermal switching of the reflection in chiral nematic mesoporous organosilica films infiltrated with liquid crystals.

    PubMed

    Giese, Michael; De Witt, Joanna C; Shopsowitz, Kevin E; Manning, Alan P; Dong, Ronald Y; Michal, Carl A; Hamad, Wadood Y; MacLachlan, Mark J

    2013-08-14

    Materials that undergo stimulus-induced optical changes are important for many new technologies. In this paper, we describe a new free-standing silica-based composite film that exhibits reversible thermochromic reflection, induced by a liquid crystalline guest in the pores of iridescent mesoporous films. We demonstrate that selective reflection from the novel mesoporous organosilica material with chiral nematic organization can be reversibly switched by thermal cycling of the 8CB guest between its isotropic and liquid crystalline states, which was proven by solid-state NMR experiments. The switching of the optical properties of the chiral solid-state host by stimulus-induced transitions of the guest opens the possibility of applications for these novel materials in sensors and displays.

  11. Effect of the annealing temperature and ion-beam bombardment on the properties of solution-derived HfYGaO films as liquid crystal alignment layers

    SciTech Connect

    Park, Hong-Gyu; Lee, Yun-Gun; Jang, Sang Bok; Lee, Ju Hwan; Jeong, Hae-Chang; Seo, Dae-Shik; Oh, Byeong-Yun

    2015-11-15

    Hafnium yttrium gallium oxide (HfYGaO) films were applied to liquid crystal displays (LCDs) as liquid crystal (LC) alignment layers, replacing conventional polyimide (PI) layers. The HfYGaO alignment layers were prepared by fabricating solution-processed HfYGaO films, annealing them, and treating them with ion-beam (IB) irradiation. The authors studied the effects of annealing temperature and IB irradiation of the solution-derived HfYGaO films on the orientation of LC molecules. The LC molecules on the solution-derived HfYGaO films were homogeneously and uniformly aligned by IB irradiation, irrespective of the annealing temperature. Atomic force microscopy analyses revealed that the surface reformation of the HfYGaO films induced by IB irradiation strengthened the van der Waals force between the LC molecules and the HfYGaO films, leading to uniform LC alignment. Enhanced electro-optical characteristics were observed in the twisted-nematic (TN) LCDs based on IB-irradiated HfYGaO films compared with those of TN-LCDs based on PI layers, demonstrating the high application potential of the proposed solution-derived HfYGaO films as LC alignment layers.

  12. Film effectiveness over a flat surface with air and CO{sub 2} injection through compound angle holes using a transient liquid crystal image method

    SciTech Connect

    Ekkad, S.V.; Zapata, D.; Han, J.C.

    1997-07-01

    This paper presents detailed film effectiveness distributions over a flat surface with one row of injection holes inclined streamwise at 35 deg for three blowing ratios (M = 0.5, 1.0, 2.0). Three compound angles of 0, 45, and 90 deg with air (D.R. = 0.98) and CO{sub 2} (D.R. = 1.46) as coolants are tested at an elevated free-stream turbulence condition (Tu {approx} 8.5%). A transient liquid crystal technique is used to measure local heat transfer coefficients and film effectiveness. Detailed film effectiveness results are presented near and around film injection holes. Compound angle injection provides higher film effectiveness than simple angle injection for both coolants. Higher density injectant produces higher effectiveness for simple injection. However, lower density coolant produces higher effectiveness obtained using the transient liquid crystal technique, particularly in the near-hole region, provided a better understanding of the film cooling process in gas turbine components.

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

    PubMed

    Oh, Seung-Won; Wok Park, Byung; Lee, Ji-Hoon; Yoon, Tae-Hoon

    2013-11-10

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

  14. 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.

  15. 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.

  16. Vertically aligned liquid crystals on a {gamma}-Al{sub 2}O{sub 3} alignment film using ion-beam irradiation

    SciTech Connect

    Park, Hong-Gyu; Kim, Young-Hwan; Oh, Byeong-Yun; Lee, Won-Kyu; Kim, Byoung-Yong; Seo, Dae-Shik; Hwang, Jeong-Yeon

    2008-12-08

    Using ion-beam (IB) irradiation, liquid crystals (LCs) were vertically aligned (VA) on a {gamma}-Al{sub 2}O{sub 3} alignment film. Atomic-layer deposition was used to orient the LCs on high-quality {gamma}-Al{sub 2}O{sub 3} alignment films. The LC molecule orientation indicates the vertical direction of the atomic-layer-deposited {gamma}-Al{sub 2}O{sub 3} alignment films. X-ray photoelectron spectroscopy showed that IB irradiation changed the chemical structure, shifting the Al-O binding energy and altering the Al-O bonding intensity. The low-voltage transmittance characteristics of the VA LC displays on the {gamma}-Al{sub 2}O{sub 3} alignment films were also measured, showing reduced voltage and power requirements.

  17. Comparison between experiment and theory in the temperature variation of film tension above the bulk isotropic transition in free-standing liquid-crystal films.

    PubMed

    Veum, M; Duelge, L; Droske, J; Nguyen, H T; Huang, C C; Mirantsev, L V

    2009-09-01

    Using differential scanning calorimetry, the transition enthalpies and temperatures for the bulk smectic-isotropic phase transition have been measured for a series of liquid-crystal compounds. For five compounds, those values were used as parameters in a microscopic mean-field model to predict the temperature dependence of the difference in free-energy density between a sample of material in a free-standing smectic film and that in the bulk. The model predicts a weak temperature dependence below the bulk clearing point and a pronounced monotonic increase with temperature above the transition temperature. The compounds used in this study were chosen specifically because they were also the subject of a previous independent experimental study [M. Veum, Phys. Rev. E 74, 011703 (2006)] that demonstrated a sudden monotonic increase in the free-standing film tension with temperature, which is qualitatively consistent with the predictions of the above-mentioned mean-field model. This study presents a direct and quantitative comparison between the predictions of the mean-field model and the results from previous tension experiments.

  18. Effect of the ion-beam bombardment and annealing temperature on sol-gel derived yttrium aluminum oxide film as liquid crystal alignment layer

    NASA Astrophysics Data System (ADS)

    Jeong, Hae-Chang; Heo, Gi-Seok; Kim, Eun-Mi; Lee, Ju Hwan; Han, Jeong-Min; Seo, Dae-Shik

    2017-02-01

    We demonstrated a homogeneous liquid-crystal (LC) alignment state on yttrium aluminum oxide (YAlO) films, where the alignment was induced by ion-beam (IB) irradiation. Topographical analysis was performed by atomic force microscopy as a function of annealing temperature. Higher annealing temperatures yielded a smoother surface, accompanied by reduced light scattering. Transparency in the visible region increased on the surface fabricated at higher annealing temperatures. LC alignment mechanism was determined by X-ray diffraction (XRD) analysis. Moreover, IB-irradiated YAlO films annealed at temperatures greater than 200 °C exhibited good thermal stability and low capacitance-voltage hysteresis. The IB-irradiated YAlO films are suitable as alternative alignment layers in advanced LC display applications.

  19. 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.

  20. All-optically controllable and highly efficient scattering mode light modulator based on azobenzene liquid crystals and poly(N-vinylcarbazole) films.

    PubMed

    Liu, Yen-Chen; Cheng, Ko-Ting; Chen, Yuan-Di; Fuh, Andy Ying-Guey

    2013-07-29

    The present study reports that isothermal phase transition induced by photoisomerization of azobenzene liquid crystals (azo-LCs) from trans- to cis-isomers results in the dissolution of poly(N-vinylcarbazole) (PVK) into azo-LCs. Transparent (scattering) states can be demonstrated using uniform (rough) morphologies of PVK generated by slow (rapid) phase separation of PVK and azo-LCs from cis- to trans-isomers. The PVK films were examined in detail using scanning electron microscopy. Scattering performance resulting from the rough PVK surface induced micron-sized LC domains, and transparent performance resulting from the reformed uniform PVK surface can be optically and reversibly switched. Finally, all-optically controllable and highly efficient (contrast ratio of 370:1) scattering mode light modulators based on azo-LCs and PVK films were demonstrated.

  1. One-dimensional ion-conductive polymer films: alignment and fixation of ionic channels formed by self-organization of polymerizable columnar liquid crystals.

    PubMed

    Yoshio, Masafumi; Kagata, Takayoshi; Hoshino, Koji; Mukai, Tomohiro; Ohno, Hiroyuki; Kato, Takashi

    2006-04-26

    We have prepared two types of one-dimensional ion-conductive polymer films containing ion nanochannels that are both perpendicular and parallel to the film surface. These films have been obtained by photopolymerization of aligned columnar liquid crystals of a fan-shaped imidazolium salt having acrylate groups at the periphery. In the columnar structure, the ionic part self-assembles into the inner part of the column. The column is oriented macroscopically in two directions by different methods: orientation perpendicular to the modified surfaces of glass and indium tin oxide with 3-(aminopropyl)triethoxysilane and orientation parallel to a glass surface by mechanical shearing. Ionic conductivities have been measured for the films with columnar orientation vertical and parallel to the surface. Anisotropic ionic conductivities are observed for the oriented films fixed by photopolymerization. The ionic conductivities parallel to the columnar axis are higher than those perpendicular to the columnar axis because the lipophilic part functions as an ion-insulating part. The film with the columns oriented vertically to the surface shows an anisotropy of ionic conductivities higher than that of the film with the columns aligned parallel to the surface.

  2. Photo-aligned blend films of azobenzene-containing polyimides with and without side-chains for inducing inclined alignment of liquid crystal molecules

    NASA Astrophysics Data System (ADS)

    Usami, Kiyoaki; Sakamoto, Kenji

    2011-08-01

    We have succeeded in controlling the pretilt angle of liquid crystal (LC) molecules over the whole range of 0 to 90° by using photo-aligned blend films of two azobenzene-containing polyimides (Azo-PIs) with and without side-chains. The Azo-PIs were synthesized from pyromellitic dianhydride and a mixture of 4,4'-diaminoazobenzene and 4-(4'-propylbi(cyclohexan)-4-yl)phenyl 3,5-diaminobenzoate (PBCP-DABA). PBCP-DABA is a diamine to introduce a side-chain structure into the polyimide. Defect-free uniform LC alignment was obtained in the pretilt angle (θp) ranges of θp ≤ 11° and θp ≥ 78°. Previously, we reported that the pretilt angle can be controlled using pure photo-aligned films of Azo-PIs with different molar fractions of PBCP-DABA. For the pure photo-aligned films, the defect-free pretilt angle ranges were θp < 5° and θp ≥ 85°. These results suggest that the azimuthal anchoring strength of the blend Azo-PI film is stronger than that of the pure films of Azo-PIs with side-chains, at least for the pretilt angle range from 5 to 11°. We found that the defect-free pretilt angle range can be extended by using the blend Azo-PI films instead of the pure Azo-PI films.

  3. 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.

  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. A droplet manipulation on a liquid crystal and polymer composite film as a concentrator and a sun tracker for a concentrating photovoltaic system

    NASA Astrophysics Data System (ADS)

    Tsou, Yu-Shih; Chang, Kai-Han; Lin, Yi-Hsin

    2013-06-01

    We demonstrate a droplet manipulation on a liquid crystal and polymer composite film (LCPCF) as a concentrator and a sun tracker for a concentrating photovoltaic (CPV) system with a steady output electric power. The CPV system adopts a liquid lens on LCPCF whose curvature is not only tunable but position is also bistably switchable based on liquid crystal orientations on LCPCF. The change of curvature of the liquid lens results in a tunable concentration ratio which helps to increase photocurrent at a low illumination and prevent the effect of the series resistance at a high illumination. Moreover, the change of the position of the liquid lens helps to track sun owing to sun movement. Therefore, the output power of such a system is steady no matter the sunlight condition and the angle of incident light. The operating principles and experiments are investigated. The concept in this paper can be extended to design optical components for obtaining steady output power of the solar cell at indoor or outdoor use and also tracking sunlight.

  6. Optimization on the Thickness of Organic Insulator Layer for Advanced Super-In-Plane Switching Mode Thin-Film-Transistor Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Lin, Jiunn-Shyong; Yang, Kei-Hsiung; Chen, Shu-Hsia

    2005-08-01

    The growth rate of thin-film-transistor liquid crystal display (TFT-LCD) industries is faster than predicted due to the possible replacement of a cathode-ray tube television (CRT-TV) by a liquid crystal display television (LCD-TV). The in-plane switching (IPS) mode has been known as an excellent technology for realizing a wide viewing angle for LCD-TV, but it has the drawback of a low aperture ratio. An advanced super-IPS (AS-IPS) structure with an organic insulator layer was invented to achieve a high aperture ratio with increasing manufacturing cost. In this paper, we proposed a simple method of analyzing the optimum thickness of the organic insulator layer for AS-IPS. We derived the capacitive coupling ratio (CCR) of the IPS cell and analyzed the delay time of the AS-IPS panel to quantify the crosstalk properties. Furthermore, we also analyzed our electrode structure (AS'-IPS), which not only increases substantially the aperture ratio over that of AS-IPS but also reduces the crosstalk using the same optimized thickness of the organic insulator layer.

  7. Photochemical on-off switching of structural color of a multi-bilayered film consisting of azobenzene-polymer liquid crystal and polyvinylalcohol

    NASA Astrophysics Data System (ADS)

    Kurihara, Seiji; Moritsugu, Masaki; Kuwahara, Yutaka; Ogata, Tomonari

    2011-10-01

    Photo-responsive multi-bilayered film consisting of azobenzene polymer liquid crystals (PAzo) and polyvinylalcohol (PVA) was prepared on a glass substrate by spin coating of the polymer solutions alternately. The reflectivity of the multi-bilayered film disappeared by annealing at 80 °C. The disappearance of the reflection by the annealing was related to the thermal out-of-plane molecular orientation of PAzo even in the multi-bilayered film, leading to a very small difference in refractive indices between PAzo and PVA. The reflectance of the multi-bilayered film was increased again by UV irradiation because of the transformation from the out-of-plane orientation to the in-plane random orientation, resulting in the restoration of difference in the refractive indices. In this way, the on-off switching of the reflection was achieved by combination of the thermally spontaneous out-of-plane molecular orientation and following photoisomerization of PAzo comprising the multi-bilayered film.

  8. Effects of Dilution, Polarization Ratio, and Energy Transfer on Photoalignment of Liquid Crystals Using Coumarin-Containing Polymer Films

    SciTech Connect

    Kim, C.; Wallace, J.U.; Chen, S.H.; Merkel, P.B.

    2008-05-27

    Orientation of a nematic liquid crystal, E-7, was investigated using coumarin-containing polymethacrylates to elucidate the roles played by the dilution of coumarin and the polarization ratio of irradiation. Dilution of coumarin by inert moieties had adverse effects on a nematic cell’s number density of disclinations and its orientational order parameter in the parallel but not the perpendicular regime. In addition, both dilution of coumarin and a decreasing polarization ratio resulted in a lower extent of coumarin dimerization at crossover, Xc. The significantly reduced Xc in a homopolymer comprising triphenylamine and coumarin was attributed to the dilution of coumarin and the diminished polarization ratio caused by competing absorption with simultaneous triplet energy transfer from triphenylamine to coumarin moieties.

  9. 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.

  10. 6.0-Inch Extended Graphics Array Reflective Liquid Crystal Display Using Oxide Semiconductor Thin Film Transistors for Electronic Paper Display

    NASA Astrophysics Data System (ADS)

    Toyotaka, Kouhei; Kusunoki, Koji; Nagata, Takaaki; Hirakata, Yoshiharu; Wakimoto, Kenichi; Koyama, Jun; Yamazaki, Shunpei; Sato, Rai; Okazaki, Kenichi; Sakakura, Masayuki

    2011-03-01

    We focused on the off-state current (Ioff) of oxide semiconductor thin film transistors (TFT) (In-Ga-Zn-oxide TFTs), which is lower than that of amorphous silicon TFTs and successfully made a prototype of a 6.0-in. extended graphics array (XGA) reflective liquid crystal display (RLCD) panel integrally including a data selection demultiplexer and a scan driver and capable of displaying still images at 1/180 fps. When still images are displayed, the frame frequency can be set low. This means that the frequency of rewrites of image data is markedly reduced. This leads to the reduction in the power consumption of an LCD panel. Our panel can solve the problems of electronic paper displays: high drive voltage and difficulty of displaying moving images. Thus, our panel is suitable for electronic paper displays.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. A fiber-optic violet sensor by using the surface grating formed by a photosensitive hybrid liquid crystal film on side-polished fiber

    NASA Astrophysics Data System (ADS)

    Yu, Jianhui; Li, Haozhi; Hsiao, V. K.; Liu, Weiping; Tang, Jieyuan; Zhai, Yanfang; Du, Yao; Zhang, Jun; Xiao, Yi; Chen, Zhe

    2013-09-01

    A fiber-optic violet sensor is demonstrated by using the surface grating formed by a photosensitive liquid crystal (LC) hybrid film on the flat area of side-polished fiber (SPF). The surface grating is constructed through a periodic intensity illuminating the hybrid LC film, where the periodic intensity is created by a phase mask through which the violet light passes. Experiment shows that a loss peak appears in the transmission spectrum between 1520 and 1620 nm, and this loss peak shifts toward shorter wavelength as the 405 nm light power increases. The wavelength shift of the peak shows very good linearity with the irradiation power between 30 and 80 mW cm-2. The very high sensitivity of the light power sensor is measured to be 1.154 nm (mW cm-2)-1, which implies that the minimum change of power intensity that can be detected is 0.866 µW cm-2 for this sensor under the limited wavelength resolution of 0.001 nm of the optical spectrum analyzer. For UV light, much higher sensitivity will be further obtained, as the LC hybrid is more sensitive to UV light than to violet light.

  16. 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.

  17. 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.

  18. 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.

  19. 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).

  20. Photoinduced reordering in thin azo-dye films and light-induced reorientation dynamics of the nematic liquid-crystal easy axis.

    PubMed

    Kiselev, Alexei D; Chigrinov, V G; Pasechnik, S V; Dubtsov, A V

    2012-07-01

    We theoretically study the kinetics of photoinduced reordering triggered by linearly polarized (LP) reorienting light in thin azo-dye films that were initially illuminated with LP ultraviolet pumping beam. The process of reordering is treated as a rotational diffusion of molecules in the light intensity-dependent mean-field potential. The two-dimensional diffusion model which is based on the free energy rotational Fokker-Planck equation and describes the regime of in-plane reorientation is generalized to analyze the dynamics of the azo-dye order parameter tensor at varying polarization azimuth of the reorienting light. It is found that, in the photosteady state, the intensity of LP reorienting light determines the scalar order parameter (the largest eigenvalue of the order parameter tensor), whereas the steady state orientation of the corresponding eigenvector (the in-plane principal axis) depends solely on the polarization azimuth. We show that, under certain conditions, reorientation takes place only if the reorienting light intensity exceeds its critical value. Such threshold behavior is predicted to occur in the bistability region provided that the initial principal axis lies in the polarization plane of reorienting light. The model is used to interpret the experimental data on the light-induced azimuthal gliding of the liquid-crystal easy axis on photoaligned azo-dye substrates.

  1. 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.

  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. 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

  4. 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.

  5. 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.

  6. Electro-optical and dielectric characterization of submicrometer-sized PDLC films

    NASA Astrophysics Data System (ADS)

    Krishna Koduru, Hari

    2017-01-01

    This report concerns thin films (25 µm thickness) of polymer-dispersed liquid crystal (PDLC) composites having submicrometer-sized nematic liquid crystal domains. Such PDLC films were prepared by performing photo-induced phase separation of mixed soft material composed from the room-temperature nematic liquid crystal 4-n-heptyl cyanobiphenyl (7CB) and photo-curable polymer NOA-65. Being of interest for electro-optical (EO) and other applications driven by alternating-current electric field, the produced composites were studied by EO measurements and complex impedance spectroscopy. For the examined soft-solid composite material with a large content of submicro-confined nematic, was obtained information about the dielectric permittivity and molecular dynamics, useful for practice.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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).

  12. Silicone-containing aqueous polymer dispersions with hybrid particle structure.

    PubMed

    Kozakiewicz, Janusz; Ofat, Izabela; Trzaskowska, Joanna

    2015-09-01

    In this paper the synthesis, characterization and application of silicone-containing aqueous polymer dispersions (APD) with hybrid particle structure are reviewed based on available literature data. Advantages of synthesis of dispersions with hybrid particle structure over blending of individual dispersions are pointed out. Three main processes leading to silicone-containing hybrid APD are identified and described in detail: (1) emulsion polymerization of organic unsaturated monomers in aqueous dispersions of silicone polymers or copolymers, (2) emulsion copolymerization of unsaturated organic monomers with alkoxysilanes or polysiloxanes with unsaturated functionality and (3) emulsion polymerization of alkoxysilanes (in particular with unsaturated functionality) and/or cyclic siloxanes in organic polymer dispersions. The effect of various factors on the properties of such hybrid APD and films as well as on hybrid particles composition and morphology is presented. It is shown that core-shell morphology where silicones constitute either the core or the shell is predominant in hybrid particles. Main applications of silicone-containing hybrid APD and related hybrid particles are reviewed including (1) coatings which show specific surface properties such as enhanced water repellency or antisoiling or antigraffiti properties due to migration of silicone to the surface, and (2) impact modifiers for thermoplastics and thermosets. Other processes in which silicone-containing particles with hybrid structure can be obtained (miniemulsion polymerization, polymerization in non-aqueous media, hybridization of organic polymer and polysiloxane, emulsion polymerization of silicone monomers in silicone polymer dispersions and physical methods) are also discussed. Prospects for further developments in the area of silicone-containing hybrid APD and related hybrid particles are presented.

  13. 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.

  14. 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

  15. Interaction between lyotropic chromonic liquid crystals and polymers

    NASA Astrophysics Data System (ADS)

    Yao, Xuxia; Park, Jung; Srinivasarao, Mohan

    2010-03-01

    Lyotropic chromonic liquid crystals (LCLCs) consist of various dyes, drugs, etc., so their importance is self-evident. The interaction of chromonic molecules and polymers is involved in their real applications, such as the dyeing process of fibers, textiles and food, and the functionalization of drugs in vivo. In our research, polymer dispersed LCLC droplets and polymer coated LCLC cells have been fabricated. Effect of interaction was observed by optical texture of LCLCs, as the different polymers induce different director configuration of LCLCs. A textile dye-Benzopurpurine 4B, food dye-Sunset Yellow FCF, and drug-Disodium Cromoglycate mixed with water soluble polymers, proteins and textile polymers have been all studied and compared.

  16. 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.

  17. Photodegradation of polymer-dispersed perylene di-imide dyes

    NASA Astrophysics Data System (ADS)

    Tanaka, Nobuaki; Barashkov, Nikolay; Heath, Jerry; Sisk, Wade N.

    2006-06-01

    Polymer-dispersed perylene di-imide dye photodegradation is investigated by monitoring the fluorescence intensity as a function of 532 nm laser pulses. Anaerobically irradiated polymer-dye films exhibited an accelerated decrease in fluorescence intensity, which was partially recovered upon exposure to oxygen. Decelerated photodegradation rates were observed for perylene di-imide ethanol solutions upon the addition of a singlet oxygen quenching antioxidant. These observations suggest reversible photoreduction and type II photo-oxidation as important photodegradation mechanisms. Type II photo-oxidation for perylene red 532 nm irradiation is supported by a singlet oxygen quantum yield of 0.09±0.03, determined via detection of time-resolved O2 (a1Δg —> X3∑g-) infrared phosphorescence.

  18. Photodegradation of polymer-dispersed perylene di-imide dyes.

    PubMed

    Tanaka, Nobuaki; Barashkov, Nikolay; Heath, Jerry; Sisk, Wade N

    2006-06-01

    Polymer-dispersed perylene di-imide dye photodegradation is investigated by monitoring the fluorescence intensity as a function of 532 nm laser pulses. Anaerobically irradiated polymer-dye films exhibited an accelerated decrease in fluorescence intensity, which was partially recovered upon exposure to oxygen. Decelerated photodegradation rates were observed for perylene di-imide ethanol solutions upon the addition of a singlet oxygen quenching antioxidant. These observations suggest reversible photoreduction and type II photo-oxidation as important photodegradation mechanisms. Type II photo-oxidation for perylene red 532 nm irradiation is supported by a singlet oxygen quantum yield of 0.09+/-0.03, determined via detection of time-resolved O2 (a1delta(g) --> X3sigma(g)-) infrared phosphorescence.

  19. Hierarchical Thin Film Architectures for Enhanced Sensor Performance: Liquid Crystal-Mediated Electrochemical Synthesis of Nanostructured Imprinted Polymer Films for the Selective Recognition of Bupivacaine

    PubMed Central

    Suriyanarayanan, Subramanian; Nawaz, Hazrat; Ndizeye, Natacha; Nicholls, Ian A.

    2014-01-01

    Nanostructured bupivacaine-selective molecularly imprinted 3-aminophenylboronic acid-p-phenylenediamine co-polymer (MIP) films have been prepared on gold-coated quartz (Au/quartz) resonators by electrochemical synthesis under cyclic voltammetric conditions in a liquid crystalline (LC) medium (triton X-100/water). Films prepared in water and in the absence of template were used for control studies. Infrared spectroscopic studies demonstrated comparable chemical compositions for LC and control polymer films. SEM studies revealed that the topologies of the molecularly imprinted polymer films prepared in the LC medium (LC-MIP) exhibit discernible 40 nm thick nano-fiber structures, quite unlike the polymers prepared in the absence of the LC-phase. The sensitivity of the LC-MIP in a quartz crystal microbalance (QCM) sensor platform was 67.6 ± 4.9 Hz/mM under flow injection analysis (FIA) conditions, which was ≈250% higher than for the sensor prepared using the aqueous medium. Detection was possible at 100 nM (30 ng/mL), and discrimination of bupivacaine from closely related structural analogs was readily achieved as reflected in the corresponding stability constants of the MIP-analyte complexes. The facile fabrication and significant enhancement in sensor sensitivity together highlight the potential of this LC-based imprinting strategy for fabrication of polymeric materials with hierarchical architectures, in particular for use in surface-dependent application areas, e.g., biomaterials or sensing. PMID:25587412

  20. 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.

  1. 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.

  2. 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).

  3. 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.

  4. 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.

  5. Generation of laser-induced periodic surface structures in indium-tin-oxide thin films and two-photon lithography of ma-N photoresist by sub-15 femtosecond laser microscopy for liquid crystal cell application

    NASA Astrophysics Data System (ADS)

    Klötzer, Madlen; Afshar, Maziar; Feili, Dara; Seidel, Helmut; König, Karsten; Straub, Martin

    2015-03-01

    Indium-tin-oxide (ITO) is a widely used electrode material for liquid crystal cell applications because of its transparency in the visible spectral range and its high electrical conductivity. Important examples of applications are displays and optical phase modulators. We report on subwavelength periodic structuring and precise laser cutting of 150 nm thick indium-tin-oxide films on glass substrates, which were deposited by magnetron reactive DC-sputtering from an indiumtin target in a low-pressure oxygen atmosphere. In order to obtain nanostructured electrodes laser-induced periodic surface structures with a period of approximately 100 nm were generated using tightly focused high-repetition rate sub-15 femtosecond pulsed Ti:sapphire laser light, which was scanned across the sample by galvanometric mirrors. Three-dimensional spacers were produced by multiphoton photopolymerization in ma-N 2410 negative-tone photoresist spin-coated on top of the ITO layers. The nanostructured electrodes were aligned in parallel to set up an electrically switchable nematic liquid crystal cell.

  6. 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.

  7. 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.

  8. 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.…

  9. 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.

  10. 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}.

  11. 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).

  12. Employ Present Five Masks Amorphous Silicon Thin-Film Transistor Design and Process Flow to Realize 5-in. InGaZnO Active-Matrix Liquid Crystal Display with Improved Stress Stability

    NASA Astrophysics Data System (ADS)

    Hung, Ming-Chin; Hsiao, Hsia-Tsai; Lin, Wei-Ting; Tu, Chun-Hao; Chang, Jiun-Jye; Chen, Po-Lun

    2011-03-01

    The present five masks bottom gate and staggered amorphous silicon (a-Si) thin-film transistor (TFT) process flow is not suitable for indium-gallium-zinc-oxide (IGZO) TFT because of its vulnerability to post etching process during the source/drain pattern. Bottom gate and coplanar IGZO TFTs were made feasible through the reverse of second (channel layer) and third (source/drain electrodes) masks process flow to avoid etching damage problem. Besides, the post IGZO nitrous oxygen (N2O) plasma treatment was employed to improve the stress instability. On the basis of secondary ion mass spectrometry (SIMS) and X-ray spectroscopy (XPS) results, it is believed that the post N2O plasma treatment passivates the interface states and converts the inhomogeneous and low quality IGZO to the homogeneous and high quality IGZO. In the end, a 5-in. IGZO active-matrix liquid crystal display was demonstrated via five masks bottom gate and coplanar TFT configuration.

  13. 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.…

  14. 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.

  15. Stabilization of lamellar oil-water liquid crystals by surfactant/ co-surfactant monolayers

    NASA Astrophysics Data System (ADS)

    Braganza, L. F.; Dubois, M.; Tabony, J.

    1989-03-01

    LIQUID crystals are divided into two main classes, thermotropic and lyotropic. Thermotropic liquid crystals are formed by melting, whereas lyotropic liquid crystals arise from the association of molecules, such as soap and water, that in general are not in themselves liquid crystalline. Thermotropic liquid crystals are used for liquid-crystal displays; lyotropic liquid crystals occur in living cells. Here we report a novel sequence of lyotropic liquid crystals comprising alternate layers of oil and water whose thickness varies linearly with the relative proportions of oil and water, and we have determined their structure using neutron diffraction methods. The oil and water layers are separated and stabilized by a monolayer film of surfactant and co-surfactant. The individual layers are typically a hundred ångströms or more in thickness, and total lamellar spacings of up to 1,000 Å were observed. This behaviour is difficult to describe in terms of the theories of colloid stability currently used to describe lyotropic liquid crystals. An understanding of the self-organization of such systems over such large distances would elucidate how long-range liquid-crystalline ordering arises in living cells. Moreover, thermotropic liquid crystals are expensive and chemically relatively unstable, and lamellar mesophases of the lyotopic type described here could lead to inexpensive, chemically stable liquid-crystalline materials suitable for industrial application.

  16. θ-2θ diffractometry of anisotropic holographic gratings composed of liquid crystal and polymer phases

    NASA Astrophysics Data System (ADS)

    Kakiuchida, Hiroshi; Tazawa, Masato; Yoshimura, Kazuki; Ogiwara, Akifumi

    2013-03-01

    We studied highly anisotropic periodic structure formed by liquid crystal and polymer phase separation, or holographic polymer dispersed liquid crystal (HPDLC), by θ-2θ optical diffractometry particularly employing the high order Bragg diffractions. Then, we revealed the relationship between microscopic structure and diffraction properties of the HPDLCs prepared at several different conditions with regard to the compositional ratio of the raw materials and the exposure temperature. The high order Bragg diffractions are closely connected to periodic boundaries between LC droplets and polymer, and is potentially able to be designed by HPDLC fabrication processes. The analysis with the information from the higher order Bragg diffraction is expected to allow you to observe more detailed and quantitative HPDLC internal structure.

  17. 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.

  18. 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.

  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. 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.

  1. 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.

  2. Polymer stabilized liquid crystals: Topology-mediated electro-optical behavior and applications

    NASA Astrophysics Data System (ADS)

    Weng, Libo

    There has been a wide range of liquid crystal polymer composites that vary in polymer concentration from as little as 3 wt.% (polymer stabilized liquid crystal) to as high as 60 wt.% (polymer dispersed liquid crystals). In this dissertation, an approach of surface polymerization based on a low reactive monomer concentration about 1 wt.% is studied in various liquid crystal operation modes. The first part of dissertation describes the development of a vertical alignment (VA) mode with surface polymer stabilization, and the effects of structure-performance relationship of reactive monomers (RMs) and polymerization conditions on the electro-optical behaviors of the liquid crystal device has been explored. The polymer topography plays an important role in modifying and enhancing the electro-optical performance of stabilized liquid crystal alignment. The enabling surface-pinned polymer stabilized vertical alignment (PSVA) approach has led to the development of high-performance and fast-switching displays with controllable pretilt angle, increase in surface anchoring energy, high optical contrast and fast response time. The second part of the dissertation explores a PSVA mode with in-plane switching (IPS) and its application for high-efficiency and fast-switching phase gratings. The diffraction patterns and the electro-optical behaviors including diffraction efficiency and response time are characterized. The diffraction grating mechanism and performance have been validated by computer simulation. Finally, the advantages of surface polymerization approach such as good optical contrast and fast response time have been applied to the fringe-field switching (FFS) system. The concentration of reactive monomer on the electro-optical behavior of the FFS cells is optimized. The outstanding electro-optical results and mechanism of increase in surface anchoring strength are corroborated by the director field simulation. The density and topology of nanoscale polymer protrusions

  3. Study of the interfacial structures and behavior of smectic liquid crystals using synchrotron light source

    NASA Astrophysics Data System (ADS)

    Hu, Yufei

    2003-10-01

    Grazing Incidence X-ray Scattering with a synchrotron X-ray source is used to study the depth dependence of the interfacial structure of smectic liquid crystal (8CB) hybrid films. The advancement and market potential of liquid crystal technologies lead to inventions of new materials and surface treatments. The knowledge of interfacial structures and behavior is very critical to these thin film devices such as Liquid Crystal Display. Photolithography in a clean room is adopted to make gratings on very thin glass, which offers better quality than conventional methods in terms of uniformity, reproducibility, reliability, and endurance. Liquid crystal thin films are bounded by a grated glass substrate and air, and have been studied as a function of both temperature and thickness. Experimental measurements indicate the existence of chevron, tilt, and bookshelf structure, as well as Twisted Grain Boundary (TGB) structure that has not previously been observed by X-ray in non-chiral smectic liquid crystals. These structures are a result of liquid crystal anchoring at two dissimilar competing confining surfaces, air-smectics and smectics-grating substrate. With deeper grating, smectic liquid crystals are more constrained in structure and more resilient to temperature change. The smectic phase also persisted at a higher temperature above the smectic-nematic transition point on a deeper grating substrate. When the thickness of liquid crystal samples is beyond a certain point, the smectic liquid crystal begins to form different layers. Chevron structures appear in most situations, which is consistent with previous research A TGB structure is not tamable in a thicker sample where liquid crystals tend to realign themselves in a more stable structure.

  4. 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.

  5. 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.

  6. 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.

  7. Formation of holographic memory for optically reconfigurable gate array by angle-multiplexing recording of multi-circuit information in liquid crystal composites

    NASA Astrophysics Data System (ADS)

    Ogiwara, Akifumi; Maekawa, Hikaru; Watanabe, Minoru; Moriwaki, Retsu

    2014-02-01

    A holographic polymer-dispersed liquid crystal (HPDLC) memory to record multi-context information for an optically reconfigurable gate array is formed by the angle-multiplexing recording using a successive laser exposure in liquid crystal (LC) composites. The laser illumination system is constructed using the half mirror and photomask written by the different configuration contexts placed on the motorized stages under the control of a personal computer. The fabricated holographic memory implements a precise reconstruction of configuration contexts corresponding to the various logical circuits such as OR circuit and NOR circuit by the laser illumination at different incident angle in the HPDLC memory.

  8. 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.

  9. 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.

  10. 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.

  11. The electro-optical and electrochromic properties of electrolyte-liquid crystal dispersions

    NASA Astrophysics Data System (ADS)

    Cupelli, Daniela; De Filpo, Giovanni; Chidichimo, Giuseppe; Nicoletta, Fiore Pasquale

    2006-07-01

    Liquid crystals are known to exhibit a reversible color change by applying a direct current electric field, if a small amount of quaternary ammonium salts is dissolved into them. Applications of such an electrochromic liquid crystal cell have been proposed as interesting laser-addressed writing and image storage devices. Liquid crystal dispersions are composite materials formed by liquid crystal droplets embedded in either a polymer or a monomer matrix. Thin films of liquid crystal dispersions can be turned from an opaque to a transparent state by application of a suitable alternating current electric field. Herein, we report our investigations on electrolyte-liquid crystal dispersions, which show independent electro-optical and electrochromic properties characterized by fast bleaching times. This cell involves the reorientation of liquid crystal molecules, trapped in droplets, for the electro-optical changes from the opaque to transparent state and the formation of complexes at the cathode, between the positive ions of electrolyte and liquid crystal dispersed in the matrix, for the electrochromic changes from the bleached to colored state. The device is able to change its electro-optical transmittance within few milliseconds and its color within few seconds.

  12. Design and implementation of film coating for tunable liquid crystal Fabry-Perot filter working in mid-infrared spectral region

    NASA Astrophysics Data System (ADS)

    Zhang, Huaidong; Fu, Anbang; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2013-10-01

    In this paper, we design and implementation anti-reflection and high reflection film for tunable LC-FP filter working in typical medium wave infrared (MWIR) spectral region. As to reflection mirror, we complete it by depositing gold film on the silicon substrate. By using the analytical method of dividing amplitude multiple beam interference to simulate the reflectance, the reflectivity result of the gold film is around 98% at the average in the MWIR spectral region. When take the absorption of the gold film into consideration, the gold film should be thin under the condition that it is conductive well. The anti-reflection film is introduced to reduce the reflection of the other side of the wafer. In anti-reflection structure, we simulate the reflection of the films with the algorithm of the equivalent membrane and fulfill our design with the technology of vapor deposition. Finally, we test the total transmittance of the wafer deposited gold films and anti-reflection films, which is about 0.2% of single chip. By making use of the wafer designed by us, we fabricate the LC-FP filter by placing two wafers side by side with the anti-reflection structure face to the direction of wavelength incident. Simultaneously, the LC layer with fixed thickness is sealed between the two high reflection mirrors formed by gold film. Compared with other method to fabricate mid-infrared FP filter, deposition of reflection and anti-reflection films on wafer have the advantage of low cost, simple technology.

  13. 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.

  14. 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

  15. 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

  16. Nonmechanical Infrared Beam Steering Using Blue Addressed Quantum Dot Doped Liquid Crystal Grating.

    PubMed

    Wang, Xiangru; Huang, Xiaoping; Huang, Ziqiang; Wu, Liang; Shang, Jiyang; Qiu, Qi; Wu, Shuanghong

    2017-12-01

    We present a scheme of nonmechanical laser beam steering using ZnS/InP quantum dots doping nematic liquid crystal as the optical recording film. Because of its internal electric field generated by blue laser-induced charge carrier distribution, liquid crystal molecules are reoriented to form a phase grating which make the incident angle steer to the angle as we desire. Being a nonmechanical programmable laser beam steering, the anisotropy of the relative permittivity tensor and blue laser-induced electric carriers play a significant effect in determining the reorientable liquid crystal molecule and reconfigurable phase modulation of the gratings, that determines the steering angle and steering efficiency.

  17. Nonmechanical Infrared Beam Steering Using Blue Addressed Quantum Dot Doped Liquid Crystal Grating

    NASA Astrophysics Data System (ADS)

    Wang, Xiangru; Huang, Xiaoping; Huang, Ziqiang; Wu, Liang; Shang, Jiyang; Qiu, Qi; Wu, Shuanghong

    2017-01-01

    We present a scheme of nonmechanical laser beam steering using ZnS/InP quantum dots doping nematic liquid crystal as the optical recording film. Because of its internal electric field generated by blue laser-induced charge carrier distribution, liquid crystal molecules are reoriented to form a phase grating which make the incident angle steer to the angle as we desire. Being a nonmechanical programmable laser beam steering, the anisotropy of the relative permittivity tensor and blue laser-induced electric carriers play a significant effect in determining the reorientable liquid crystal molecule and reconfigurable phase modulation of the gratings, that determines the steering angle and steering efficiency.

  18. 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.

  19. 3D interconnected ionic nano-channels formed in polymer films: self-organization and polymerization of thermotropic bicontinuous cubic liquid crystals.

    PubMed

    Ichikawa, Takahiro; Yoshio, Masafumi; Hamasaki, Atsushi; Kagimoto, Junko; Ohno, Hiroyuki; Kato, Takashi

    2011-02-23

    Thermotropic bicontinuous cubic (Cub(bi)) liquid-crystalline (LC) compounds based on a polymerizable ammonium moiety complexed with a lithium salt have been designed to obtain lithium ion-conductive all solid polymeric films having 3D interconnected ionic channels. The monomer shows a Cub(bi) phase from -5 to 19 °C on heating. The complexes retain the ability to form the Cub(bi) LC phase. They also form hexagonal columnar (Col(h)) LC phases at temperatures higher than those of the Cub(bi) phases. The complex of the monomer and LiBF(4) at the molar ratio of 4:1 exhibits the Cub(bi) and Col(h) phases between -6 to 19 °C and 19 to 56 °C, respectively, on heating. The Cub(bi) LC structure formed by the complex has been successfully preserved by in situ photopolymerization through UV irradiation in the presence of a photoinitiator. The resultant nanostructured film is optically transparent and free-standing. The X-ray analysis of the film confirms the preservation of the self-assembled nanostructure. The polymer film with the Cub(bi) LC nanostructure exhibits higher ionic conductivities than the polymer films obtained by photopolymerization of the complex in the Col(h) and isotropic phases. It is found that the 3D interconnected ionic channels derived from the Cub(bi) phase function as efficient ion-conductive pathways.

  20. Impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand on nitrification performance of a full-scale membrane bioreactor treating thin film transistor liquid crystal display wastewater.

    PubMed

    Wu, Yi-Ju; Whang, Liang-Ming; Chang, Ming-Yu; Fukushima, Toshikazu; Lee, Ya-Chin; Cheng, Sheng-Shung; Hsu, Shu-Fu; Chang, Cheng-Huey; Shen, Wason; Yang, Charn-Yi; Fu, Ryan; Tsai, Tsair-Yuan

    2013-08-01

    This study investigated impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand (COD) on nitrification performance in one full-scale membrane bioreactor (MBR) treating monoethanolamine (MEA)/dimethyl sulfoxide (DMSO)-containing thin film transistor liquid crystal display (TFT-LCD) wastewater. Poor nitrification was observed under high organic loading and high colloidal COD conditions, suggesting that high F/M ratio and colloidal COD situations should be avoided to minimize their negative impacts on nitrification. According to the nonmetric multidimensional scaling (NMS) statistical analyses on terminal restriction fragment length polymorphism (T-RFLP) results of ammonia monooxygenase (amoA) gene, the occurrence of Nitrosomonas oligotropha-like ammonia oxidizing bacteria (AOB) was positively related to successful nitrification in the MBR systems, while Nitrosomonas europaea-like AOB was positively linked to nitrification rate, which can be attributed to the high influent total nitrogen condition. Furthermore, Nitrobacter- and Nitrospira-like nitrite oxidizing bacteria (NOB) were both abundant in the MBR systems, but the continuously low nitrite environment is likely to promote the growth of Nitrospira-like NOB.

  1. Polymer Alignment Behavior with Molecular Switching of Ferroelectric Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2007-01-01

    This paper describes the molecular alignment behavior of polymer networks with switching of a ferroelectric liquid crystal (FLC) in a molecularly aligned FLC/polymer composite film. The polymer alignment in the composite film, which was slowly formed by photopolymerization-induced phase separation of a heated nematic-phase solution of FLC and monomers, was observed by polarization Raman spectral microscopy. Raman peak intensities originating from the polymers were changed with those from the FLC, when the applied voltage polarity was changed. The trace patterns of the Raman peak intensity with in-plane rotation of the composite film indicated that the formed flexible polymers can follow FLC molecular switching.

  2. 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.

  3. 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…

  4. 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…

  5. 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.

  6. 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.

  7. Flexo-dielectro-optical spectroscopy of PDLC films modified by nano-rubbed PTFE layers

    NASA Astrophysics Data System (ADS)

    Popova, Lidia T.

    2016-02-01

    The electro-optical (EO) response of planar single layers of polymer-dispersed liquid crystal (PDLC) composites of relatively large nematic microdroplets modified by layers of teflon (PTFE), was studied. The PDLC films were prepared from liquid crystal E7 and photopolymer NOA-65 in cells assembled with parallel or orthogonal PTFE-covered glass plates. The influence of nanostructured PTFE polymer nanolayers on both the polarized and depolarized component of laser light transmitted through PDLC cells of both geometry of layer rubbing directions was determined. Flexo-dielectro-optical spectroscopy in the range of 10 Hz - 1 kHz was applied to examine the amplitude-frequency EO modulation by PTFE-modified PDLCs in dependence on the applied alternating-current electric field. Specific fall-downs in the frequency spectra of the first and second harmonic EO modulation by PTFE-modified PDLCs were observed, that could be tuned by the driving electric field.

  8. 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.

  9. 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.

  10. Holographic Polymer Dispersed Liquid Crystal (HPDLC) Transmission Gratings Formed by Visible Light Initiated Thiol-Ene Photopolymerization (Postprint)

    DTIC Science & Technology

    2006-10-01

    ion laser. The photoinitiator system consists of the dye oxazine 170 perchlorate and the co-initiator benzoyl peroxide . Electron transfer occurs...between the singlet excited state of the oxazine dye and benxoyl peroxide with subsequent decomposition of the peroxide yielding benzoyl oxy radicals...initiator benzoyl peroxide . Electron transfer occurs between the singlet excited state of the oxazine dye and benzoyl peroxide with subsequent

  11. 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

  12. Engineered complex molecular order in liquid crystals towards unusual optics and responsive mechanics

    NASA Astrophysics Data System (ADS)

    Sánchez-Somolinos, Carlos; de Haan, Laurens T.; Schenning, Albert P. H. J.; Bastiaansen, Cees W. M.; Broer, Dirk J.

    2013-03-01

    Defects in liquid crystals have been studied over decades to disclose information and knowledge on the structure of LC phases. More recently, LC defects have been identified as a tool to implement new physical functions useful in optical films for polarization conversion or mechanical actuators able to adopt novel exotic shapes. In the present paper we describe a general methodology to engineer different defect patterns by combining the use of linear photopolymerizable polymers and liquid crystals.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Structure and Dynamics of Freely Suspended Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2004-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1 D) 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 or quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enables 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 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 LC 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 Kosterlitz Thouless phase

  7. 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.

  8. 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.

  9. The use of photolithography on molecular orientation of the liquid crystals

    NASA Astrophysics Data System (ADS)

    Yilmaz, Suleyman

    2017-02-01

    The photolithography was used on molecular orientation of liquid crystals as an alternative to other conventional methods. Either planar or homeotropic orientation were provided with surface anchoring energy for the molecular alignment. The photolithography were applied to provide micro-grooving on the film surface, which is including polyimide coatings, UV exposure, chemical etching and thermal curing process, respectively. Three type liquid crystal cells were made by provided rubbing and photolithography for planar alignment and also homeotropic alignment. Electro-optical properties of the liquid crystals were examined under the electric field at phase transition region for three type liquid crystal cells. It was observed that the photolithographic method was the more effective and acceptable results than the other conventional methods on the molecular orientations.

  10. Liquid crystal panel for high efficiency barrier type autostereoscopic three-dimensional displays.

    PubMed

    Chen, Cheng-Huan; Huang, Yi-Pai; Chuang, Shang-Chih; Wu, Chi-Lin; Shieh, Han-Ping D; Mphepö, Wallen; Hsieh, Chiu-Ting; Hsu, Shih-Chia

    2009-06-20

    An autostereoscopic display with parallax barrier attached onto a liquid crystal panel suffers from the trade-off between brightness and crosstalk. One approach for making improvement by modifying the layout of light blocking components, such as thin film transistor, storage capacitor, and protrusion, in the liquid crystal pixel has been proposed. Ray tracing simulation shows that the aperture of the slanted barrier can be significantly increased, hence increasing efficiency, while keeping the same crosstalk level if those light blocking components can be shifted to the corner of the pixel. A six-view 2.83 in. (7.19 cm) prototype has shown improvement on both brightness and crosstalk compared to its counterpart using a traditional liquid crystal panel, which demonstrates an effective approach for a high-efficiency barrier-type autostereoscopic 3D display with a liquid crystal panel.

  11. Retrieval of computer-generated holograms projected onto liquid crystal-photoconducting polymer system

    NASA Astrophysics Data System (ADS)

    Miniewicz, Andrzej; Mysliwiec, Jaroslaw; Gryga, Lukasz; Kajzar, Francois

    2004-06-01

    Simple liquid crystal panel equipped with a polymeric photoconducting layer can be used for displaying dynamic holographic images. It is sufficient to compute the hologram of the object and reconstruct the wavefield optically. This can be done by projection of the binary hologram onto liquid crystal panel with the help of standard video-projector. Illumination of the photoconducting polymeric layer by a white light interferogram leads to tiny molecular rearrangements within the bulk of the liquid crystal layer which form a refractive index grating. They occur as a result of spatially modulated electric space charge field produced in a polymer. Short holographic films displayed at video-rates are achievable with the system based on PVK:TNF polymer and planar nematic liquid crystal mixture. The underlying electrical and optical processes as well as characteristics, performances and limitations of the system are discussed.

  12. Multiwall carbon nanotubes doped ferroelectric liquid crystal composites: A study of modified electrical behavior

    NASA Astrophysics Data System (ADS)

    Neeraj; Raina, K. K.

    2014-02-01

    We systematically investigated the role of carbon nanotubes and their nature of interaction with the high polarization ferroelectric liquid crystal molecules that causes a change in the dynamic behavior of the liquid crystals. The carbon nanotubes were functionalized with carboxyl group (-COOH) before dispersion in order to enhance their stability in the liquid crystal medium. For the systematic investigation of a non linear behavior of dispersed composite systems, results for various physical properties were determined by thermal, morphological and dielectric studies in the planer aligned 5 μm thickness cells. An effort has also gone into detail to investigate these properties with varying concentration (0.02 wt%, 0.05 wt% and 0.1 wt%) of multiwall carbon nanotubes. The various carbon nanotubes doped ferroelectric liquid crystal thin film composites have shown enhanced dielectric strength and dielectric permittivity values as compared to the undoped sample.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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)....

  6. 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.

  7. 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)....

  8. 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)....

  9. 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)....

  10. 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)....

  11. 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

  12. 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

  13. 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

  14. A transient liquid crystal thermography technique for gas turbine heat transfer measurements

    NASA Astrophysics Data System (ADS)

    Ekkad, Srinath V.; Han, Je-Chin

    2000-07-01

    This paper presents in detail the transient liquid crystal technique for convective heat transfer measurements. A historical perspective on the active development of liquid crystal techniques for convective heat transfer measurement is also presented. The experimental technique involves using a thermochromic liquid crystal coating on the test surface. The colour change time of the coating at every pixel location on the heat transfer surface during a transient test is measured using an image processing system. The heat transfer coefficients are calculated from the measured time responses of these thermochromic coatings. This technique has been used for turbine blade internal coolant passage heat transfer measurements as well as turbine blade film cooling heat transfer measurements. Results can be obtained on complex geometry surfaces if visually accessible. Some heat transfer results for experiments with jet impingement, internal cooling channels with ribs, flow over simulated TBC spallation, flat plate film cooling, cylindrical leading edge and turbine blade film cooling are presented for demonstration.

  15. Hybrid graphene nematic liquid crystal light scattering device

    NASA Astrophysics Data System (ADS)

    Qasim, M. M.; Khan, A. A.; Kostanyan, A.; Kidambi, P. R.; Cabrero-Vilatela, A.; Braeuninger-Weimer, P.; Gardiner, D. J.; Hofmann, S.; Wilkinson, T. D.

    2015-08-01

    A hybrid graphene nematic liquid crystal (LC) light scattering device is presented. This device exploits the inherent poly-crystallinity of chemical vapour deposited (CVD) graphene films to induce directional anchoring and formation of LC multi-domains. This thereby enables efficient light scattering without the need for crossed polarisers or separate alignment layers/additives. The hybrid LC device exhibits switching thresholds at very low electric fields (< 1 V μm-1) and repeatable, hysteresis free characteristics. This exploitation of LC alignment effects on CVD graphene films enables a new generation of highly efficient nematic LC scattering displays as well as many other possible applications.A hybrid graphene nematic liquid crystal (LC) light scattering device is presented. This device exploits the inherent poly-crystallinity of chemical vapour deposited (CVD) graphene films to induce directional anchoring and formation of LC multi-domains. This thereby enables efficient light scattering without the need for crossed polarisers or separate alignment layers/additives. The hybrid LC device exhibits switching thresholds at very low electric fields (< 1 V μm-1) and repeatable, hysteresis free characteristics. This exploitation of LC alignment effects on CVD graphene films enables a new generation of highly efficient nematic LC scattering displays as well as many other possible applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04094a

  16. Liquid crystal deposition on poled, single crystalline lithium niobate

    NASA Astrophysics Data System (ADS)

    Bharath, S. C.; Pimputkar, K. R.; Pronschinske, A. M.; Pearl, T. P.

    2008-01-01

    For the purpose of elucidating the mechanisms for molecular organization at poled ferroelectric surfaces, single crystalline lithium niobate (LN), 'Z-cut' along the (0 0 0 1) plane, has been prepared and characterized and subsequently exposed to liquid crystal molecules. As a model system we chose to study the anchoring of 4- n-octyl-4'-cyanobiphenyl (8CB) to LN. Liquid crystalline films are of interest because of their useful electronic and optical properties as well as chemical sensing attributes. Low-energy electron diffraction (LEED), atomic force microscopy (AFM), surface contact angle measurements (CA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface of lithium niobate as well as the nature of 8CB films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. 8CB liquid crystal molecules were deposited by an ambient vaporization technique and the films were analyzed using XPS and CA. Understanding electrostatic anchoring mechanisms and thin film organization for this molecule on uniformly poled surfaces allows for a fuller appreciation of how molecular deposition of other polarizable molecules on periodically poled and patterned poled lithium niobate surfaces would occur.

  17. 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

  18. Effects of photocrosslinking on photorefractive properties in polymer-liquid crystal composites

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Hasebe, Ryoya; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

    2014-03-01

    This article presents effects of photocrosslinking on photorefractive properties in polymer-liquid crystal composites doped with fullerene (C60) as a photoconductive agent. The efficiency of the photorefraction was improved by crosslinking the polymer network and reached near to the theoretical limit for the thin phase grating. The carrier conduction in the composite films was investigated and the high-performance photorefractivity of the photocrosslinked mesogenic composite was explained by low dark current and high photocurrent. The firm crosslinked polymer network in the polymer-liquid crystal composite has also employed for the stable photorefractive diffraction at elevated temperature and under a static dc field applied the mesogenic composite film.

  19. Layer thinning transition in an achiral four-ring hockey stick shaped liquid crystal

    NASA Astrophysics Data System (ADS)

    Paul, Manoj Kr.; Nath, Rahul K.; Moths, Brian; Pan, LiDong; Wang, Shun; Deb, Rajdeep; Shen, Yongqiang; Rao, Nandiraju V. S.; Huang, C. C.

    2012-12-01

    Depolarized reflected light microscopy and high resolution optical reflectivity measurements have been conducted on free-standing films of an achiral four-ring hockey stick shaped liquid crystal exhibiting SmA-B2-SmX* transition sequence. A layer thinning transition above the bulk isotropic-SmA phase transition has been observed. This behaviour was highly irreproducible, indicating an irregular layer thinning transition. From optical reflectivity data, both thickness of the free-standing films and the smectic interlayer spacing were determined. This is the first report of the layer thinning transition in a hockey stick shaped liquid crystal.

  20. Fluctuation and Dissipation in Liquid-Crystal Electroconvection

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

    In this experiment a steady-state current is maintained through a liquid-crystal thin film. When the applied voltage is increased through a threshold, a phase transition is observed to a convective state characterized by the chaotic motion of rolls. Above the threshold, an increase in power consumption is observed that is manifested by an increase in the mean conductivity. A sharp increase in the ratio of the power fluctuations to the mean power dissipated is observed above the transition. This ratio is compared to the predictions of the fluctuation theorem of Gallavotti and Cohen using an effective temperature associated with the rolls' chaotic motion.

  1. Fluctuation and dissipation in liquid-crystal electroconvection.

    PubMed

    Goldburg, W I; Goldschmidt, Y Y; Kellay, H

    2001-12-10

    In this experiment a steady-state current is maintained through a liquid-crystal thin film. When the applied voltage is increased through a threshold, a phase transition is observed to a convective state characterized by the chaotic motion of rolls. Above the threshold, an increase in power consumption is observed that is manifested by an increase in the mean conductivity. A sharp increase in the ratio of the power fluctuations to the mean power dissipated is observed above the transition. This ratio is compared to the predictions of the fluctuation theorem of Gallavotti and Cohen using an effective temperature associated with the rolls' chaotic motion.

  2. Micropatterning of light-sensitive liquid-crystal elastomers.

    PubMed

    Devetak, Miha; Zupancic, Blaz; Lebar, Andrija; Umek, Polona; Zalar, Bostjan; Domenici, Valentina; Ambrozic, Gabriela; Zigon, Majda; Copic, Martin; Drevensek-Olenik, Irena

    2009-11-01

    We demonstrate that photoisomerizable liquid-crystal elastomer soft films can be used as tunable holographic gratings. Optomechanical mechanism of imprinting one-dimensional grating structure into the soft matrix by two-beam uv laser interference can be clearly resolved from the time dependence of the reading beam diffraction patterns. We analyze the observed response in terms of cis-trans isomerization-controlled modulation of the grating profile. The grating period can be tuned reversibly by stretching or contraction of the specimen, either thermomechanically or by applying external stress. Temperature-induced modifications of the grating parameters in the vicinity of the nematic-paranematic phase transition are also examined.

  3. 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.

  4. 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.

  5. 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.

  6. 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?

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Recovery of valuable materials from waste liquid crystal display panel.

    PubMed

    Li, Jinhui; Gao, Song; Duan, Huabo; Liu, Lili

    2009-07-01

    Associated with the rapid development of the information and electronic industry, liquid crystal displays (LCDs) have been increasingly sold as displays. However, during the discarding at their end-of-life stage, significant environmental hazards, impacts on health and a loss of resources may occur, if the scraps are not managed in an appropriate way. In order to improve the efficiency of the recovery of valuable materials from waste LCDs panel in an environmentally sound manner, this study presents a combined recycling technology process on the basis of manual dismantling and chemical treatment of LCDs. Three key processes of this technology have been studied, including the separation of LCD polarizing film by thermal shock method the removal of liquid crystals between the glass substrates by the ultrasonic cleaning, and the recovery of indium metal from glass by dissolution. The results show that valuable materials (e.g. indium) and harmful substances (e.g. liquid crystals) could be efficiently recovered or separated through above-mentioned combined technology. The optimal conditions are: (1) the peak temperature of thermal shock to separate polarizing film, ranges from 230 to 240 degrees C, where pyrolysis could be avoided; (2) the ultrasonic-assisted cleaning was most efficient at a frequency of 40 KHz (P = 40 W) and the exposure of the substrate to industrial detergents for 10 min; and (3) indium separation from glass in a mix of concentrated hydrochloric acid at 38% and nitric acid at 69% (HCl:HNO(3):H(2)O = 45:5:50, volume ratio). The indium separation process was conducted with an exposure time of 30 min at a constant temperature of 60 degrees C.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Liquid crystals as on-demand, variable thickness targets for intense laser applications

    NASA Astrophysics Data System (ADS)

    Poole, Patrick L.; Andereck, C. David; Schumacher, Douglass W.

    2014-10-01

    Laser-based ion acceleration is currently studied for its applications to advanced imaging and cancer therapy, among others. Targets for these and other high-intensity laser experiments are often small metallic foils with few to sub-micron thicknesses, where the thickness determines the physics of the dominant acceleration mechanism. We have developed liquid crystal films that preserve the planar target geometry advantageous to ion acceleration schemes while providing on-demand thickness variation between 50 and 5000 nm. This thickness control is obtained in part by varying the temperature at which films are formed, which governs the phase (and hence molecular ordering) of the liquid crystal material. Liquid crystals typically have vapor pressures well below the 10-6 Torr operating pressures of intense laser target chambers, and films formed in air maintain their thickness during chamber evacuation. Additionally, the minute volume that comprises each film makes the cost of each target well below one cent, in stark contrast to many standard solid targets. We will discuss the details of liquid crystal film control and formation, as well as characterization experiments performed at the Scarlet laser facility. This work was performed with support from DARPA and NNSA.

  19. Optical diffractometry of highly anisotropic holographic gratings formed by liquid crystal and polymer phase separation

    NASA Astrophysics Data System (ADS)

    Kakiuchida, Hiroshi; Tazawa, Masato; Yoshimura, Kazuki; Ogiwara, Akifumi

    2012-12-01

    Optical diffractometry is proposed as a practical method of quantitatively analyzing the microscopic structural origins of a wide range of highly efficient and linearly polarized optical diffraction grating produced from holographic polymer-dispersed liquid crystal. The structure is organized by a spatially periodical distribution of submicrometer-scale liquid crystal (LC) droplets in a polymer matrix. Six independent Bragg diffraction spectra were obtained at two orthogonal polarization states at temperatures below, at, and above the nematic-to-isotropic phase transition point. These spectra were simultaneously analyzed by employing anisotropic diffraction theory under the restraint of a simple and widely useful structural model constructed on the basis of the previously reported microscopic observations. The refractive indices of spatially periodic LC- and polymer-rich phases were analyzed using Cauchy's equation as a function of optical wavelength. The present diffractometry was demonstrated for a variety of holographic structures, and the structural parameters were discussed such as the filling ratio of LC droplets to polymer matrix, the orientational order in the droplets, and the thermo-optic properties in the LC droplets. Furthermore, the higher order Bragg diffractions were measured and discussed. The proposed method was examined in consistency by comparisons with polarizing optical microscopy and scanning electron microscopy.

  20. Optical diffractometry of highly anisotropic holographic gratings formed by liquid crystal and polymer phase separation.

    PubMed

    Kakiuchida, Hiroshi; Tazawa, Masato; Yoshimura, Kazuki; Ogiwara, Akifumi

    2012-12-01

    Optical diffractometry is proposed as a practical method of quantitatively analyzing the microscopic structural origins of a wide range of highly efficient and linearly polarized optical diffraction grating produced from holographic polymer-dispersed liquid crystal. The structure is organized by a spatially periodical distribution of submicrometer-scale liquid crystal (LC) droplets in a polymer matrix. Six independent Bragg diffraction spectra were obtained at two orthogonal polarization states at temperatures below, at, and above the nematic-to-isotropic phase transition point. These spectra were simultaneously analyzed by employing anisotropic diffraction theory under the restraint of a simple and widely useful structural model constructed on the basis of the previously reported microscopic observations. The refractive indices of spatially periodic LC- and polymer-rich phases were analyzed using Cauchy's equation as a function of optical wavelength. The present diffractometry was demonstrated for a variety of holographic structures, and the structural parameters were discussed such as the filling ratio of LC droplets to polymer matrix, the orientational order in the droplets, and the thermo-optic properties in the LC droplets. Furthermore, the higher order Bragg diffractions were measured and discussed. The proposed method was examined in consistency by comparisons with polarizing optical microscopy and scanning electron microscopy.

  1. Investigation of Polymer Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.

    1996-01-01

    The positron annihilation lifetime spectroscopy (PALS) using a low energy flux generator may provide a reasonably accurate technique for measuring molecular weights of linear polymers and characterization of thin polyimide films in terms of their dielectric constants and hydrophobity etc. Among the tested samples are glassy poly arylene Ether Ketone films, epoxy and other polyimide films. One of the proposed techniques relates the free volume cell size (V(sub f)) with sample molecular weight (M) in a manner remarkably similar to that obtained by Mark Houwink (M-H) between the inherent viscosity (eta) and molecular wieght of polymer solution. The PALS has also demonstrated that free-volume cell size in thermoset is a versatile, useful parameter that relates directly to the polymer segmental molecular weight, the cross-link density, and the coefficient of thermal expansion. Thus, a determination of free volume cell size provides a viable basis for complete microstructural characterization of thermoset polyimides and also gives direct information about the cross-link density and coefficient of expansion of the test samples. Seven areas of the research conducted are reported here.

  2. 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…

  3. 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.

  4. 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>.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Features of electro-optical characteristics of composite liquid crystal media (a review)

    NASA Astrophysics Data System (ADS)

    Amosova, L. P.; Venediktov, V. Yu.

    2016-11-01

    Main patterns of structure formation of composite liquid crystal (LC) media and their classification according to the percentage content of liquid crystal and polymer are considered. Their properties are compared with the properties of homogeneous LC layers and the opportunities of their practical use in optical modulators are discussed. It is shown that, at small (10 wt %) monomer concentrations in the composite, its polymerization leads to formation of a thin-wall network which separates the liquid crystal into domains and provides an uniform orientation in the bulk. The polymer network increases the elasticity of the layer and decreases the relaxation time, but the devices usually work in polarized light and use the same principle as the devices filled with pure LC; i.e. the phase of the light or its polarization changes due to a change in the effective refraction index. However, the division of the LC volume into relatively autonomous domains also allows one to create a polarization-independent device based on the scattering effect. By increasing the relative content of the monomer, it is possible to ensure formation of a porous polymer matrix with inclusions of isolated from each other LC droplets. Such polymer-dispersed LC in its initial state either scatter the light of any polarization and becomes transparent state when an electric field is applied, or, with the use of special methods, the switch-off and switch-on states are swapped ("reverse mode" devices). The main advantages of the composite media are independence of polarization, mechanical strength, and small relaxation times, while the main disadvantages are increased power consumption, high polarization-independent optical losses, and significantly lower contrast. Possible ways to increase the contrast are described.

  10. 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.

  11. A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Characteristics of a liquid crystal system, comprised of a shear-sensitive cholesteric-monomer liquid crystal thin-film coated on a liquid-crystal polymer substrate, are described. The system provides stable Grandjean texture, a desirable feature for shear-stress measurements using selective reflection from the monomer liquid-crystal helix structure. Impingement of gas or air flow on the monomer liquid-crystal free surface changes the wavelength of the selective reflection for an incident white light from red toward blue with increase in the rate of gas flow. The contrast of the selectively reflected light improves considerably by providing a thin black coating of about 5 microns at the monomer-polymer interface. The coating thickness is such that the steric interactions are still sufficiently strong to maintain Grandjean texture. For a small angle of incidence of a monochromatic light, the measurement of the reflected light intensity normal to the monomer-polymer liquid-crystal interface enables the determination of the wavelength for selective reflection as a function of the gas-flow differential pressure applied in the plane of the interface. The variation of the wavelength with the pressure is linear with a slope of about 2 nm/mmHg. Furthermore, the shear-stress effects are reversible unlike for monomer liquid crystal-metal systems used for flow visualization on wind-tunnel model surfaces. The present system offers a suitable method for direct on-line measurement of shear stress field from measurements of the wavelength for selective reflection for an incident white light.

  12. Self-organization and electrooptical characteristics of a nematic liquid crystal-cellulose diacetate composite

    NASA Astrophysics Data System (ADS)

    Sadovoy, A. V.; Shipovskaya, A. B.; Nazvanov, V. F.

    2008-12-01

    Stable self-organization process has been observed during the formation of thin films of a composite based on a nematic liquid crystal and a cellulose acetate polymer matrix. Optical transmission characteristics and electrooptical response time of the composite have been theoretically calculated and experimentally studied.

  13. Digital photofinishing system based on liquid crystal on silicon

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

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

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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)

  20. 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

  1. [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.

  2. Reversal of helicoidal twist handedness near point defects of confined chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Ackerman, Paul J.; Smalyukh, Ivan I.

    2016-05-01

    Handedness of the director twist in cholesteric liquid crystals is commonly assumed to be the same throughout the medium, determined solely by the chirality of constituent molecules or chiral additives, albeit distortions of the ground-state helicoidal configuration often arise due to the effects of confinement and external fields. We directly probe the twist directionality of liquid crystal director structures through experimental three-dimensional imaging and numerical minimization of the elastic free energy and show that spatially localized regions of handedness opposite to that of the chiral liquid crystal ground state can arise in the proximity of twisted-soliton-bound topological point defects. In chiral nematic liquid crystal confined to a film that has a thickness less than the cholesteric pitch and perpendicular surface boundary conditions, twisted solitonic structures embedded in a uniform unwound far-field background with chirality-matched handedness locally relieve confinement-imposed frustration and tend to be accompanied by point defects and smaller geometry-required, energetically costly regions of opposite twist handedness. We also describe a spatially localized structure, dubbed a "twistion," in which a twisted solitonic three-dimensional director configuration is accompanied by four point defects. We discuss how our findings may impinge on the stability of localized particlelike director field configurations in chiral and nonchiral liquid crystals.

  3. Fundamental display properties of flexible devices containing polymer-stabilized ferroelectric liquid crystal between plastic substrates

    NASA Astrophysics Data System (ADS)

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

    2002-09-01

    We describe several fundamental display properties of a flexible ferroelectric liquid crystal device containing polymer fibers between thin plastic substrates. The composite film of liquid crystal and polymer was created from a solution of liquid crystal and monomer materials between the plastic substrates under ultraviolet light irradiation. The dynamic electrooptic response to analog voltage pulses was examined with an incidence of laser beam light, and its light modulation property exhibited good linearity in continuous gray-scale capability. The excellent spatial uniformity of liquid crystal alignment formed between the flexible substrates resulted in high-contrast light modulation, although slight spontaneous bending of liquid crystal alignment in the device plane was recognized. When the laser light beam was obliquely incident on the flexible display device, the measured transmittance revealed that the device has a wide viewing angle of more than 100 deg without contrast reversal. This is considered to be caused by the molecular switching in the device plane and the thin electrooptic layer in the display device.

  4. Self-Restoration by Smectic Layer Structures of Monostable Ferroelectric Liquid Crystal in Flexible Devices

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Sato, Hiroto; Isaka, Fumito; Murashige, Takeshi; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2004-12-01

    In this paper, we discuss a self-restoration phenomenon affecting smectic layer deformation and molecular alignment in monostable ferroelectric liquid crystals used for flexible displays. First, the mechanical stability of tilted ‘bookshelf’ structures of smectic layers anchored on substrates using alignment layers was examined by precisely shearing two substrates. The microscopic texture of a monostable ferroelectric liquid crystal showed tolerance to shearing and the self-restoration was thought to be due to a smectic layer reconnection phenomenon, whereas a conventional bistable ferroelectric liquid crystal film generated alignment defects due to the tilting of the stable molecular direction. We then fabricated a flexible monostable device containing fine polymer fiber networks, where anchoring of molecularly aligned polymer fibers led to the observation of monostable liquid crystal switching. A uniform liquid crystal alignment was maintained in a 100 mm× 100 mm device even after bending more than 10000 times at a minimum radius of curvature of 20 mm, due to the enhanced shearing tolerance of the smectic layer structure.

  5. Studies of Islands on Freely Suspended Bubbles of Smectic Liquid Crystal

    NASA Technical Reports Server (NTRS)

    Pattanaporkratana, A.; Mavel, B.; Park, C. S.; Maclennan, J. E.; Clark, N. A.

    2002-01-01

    We have constructed an optical system for observing the internal structure of freely suspended smectic liquid crystal bubbles using a reflected light microscope. Liquid crystal bubbles can have thicker circular regions (islands) which can easily be generated by shrinking the bubble diameter. The diameter of these islands is approximately 10 microns and they are typically up to five times thicker than the surrounding liquid crystal film (500 angstroms). In the Laboratory, the location of the islands is strongly influenced by gravity, which causes the majority of islands to migrate to the bottom half of the bubble. We will describe the size and thickness distributions of islands and their time evolution, and also discuss two-dimensional hydrodynamics and turbulence of smectic bubbles, the shapes of islands and holes affected by bubble vibrations, and the interactions between islands, which we have probed using optical tweezers.

  6. Large Area Microencapsulated Reflective Guest-Host Liquid Crystal Displays and Their Applications

    NASA Astrophysics Data System (ADS)

    Nakai, Yutaka; Tanaka, Masao; Enomoto, Shintaro; Iwanaga, Hiroki; Hotta, Aira; Kobayashi, Hitoshi; Oka, Toshiyuki; Kizaki, Yukio; Kidzu, Yuko; Naito, Katsuyuki

    2002-07-01

    We have developed reflective liquid crystal displays using microencapsulated guest-host liquid crystals, whose size was sufficiently large for viewing documents. A high-brightness image can be realized because there is no need for polarizers. Easy fabrication processes, consisting of screen-printing of microencapsulated liquid crystal and film adhesion, have enabled the realization of thinner and lighter cell structures. It has been confirmed that the display is tolerant of the pressures to which it would be subject in actual use. The optimization of fabrication processes has enabled the realization of reflectance uniformity in the display area and reduction of the driving voltage. Our developed display is suitable for portable information systems, such as electronic book applications.

  7. 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

  8. Fast Electromechanical Response in Liquid Crystal Elastomer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Verduzco, Rafael; Agrawal, Aditya; Jacot, Jeff; Adetiba, Tomi

    2014-03-01

    Liquid crystal elastomers (LCEs) combine the elasticity of polymer networks with the fluidity and responsiveness of liquid crystals. LCEs can respond to a variety of external stimuli - heat, light, electric and magnetic fields - with large and reversible shape-changes. However, the response can be slow and/or require large external fields. Here, we present our recent work with LCE bilayers and LCE composite materials that demonstrates LCEs can respond quickly and with 3-D shape changes. Nematic LCE bilayers are prepared by depositing a PS film on top of a nematic LCE, and the bilayers exhibit reversible wrinkling, folding, and curling with temperature. The shape change of LCE bilayers is quantitatively predicted using finite-element modeling. Next, we show that a fast response to an electric field is achieved in nematic LCE composites. While typical nematic LCEs are relatively unresponsive to electric fields, LCE composites with 2 wt % carbon black can reversibly contract and expand in response to a 40 V electric field. The response time (0.1 - 10 Hz) and amplitude of shape change (1 - 20 %) depends on the external field and carbon black content. These composites may be useful for biomedical applications, such as substrates for dynamic cell culture and biocompatible scaffolds for heart tissue regeneration. Neonatal rat ventricular myocytes remain viable on LCE-carbon black bilayer substrates, and aligned myocyte cell sheets were successfully grown on LCE-composite bilayers.

  9. Surface dynamics and mechanics in liquid crystal polymer coatings

    NASA Astrophysics Data System (ADS)

    Liu, Danqing; Broer, Dirk J.

    2015-03-01

    Based on liquid crystal networks we developed `smart' coatings with responsive surface topographies. Either by prepatterning or by the formation of self-organized structures they can be switched on and off in a pre-designed manner. Here we provide an overview of our methods to generate coatings that form surface structures upon the actuation by light. The coating oscillates between a flat surface and a surface with pre-designed 3D micro-patterns by modulating a light source. With recent developments in solid state lighting, light is an attractive trigger medium as it can be integrated in a device for local control or can be used remotely for flood or localized exposure. The basic principle of formation of surface topographies is based on the change of molecular organization in ordered liquid crystal polymer networks. The change in order leads to anisotropic dimensional changes with contraction along the director and expansion to the two perpendicular directions and an increase in volume by the formation of free volume. These two effects work in concert to provide local expansion and contraction in the coating steered by the local direction of molecular orientation. The surface deformation, expressed as the height difference between the activated regions and the non-activated regions divided by the initial film thickness, is of the order of 20%. Switching occurs immediately when the light is switched `on' and `off' and takes several tens of seconds.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Influence of the porosity on the photoresponse of a liquid crystal elastomer

    PubMed Central

    Strueben, Jan; Jin, Xin; Schaber, Clemens F.; Adelung, Rainer; Staubitz, Anne; Gorb, Stanislav N.

    2016-01-01

    Azobenzene containing liquid crystal elastomers (LCEs) are among of the most prominent photoresponsive polymers due to their fast and reversible response to different light stimuli. To bring new functions into the present framework, novel modifications in bulk material morphology are required. Therefore, we produced azobenzene LCE free-standing films with different porosities. While the porosity provided macroscopic morphological changes, at the same time, it induced modifications in alignment of liquid crystal azobenzene units in the films. We found that a high porosity increased the photoresponse of the LCE in terms of bending angle with high significance. Moreover, the porous LCE films showed similar bending forces to those of pore-free LCE films. PMID:27152212

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Photochemical manipulation of colloidal structures in liquid-crystal colloids

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Tabe, Y.; Yokoyama, H.

    2007-05-01

    We investigated photochemical manipulation of physical properties and colloidal structures in liquid-crystal (LC) colloids containing azobenzene compounds. In a LC suspension where polymeric particles were dispersed in a host LC, we achieved photochemical control of light-scattering properties of the suspension. In a nematic phase, when the suspension was sandwiched with two glass plates, the film became opaque. This would be attributable to an appearance of both multidomain structures of LC alignment and mismatches of refractive indices between the materials. The opaque state turned into a transparent one when a nematic-to-isotropic phase transition was induced by the trans-to-cis photoisomerization of the azo-dye. This will result from a disappearance of both the multidomain structures and the refractive-index mismatches in the isotropic phase. The transparent film went back into the initial opaque film when the nematic phase was obtained by the cis-to-trans photoisomerization. In a LC emulsion in which glycerol or water droplets were dispersed in liquid crystals, we examined photochemical change of defect structures and inter-droplet distances by the photochemical manner. At the initial state, Saturn ring and hedgehog defects were formed around the droplets. For the glycerol droplets, we observed structural transformations between Saturn ring and boojums on irradiation with ultra-violet and visible light. For the water droplets, the inter-droplet distances varied by changing defect size on the irradiation. These phenomena would result from modulation of anchoring conditions of the droplets by the photoisomerization of the azo-dyes.

  8. Longitudinal and transverse pyroelectric effects in a chiral ferroelectric liquid crystal

    SciTech Connect

    Yablonskii, S. V. Bondarchuk, V. V.; Soto-Bustamante, E. A.; Romero-Hasler, P. N.; Ozaki, M.; Yoshino, K.

    2015-04-15

    In this study, we compare the results of experimental investigations of longitudinal and transverse pyroelectric effects in a chiral ferroelectric crystal. In a transverse geometry, we studied freely suspended liquid-crystal films. In both geometries, samples exhibited bistability, demonstrating stable pyroelectric signals of different polarities at zero voltage. It is shown that a bistable cell based on a freely suspended film requires 40 times less energy expenditures as compared to the conventional sandwich-type cell.

  9. Microstructure and phase behavior in colloids and liquid crystals

    NASA Astrophysics Data System (ADS)

    Lohr, Matthew Alan

    This thesis describes our investigation of microstructure and phase behavior in colloids and liquid crystals. The first set of experiments explores the phase behavior of helical packings of thermoresponsive microspheres inside glass capillaries as a function of volume fraction. Stable helical packings are observed with long-range orientational order. Some of these packings evolve abruptly to disordered states as the volume fraction is reduced. We quantify these transitions using correlation functions and susceptibilities of an orientational order parameter. The emergence of coexisting metastable packings, as well as coexisting ordered and disordered states, is also observed. These findings support the notion of phase-transition-like behavior in quasi-one-dimensional systems. The second set of experiments investigates cross-over behavior from glasses with attractive interactions to sparse gel-like states. In particular, the vibrational modes of quasi-two-dimensional disordered colloidal packings of hard colloidal spheres with short-range attractions are measured as a function of packing fraction. A crossover from glassy to sparse gel-like states is indicated by an excess of low-frequency phonon modes. This change in vibrational mode distribution appears to arise from highly localized vibrations that tend to involve individual and/or small clusters of particles with few local bonds. These mode behaviors and corresponding structural insights may serve as a useful signature for glass-gel transitions in wider classes of attractive packings. A third set of experiments explores the director structures of aqueous lyotropic chromonic liquid crystal (LCLC) films created on square lattice cylindrical-micropost substrates. The structures are manipulated by modulating of the concentration-dependent elastic properties of LCLC s via drying. Nematic LCLC films exhibit preferred bistable alignment along the diagonals of the micropost lattice. Columnar LCLC films form two distinct

  10. Elimination of off-axis light leakage in a homogeneously aligned liquid crystal cell

    NASA Astrophysics Data System (ADS)

    Oh, Seung-Won; Park, Byung Wok; Yoon, Tae-Hoon

    2015-03-01

    Among various liquid crystal display modes, the in-plane switching mode exhibits the widest viewing angle because the liquid crystals are homogeneously-aligned initially and rotate within a plane parallel to the substrates when an in-plane field is applied. However, further improvement is still needed for viewing high-quality dark images from the bisector direction of the crossed polarizers. Several compensation schemes have been proposed to eliminate the off-axis light leakage in a homogeneously-aligned liquid crystal cell. Although a 100:1 iso-contrast contour at an wavelength of 550 nm can cover the entire viewing cone, light leakage at other wavelengths still remains very severe. In this paper we introduce achromatic optical compensation methods using uniaxial films to eliminate the off-axis light leakage at the dark state in homogeneously-aligned liquid crystal cell.Uniaxial films with different dispersion characteristics are used so that they can compensate one another to achieve achromatic optical compensation. The retardation values are optimized through numerical research with the aid of the Poincaré sphere.

  11. Acetone vapor fiber sensor based on side polished fiber coated with cholesteric liquid crystal

    NASA Astrophysics Data System (ADS)

    Tang, Jieyuan; Chen, Zhe; Luo, Yunhan; Yu, Jianhui; Lu, Huihui; Zhang, Jun; Hsiao, Vincent K. S.

    2015-09-01

    The organic acetone vapor sensing characteristics of side-polished fiber coating with cholesteric liquid crystal film were investigated. The cholesteric liquid crystal used in our experiments is a mixture compound, which contains 30% cholesteryl oleyl carbonate, 60% cholesteryl pelargonat, and 25% cholesteryl chloride. When cholesteric liquid crystal film was coated on the surface of side-polished fiber, an interference transmission spectrum of fiber could be observed. When the fiber is exposing in acetone vapor, a blue shift of the interference spectrum was found. The higher concentration of acetone vapor is, the larger blue shift of spectrum is found. The shift of transmission spectrum is linear to the concentration of acetone vapor. The sensitivity is 1.356nm/vol% when the concentration of acetone vapor ranges from 3vol% to 16vol%. This study demonstrates a new all-fiber low-cost and portable acetone vapor sensor. It can be also used to investigate the helical structure and molecular orientation of cholesteric liquid crystal.

  12. Red-green-blue 2 D tuneable liquid crystal laser devices

    NASA Astrophysics Data System (ADS)

    Coles, H. J.; Morris, S. M.; Ford, A. D.; Hands, P. J. W.; Wilkinson, T. D.

    2009-08-01

    In this paper, we review our recent experimental work on coherent and blue phase liquid crystal lasers.We will present results on thin-film photonic band edge lasing devices using dye-doped low molar mass liquid crystals in self-organised chiral nematic and blue phases. We show that high Q-factor lasers can be achieved in these materials and demonstrate that a single mode output with a very narrow line width can be readily achievable in well-aligned mono-domain samples. Further, we have found that the performance of the laser, i.e. the slope efficiency and the excitation threshold, are dependent upon the physical parameters of the low molar mass chiral nematic liquid crystals. Specifically, slope efficiencies greater than 60% could be achieved depending upon the materials used and the device geometry employed. We will discuss the important parameters of the liquid crystal host/dye guest materials and device configuration that are needed to achieve such high slope efficiencies. Further we demonstrate how the wavelength of the laser can be tuned using an in-plane electric field in a direction perpendicular to the helix axis via a flexoelectric mechanism as well as thermally using thermochromic effects. We will then briefly outline data on room temperature blue phase lasers and further show how liquid crystal/lenslet arrays have been used to demonstrate 2D laser emission of any desired wavelength. Finally, we present preliminary data on LED/incoherent pumping of RG liquid crystal lasers leading to a continuous wave output.

  13. Charge retention of twisted nematic liquid-crystal displays

    NASA Astrophysics Data System (ADS)

    Yang, K. H.

    1990-01-01

    A simulated thin-film transistor (TFT) circuit has been built to drive the twisted nematic (TN) cell for the measurements of charge retention and the transmission versus peak voltage applied to the drain electrode of the simulated TFT using the gate pulse width as a parameter. The established rule that the transmission of the TN cell depends only on the rms voltage applied to the cell has been confirmed by calculating the rms voltage of the charge retention curves in correlation with the measured transmissions. The deviation of the decaying charge retention curves from the exponential behavior has been observed and can be qualitatively explained by a combination of the dielectric and transport properties of nematic liquid-crystal medium.

  14. Control of nanoparticle self-assemblies using distorted liquid crystals

    NASA Astrophysics Data System (ADS)

    Lacaze, Emmanuelle; Coursault, Delphine

    This chapter concerns the structure and the optical properties of nanoparticle (NP)/liquid crystal (LC) composites in the presence of LC distortion. After a first description of the general behaviour of NPs at the proximity of distorted LC areas, the first section of the chapter discusses the stabilization of the LC phases, characterized by the presence of topological defects in presence of NPs. The assemblies of NPs induced by distorted LC films is addressed in the second section. The last section then extensively develops the structure and optical properties of NP assemblies created within topological defects. Specific localisation and orientations of the NPs will be discussed, but also possible control of the size and shape of the NP assemblies, together with control of the distances between NPs in the assemblies, leading to original optical properties of the composites as far as uorescent or gold NPs are concerned.

  15. 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.

  16. 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.

  17. A cellulose liquid crystal motor: a steam engine of the second kind

    PubMed Central

    Geng, Yong; Almeida, Pedro Lúcio; Fernandes, Susete Nogueira; Cheng, Cheng; Palffy-Muhoray, Peter; Godinho, Maria Helena

    2013-01-01

    The salient feature of liquid crystal elastomers and networks is strong coupling between orientational order and mechanical strain. Orientational order can be changed by a wide variety of stimuli, including the presence of moisture. Changes in the orientation of constituents give rise to stresses and strains, which result in changes in sample shape. We have utilized this effect to build soft cellulose-based motor driven by humidity. The motor consists of a circular loop of cellulose film, which passes over two wheels. When humid air is present near one of the wheels on one side of the film, with drier air elsewhere, rotation of the wheels results. As the wheels rotate, the humid film dries. The motor runs so long as the difference in humidity is maintained. Our cellulose liquid crystal motor thus extracts mechanical work from a difference in humidity. PMID:23293743

  18. A cellulose liquid crystal motor: a steam engine of the second kind.

    PubMed

    Geng, Yong; Almeida, Pedro Lúcio; Fernandes, Susete Nogueira; Cheng, Cheng; Palffy-Muhoray, Peter; Godinho, Maria Helena

    2013-01-01

    The salient feature of liquid crystal elastomers and networks is strong coupling between orientational order and mechanical strain. Orientational order can be changed by a wide variety of stimuli, including the presence of moisture. Changes in the orientation of constituents give rise to stresses and strains, which result in changes in sample shape. We have utilized this effect to build soft cellulose-based motor driven by humidity. The motor consists of a circular loop of cellulose film, which passes over two wheels. When humid air is present near one of the wheels on one side of the film, with drier air elsewhere, rotation of the wheels results. As the wheels rotate, the humid film dries. The motor runs so long as the difference in humidity is maintained. Our cellulose liquid crystal motor thus extracts mechanical work from a difference in humidity.

  19. A cellulose liquid crystal motor: a steam engine of the second kind

    NASA Astrophysics Data System (ADS)

    Geng, Yong; Almeida, Pedro Lúcio; Fernandes, Susete Nogueira; Cheng, Cheng; Palffy-Muhoray, Peter; Godinho, Maria Helena

    2013-01-01

    The salient feature of liquid crystal elastomers and networks is strong coupling between orientational order and mechanical strain. Orientational order can be changed by a wide variety of stimuli, including the presence of moisture. Changes in the orientation of constituents give rise to stresses and strains, which result in changes in sample shape. We have utilized this effect to build soft cellulose-based motor driven by humidity. The motor consists of a circular loop of cellulose film, which passes over two wheels. When humid air is present near one of the wheels on one side of the film, with drier air elsewhere, rotation of the wheels results. As the wheels rotate, the humid film dries. The motor runs so long as the difference in humidity is maintained. Our cellulose liquid crystal motor thus extracts mechanical work from a difference in humidity.

  20. Zinc oxide nanolevel surface transformation for liquid crystal orientation by ion bombardment

    SciTech Connect

    Oh, Byeong-Yun; Lee, Won-Kyu; Kim, Young-Hwan; Seo, Dae-Shik

    2009-03-01

    This paper introduces the characteristics of the zinc oxide (ZnO) inorganic film deposited by radio-frequency magnetron sputtering as an alternative alignment layer for liquid crystal display (LCD) applications. The crystalline structure related to the texture formation of ZnO (1013) was observed with a tilt angle of approximately 28.1 deg. to the ZnO (0001) plane, leading to a smooth surface and high-density structure. Ion beam (IB) bombardment at various incident angles was used to induce liquid crystal (LC) alignment and cause the measured pretilt angle on ZnO films to assume a triangular contour. The orientation order of liquid crystal molecules was due to the van der Waals force for the vertical alignment of LCs with selective breaking of O-Zn bonds by IB bombardment. The contact angle contour as a function of the IB incident angle resembled the behavior of the pretilt angle. The pretilt angle is controllable by adjusting the surface features on ZnO films with IB bombardment. The electro-optic characteristics of vertically aligned (VA)-LCD based on ZnO film were comparable to those of VA-LCD based on polyimide, showing good potential of ZnO film as a LC alignment layer.

  1. 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%.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Investigation of the structure and thermal behaviour of polymer liquid crystal / single wall carbon nanotubes nanocomposite

    NASA Astrophysics Data System (ADS)

    Exner, G.; Marinov, Y.; Perez, E.

    2017-01-01

    In the present work, nanocomposite of thermotropic polymer liquid crystal poly(heptane-1,7-dyil biphenyl-4,4’-dicarboxilate) and single wall carbon nanotubes was investigated. Nanocomposite films were casted from solution blended polymer liquid crystal and nanotubes. The structure and thermal behaviour of the nanocomposite were investigated by means of X-ray scattering and differential scanning calorimetry. The results show that there are two phase transitions on cooling and a single one on subsequent heating for both the neat polymer liquid crystal and nanocomposite. Hence, the smectic order of the polymer liquid crystal as well as its monotropic behaviour are preserved in the nanocomposite. The isotropic melt - smectic transition temperature in the nanocomposite is several degrees higher and the enthalpy of this process is much lower, suggesting heterogeneous nucleation of this phase on the surface of the nanotubes. The temperature of crystal structure formation during further cooling decreases in the nanocomposite showing a stabilization effect of the nanotubes on the smectic phase. Judging from the smaller enthalpy of the smectic-crystal phase transition and the new crystalline peak in the X-ray scattering patterns of the nanocomposite one could suggest a new crystalline form formation and this crystalline phase coexistence with smectic phases at lower temperatures.

  19. Single-substrate liquid-crystal displays by photo-enforced stratification

    NASA Astrophysics Data System (ADS)

    Penterman, Roel; Klink, Stephen I.; de Koning, Henk; Nisato, Giovanni; Broer, Dirk J.

    2002-05-01

    Data visualization plays a crucial role in our society, as illustrated by the many displays that surround us. In the future, displays may become even more pervasive, ranging from individually addressable image-rendering wall hangings to data displays integrated in clothes. Liquid-crystal displays (LCDs) provide most of the flat-panel displays currently used. To keep pace with the ever-increasing possibilities afforded by developments in information technology, we need to develop manufacturing processes that will make LCDs cheaper and larger, with more freedom in design. Existing batch processes for making and filling LCD cells are relatively expensive, with size and shape limitations. Here we report a cost-effective, single-substrate technique in which a coated film is transformed into a polymer-covered liquid-crystal layer. This approach is based on photo-enforced stratification: a two-step photopolymerization-induced phase separation of a liquid-crystal blend and a polymer precursor. The process leads to the formation of micrometre-sized containers filled with a switchable liquid-crystal phase. In this way, displays can be produced on a variety of substrates using current coating technology. The developed process may be an important step towards new technologies such as `display-on-anything' and `paintable displays'.

  20. Cholesteric liquid crystal formation in suspensions of cellulose nanocrystals

    NASA Astrophysics Data System (ADS)

    Honorato-Rios, Camilla; Bruckner, Johanna; Schütz, Christina; Wagner, Sammy; Tosheva, Zornitza; Bergström, Lennart; Lagerwall, Jan P. F.

    With the strong current trend in nanotechnology to focus on sustainably produced nanomaterials, cellulose nanocrystals (CNC) are emerging as a particularly interesting candidate. They are mechanically strong, optically transparency and birefringent, have low weight and low thermal expansion coefficient. A most desirable feature of CNC is that aqueous suspensions form cholesteric liquid crystal phases already at low concentration, and when dried into thin solid films, the periodicity of the helical structure can be reduced to the range of visible selective reflection, in practice making the film a photonic crystal paper. We begin the chapter by briefly explaining how CNC is extracted from cellulose-rich bioresources, followed by a summary of the typical characteristics in terms of dimensions and surface charge, and how these depend on the production method. The current understanding of the phase diagram of CNC suspensions is then discussed, from the low-concentration regime around the isotropic-cholesteric transition to the less well understood regime where the system is kinetically arrested in a non-equilibrium state. We discuss the influences on phase behavior and cholesteric pitch of the solvent and its ionic strength. Finally, we discuss the production of photonic crystal films and we give a brief outlook.

  1. 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.

  2. Liquid Crystal properties of Silver (Ag) Nanowires as a Function of Flow

    NASA Astrophysics Data System (ADS)

    Martinez-Miranda, Luz J.; Hu, Liangbing; Preston, Colin D.

    2014-03-01

    We study the liquid crystal properties of nanowires of silver (Ag) as a function of flow of the solvent. Specifically, we are interested in finding the flow-concentration point where the electrical properties (IV curve) are: 1. Along one direction; and, 2. At a maximum along that particular direction. We are interested in the structure intermediate between the liquid crystal phase and the isotropic phase (the heterogenous phase) and how ``ordered'' this phase becomes with flow. Flow is varied in our case by having a substrate with gratings of varying depth in them. The flow due to the grating and the thickness of the film, plus the size of the nanowires will dictate the degree of order in the heterogeneous phase. This order dictates how the electrical properties orient in the resulting film. These studies can be expanded to include other semiconducting and/or metallic nanowires.

  3. Concurrent solution-like decoloration rate and high mechanical strength from polymer-dispersed photochromic organogel.

    PubMed

    Long, Shijun; Bi, Shuguang; Liao, Yonggui; Xue, Zhigang; Xie, Xiaolin

    2014-04-01

    To achieve a fast photochromic response in solid matrix, photochromic molecules/segments have been either dispersed into elastomers via physical doping or linked to glassy polymers by soft units through covalent bonding. However, the former is lack of high mechanical strength and the latter owes the drawback of time-consumption of synthesis. Here, we propose a facile strategy of co-solvent evaporation to prepare polymer-dispersed photochromic organogel where both high mechanical strength of the glassy polymer matrix and solution-like fast photochromism of the photochromic molecule within organogel can be retained concurrently. Glassy PVA matrix and dispersed organogel of 1,3:2,4-di-O-benzylidene-d-sorbitol/poly(propylene glycol) (DBS/PPG) provide high mechanical strength and sufficient free volume for intramolecular rotation of photochromic spiropyran (SP), respectively. Interestingly, these thin films behave a solution-like decoloration the decay rate of which is 65-70 fold faster than that in the SP-directly doped PVA film and only slightly slower than those in their corresponding PPG solutions.

  4. 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

  5. Liquid crystal-based sensors for selective and quantitative detection of nitrogen dioxide

    PubMed Central

    Sen, Avijit; Kupcho, Kurt A.; Grinwald, Bart A.; VanTreeck, Heidi J.; Acharya, Bharat R.

    2013-01-01

    A highly sensitive nitrogen dioxide (NO2) sensor based on orientational transition of a thin film of liquid crystal (LC) supported on a gold surface is reported. Transport of NO2 molecules through the LC film to the LC-gold interface induces an orientation transition in the LC film. The dynamic behavior of the sensor response exhibits a concentration-dependent response rate that is employed to generate an algorithm for quantitative determination of unknown concentrations. Sensitive, selective and reversible detection with minimal effects of environmental fluctuations suggest that these sensors can be used for quantitative NO2 detection for a number of applications. PMID:23526230

  6. 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.

  7. 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…

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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…

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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) .

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Field-driven dynamics of microcapillaries filled with nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Fu, Fred; Khayyatzadeh, Pouya; Abukhdeir, Nasser M.

    Polymer-dispersed liquid crystal (PDLC) composites have long been a focus of study for their unique electro-optical properties and the feasibility of manufacturing them on a large scale, resulting in applications such as switchable windows. LC domains within PDLCs are typically spheroidal, as opposed to rectangular in LCD technology, and thus exhibit substantially different behaviour in the presence of an external field. In this work, continuum simulations were performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. A simplified elliptic cylinder (microcapillary) geometry is used and the effects of varying aspect ratio, surface anchoring, and external field strength were studied using the Landau-de Gennes model. The observed nematic formation and reorientation dynamics were found to be governed by the presence and motion of defects within the domain. Aspect ratio was found to strongly influence domain texture by providing regions of high curvature to which defects are attracted. Simulations also predict the presence of a geometry-controlled transition from nematic order enhanced by an external field (low aspect ratio) to nematic order frustrated by an external field (high aspect ratio). This work was made possible by the Natural Sciences and Engineering Research Council of Canada and Compute Ontario.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Material Flows in an Active Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Decamp, Stephen; Redner, Gabriel; Baskaran, Aparna; Hagan, Michael; Dogic, Zvonimir

    Active matter systems are composed of energy consuming constituent components which drive far-from-equilibrium dynamics. As such, active materials exhibit energetic states which would be unfavorable in passive, equilibrium materials. We study one such material; an active nematic liquid crystal which exists in a dynamical steady state where +/-1/2 defects are continuously generated and annihilated at a constant rate. The active nematic is composed of micron-sized microtubule filaments which are highly concentrated into a quasi-2D film that resides on an oil-water interface. Kinesin motor proteins drive inter-filament sliding which results in net extensile motion of the microtubule film. Notably, we find a mesophase in which motile +1/2 defects, acquire system-spanning orientational order. Currently, we are tracking material flows generated by the active stresses in the system to measure length scales at which energy is dissipated, and to measure the relation between internally generated flows and bend in the nematic field.

  1. Petascale Molecular Dynamics Simulations of Polymers and Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Nguyen, Trung Dac; Carrillo, Jan-Michael; Brown, W. Michael

    2014-03-01

    The availability of faster and larger supercomputers and more efficient parallel algorithms now enable us to perform unprecedented simulations approaching experimental scales. Here we present two examples of our latest large-scale molecular dynamics simulations using the Titan supercomputer in the Oak Ridge Leadership Computing Facility (OLCF). In the first study, we address the rupture origin of liquid crystal thin films wetting a solid substrate. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation. Importantly, we found evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. In the second study, we used coarse-grained molecular dynamics to simulate the thermal annealing of poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM) blends in the presence of a silicon substrate found in organic solar cells. Our simulations show different phase segregated morphologies dependent on the P3HT chain length and PCBM volume fraction in the blend. Furthermore, the ternary blend of short and long P3HT chains with PCBM affects the vertical phase segregation of PCBM decreasing its concentration in the vicinity of the substrate. U.S. DOE Contract No. DE-AC05-00OR22725.

  2. Analysis of Anionic Polymer Dispersant Behavior in Dense Silicon Nitride and Carbide Suspensions Using an AFM

    NASA Astrophysics Data System (ADS)

    Nojiri, M.; Matsui, S.; Hasegawa, H.; Ono, T.; Fukuda, Y.; Tsukada, M.; Kamiya, H.

    2001-06-01

    The paper focuses on the interaction mechanism caused by anionic polymer dispersants in dense silicon nitride and silicon carbide suspensions. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic structure adsorbing of a polymer dispersant at the solid/liquid interface. The surface interactions within the suspensions were analyzed under various dispersant pH values and additive conditions. The addition of an anionic polymer dispersant decreased the viscosity of silicon nitride and silicon carbide suspension and increased the electrosteric repulsive force on the non-oxide surface in solution at pH > 6, which was the isoelectric point of the materials. Based on the above results, we estimated the adsorption mechanism of anionic polymer dispersants on each solid surface in solution under relatively high pH conditions.

  3. Viewing Angle Characteristics of Transflective Display in a Homogeneously Aligned Liquid Crystal Cell Driven by Fringe-Field

    NASA Astrophysics Data System (ADS)

    Jung, Tae Bong; Song, Je Hoon; Seo, Dae-Shik; Lee, Seung Hee

    2004-09-01

    We have studied the optimal cell configuration for a fringe-field driven transflective liquid crystal display that exhibits high image quality. The cell is composed of two half-plate compensation films, liquid crystal, and two parallel polarizers in the transmissive region. Viewing angle characteristics of the device mainly depends on the orientation of the polarizer axis. The measured contrast ratio in an optimized configuration is greater than 5 in polar angles of over 50° in all directions and in those over 80° in certain azimuthal cross-sectional planes.

  4. Optical data recording by laser pulses in liquid-crystal cells with an azo-modified surface

    SciTech Connect

    Serak, S V; Agashkov, A V; Reshetnyak, V Yu

    2001-03-31

    The effect of trans-cis photoisomerisation of azofragments of a polymer film on the molecular reorientation of a liquid crystal is studied. It is shown that, using nanosecond laser pulses, one can perform both the reversible and static data recording in liquid-crystal cells with an azo-modified surface. The rise time of the reorientation is measured by the methods of dynamic holography to be about {approx} 30 {mu}s, and the grating efficiency achieves 15 %. (laser applications and other topics in quantum electronics)

  5. Milestone in the History of Field-Effect Liquid Crystal Displays and Materials

    NASA Astrophysics Data System (ADS)

    Schadt, Martin

    2009-03-01

    The history of digital electronics would have been very different without the invention of field-effect liquid crystal displays (LCDs) in 1970 and their sophisticated development and implementation into numerous products. Transmissive and reflective LCDs have become a key interface between man and machine. After almost 40 years of interdisciplinary R+D and engineering, today's LCDs enable virtually all display applications, including high definition television. Field-effect LCDs are characterized by flat design, low weight, low driving voltage, design flexibility, compatibility with silicon-on-glass and very low power consumption, especially in reflection. Their polarization-sensitive layer concept is the basis for sandwiching and integration of optical and electronic thin-film functions. The liquid crystal technology has become a fast growing industry over the past 38 years, today surpassing 100 billion, with many spin-offs into new areas. Prerequisite for field-effect LCDs and their large diversification potential is the unique self-organization of liquid crystals. New applications beyond displays based on self-organisation, smart boundary alignment, dedicated liquid crystalline materials and the ability of LCs to respond to electromagnetic fields, including light, are being developed. Examples for new applications are LC polymer thin-film optics, or synergies between LCDs and solid state back-lighting, such as inorganic and organic light emitting diodes (LEDs/OLEDs).

  6. 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

  7. Panoramic diagnostics of shear stresses on the channel wall with a step using the liquid crystals

    NASA Astrophysics Data System (ADS)

    Zharkova, G. M.; Kovrizhina, V. N.; Petrov, A. P.; Pod'yachev, S. P.

    2016-11-01

    Measurements results on the shear stresses of surface friction by means of thin-film coatings based on cholesteric liquid crystals and specialized software for digital processing of experimental video are presented in the paper. The calibration dependencies of shear stress relative to the hue and azimuth angle as well as shear stress spatial distribution at subsonic turbulent flow ( V ∝ = 84 m/s) around a step, trapezoidal in plane (Reynolds number calculated for step height h, Re h = 2.57•104), with a base angle of 46° were derived for two geometries of experiment. The experiments demonstrated high sensitivity of liquid crystals to rearrangement of the near-wall flow structure and possibility to obtain quantitative data about mean shear stress levels.

  8. Coarsening Dynamics of Inclusions and Thermocapillary Phenomena in Smectic Liquid Crystal Bubbles

    NASA Astrophysics Data System (ADS)

    Park, Cheol; Maclennan, Joseph; Glaser, Matthew; Clark, Noel; Trittel, Torsten; Eremin, Alexey; Stannarius, Ralf; Tin, Padetha; Hall, Nancy

    The Observation and Analysis of Smectic Islands in Space (OASIS) project comprises a series of experiments that probe interfacial and hydrodynamic behavior of thin spherical-bubbles of smectic liquid crystal in microgravity. Smectic films are the thinnest known stable condensed phase structures, making them ideal for studies of two-dimensional (2D) coarsening dynamics and thermocapillary phenomena in microgravity. The OASIS flight hardware was launched on SpaceX-6 in April 2015 and experiments were carried out on the International Space Station using four different smectic A and C liquid crystal materials in separate sample chambers. We will describe the behavior of collective island dynamics on the bubbles, including temperature gradient-induced themomigration, and the diffusion and coalescence-driven coarsening dynamics of island emulsions in microgravity. This work was supported by NASA Grant No. NNX-13AQ81G, and NSF MRSEC Grants No. DMR-0820579 and DMR-1420736.

  9. Stimulated orientational and thermal scatterings and self-starting optical phase conjugation with nematic liquid crystals

    PubMed

    Khoo; Liang

    2000-11-01

    A quantitative theory and experimental results on self-starting optical phase conjugation, using stimulated orientational and thermal scattering in nematic liquid crystal films, are presented. The coupled wave-material equations for the laser-induced refractive index changes, grating formation, and coherent wave mixing effects are developed. Analytical solutions are obtained for the case of negligible pump depletion, and numerical solutions for various input and generated signals, taking losses into account, are obtained. Experimentally, we demonstrate the feasibility of realizing these stimulated scattering and phase conjugation processes in thin (200 &mgr;m) nematic liquid crystal with a milliwatt-power cw laser. Theoretical estimates for various gain constants and threshold intensities, and their dependence on various physical parameters, are found to be in good agreement with experimental observations.

  10. Determination of ordinary and extraordinary refractive indices of nematic liquid crystals by using wedge cells

    NASA Astrophysics Data System (ADS)

    Kędzierski, J.; Raszewski, Z.; Kojdecki, M. A.; Kruszelnicki-Nowinowski, E.; Perkowski, P.; Piecek, W.; Miszczyk, E.; Zieliński, J.; Morawiak, P.; Ogrodnik, K.

    2010-06-01

    A new accurate and fast interference method for determining ordinary and extraordinary refractive indices of nematic liquid crystals is presented and discussed. The method relies on microscopic measurements of distances between interference fringes appearing in polarised parallel coherent monochromatic light beam transmitted normally to the surfaces through a wedge cell filled with a nematic. Both glass plates confining the cell are coated with a partly transparent thin film of metal which is deposited by evaporation in vacuum. Owing to the multiple reflections between the surfaces and a small edge angle, the interference fringes observed near the wedge apex edge are sharp and equidistant. To apply this method one needs only small amount of an investigated liquid crystal. Basic mathematical formulae and results of an experiment are briefly discussed.

  11. Distant optical detection of small rotations and displacements by means of chiral liquid crystals

    SciTech Connect

    Shibaev, Petr V. E-mail: shibayev@fordham.edu; Troisi, Juliana; Reddy, Kathryn; Iljin, Andrey

    2014-01-15

    The paper describes novel chiral viscoelastic liquid crystalline mixtures and their application for the detection of small rotational displacements of two plates confining cholesteric liquid crystals (CLC). The mixtures are characterized by extremely high viscosities and stability of the selective reflection band (SRB) at ambient temperatures. Even a small rotation applied to the chiral liquid crystal (CLC) cell results in dramatic changes of the reflective properties of sandwiched CLC films. The angle and direction of rotation as well as the magnitude of CLC's shear deformation can be determined for a variety of experimental geometries, each of which is characterized by its own response function. The proposed model explains changes in the reflection spectra for different experimental geometries and relates them to the angle of rotation and magnitude of shear. The method was tested for a detection of small rotations from a distance of up to 50 m and allows for resolving small rotations of the order of fractions of degrees.

  12. Distant optical detection of small rotations and displacements by means of chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Shibaev, Petr V.; Iljin, Andrey; Troisi, Juliana; Reddy, Kathryn

    2014-01-01

    The paper describes novel chiral viscoelastic liquid crystalline mixtures and their application for the detection of small rotational displacements of two plates confining cholesteric liquid crystals (CLC). The mixtures are characterized by extremely high viscosities and stability of the selective reflection band (SRB) at ambient temperatures. Even a small rotation applied to the chiral liquid crystal (CLC) cell results in dramatic changes of the reflective properties of sandwiched CLC films. The angle and direction of rotation as well as the magnitude of CLC's shear deformation can be determined for a variety of experimental geometries, each of which is characterized by its own response function. The proposed model explains changes in the reflection spectra for different experimental geometries and relates them to the angle of rotation and magnitude of shear. The method was tested for a detection of small rotations from a distance of up to 50 m and allows for resolving small rotations of the order of fractions of degrees.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.