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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. Low switching voltage ZnO quantum dots doped polymer-dispersed liquid crystal film.

    PubMed

    Hsu, Chuan-Chun; Chen, Yi-Xuan; Li, Hui-Wen; Hsu, Jy-Shan

    2016-04-01

    This paper investigates the effects of ZnO nanoparticles (NPs) on the switching voltages of polymer dispersed liquid crystal (PDLC) films. The threshold and driving electric fields of PDLC film doped with 2.44 wt% ZnO NPs were 0.13 and 0.31 V/μm, respectively, with a contrast ratio of 26. The results of field emission scanning electron microscopy show that the size of the droplets in doped PDLC films increases with the doping concentration. The development of ZnO-doped PDLC films with low driving voltages greatly broadens the applicability of these devices. PMID:27137000

  3. High transmittance optical films based on quantum dot doped nanoscale polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Gandhi, Sahil Sandesh; Chien, Liang-Chy

    2016-04-01

    We propose a simple way to fabricate highly transparent nanoscale polymer dispersed liquid crystal (nano-PDLC) films between glass substrates and investigate their incident angle dependent optical transmittance properties with both collimated and Lambertian intensity distribution light sources. We also demonstrate that doping nano-PDLC films with 0.1% InP/ZnS core/shell quantum dots (QD) results in a higher optical transmittance. This work lays the foundation for such nanostructured composites to potentially serve as roll-to-roll coatable light extraction or brightness enhancement films in emissive display applications, superior to complex nanocorrugation techniques proposed in the past.

  4. 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.

  5. Monolithically integrated, flexible display of polymer-dispersed liquid crystal driven by rubber-stamped organic thin-film transistors

    SciTech Connect

    Mach, P.; Rodriguez, S. J.; Nortrup, R.; Wiltzius, P.; Rogers, J. A.

    2001-06-04

    This letter describes the monolithic integration of rubber-stamped thin-film organic transistors with polymer-dispersed liquid crystals (PDLCs) to create a multipixel, flexible display with plastic substrates. We report the electro-optic switching behavior of the PDLCs as driven by the organic transistors, and we show that our displays operate robustly under flexing and have a contrast comparable to that of newsprint. {copyright} 2001 American Institute of Physics.

  6. 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. PMID:26592303

  7. Current trends in studies on reverse-mode polymer dispersed liquid-crystal films — A review

    NASA Astrophysics Data System (ADS)

    Ahmad, Farzana; Jamil, M.; Jeon, Y. J.

    2014-07-01

    Reverse-mode polymer dispersed liquid crystals (PDLCs) comprise an important new class of materials for optical device applications. Generally reverse-mode PDLCs are transparent and opaque in the absence and presence of an external field, respectively. Display devices based on reverse-mode PDLC technology are useful for large-area displays; because their fabrication for manufacturing shutters is considered to be easier and faster, they are also employed for automotive technology and smart windows. These devices can be operated at a low voltage, which conserves energy in intelligent-device applications. This work presents a comprehensive review of past research regarding reverse-mode PDLCs and includes the advantageous features, applications, and various fabrication methods of reverse-mode PDLCs and photo-chromic reverse-mode PDLCs. In addition, some new features of this technology that have recently been reported and future investigations by a variety of research groups are presented.

  8. 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.

  9. 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.

  10. Transparent conductive ZnInSnO-Ag-ZnInSnO multilayer films for polymer dispersed liquid-crystal based smart windows

    NASA Astrophysics Data System (ADS)

    Kim, Eun Mi; Choi, In-Seok; Oh, Jeong-Pyo; Kim, Young-Baek; Lee, Jong-Ho; Choi, Yong-Sung; Cho, Jung-Dae; Kim, Yang-Bae; Heo, Gi-Seok

    2014-09-01

    Multilayer transparent films with electrical resistances lower than those in conventionally used transparent conductive electrodes were prepared at room temperature on glass substrates in an RF/DC magnetron sputtering system. The multilayer structure of the films consisted of three layers, ZnInSnO (ZITO)-Ag-ZITO. The optical and electrical properties of the multilayer structures were investigated with respect to the thickness of each ZITO-Ag-ZITO layer. Transparent conductive films with a sheet resistance of 9.4 Ω/square and an average transmittance of 92% at 550 nm were obtained at the following thicknesses of the glass substrate: ZITO (100 nm)-Ag (8 nm)-ZITO (42 nm). The surface roughness (RRMS) of the obtained ZITO-Ag-ZITO multilayer films was below 0.8 nm. Overall, the properties of the ZITO-Ag-ZITO multilayer films were comparable or superior to those of other multilayers such as InSnO (ITO)-Ag-ITO and InZnO (IZO)-Ag-IZO. The deposited ZITO single layer and ZITO-Ag-ZITO multilayer films were used in the fabrication of polymer-dispersed liquid-crystal (PDLC)-based smart windows. The ZITO-Ag-ZITO multilayer-based smart windows exhibited a lower operating voltage (16 V) and a higher cutoff rate of infrared light than ITO or ZITO-based smart windows 20-26 V. However, they showed a lower PDLC-ON transmittance than ITO-based smart windows.

  11. 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.

  12. 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.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Tsou, Yu-Shih

    2011-12-01

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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal.

    PubMed

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm(-2), which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm(-2)). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE. PMID:27196786

  20. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm‑2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm‑2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  1. Development of a Reflective Polymer-Dispersed Liquid Crystal Shear Measurement System

    NASA Astrophysics Data System (ADS)

    DeBenedictis, Gina

    Polymer-dispersed liquid crystals as a shear force measurement system offer many advantages over conventional single-point measurement systems. They are non-intrusive while offering ideal 2-dimensional mapping of shear stresses across a surface. Furthermore, the inclusion of the liquid crystals within a polymer matrix allows for a reversible sensor that is self-adherent to testing surfaces. Previous testing has examined small-scale surface mapping and clear samples through which light may pass. This paper examines the expansion of polymer-dispersed liquid crystals to larger area mapping as well as reflective measurements, with measurements taken in multiple shear force configurations, confirming the validity of the reflective data.

  2. Multiplexing studies of holographically-formed polymer-dispersed liquid crystals: Morphology, structure, and device applications

    NASA Astrophysics Data System (ADS)

    Fontecchio, Adam Kent

    Holographically-formed Polymer Dispersed Liquid Crystals (H-PDLC) are phase-segregated liquid crystal/polymer composites which enable electrically switchable holographic recordings. They are formed using a holographic exposure apparatus to create an interference pattern, which is recorded through polymerization to produce Bragg-mode gratings. Application of an electric field eliminates the Bragg grating, and the material appears optically transparent. Optical applications are being evaluated for H-PDLC implementation. Therefore, there is an increasing need to understand the fundamental physics of their formation and operation, and to optimize the electro-optical performance. This work describes H-PDLC formation, characterization, and fundamental investigations into the physics of liquid crystals confined in polymer droplet cavities. Systematic materials studies were performed, and Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) are used to examine morphological details of the polymer. The results indicate a difference in phase-separation between materials sets. Examination of droplet cavities reveals a novel rough texture that is used to explain electro-optic performance differences between materials sets. Solid-state Nuclear Magnetic Resonance (NMR) results are presented for H-PDLC samples formed with deuterated liquid crystal. The findings indicate a change in the nematic temperature range in the confined liquid crystal as compared to bulk. The onset of the nematic phase is found to occur gradually, and the phase transition is non-continuous with regard to the order parameter. Using the electro-optic properties of transmission-mode grating, the size, shape, and distribution of droplets is characterized. These attributes are found to vary with temperature when confined to the small droplets of H-PDLC films, and a coupled-wave theory is used to model these findings. New techniques for H-PDLC formation are reported, including multiplexing

  3. Heat transport in polymer-dispersed liquid crystals under electric field

    NASA Astrophysics Data System (ADS)

    Hadj Sahraoui, Abdelhak; Delenclos, Sylvain; Longuemart, Stéphane; Dadarlat, Dorin

    2011-08-01

    The concepts of effective thermal conductivity and interfacial thermal contact resistance in composite media are applied to study heat transport in polymer-dispersed liquid crystals (PDLC). In these systems, the thermal properties of liquid crystal inclusions are changed by an imposed electric field. The photopyroelectric (PPE) technique with a cell allowing the application of an electric field to the sample is used to measure the thermal parameters. A model based on effective medium approximation is used to assess the impact of interfaces on the flow of heat through the determination of the Kapitza radius. It was found that the effect of interfaces becomes dominant compared to the volume conduction of the droplet when the liquid crystal (LC) droplet radius becomes smaller than 1 micron. The comparison of the thermal behavior of LC in the droplets with that of bulk liquid crystal allowed to evaluate the effect of confinement on the LC nematic phase.

  4. 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. PMID:22909448

  5. Electro-optic system for online light transmission control of polymer-dispersed liquid crystal windows

    NASA Astrophysics Data System (ADS)

    Sanchez-Pena, Jose M.; Vazquez, Carmen; Perez, I.; Rodriguez, Inmaculada; Oton, Jose M.

    2002-07-01

    Polymer-dispersed liquid crystals (PDLCs) are formed by microdroplets of liquid crystal embedded in a flexible matrix and sandwiched between transparent electrodes. Large area units (several square meters) can be easily prepared. Opaque, transparent, and intermediate light transmission states can be achieved by applying appropriate electric fields. These features allow their use in active windows for illumination, greenhouse regulation, and privacy, both on buildings and vehicles. An electro-optic system based on a microcontrolled driver was implemented for on-line control of PDLC windows. The system may self-regulate daylight or may be used as remote control.

  6. 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.

  7. 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.

  8. 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.

  9. Control of the anchoring behavior of polymer-dispersed liquid crystals: effect of branching in the side chains of polyacrylates.

    PubMed

    Zhou, Jian; Collard, David M; Park, Jung O; Srinivasarao, Mohan

    2002-08-28

    A temperature-driven anchoring transition in a polymer/nematic fluid composite that is far from the bulk nematic-isotropic transition temperature is reported. A series of poly(methylheptyl acrylates) were studied to probe the subtle effects of the side chain structure of the polymer on control of the anchoring. A polymer-dispersed liquid crystal film made from TL205 and 1-methylheptyl acrylate shows only planar anchoring over the temperature range studied, while the films made from TL205 and each of the other methylheptyl acrylates or n-heptyl acrylate show the homeotropic-to-planar anchoring transition at temperatures between 70 and 78 degrees C. An interfacial model is proposed in which the different conformation of the side chains is suggested as the cause for the dramatic difference in the observed anchoring behavior. PMID:12188649

  10. Thermo-optical effects and fiber optic sensing device based on polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Sirleto, Luigi; Righini, Giancarlo C.; Ciaccheri, Leonardo; Rish, Mahmoud A.; Simoni, Francesco F.

    2001-05-01

    In this paper an experimental study of thermo-optical properties of polymer dispersed liquid crystals (PDLC), prepared by PIPS in bulk and in confined cylindrical geometry, is presented. The transmissivity of PDLC In bulk as a function of temperature proves the existence of temperature optical switching. We have also demonstrated the existence of optical bistability, which could be interesting in develop of logical optical devices as optical memory elements. A bistable al fiber optic sensors based on PDLC is also presented. In this device PDLC permits at the same time the optomechanical interconnection of tow fibers and the modulation of the light crossing the device. As the modulation can be controlled by external temperature, the device has been proved to be suitable for the realization of a heat flow sensor. Without any optimization of the device we have obtained an ON-OFF contrast of 8 dB and a response time comparable with other conventional device using nematic LCs. This sensor is compact, rugged and is cheap, because it does not require a complex fabrication and alignment technology. It presents the typical advantages of both the fiber optic sensor and the liquid crystal technology. We note that its main advantage is a small thermal capacity, which is comparable with electronic device as thermistors, and it represents a significant improvement for the sensor based on liquid crystals. Further theoretical studies are necessary in order to understand in depth it thermo-optical characteristics.

  11. Thermo-Optical Effects and Fiber Optic Sensing Device Based on Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Sirleto, L.; Righini, G. C.; Mahmoud, Aburish; Simoni, F.

    In this article, the thermo-optical properties of polymer dispersed liquid crystals (PDLCs) in confined geometry are experimentally investigated to demonstrate the feasibility of a fiber optic sensing device based on PDLCsE Since an unexpected behavior of PDLCs in confined geometry has been experienced, a systematic study of PDLCs' thermo-optical properties in bulk is presented also to point out principal differences. Finally, bistable all fiber optic temperature sensors, in which a PDLC permits at the same time the opto-mechanical interconnection of two fibers and the modulation of light crossing the device, has been realized and characterized, for the first time. Being the modulation controlled by external temperature, the device has been proven to be suitable for the realization of a heat flow sensor. The sensor presents the typical advantages of both fiber optic sensors and liquid crystal technology. Moreover, due to its small thermal capacity, it should exhibit little influence on thermal equilibrium and, above all, it represents a significant improvement compared to a temperature fiber optic sensor based on liquid crystals (presented in the literature).

  12. 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. PMID:26192469

  13. 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.

  14. Toward measuring concentration gradients in polymer-dispersed liquid crystals with secondary ion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Kjellander, B. K. Charlotte; van IJzendoorn, Leo J.; de Jong, Arthur M.; Broer, Dirk J.; van Gennip, Wouter J. H.; de Voigt, Martien J. A.; Niemantsverdriet, Hans J. W.

    2004-05-01

    Dynamic secondary ion mass spectrometry (SIMS) is usually applied to measure depth profiles in inorganic multi-layer systems. SIMS on organic multi-layer samples is highly complicated due to the complex fragmentation of the sample which results in fingerprint of masses representing the components in the sample. Using multivariate statistics, we succeeded to interpret the SIMS spectra and were able to identify layers with different compositions in artificially produced two-layer samples. The method is demonstrated for samples of a poly(isobornylmethacrylate) coating on a polymer dispersed liquid crystal consisting of the nematic liquid crystal (E7) and poly(isobornylmethacrylate). Quantification of the E7 concentration is complicated by evaporation in the vacuum system. Infrared spectroscopy proved that the loss of E7 from poly(isobornylmethacrylate) can be prevented by capping the sample with poly(vinyl alcohol). Cooling to cryogenic temperatures will be required to suppress further evaporation during SIMS analysis. The SIMS depth resolution of a two-layered sample was determined by discriminant function analysis to be 130 nm at a depth of one micrometer, which allows the application of SIMS for a typical optical grating.

  15. The effect of UV intensities and curing time on polymer dispersed liquid crystal (PDLC) display: A detailed analysis study

    NASA Astrophysics Data System (ADS)

    Ahmad, Farzana; Jamil, Muhammad; Lee, Jin Woo; Kim, Seo Rok; Jeon, Young Jae

    2016-08-01

    In current study polymer dispersed liquid crystal (PDLC) films whose composition based on nematic liquid crystal (LC) E7 and prepolymeric NOA65 were formed via the photo induced phase separation method, in a wide intensity range of the UV light (I = 0.33-1.8 mW/cm2) and curing duration (t = 120-600 sec). The PDLC characteristics were monitored by surface morphology, electro optical studies, as well as by phase separation process through measuring the FTIR absorption of the composite layers. Increase of curing light intensity accelerates the phase separation and drastically influences the final morphology of LC droplets inside PDLCs. Likewise by widening the curing duration the enhancement in phase separation was observed. Increase of light intensity from 0.89 mW/cm2 and duration t = 120-240 sec resulted into transition from large LC domains of irregular shape (due to aggregation of droplets) to fine mono dispersed LC droplets. This morphology caused increase in optical scattering on zero voltage and high driving voltage. However unexpectedly, this response was not directly related with the curing conditions (intensity and time). These findings extend the potential applications of thiol-ene based PDLCs. [Figure not available: see fulltext.

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

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Hoon; Yoon, Tae-Hoon

    2013-09-01

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

  17. Topological polymer dispersed liquid crystals with bulk nematic defect lines pinned to handlebody surfaces.

    PubMed

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

    2014-05-16

    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. PMID:24877965

  18. Optically switchable, polarization-independent holographic polymer dispersed liquid crystal (H-PDLC) gratings

    NASA Astrophysics Data System (ADS)

    Hsiao, V. K. S.; Chang, W.-T.

    2010-09-01

    An optically switchable, polarization-independent holographic polymer dispersed liquid crystal (H-PDLC) transmission grating is demonstrated by adding azobenzene-LC and chiral molecules into the H-PDLC formulation. The optical switchable mechanism is from the trans-cis photoisomerization of the doped azobenzene-LC, which modulates the refractive index of the LC rich area. The dependence of the diffraction efficiency of the H-DPLC grating without chiral molecules on light polarization suggests that the orientation of LC directors within the droplet is ellipsoidal and uniaxial. However, the addition of chiral molecules into the H-PDLC formulation helps the formation of isotropic and non-uniaxial LC directors within the droplets. The polarization properties of the grating are investigated and analyzed by the coupled and modified coupled wave theory with a model of sinusoidal dielectric modulation. The results show that the addition of chiral molecules changes the LC phase from nematic to chiral-nematic, where the grating efficiency, which is modulated by the photoinduced phase transition, is independent of the polarization of incident light. Our findings may help improve optical systems that utilize non-polarized light.

  19. Varied-line-spacing switchable holographic grating using polymer-dispersed liquid crystal.

    PubMed

    Wang, Kangni; Zheng, Jihong; Lu, Feiyue; Gao, Hui; Palanisamy, Aswin; Zhuang, Songlin

    2016-06-20

    A varied-line-spacing switchable holographic grating is demonstrated through a changeable interference pattern recorded in polymer-dispersed liquid crystal. The pattern is generated by the interference between one plane wave and another cylindrical wave. The line spacing and the period of grating can be controlled by varying the distance between the cylindrical lens and the grating sample and by changing the exposure angle between the two beams. Experimental period measurements and calculations show good agreement with the theoretical results. High diffraction efficiency of more than 80% for the middle period of the grating has been achieved under appropriate exposure time of 120 s and intensity of 19.1  mW/cm2. In addition, the diffraction can be switched on and off by virtue of the external driving voltage of approximately 120 V. The grating also possesses a fast response with a rise time of 300 μs and a fall time of 750 μs. This grating, which can change the period in the grating structure to allow switchable diffraction of transmitted light, shows great potential application for diffractive optics. PMID:27409124

  20. 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.

  1. 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.

  2. 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.

  3. 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. PMID:23988927

  4. Platinum-scatterer-based random lasers from dye-doped polymer-dispersed liquid crystals in capillary tubes.

    PubMed

    Wang, Jianlong; Zhang, Yating; Cao, Mingxuan; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Zhang, Heng; Yao, Jianquan

    2016-07-20

    The resonance characteristics of platinum-scatter-based random lasers from dye-doped polymer-dispersed liquid crystals (DDPDLCs) in capillary tubes were researched for the first time, to the best of our knowledge. After adding platinum nanoparticles (Pt NPs) into the liquid crystal mixtures, the emission spectra of DDPDLCs revealed a lower lasing threshold in comparison with those of DDPDLCs without Pt NPs due to light scattering of liquid crystal droplets and the local field enhancement around Pt NPs. Furthermore, the full width at half-maximum (FWHM) and the lasing threshold were determined by the doping density of the Pt NPs. The threshold was decreased by about half from 17.5  μJ/pulse to 8.7  μJ/pulse on the condition that around 1.0 wt. % was the optimum concentration of Pt NPs doped into the DDPDLCs. The FWHM of the peaks sharply decreased to 0.1 nm. Our work provides an extremely simple method to enhance random lasers from DDPDLCs doped with Pt NPs, and it has potential applications in random fiber lasers or laser displays. PMID:27463926

  5. Study of anchoring behavior of nematic fluids at the interface of polymer-dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Zhou, Jian

    A liquid crystal (LC) at its boundary surface adopts a preferential alignment, which is referred to as anchoring. The direction of this alignment (i.e., anchoring direction) may be perpendicular, parallel or tilted with respect to the surface. Transitions from one anchoring condition to another may occur when the parameters (e.g., temperature) charactering the surface change, as referred to as anchoring transitions. In the LC-polymer composite systems under our study, the anchoring and temperature-driven anchoring transitions of nematic fluids is very sensitive to the structure of the side chain of poly (alkyl acrylate) matrixes that encapsulate the LC. We have shown that the anchoring transition temperature of these systems can be tuned far below the nematic-to-isotropic transition temperature, by varying either the length, branching structure of the side chains of homopolymers, or the composition of copolymer of two dissimilar monomers. Both sharp and broad anchoring transitions with respect to the temperature range over which a transition occurs were observed. It is postulated that microscopic interactions between the polymer side chains and LC molecules play an important role in determining the anchoring. In particular, the conformation of the polymer side chain is proposed to have important control over the anchoring. Anchoring strength and tilt angle as a function of temperature during the anchoring transitions were also experimentally investigated, which contribute to understanding of the microscopic mechanism for such transitions. Based on the LC-polymer composites with controlled anchoring, a LC display with reverse switching mode and a novel electrically switchable diffraction grating have been demonstrated. The advantages of these devices are ease of manufacturing, low operation voltage, and mechanical stability offered by polymer matrix. Moreover, a detailed study of the director configuration of wall defects found in these composite films was carried

  6. Patterned cholesteric liquid crystal polymer film.

    PubMed

    Hsu, Wei-Liang; Ma, Ji; Myhre, Graham; Balakrishnan, Kaushik; Pau, Stanley

    2013-02-01

    Herein, the ability to create arbitrarily patterned circular polarized optical devices is demonstrated by using cholesteric liquid crystal polymer. Photoalignment with polarized ultraviolet light is utilized to create aligned cholesteric liquid crystal films. Two different methods, thermal annealing and solvent rinse, are utilized for patterning cholesteric liquid crystal films over large areas. The patterned cholesteric liquid crystal films are measured using a Mueller matrix imaging polarimeter, and the polarization properties, including depolarization index, circular diattenuation (CD), and circular retardance are derived. Patterned nonlinearly polarized optical devices can be fabricated with feature sizes as small as 20 μm with a CD of 0.812±0.015. Circular polarizing filters based on polymer cholesteric liquid crystal films have applications in three-dimensional displays, medical imaging, polarimetry, and interferometry. PMID:23456060

  7. Near-infrared sensitive photorefractive device using polymer dispersed liquid crystal and BSO:Ru hybrid structure.

    PubMed

    Liu, Ren Chung; Marinova, Vera; Lin, Shiuan Huei; Chen, Ming-Syuan; Lin, Yi-Hsin; Hsu, Ken Yuh

    2014-06-01

    A near-infrared sensitive hybrid device, based on a Ru-doped BSO photorefractive substrate and polymer dispersed liquid crystal (PDLC) layer, is reported. It is found that the photoexcited charge carriers generated in the BSO:Ru substrate create an optically induced space charge field, sufficient to penetrate into the PDLC layer and to re-orient the LC molecules inside the droplets. Beam-coupling measurements at the Bragg regime are performed showing prospective amplification values and high spatial resolution. The proposed structure does not require indium tin oxide (ITO) contacts and alignment layers. Such a device allows all the processes to be controlled by light, thus opening further potential for real-time image processing at the near-infrared range. PMID:24876043

  8. Orientational photorefractive properties in polymer-dispersed liquid crystals with different polymer matrixes

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

    1998-10-01

    We report orientational photorefractive effects observed in photoconductive liquid crystals (LCs) contained with three kinds of polymer, i.e., poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA) and a side-chain liquid crystalline polymer (SLCP1). The morphology of the photorefractive composites depended on the kind of polymer strongly. In both PMMA and PVA cases, LC and polymer were phase-separated and the composite showed memory effects. In SLCP1 case, the phase-separation in the composite dose not occur and the high resolution could be achieved. In this case, the photorefractive Bragg gratings were generated and a high two-beam coupling gain coefficient with a low applied field of 4 V/micrometers was observed.

  9. 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.

  10. Thermal behavior of nano cellulose doped polymer dispersed liquid crystal (PDLC)

    NASA Astrophysics Data System (ADS)

    Kashyap, Swati; Saxena, S. K.; Gupta, S. J.; Mahajan, Jyoti

    2016-05-01

    Nano cellulose or cellulose nanofibers (CNF) material is composed of Nano sized cellulose fibrils with a high aspect ratio and typical lateral dimensions are 20-50 nm. Its pseudo-plastic characteristics exhibit the property of certain gels or fluids (viscous) and over a period of time, becomes, Thixotropic. The ability of CNFs to go into a PDLC ultrasonically with a helical arrangement results in dried CNF films. The films thus acquire attractive thermal properties, creating possibilities for their use in various applications. In this presentation, we discuss the thermal behavior of Nano cellulose doped in PDLC that governs the formation of the desired helical structure. By comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes particles, we outline in the present paper the variation in the number of mesogen phases in varying compositions of Nano Cellulose doped PDLCs.

  11. Three-Dimensional Microstructure of a Polymer-Dispersed Liquid Crystal Observed by Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Pierron, Jean; Tournier-Lasserve, Valérie; Sopena, Pierre; Boudet, Alain; Sixou, Pierre; Mitov, Michel

    1995-11-01

    A film consisting of an amorphous photo-crosslinkable polymer matrix and a dispersion of microinclusions of a cholesteric polymer was investigated by transmission electron microscopy (TEM). The polymerization procedure of the blend provides a composite with many small nodules of spherical or ellipsoidal shapes, with sizes between 0.4 and 6 μm. The cholesteric stratification is well evidenced in transmission electron microscopy by dark lines due to diffraction contrast. The 3D organization was reconstructed by the observation of successive ultramicrotomed sections. Six types of nodules were distinguished according to the number of defects (foci or disclination lines), among which only three had already been observed and theoretically calculated. The confined geometry inherent in the size of the nodules, close to the cholesteric pitch, is responsible of these unexpected structures. In these conditions, the surface forces are in tight competition with the cholesteric elastic forces.

  12. Effect of SiO2 nanoparticle doping on electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Eunju; Liu, Yang; Hong, Sung-Jei; Han, Jeong In

    2015-03-01

    In this paper, SiO2 nanoparticle doped polymer dispersed liquid crystal (PDLC) lenses were made from a mixture of prepolymer, E7 liquid crystal and SiO2 nanoparticles by the polymerization induced phase separation (PIPS) process for smart electronic glasses with auto-shading and auto-focusing functions. Electro-optical properties of doped and undoped samples including transmittance, driving voltage, contrast ratio and slope of the linear region of the transmittance-voltage were measured, compared and analyzed. Driving voltage of SiO2 nanoparticle doped PDLC lenses moderately improved. But the slope of linear region, response time and contrast ratio deteriorated, especially the latter two. It can be assumed that these doping effects were due to the mechanistic change from liquid-gel separation to liquid-liquid separation by the fast heterogeneous nucleation rate caused by the increased nucleation at the surface of SiO2 nanoparticles. The marked deteriorations of falling response time and contrast ratio were due to well defined liquid crystal molecules in LC droplets, which induced slow and imperfect random rearrangement of LC molecules at the off state.

  13. Water-in-water emulsions stabilized by non-amphiphilic interactions: polymer-dispersed lyotropic liquid crystals.

    PubMed

    Simon, Karen A; Sejwal, Preeti; Gerecht, Ryan B; Luk, Yan-Yeung

    2007-01-30

    Emulsion systems involving surfactants are mainly driven by the separation of the hydrophobic interactions of the aliphatic chains from the hydrophilic interactions of amphiphilic molecules in water. In this study, we report an emulsion system that does not include amphiphilic molecules but molecules with functional groups that are completely solvated in water. These functional groups give rise to molecular interactions including hydrogen bonding, pi stacking, and salt bridging and are segregated into a dispersion of droplets forming a water-in-water emulsion. This water-in-water emulsion consists of dispersing droplets of a water-solvated biocompatible liquid crystal--disodium cromoglycate (DSCG)--in a continuous aqueous solution containing specific classes of water-soluble polymers. Whereas aqueous solutions of polyols support the formation of emulsions of spherical droplets consisting of lyotropic liquid crystal DSCG with long-term stability (for at least 30 days), aqueous solutions of polyamides afford droplets of DSCG in the shape of prolate ellipsoids that are stable for only 2 days. The DSCG liquid crystal in spherical droplets assumes a radial configuration in which the optical axis of the liquid crystal aligns perpendicular to the surface of the droplets but assumes a tangential configuration in prolate ellipsoids in which the optical axis of the liquid crystal aligns parallel to the surface of the droplet. Other classes of water-soluble polymers including polyethers, polycations, and polyanions do not afford a stable emulsion of DSCG droplets. Both the occurrence and the stability of this unique emulsion system can be rationalized on the basis of the functional groups of the polymer. The different configurations of the liquid crystal (DSCG) droplets were also found to correlate with the strength of the hydrogen bonding that can be formed by the functional groups on the polymer. PMID:17241072

  14. Spatial and electrical switching of defect modes in a photonic bandgap device with a polymer-dispersed liquid crystal defect layer.

    PubMed

    Wu, Po-Chang; Yeh, En-Rong; Zyryanov, Victor Ya; Lee, Wei

    2014-08-25

    This paper investigates the spectral properties of a one-dimensional photonic crystal (PC) containing an inhomogeneous polymer- dispersed liquid crystal (PDLC) as a defect layer. Experimental results indicate that the voltage-induced reorientation of LC molecules between the light-scattering and transparent states in the PDLC enables the electrical tuning of the transmittance of defect-mode peaks in the spectrum of the PC/PDLC cell. Specifically, owing to the unique configuration of the spatial distribution of LC droplet sizes in the defect layer, a concept concerning the spatial switching in the wavelength of defect modes is proposed. As a result, the PC/PDLC hybrid cell is suggested as a potential element for realizing an electrically tunable and spatially switchable photonic bandgap device, which is polarizer-free and requires no alignment layers in the fabrication process. PMID:25321237

  15. Application of liquid crystal polymer films for photolithographic fabrication of 3D structures

    NASA Astrophysics Data System (ADS)

    Fox, Anna E.; Fontecchio, Adam K.

    2008-02-01

    In this paper, we demonstrate a silicon etching application of a holographically formed polymer dispersed liquid crystal (H-PDLC) photomask. H-PDLC is a periodically nanostructured material consisting of stratified layers of polymer and liquid crystal. Due to the natural random alignment of the liquid crystal axes with respect to the polymer layers, an index of refraction mismatch exists and a reflection occurs. Application of bias across the film aligns the liquid crystals and eliminates the index mismatch causing the film to become transparent. H-PDLC films have been shown to sufficiently attenuate the UV exposure dose in the photolithographic process when in the unbiased state, and can be electrically controlled to modulate the amount of UV transmission when electric field is applied. We show etch depth profiles of patterns masked on a silicon substrate using the H-PDLC photomask device compared with etch profiles of similar structures patterned with more conventional ink jet printed photomasks and chrome on quartz glass photomasks. We investigate reactive ion etching technique and potassium hydroxide wet etch technique.

  16. Tunable liquid crystal lasers

    NASA Astrophysics Data System (ADS)

    Woltman, Scott J.

    Liquid crystal lasers are dye-doped distributed feedback lasing systems. Fabricated by coupling the periodic structure of a liquid crystal medium with a fluorescent dye, the emission from these systems is tunable by controlling the liquid crystal system---be it through electric or thermal field effects, photochemical reactions, mechanical deformations, etc. The laser action arises from an extended interaction time between the radiation field, the laser emission, and the matter field, the periodic liquid crystal medium, at the edge of the photonic band gap. In this thesis, several tunable liquid crystal laser systems are investigated: cholesteric liquid crystals, holographic-polymer dispersed liquid crystals and liquid crystal polarization gratings. The primary focus has been to fabricate systems that are tunable through electrical means, as applications requiring mechanical or thermal changes are often difficult to control. Cholesteric liquid crystal lasers are helical Bragg reflectors, with a band gap for circularly polarized light of equivalent handedness to their helix. These materials were doped with a laser dye and laser emission was observed. The use of an in-plane electric field tends to unwind the helical pitch of the film and in doing so tunable emission was demonstrated for ˜15 nm. Holographic-polymer dispersed liquid crystals (H-PDLCs) are grating structures consisting of alternating layers of polymer and liquid crystal, with different indices of refraction. The application of an electric field index matches these layers and switches off the grating. Thus, laser emission can be switched on and off through the use of an electric field. Spatially tunable H-PDLC lasers were fabricated by creating chirped gratings, formed by divergent beams. The emission was shown to tune ˜5 nm as the pump beam was translated across a 1 inch film. Liquid crystal polarization gratings use photo-patterned alignment layers, through a polarization holography exposure, to

  17. Nano-polymer-dispersed liquid crystal as phase modulator for a tunable vertical-cavity surface-emitting laser at 1.55 mum.

    PubMed

    Levallois, C; Caillaud, B; de Bougrenet de la Tocnaye, J-L; Dupont, L; Lecorre, A; Folliot, H; Dehaese, O; Loualiche, S

    2006-11-20

    We demonstrate what we believe is the first nonmechanical tunable vertical-cavity surface-emitting laser operating in the C band. This was achieved as a result of the combination of an InGaAs quantum well structure with a 6lambda thickness tunable index nano-polymer-dispersed liquid-crystal material. Experimental results exhibited a potential tunable range close to 10 nm, in the preliminary version, and excellent single mode locking due to the side-mode suppression ratio (more than 20 dB) over the whole spectral range. Another decisive advantage, compared to mechanical solutions, was the tuning response time of a few tens of microseconds (>30 micros) to scan the full spectral range (10 nm), making this device appropriate for some access network functions, as well as being robust and low cost. The voltage values are the main limitation to wavelength range extension. We present a first version of the device optically pumped. The next version will be electrically pumped as required for the access network applications targeted here. PMID:17086259

  18. 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.

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

    NASA Technical Reports Server (NTRS)

    Hippensteele, Steven A.

    1997-01-01

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

  20. Liquid crystal film development for plasma mirrors and waveplates

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  1. Droplet manipulation on a liquid crystal and polymer composite film

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Tsou, Yu-Shih; Chu, Ting-Yu; Chen, Jun-Lin

    2010-08-01

    A droplet manipulation on a switchable surface using a liquid crystal and polymer composite film (LCPCF) based on phase separation is developed recently. The wettability of LCPCF is electrically tunable because of the orientation of liquid crystal directors anchored among the polymer grains. A droplet on LCPCF can be manipulated owning to the wettability gradient induced by spatially orientation of LC directors. We discuss the droplet manipulation on LCPCF and demonstrate several applications of LCPCF, such as polarizer-free displays, and human semen sensing.

  2. Ferroelectric thin films with liquid crystal for gradient index applications.

    PubMed

    Willekens, Oliver; George, John Puthenparampil; Neyts, Kristiaan; Beeckman, Jeroen

    2016-04-18

    We report on the first ever combination of a thin film of lead zirconate titanate (PZT) with a liquid crystal (LC) layer. Many liquid crystal applications use a transparent conductive oxide to switch the liquid crystal. Our proposed processing does not, instead relying on the extremely high dielectric constant of the ferroelectric layer to extend the electric field from widely spaced electrodes over the liquid crystal. It eliminates almost entirely the fringe field problems that arise in nearly all the liquid crystal devices that use multiple addressing electrodes. We show, both via rigorous simulations as well as experiments, that the addition of a PZT layer over the addressing electrodes leads to a markedly improved LC switching performance at distances of up to 30 μm from the addressing electrodes with the current PZT-layer thickness of 0.84 μm. This improvement in switching is used to tune the focal length of the microlens with electrodes spaced at 30 μm. PMID:27137248

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  4. Anchoring transition in confined discotic columnar liquid crystal films

    NASA Astrophysics Data System (ADS)

    Brunet, Thomas; Thiebaut, Olivier; Charlet, Émilie; Bock, Harald; Kelber, Julien; Grelet, Éric

    2011-01-01

    We report the achievement of ultrathin films (down to 25 nm thick) of thermotropic columnar liquid crystals in homeotropic alignment (columns normal to the interface) confined between a glass slide and a thin metallic electrode (about 150 nm thick). The face-on orientation of the discotic compound is obtained by anchoring transition of a columnar liquid crystalline phase from a degenerate planar orientation to the homeotropic alignment without any phase transition to the isotropic liquid phase. The kinetic dependence on temperature of such anchoring transition is investigated revealing various diffusive growth regimes of the homeotropic domains. Finally, confining effects are also considered by varying the thickness of the columnar liquid crystal film to reach the typical value required in organic solar cells thus demonstrating the reliability of such alignment process in a photovoltaic context.

  5. Spinodal dewetting of a nematic liquid crystal film

    PubMed

    Braun; Yokoyama

    2000-08-01

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

  6. Computer simulations of adsorbed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Wall, Greg D.; Cleaver, Douglas J.

    2003-01-01

    The structures adopted by adsorbed thin films of Gay-Berne particles in the presence of a coexisting vapour phase are investigated by molecular dynamics simulation. The films are adsorbed at a flat substrate which favours planar anchoring, whereas the nematic-vapour interface favours normal alignment. On cooling, a system with a high molecule-substrate interaction strength exhibits substrate-induced planar orientational ordering and considerable stratification is observed in the density profiles. In contrast, a system with weak molecule-substrate coupling adopts a director orientation orthogonal to the substrate plane, owing to the increased influence of the nematic-vapour interface. There are significant differences between the structures adopted at the two interfaces, in contrast with the predictions of density functional treatments of such systems.

  7. Molecular theory of liquid crystal thin films

    NASA Astrophysics Data System (ADS)

    Meng, Shihong

    A molecular theory has been developed to describe the isotropic-nematic transitoon of model nematogens in bulk and in thin films. The surfaces of thin films can be hard surfaces or coated with surfactant monolayers. The theory only includes hard body interactions between all molecule species: solvent, nematogens and surfactants. We have studied the influence of the separation between confining walls, concentration of nematogens, as well as the surface anchoring and areal density of surfactant at the interface upon the phases of nematogens. We have explained the possible existence of planar degenerate phase through entropic pictures and have confirmed close to the bulk isotropic-nematic transition point, the order of the phases of nematogens from isotropic to nematic then back to isotropic when varying the areal density of surfactant monolayers at interfaces. From the results obtained, we believe that we have captured the main competing interactions between surfactants and nematogens and our molecular level theory is capable of describing these two interactions of different natures. Our results can provide a guideline for molecular design of biosensors. We have modeled the molecular systems with as much simplification as possible while retaining the main features. The thesis is arranged into introduction, results on bulk, thin films confined between hard walls and between surfactant monolayers.

  8. 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.

  9. Liquid crystals for organic thin-film transistors

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V-1 s-1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

  10. 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. PMID:24470318

  11. Two-Dimensional Microrheology of Freely Suspended Liquid Crystal Films

    NASA Astrophysics Data System (ADS)

    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.

    2011-12-01

    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.

  12. Hydrodynamics of Inclusions in Freely Suspended Liquid Crystal Films

    NASA Astrophysics Data System (ADS)

    Qi, Zhiyuan

    Hydrodynamic interaction of pairs of circular inclusions in two-dimensional (2D), fluid smectic membranes suspended in air has been studied systematically. By analyzing their Brownian motion, it is found that the radial mutual mobilities of identical inclusions are independent of their size but that the angular coupling becomes strongly size-dependent when their radius exceeds a characteristic hydrodynamic length. These observations are described well for arbitrary inclusion separations by a model that generalizes the Levine/MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. Beyond that, 2D flow fields generated by a rigid, oscillating post inserted in the film have been measured by analyzing the motion of tracer particles and provide a detailed understanding of the hydrodynamic behavior in the film/gas system. The Brownian diffusion of micron-scale inclusions in freely suspended smectic A liquid crystal films a few nanometers thick and several millimeters in diameter depends strongly on the air surrounding the film. Near atmospheric pressure, the three-dimensionally coupled film/gas system is well described by Hughes/Pailthorpe/White hydrodynamic theory but at lower pressure, the diffusion coefficient increases substantially, tending in high vacuum toward the two-dimensional limit where it is determined by film size. In the absence of air, the films are found to be a nearly ideal physical realization of a two-dimensional, incompressible Newtonian fluid.

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

    PubMed

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

    2016-06-01

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

  14. 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. PMID:26511159

  15. Strongly Dichroic Organic Films via Controlled Assembly of Modular Aromatic Charge-Transfer Liquid Crystals.

    PubMed

    Bé, Ariana Gray; Tran, Cheryl; Sechrist, Riley; Reczek, Joseph J

    2015-10-01

    The formation of highly anisotropic organic thin films based on the designed self-assembly of mixed-stack liquid crystals is reported. A series of alkoxyanthracene donors is combined in a modular fashion with a naphthalenediimide acceptor to generate new charge-transfer columnar liquid crystals. Materials characterization and molecular modeling provides insight into structure-function relationships in these organic materials that lead to the striking bulk dichroic properties of certain molecular assemblies. PMID:26375256

  16. 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

  17. 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.

  18. Liquid crystal surface alignments by using ion beam sputtered magnetic thin films

    SciTech Connect

    Wu, H.-Y.; Pan, R.-P.

    2007-08-13

    A method for liquid crystal surface alignment by using a one-step, ion beam bombardment of the glass substrates is demonstrated. Precoating by polyimide is not necessary. The authors show that the homeotropic alignment is achieved due to orientation of the diamagnetic nematogenic molecules by the magnetic field from the {gamma}-Fe{sub 2}O{sub 3} ferrimagnetic thin films created on the substrates by ion beam bombardment. The film exhibits a high Curie temperature well above 300 K and a compensation temperature which is the typical feature of ferrimagnetism. This is a simple, noncontact, and reliable alignment method for liquid crystal devices.

  19. Rewritable Optical Storage with a Spiropyran Doped Liquid Crystal Polymer Film.

    PubMed

    Petriashvili, Gia; De Santo, Maria Penelope; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Gary, Ramla; Barberi, Riccardo

    2016-03-01

    Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real-time image recording feature. PMID:26864876

  20. Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Mohammadimasoudi, Mohammad; Neyts, Kristiaan; Beeckman, Jeroen

    2015-03-01

    We present a method to fabricate a thin film color filter based on a mixture of photo-polymerizable liquid crystal and chiral dopant. A chiral nematic liquid crystal layer reflects light for a certain wavelength interval Δλ (= Δn.P) with the period and Δn the birefringence of the liquid crystal. The reflection band is determined by the chiral dopant concentration. The bandwidth is limited to 80nm and the reflectance is at most 50% for unpolarized incident light. The thin color filter is interesting for innovative applications like polarizer-free reflective displays, polarization-independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. The reflected light has strong color saturation without absorption because of the sharp band edges. A thin film polarizer is developed by using a mixture of photo-polymerizable liquid crystal and color-neutral dye. The fabricated thin film absorbs light that is polarized parallel to the c axis of the LC. The obtained polarization ratio is 80% for a film of only 12 μm. The thin film polarizer and the color filter feature excellent film characteristics without domains and can be detached from the substrate which is useful for e.g. flexible substrates.

  1. Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

    PubMed Central

    Morales, Piero; Lagerwall, Jan; Vacca, Paolo; Laschat, Sabine

    2010-01-01

    Summary Thin films of the discotic liquid crystal hexapentyloxytriphenylene (HAT5), prepared from solution via casting or spin-coating, were investigated by atomic force microscopy and polarizing optical microscopy, revealing large-scale ordered structures substantially different from those typically observed in standard samples of the same material. Thin and very long fibrils of planar-aligned liquid crystal were found, possibly formed as a result of an intermediate lyotropic nematic state arising during the solvent evaporation process. Moreover, in sufficiently thin films the crystallization seems to be suppressed, extending the uniform order of the liquid crystal phase down to room temperature. This should be compared to the bulk situation, where the same material crystallizes into a polymorphic structure at 68 °C. PMID:20625522

  2. 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. PMID:26457810

  3. 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…

  4. Interaction of a bi-molecular liquid crystal film with functionalized nanoparticles

    NASA Astrophysics Data System (ADS)

    Taylor, Jefferson W.; Martinez-Miranda, L. J.

    2010-03-01

    We investigate the properties of a bi-molecular film of liquid crystal close to a magnetic nanoparticle (CoFe) with a functionalization compound (MHDA) with the atomic force microscope (AFM). We seek to investigate if the functionalization compound has an effect on the ordering of the liquid crystal in the vicinity of the nanoparticle. Studies in bulk liquid crystals have shown that the functionalization compound influences how the liquid crystal reorganize [1]. The results of this investigation will be compared to the results of work done on phospholipids in close contact with uncovered silica nanoparticles [2]. Preliminary studies of the liquid crystal in contact with the nanoparticles show that it behaves similarly to the way the phospholipids behave. More functionalization compounds are studied in order to establish whether it behaves differently depending on the functionalization compound. [4pt] [1] L. J. Mart'inez-Miranda, L. K. Kurihara, J. Appl. Phys 105, 084305 (2009). [0pt] [2] Yuri Roiter, Maryna Ornatska, Aravind R. Rammohan, Jitendra Balakrishnan, David R. Heine, and Sergiy Minko, Langmuir, 25, 6287-6299 (2009).

  5. Liquid Crystal Alignment on Solution Derived Zinc Oxide Films via Ion Beam Irradiation.

    PubMed

    Park, Hong-Gyu; Han, Jae-Jun; Seo, Dae-Shik

    2016-03-01

    A 75-nm-thick ZnO film was deposited by a sol-gel method on indium-tin oxide (ITO)-coated glass. This film served as a liquid crystal (LC) alignment layer. We report the fabrication and characteristics of this film after ion-beam (IB) irradiation. Uniform LC alignment was achieved at an IB incident energy above 2400 eV. The IB-treated ZnO surface was analyzed by X-ray photoelectron spectroscopy (XPS), monitoring the intensity of the Zn 2p and O 1s peaks as a function of IB-irradiation energy density. The electro-optical (EO) characteristics of a twisted nematic-liquid crystal display (TN-LCD) were comparable to rubbed polyimide. PMID:27455726

  6. Layer Thinning in Freely-Suspended Thin Liquid Films of a Symmetric Liquid Crystal Dimer

    NASA Astrophysics Data System (ADS)

    Pardaev, Shokir; Parsouzi, Zeinab; Gleeson, James; Jakli, Antal; Sprunt, Samuel

    We report optical reflectivity and dynamic light scattering (DLS) studies on freely suspended smectic films of a symmetric liquid crystal dimer, which exhibits the phase sequence isotropic--nematic--twist-bend nematic--smectic in cooling. In sufficiently thin films the reflectivity R is expected to scale as the square of the number of smectic layers (N2) while the frequency f of underdamped layer fluctuations scales as N - 1 / 2. On heating thin films drawn in the smectic phase, we observe a sequence of layer thinning transitions, with R and f following the expected scaling relations, provided the stepwise melting involves double rather than single layers. We will describe a model to explain the unusual layer thinning process. We thank M. G. Tamba and G. Mehl for providing the liquid crystal compound: NSF grant DMR-1307674.

  7. Liquid crystal catalytic surfactant films for decomposing and sensing pollutants by electrolysis

    SciTech Connect

    Rusling, J.F.; Howe, D.J.; Nassar, A.E.

    1993-12-31

    Living organisms utilize protein biocatalysts incorporated in lipid bilayer membranes. Some synthetic lipid-like surfactant molecules can be self assembled into bilayer structures resembling biomembranes. Films composed of stacks of bilayers were prepared by casting solutions of insoluble surfactants onto solid electrodes. Catalysts were incorporated either after or before casting. In their liquid crystal forms, films containing metal phthalocyanine tetrasulfonates or the redox protein myoglobin were excellent, stable electrochemical catalysts for dehalogenation of pollutants such as trichloracetic acid and ethylene dibromide. Electrons are transported to reactions sites via the incorporated catalysts, and the films also preconcentrate the organohalides to enhance reaction rates. Characterization and applications of these films will be discussed.

  8. Liquid crystal polymer networks: preparation, properties, and applications of films with patterned molecular alignment.

    PubMed

    Liu, Danqing; Broer, Dirk J

    2014-11-18

    Monolithically ordered liquid crystal polymer networks are formed by the photoinitiated polymerization of multifunctional liquid crystal monomers. This paper describes the relevant principles and methods, the basic structure-property relationships in terms of mesogenic properties of the monomers, and the mechanical and optical properties of the polymers. Strategies are discussed to control the molecular orientation by various means and in all three dimensions. The versatility of the process is demonstrated by two examples of films with a patterned molecular order. It is shown that patterned retarders can be made by a two-step polymerization process which is successfully employed in a transflective display principle. A transflective display is a liquid crystal display that operates in both a reflective mode using ambient light and a transmissive mode with light coming from a backlight system. Furthermore, a method is discussed to create a patterned film in a single polymerization process. This film has alternating planar chiral nematic areas next to perpendicularly oriented (so-called homeotropic) areas. When applied as a coating to a substrate, the film changes its surface texture. During exposure to UV light, it switches from a flat to a corrugated state. PMID:24707811

  9. Mechanisms of liquid crystal and biopolymer alignment on highly-oriented polymer thin films

    NASA Astrophysics Data System (ADS)

    Dennis, John Raymond

    1998-12-01

    Molecular order can strongly enhance material properties, or produce materials which perform advanced functions. Many materials, from small crystals to large macromolecules, may be aligned on highly-oriented poly(tetrafluoroethylene) (PTFE) or high-density polyethylene (HDPE) thin films, prepared by a simple shear deposition procedure. Here, processes by which these films produce order are examined, first in a well- characterized liquid crystal, then in two more complex polymer liquid crystals, and finally in an adsorbed motor protein system. Optical second harmonic generation (SHG) was used to study surface molecular order in the liquid crystal 4'-n-octyl-4-cyano-biphenyl (8CB) on PTFE and HDPE films. In nematic 8CB cells with bulk alignment along the polymer orientation axis, the surface monolayers of 8CB were also aligned, and showed C2ν symmetry. In the isotropic phase, the surface monolayer alignment was lost. Monolayers of 8CB evaporated onto either polymer showed little or no alignment. The bulk 8CB alignment appears to be primarily caused by surface ridges through an elastic, bulk- mediated mechanism, unlike the epitaxy-like alignment found on some cloth-rubbed polymer surfaces. For the polymer liquid crystal poly-γ-benzyl- glutamate (PBG), uniform homogeneous surface alignment was observed on PTFE films; this is the first report of PBG surface alignment. However, liquid crystalline samples of microtubules were not aligned. PTFE films show promise for aligning some other polymer liquid crystals via elastic interactions. The motor protein kinesin, adsorbed to PTFE films, transported fluorescently labeled microtubules predominantly in straight lines along the films' orientation axis, not in random directions as observed on glass surfaces. As the kinesin surface density was increased, the degree of alignment peaked and then declined. The results indicate that directed motion occurs because active kinesin preferentially adsorbs to surface sites along linear

  10. An electrically switchable surface free energy on a liquid crystal and polymer composite film

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chu, Ting-Yu; Tsou, Yu-Shih; Chang, Kai-Han; Chiu, Ya-Ping

    2012-12-01

    An electrically switchable surface free energy on a liquid crystal and polymer composite film (LCPCF) resulting from the orientations of liquid crystal molecules is investigated. By modification of Cassie's model and the measurement based on the Chibowski's film pressure model (E. Chibowski, Adv. Colloid Interface Sci. 103, 149 (2003)), the surface free energy of LCPCF is electrically switchable from 36×10-3J/ m2 to 51×10-3J/ m2 while the average tilt angle of LC molecules changes from 0° to 32° with the applied pulsed voltage. The switchable surface free energy of LCPCF can help us to design biosensors and photonics devices, such as electro-optical switches, blood sensors, and sperm testers.

  11. 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)

  12. Characterisation of protein adsorption on different liquid crystal phthalocyaninethin films.

    PubMed

    Paul, S; Paul, D; Basova, T; Ray, A K

    2010-03-01

    Bovine serum albumin (BSA) protein adsorption on thin spun films of different metal octakishexylthiophthalocyanine [(C(6)S)(8)PcM, M=Cu, Ni] derivatives is investigated by using three independent spectroscopic measurements namely Raman spectroscopy, ellipsometry and surface plasmon resonance imaging. Thermally induced molecular self-reorganisations in the phthalocyanine films are found to have produced the changes in the surface energy which, in turn, control protein adsorption. The amount of BSA adsorption on [(C(6)S)(8)PcNi] is more limited than that on [(C(6)S)(8)PcCu] and this observation is consistent with the results on the surface wettability obtained from the contact angle measurements. The shift from the plasmonic resonance wavelength because of the BSA adsorption was significantly larger for the heat-treated [(C(6)S)(8)PcCu] than as-deposited film. Similar measurements on the [(C(6)S)(8)PcNi] films showed a limited BSA adsorption. The results of surface plasmon resonance experiments are consistent with those obtained from Raman spectroscopic and ellipsometric techniques. PMID:20170253

  13. Photoinduced Directional Motions of Microparticles at Air-Liquid-Crystal Interfaces of Azobenzene-Doped Liquid-Crystal Films with Homeotropic or Homogeneous Alignment Structures

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takahiro; Yoshida, Masaru

    2012-10-01

    We investigated the effects of liquid-crystal (LC) alignments on photoinduced motions of microparticles at air-LC interfaces of azobenzene-doped LC films. In homeotropically aligned LC films, the lattice spacings of pseudo-hexagonal structures of microparticles site-selectively exhibited reversible expansion or contraction on alternating irradiation with ultraviolet and visible light. The particle motions were probably driven by photochemical deformation of LC surfaces. In homogeneously aligned films, alternating irradiation induced macroscopic convective flows followed by rapid gathering or dispersion of linear chains of microparticles. Particle motions were significantly influenced by LC alignments as well as the light wavelength.

  14. Anisotropic light absorption, refractive indices, and orientational order parameter of unidirectionally aligned columnar liquid crystal films.

    PubMed

    Charlet, Emilie; Grelet, Eric

    2008-10-01

    The anisotropic optical properties of thermotropic columnar liquid crystals absorbing in the visible range are investigated for different discotic compounds unidirectionally oriented in open supported thin films. Two methods to monitor the alignment of columnar mesophases in thin films are reported, making possible to achieve either homeotropic anchoring (columns normal to the substrate) by a specific thermal annealing, or unidirectional planar orientation (columns parallel to the substrate) by using a rubbed Teflon coating. The columnar liquid crystal anchoring is found to depend on the nature of the compound, either parallel or perpendicular to the Teflon orientation. Based on this control of the mesophase alignment, the dichroic ratio and the orientational order parameter of oriented samples are measured, and a high order parameter of 0.9 is found in the case of parallel alignment. From the polarized absorption data of the columnar liquid crystal films, the light wavelength dependence of the birefringence and of the real and imaginary parts (refractive index and extinction coefficient, respectively) of the anisotropic optical indices are determined over the whole visible range. PMID:18999445

  15. Liquid Crystal Alignment with a Photo-Crosslinkable and Solvent-Soluble Polyimide Film

    NASA Astrophysics Data System (ADS)

    Lee, Wen-Chin; Hsu, Chain-Shu; Wu, Shin-Tson

    2000-05-01

    A new photo-crosslinkable and solvent-soluble polyimide containing cinnamate side chains (PICA) was developed for aligning nematic liquid crystals (LCs). Good LC alignment was achieved by exposing a long-wave linearly polarized ultraviolet (LPUV) light to the PICA film. The LC alignment direction is found perpendicular to the polarization axis of the incident LPUV light. The uniform alignment of LC molecules induced by PICA films remains intact after being heated at 85°C for 450 hours. A small pretilt angle on the PICA film was generated by the double exposure method.

  16. Computer simulation studies of confined liquid-crystal films

    NASA Astrophysics Data System (ADS)

    Wall, Greg D.; Cleaver, Douglas J.

    1997-10-01

    In this paper we present results from molecular dynamics simulations performed using a system of Gay-Berne particles confined between two substrates in a slab geometry. We use a nonseparable anisotropic molecule-substrate interaction potential and investigate weak and moderate molecule-substrate coupling strengths. We find that for both coupling strengths a well-defined, tilted molecular layer forms at each wall and that the pretilt angle and layer density are only weakly dependent on temperature as the central region is cooled through isotropiclike and nematiclike regions. The orientationally ordered fluid formed at the center of the film is tilted in sympathy with the surface layers. At low temperatures, however, where the central region adopts a layered arrangement, a sharp change is observed in the pretilt angle. This transition is more marked in the weak-coupling system where the high-temperature tilted surface layers adopt an approximately planar arrangement at low temperatures and the system resembles a bookshelf-geometry smectic film. In the moderate-coupling system, the surface layers maintain some tilt in the presence of the layered central region, leading to a smectic-stripe phase arrangement.

  17. Liquid crystal orientation on solution processed zinc oxide inorganic films according to molecular concentration

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Jin; Han, Jae-Jun; Park, Hong-Gyu; Kim, Dai-Hyun; Byun, Sang-Un; Seo, Dae-Shik

    2013-10-01

    In this paper we present the characteristics of molar concentration-dependent zinc oxide (ZnO) inorganic films deposited by the solution process for application in liquid crystal displays. ZnO surfaces supported homogeneously aligned liquid crystal (LC) molecules based on an ion-beam (IB) irradiation system. Uniform LC alignment was obtained at ZnO molar concentrations greater than 0.25 mol l-1. X-ray photoelectron spectroscopic (XPS) analysis revealed that changes in the orientation of LC molecules occurred on the ZnO layer. The electro-optic characteristics of the aligned homogenous LCs and twisted nematic (TN) mode based on the ZnO layer were comparable to those based on polyimide, which showed good potential as ZnO surfaces as an alignment layer.

  18. Solvent vapour mediated spontaneous healing of self-organized defects of liquid crystal films.

    PubMed

    Ravi, Bolleddu; Mukherjee, Rabibrata; Bandyopadhyay, Dipankar

    2015-01-01

    Ultrathin liquid crystal films showed a nematic to isotropic transition when exposed to solvent vapour for a short duration while a reverse isotropic to nematic transition was observed when the film was isolated from the solvent exposure. The phase transitions were associated with the appearance and fading of surface patterns as the solvent molecules diffused into and out of the film matrix, resulting in the destruction or restoration of the orientational order. A long-time solvent vapour exposure caused the dewetting of the film on the surface, which was demonstrated by the formation of holes and their growth in size with the progress of time. Even at this stage, withdrawal of the solvent exposure produced an array of nematic fingers, which nearly self-healed the dewetted holes. The change in contact angle due to the phase transition coupled with the imbalance of osmotic pressure across the contact line due to the differential rate of solvent evaporation from the film and the hole helped the fingers to grow towards the centre of the hole. The appearance of the fingers upon withdrawal of the solvent exposure and their disappearance upon exposure to solvent were also found to be a nearly reversible process. These findings could significantly contribute to the development of vapour sensors and self-healing surfaces using liquid crystal thin films. PMID:25372336

  19. 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.

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

    PubMed

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

    2014-03-21

    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. PMID:24264516

  1. 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.

  2. 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)

  3. 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.

  4. 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. PMID:24992456

  5. Enhanced solar cell conversion efficiency using birefringent liquid crystal polymer homeotropic films from reactive mesogens.

    PubMed

    Wu, Gwomei; Hsieh, Li-Hang; Chien, How-Wen

    2013-01-01

    Novel birefringent liquid crystal polymer homeotropic films have been coated on semiconductor solar cells to improve the effective incident sunlight angles. The liquid crystal polymer precursor, based on reactive mesogens, is fluidic and flows like liquid. It would distribute uniformly on the solar cell sample surface by any traditional coating technique. The birefringence for light, due to the liquid crystal retardation properties, manipulated the optical length and the deflection of incident light, thus allowed an increase in the energy conversion efficiency. The expensive sunlight tracking systems could be avoided. The processing parameters can be tuned such as different mesogen concentrations and plate speeds of spin-coating. The results showed that the solar cell conversion efficiency was improved from 14.56% to 14.85% at an incident sunlight angle of 15°. It was further improved from 13.40% to 13.81% when the angle was 30°. The interesting angular dependency on solar cell efficiency enhancement has been evaluated. PMID:24232577

  6. Enhanced Solar Cell Conversion Efficiency Using Birefringent Liquid Crystal Polymer Homeotropic Films from Reactive Mesogens

    PubMed Central

    Wu, Gwomei; Hsieh, Li-Hang; Chien, How-Wen

    2013-01-01

    Novel birefringent liquid crystal polymer homeotropic films have been coated on semiconductor solar cells to improve the effective incident sunlight angles. The liquid crystal polymer precursor, based on reactive mesogens, is fluidic and flows like liquid. It would distribute uniformly on the solar cell sample surface by any traditional coating technique. The birefringence for light, due to the liquid crystal retardation properties, manipulated the optical length and the deflection of incident light, thus allowed an increase in the energy conversion efficiency. The expensive sunlight tracking systems could be avoided. The processing parameters can be tuned such as different mesogen concentrations and plate speeds of spin-coating. The results showed that the solar cell conversion efficiency was improved from 14.56% to 14.85% at an incident sunlight angle of 15°. It was further improved from 13.40% to 13.81% when the angle was 30°. The interesting angular dependency on solar cell efficiency enhancement has been evaluated. PMID:24232577

  7. 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.

  8. Morphology of open films of discotic hexagonal columnar liquid crystals as probed by grazing incidence X-ray diffraction.

    PubMed

    Grelet, Eric; Dardel, Sébastien; Bock, Harald; Goldmann, Michel; Lacaze, Emmanuelle; Nallet, Frédéric

    2010-04-01

    The structure and the orientation of thermotropic hexagonal columnar liquid crystals are studied by grazing incidence X-ray diffraction (GIXD) for different discotic compounds in the geometry of open supported thin films. Whatever the film deposition mode (either spin-coating or vacuum evaporation) and the film thickness, a degenerate planar alignment with the liquid crystalline columns parallel to the substrate is found. However, if a specific thermal process is applied to the liquid crystal film, homeotropic anchoring (columns normal to the interface) can be stabilized in a metastable state. PMID:20411293

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2014-06-01

    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 10-6 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.

  11. Superior switching behavior of liquid crystals on surface-modified compound oxide films

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We demonstrate high-performance liquid crystal (LC) devices using alignment layers formed of solution-processed HfYO films that were subjected to ion-beam (IB) irradiation. IB irradiation entails the increment of the surface roughness and chemical modification of the surface. Our X-ray photoelectron spectroscopy (XPS) analysis revealed that IB irradiation also breaks oxygen bonds, and thereby creates oxygen vacancies with lattice displacement of the metal atoms. This variation stabilizes the homogeneous LC alignment. The LC cells formed using the IB-irradiated HfYO films with an intensity of 2200 eV yielded a rapid response time of 6.579 ms. Therefore, our fast switching application based on IB-irradiated HfYO films has great potential for application of display devices.

  12. Molecular dynamics in azobenzene liquid crystal polymer films studied by transient grating technique

    NASA Astrophysics Data System (ADS)

    Katayama, Kenji; Fujii, Tomomi; Kuwahara, Shota; Takado, Kiyohide; Ikeda, Tomiki

    2014-10-01

    We studied the effect of the ratio between the monomer and cross-linker molecules in the azobenene included liquid crystal polymer films by using the heterodyne transient grating (HD-TG) technique, which is one of the time-resolved measurement techniques. Depending on the ratio, the magnitude of the refractive index change, its anisotropy, and the lifetime of the cis isomer of azobenzene, generated by a UV pulse irradiation. By increasing the cross-linker ratio, the refractive index change and its anisotropy was reduced, indicating less ability for the motion, while slower lifetime was observed by increasing the monomer ratio, indicating that the film is difficult to return the original shape by a visiblelight irradiation. The obtained dynamics was consistent with the functionality of the films.

  13. Elasticity-dependent self-assembly of micro-templated chromonic liquid crystal films.

    PubMed

    Lohr, Matthew A; Cavallaro, Marcello; Beller, Daniel A; Stebe, Kathleen J; Kamien, Randall D; Collings, Peter J; Yodh, Arjun G

    2014-05-21

    We explore micropatterned director structures of aqueous lyotropic chromonic liquid crystal (LCLC) films created on square-lattice cylindrical-micropost substrates. The structures are manipulated by modulating the LCLC mesophases and their elastic properties via concentration through drying. Nematic LCLC films exhibit preferred bistable alignment along the diagonals of the micropost lattice. Columnar LCLC films, dried from nematics, form two distinct director and defect configurations: a diagonally aligned director pattern with local squares of defects, and an off-diagonal configuration with zig-zag defects. The formation of these states appears to be tied to the relative splay and bend free energy costs of the initial nematic films. The observed nematic and columnar configurations are understood numerically using a Landau-de Gennes free energy model. Among other attributes, the work provide first examples of quasi-2D micropatterning of LC films in the columnar phase and lyotropic LC films in general, and it demonstrates alignment and configuration switching of typically difficult-to-align LCLC films via bulk elastic properties. PMID:24651876

  14. 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)

  15. Use of black diamond-like carbon films as a contrast enhancement layer for liquid-crystal displays

    NASA Astrophysics Data System (ADS)

    Singh, B.; McClelland, S.; Tams, F., III; Halon, B.; Mesker, O.

    1990-11-01

    This paper describes the preparation of a highly durable single-layer pinhole-free abrasion-resistant chemically inert black diamondlike coating which is suitable for use as a contrast enhancement layer for liquid-crystal display devices. The diamondlike films prepared have an optical transmission of less than 2 percent over the visible spectrum, and a reflectance of about 20 percent. The coating is also electrically insulating and chemically compatible with liquid-crystal display materials. Data on the optical and mechanical properties of these films are presented.

  16. 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.

  17. 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.

  18. 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. PMID:27575192

  19. 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.

  20. 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.

  1. 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.

  2. Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam.

    PubMed

    Choi, Yoonseuk; Yoon, Tae-Hoon; Kwon, Jin Hyuk; Yi, Jonghoon; Gwag, Jin Seog

    2012-01-01

    We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because the side chain with hydrophobicity in the used polyimide is broken by ion beam exposure. To confirm it, contact angle measurement was carried out. With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality. PMID:22221956

  3. Bistable liquid crystal devices with nanoparticle-coated polyimide alignment films.

    PubMed

    Lee, Chuan-En; Jeng, Shie-Chang

    2013-04-01

    Bistable hybrid-aligned nematic (HAN) liquid crystal devices (LCDs) with silica nanoparticle-coated polyimide alignment films were investigated. It was observed that the existence of the internal electric field produced from the triboelectrically charged silica nanoparticles layer and impurity ions in the LC reduced the total free energy of the HAN-LCD and stabilized the cell in the homeotropic state. The stable homeotropic state can be switched back to the HAN state by changing the ion distribution through a voltage pulse with proper polarity. The capability of controlling bistability through modification of ion density in the LC layer may have some applications, such as displaying a one-time password requiring a specific stable time. PMID:23546227

  4. Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam

    PubMed Central

    2012-01-01

    We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because the side chain with hydrophobicity in the used polyimide is broken by ion beam exposure. To confirm it, contact angle measurement was carried out. With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality. PMID:22221956

  5. Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam

    NASA Astrophysics Data System (ADS)

    Choi, Yoonseuk; Yoon, Tae-Hoon; Kwon, Jin Hyuk; Yi, Jonghoon; Gwag, Jin Seog

    2012-01-01

    We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because the side chain with hydrophobicity in the used polyimide is broken by ion beam exposure. To confirm it, contact angle measurement was carried out. With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality.

  6. 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.

  7. Study of the properties of liquid crystals modified by nanoparticles

    NASA Astrophysics Data System (ADS)

    Kalashnikov, S. V.; Romanov, N. A.; Nomoev, A. V.

    2016-03-01

    The dielectric anisotropy and the response time of polymer-dispersed liquid-crystal films mixed with various nanoparticles were measured. The different types of nanoparticles used included metallic, dielectric, and biphasic core-shell or Janus type nanoparticles. Two methods were used for the determination of the dielectric anisotropy: a bridge method and a current-voltage method. The dipole moments of the nanoparticles were measured by the method of diluted solutions (Debye method). It was shown that the dielectric anisotropy plays a crucial role in the electro-optical properties of modified liquid crystals which in turn depend on the dipole moment and thus on the physical nature of the introduced nanoparticles.

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

    SciTech Connect

    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 ReO{sub 3} 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 H{sub x}ReO{sub 3} compound, with distorted perovskite structures, like in the bulk material, and ordered HReO{sub 4} crystals based on tetrahedral perrhenate ions. Because of its conduction properties, the electrical and electro-optical behaviors of ReO{sub 3} 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.

  9. Alignment structures and diffraction properties of chiral nematic liquid crystal cells with periodically patterned photoalignment films

    NASA Astrophysics Data System (ADS)

    Sasaki, Tomoyuki; Shimura, Rei; Kawai, Kotaro; Noda, Kohei; Sakamoto, Moritsugu; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2016-01-01

    Liquid crystal (LC) cells with periodic alignment distributions were fabricated using chiral nematic LCs (N*LCs), which were prepared using mixtures of a nematic LC and a chiral dopant, along with photoreactive liquid crystalline polymer (PLCP) films. Periodic structures were formed by polarization holographic recording in the PLCP films. The director distribution in each cell depended on the ratio of chiral dopant present, i.e., the inherent helical pitch of the N*LCs. These periodic alignment structures with line defects in the LC grating cells were well explained on the basis of the elastic continuum theory of the N*LCs and the photoalignment effect of the PLCP films. The diffraction properties of the grating LC cells were also investigated using a polarized visible laser. The observed intensity and polarization states of the diffracted beams were consistent with theoretical ones calculated using the director distribution models. Our results clarify that the diffraction properties of the grating LC cells can be controlled by the helical pitch of the N*LCs.

  10. X-ray microscopy study of chromonic liquid crystal dry film texture

    NASA Astrophysics Data System (ADS)

    Kaznatcheev, K. V.; Dudin, P.; Lavrentovich, O. D.; Hitchcock, A. P.

    2007-12-01

    Soft x-ray spectromicroscopy has been used to investigate the degree of the molecular alignment of sulfonated benzo[de]benzo[4.5]imidazo[2,1-a]isoquinoline[7,1], a lyotropic chromonic liquid crystal (LCLC). LCLC thin films cast from concentrated aqua solution (20%wt.) , aligned by shear flow and dried, show strong linear dichroism in their C-, N-, O-, S- K edge near edge x-ray spectra (NEXAFS). The carbon K edge has been used for quantitative evaluation of the orientational texture of the films at a submicron spatial scale. This has verified there is predominantly in-plane alignment of the LC director. To highlight the role of hydrophobic-hydrophilic interactions, two stereoisomers of the same dye has been synthesized with different positioning of terminal sulfonate groups, in the form of a mixture of isomers with sulfonate groups in 2,10 and 2,11 positions (Y104 compound) and in a 5,10-disulfo arrangement (Y105). Both compounds develop characteristic herringbone-type texture with similar domain sizes. Polarized optical microscopy and higher resolution x-ray microscopy show sinusoidal-like undulations of the molecular director, with occasional crisscross appearance. Such behavior is found to be consistent with earlier observation of striations, characteristic of the columnar phase. The drastic difference in the degree of undulation ( ±15° in Y104 and ±7° in Y105 films) and long period of undulation (approaching the film thickness) requires further analysis. It was also found that the degree of in-plane order within domains changes from 0.8 for Y104 to >0.9 in Y105 films.

  11. X-ray microscopy study of chromonic liquid crystal dry film texture.

    PubMed

    Kaznatcheev, K V; Dudin, P; Lavrentovich, O D; Hitchcock, A P

    2007-12-01

    Soft x-ray spectromicroscopy has been used to investigate the degree of the molecular alignment of sulfonated benzo[de]benzo[4.5]imidazo[2,1-a]isoquinoline[7,1], a lyotropic chromonic liquid crystal (LCLC). LCLC thin films cast from concentrated aqua solution (20%wt.) , aligned by shear flow and dried, show strong linear dichroism in their C-, N-, O-, S- K edge near edge x-ray spectra (NEXAFS). The carbon K edge has been used for quantitative evaluation of the orientational texture of the films at a submicron spatial scale. This has verified there is predominantly in-plane alignment of the LC director. To highlight the role of hydrophobic-hydrophilic interactions, two stereoisomers of the same dye has been synthesized with different positioning of terminal sulfonate groups, in the form of a mixture of isomers with sulfonate groups in 2,10 and 2,11 positions (Y104 compound) and in a 5,10-disulfo arrangement (Y105). Both compounds develop characteristic herringbone-type texture with similar domain sizes. Polarized optical microscopy and higher resolution x-ray microscopy show sinusoidal-like undulations of the molecular director, with occasional crisscross appearance. Such behavior is found to be consistent with earlier observation of striations, characteristic of the columnar phase. The drastic difference in the degree of undulation ( +/-15 degrees in Y104 and +/-7 degrees in Y105 films) and long period of undulation (approaching the film thickness) requires further analysis. It was also found that the degree of in-plane order within domains changes from 0.8 for Y104 to >0.9 in Y105 films. PMID:18233857

  12. Substrate-induced order in confined nematic liquid-crystal films

    NASA Astrophysics Data System (ADS)

    Gruhn, Thomas; Schoen, Martin

    1998-06-01

    In orientationally biased grand canonical ensemble Monte Carlo (GCEMC) simulations we investigated the microscopic structure of liquid-crystalline films confined between two plane parallel solid surfaces (i.e., walls) consisting of Ns discrete, rigidly fixed atoms. These wall atoms are distributed across the plane of a wall according to the (100) structure of the face-centered cubic lattice. Parameters of the film-wall interaction potential are chosen such that a homeotropic alignment of film molecules is favored. In the simulations the thermodynamic state of the film is determined by the temperature T, the chemical potential μ, the distance between the walls sz, and the film-wall interfacial area A. Thermodynamic states of the film are chosen such that a corresponding bulk liquid crystal is nematic. To simulate nematic phases in the GCEMC we modified the classic Gay-Berne potential for the interaction between a pair of film molecules so that the isotropic-nematic phase transition in the bulk occurs at sufficiently low densities. Reliability of the GCEMC method under these conditions is illustrated by a self-consistent comparison between Monte Carlo simulations in the canonical and grand canonical ensembles. In the bulk the nematic nature of the modified Gay-Berne fluid is established by computing the Mayer-Saupe order parameter S and suitably defined pair correlation functions which show that the bulk phase is not smectic even though S is fairly large. For a single temperature we investigate the isotropic-nematic phase transition in the modified Gay-Berne fluid which turns out to be a first-order phase transition. In the corresponding confined film variations of the microscopic structure with increasing sz are correlated with the normal component of the stress tensor Tzz(sz). Our results show that molecules in inner portions of the film undergo a reorganization from an originally planar orientation of their symmetry axes to a perpendicular one with respect to the

  13. The mechanism of controlling liquid crystal surface pretilt angle on plasma beam sputtered films

    NASA Astrophysics Data System (ADS)

    Pan, Ru-Pin; Huang, Meng-Chiou; Wu, Wei-Ta; Lai, Cheng-Wei; Wu, Hsin-Ying

    2012-02-01

    In liquid crystal (LC) devices, the surface alignment is essential. The polyimide (PI) film is commonly used to make LC molecules parallel to the surface. A rubbing process is usually applied to choose a particular direction on the surface. A pretilt angle is also induced, which is useful but usually very small. In previous works, we have found out that the sputtered ion-oxide films can give a homeotropic alignment to LC, i,e, the LC molecules are perpendicular to the surface. In this work, we combine these two effects by sputtering the ion-oxide particles onto the PI coated glasses. By adjusting the sputtering conditions, the LC alignment are controlled. A wide range of pretilt angles have been achieved, while the rubbing process is no longer required. A thorough study by varying the sputtering conditions, such as voltage, current, and time duration, and observing the pretilt angles is carried out. The sputtered surfaces are examined with scanning electron microscope to see the coverage. By considering the charge distribution and electric field within the sputter, a quantitative model is then developed, which explains how the sputtering conditions affect the pretilt angles almost perfectly.

  14. 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.

  15. 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

  16. 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.

  17. Light and thermal responses of liquid-crystal-network films: A finite element study

    NASA Astrophysics Data System (ADS)

    Chung, Hayoung; Choi, Joonmyung; Yun, Jung-Hoon; Cho, Maenghyo

    2015-04-01

    As a polymeric system incorporating rigid molecules within its structure, the liquid-crystal network (LCN) has been envisaged as a novel heterogeneous material. Under the influence of external stimuli, the orientational order of the liquid-crystalline phase becomes dilute and overall anisotropy is hence decreased; the actinic light absorbed by photochromic molecules, for example, induces the geometric isomerization and subsequently yields internal stress within the local network. In this study we investigate light- and temperature-induced spontaneous deformations of the LCN structure via a three-dimensional finite element model that incorporates geometric nonlinearity with a photomechanical constitutive model. We first examine the bending behavior and its nonlinearity and then parametrically study the various behaviors that stem from different origins ranging from the microscale to the macroscale: (i) the geometry of the LCN film, (ii) the macroscopic global order, (iii) the distorted mesogenic orientation due to the Fredericks distortion, and (iv) defect-induced instability. These interrelated behaviors demonstrate both the simulation capability and the necessity of the presenting framework. By employing a nonlinear consideration along with a microscopic shape parameter r the present approach facilitates further understanding of photomechanical physics such as the deconvolution of various stimuli and the deformed shape obtained due to snap-through instability. Furthermore, this study may offer insight into the design of light-sensitive actuation systems by deepening our knowledge and providing an efficient measure.

  18. Smart electro-optical iris diaphragm based on liquid crystal film coating with photoconductive polymer of poly(N-vinylcarbazole).

    PubMed

    Fuh, Andy Ying-Guey; Chen, Ko Nan; Wu, Shing-Trong

    2016-08-01

    This study develops a light shutter whose transmittance can be tuned electro-optically. The liquid crystal (LC) film applies the photoconductive material of poly(N-vinylcarbazole) (PVK) based on twisted nematic (TN) liquid crystals (LCs). The hole-transport layer of PVK could reduce the built-in electric field of the LC film under the exposure of UV light. The driving voltage is considerably decreased with the aid of UV light exposure. The repeating optical switching is performed under sunlight illumination with an external bias of electric field ∼5  V. Further, it could be operated under a parallel/cross-polarizer to change the light beam/ring as an iris and used to automatically block the UV light to protect an optical integrated system. PMID:27505385

  19. Controlling the alignment of liquid crystals by nanoparticle-doped and UV-treated polyimide alignment films

    NASA Astrophysics Data System (ADS)

    Jeng, Shie-Chang; Hwang, Su-June; Chen, Tai-An; Liu, Han-Shiang; Chen, Mu-Zhe

    2012-03-01

    We have developed two approaches for controlling the pretilt angles of liquid crystal molecules by using conventional polyimide (PI) alignment materials either doping homogeneous PIs with Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles or treating homeotropic PIs with ultraviolet light. These techniques are very simple and are compatible with current methods familiar in the LCD industry. The characteristics of modified PI alignment films and their applications for photonic devices are demonstrated in this paper.

  20. 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.

  1. Liquid Crystals

    NASA Astrophysics Data System (ADS)

    1990-01-01

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

  2. Homeotropic alignment and director structures in thin films of triphenylamine-based discotic liquid crystals controlled by supporting nanostructured substrates and surface confinement.

    PubMed

    Choudhury, Trirup Dutta; Rao, Nandiraju V S; Tenent, Robert; Blackburn, Jeffrey; Gregg, Brian; Smalyukh, Ivan I

    2011-02-01

    We explore the effects of nanoscale morphology of supporting solid substrates on alignment, defects, and director structures exhibited by thin films of triphenylamine-based discotic liquid crystals. Fluorescence confocal polarizing microscopy and intrinsic polarized fluorescence properties of studied molecules are used to visualize three-dimensional director fields in the liquid crystal films. We demonstrate that, by controlling surface anchoring on supporting or confining solid substrates such as those of carbon nanotube electrodes on glass plates, both uniform homeotropic and in-plane (edge-on) alignment and nonuniform structures with developable domains can be achieved for the same discotic liquid crystal material. PMID:21214228

  3. Equilibrium and Nonequilibrium Statistical Mechanics of Membranes, Liquid Crystal Films, and Other Layered Structures.

    NASA Astrophysics Data System (ADS)

    Chen, Chi-Ming

    In this thesis, we develop and analyze a continuum Landau theory for chiral and achiral lipid bilayers. This theory contains couplings between tangent-plane orientational order and curvature that lead to "rippled" phases with one-dimensional height modulations and to phases with two -dimensional height modulations. We calculate the mean -field phase diagrams by using both analytical and numerical methods. We generalize our theory to study the equilibrium phase diagrams of liquid crystal films. Both bulk smectics and freely suspended films are considered. For flexoelectric systems, continuous structural phase transitions are predicted among square-lattice, hexagonal, and distorted square-lattice phases as a function of the applied electric field. It is also shown that only uniform flat phases are predicted for thin films. One-dimensional ripple phases and two -dimensional square lattice phases can occur with increasing film thickness. Secondly we study the growth and instability of Myelin figures. For quasi-equilibrium growth, we predict a growth rate proportional to t^{-1/2 }, where t is the growth time. The proportional constant is inversely proportional to the viscosity of the fluid. Myelin figures are unstable under dehydration. The initial instability of myelin figures develops periodic arrays of bumps at the surface with a wave length of about 1 mum. This morphological change is induced by increasing the ratio of surface area to volume of myelin figures due to dehydration. We interpret this initial instability from energetical considerations and calculate the preferred wave length. Finally, we study theoretically the swelling kinetics of layered structures, particularly triblock copolymer mesogels. The gels are swollen by a solvent good for the bridging block but poor for the nonbridging block. At late stages the penetration front moves as in ordinary diffusion. However, the bending elasticity of the non -bridging layers leads to an initial t^{1/6 } relaxation

  4. 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". PMID:25915068

  5. 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.

  6. Radial liquid crystal alignment based on circular rubbing of a substrate coated with poly(N-vinyl carbazole) film

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    This paper presents a simple method to produce radial liquid crystal (LC) alignment layers using circular rubbing of poly(N-vinyl carbazole) (PVK) films. The produced layer can be used for fabricating axially symmetric homogeneous-radial, homeotropic-radial and radial-radial LC alignment devices by combining a rubbed PVK-coated substrate with another one with a desired LC alignment layer. The transmittance-voltage curves of the fabricated LC devices at various positions are measured to examine the uniformity of the alignment effect. Additionally, the PVK film does not absorb visible light, and can be operated at high temperatures.

  7. Intermediate pre-tilt angle control by a composite alignment thin film structure for liquid crystal displays.

    PubMed

    Wu, G M; Chien, H W; Huang, J W; Zeng, H L

    2010-04-01

    We designed a patterned composite alignment thin film structure using a horizontal alignment polyimide (PI) layer and vertical alignment liquid crystal polymer (LCP) pillars. The LCP polymer precursor concentration was varied at 0-10% and the pillars were introduced by a photolithography process. Both single-sided and double-sided liquid crystal display cells were assembled for a series of electro-optical characterization techniques. The horizontal PI alignment layer alone had a designated control of the pre-tilt angle of 7 degrees after the prescribed mechanical rubbing process. The pre-tilt angle was improved to 24 degrees when the LCP precursor concentration was 5%. It was further increased to 61 degrees at the concentration of 10%. In addition, the study on the electrical response time and gray level variation demonstrated promising results for potential applications. The field-on response time was only 2.79 ms and the field-off response time was 0.35 ms for the double-sided liquid crystal display cells using a ramping voltage of 5.5 V. The effective control of the cell pre-tilt angle suggested that the display power consumption and response time would be greatly improved. PMID:20208122

  8. Homogeneous liquid crystal alignment characteristics on solution-derived HfYGaO films treated with IB irradiation.

    PubMed

    Lee, Yun-Gun; Park, Hong-Gyu; Jeong, Hae-Chang; Lee, Ju Hwan; Heo, Gi-Seok; Seo, Dae-Shik

    2015-06-29

    Solution-derived HfYGaO films have been treated by ion beam (IB) irradiation and used as liquid crystal (LC) alignment layers. Solution processing was adopted due to its simplicity, high throughput, and facile composition modification. Homogeneous and uniform LC alignment was achieved on the IB-irradiated HfYGaO films, and when these films were adopted in twisted nematic (TN) cells, electro-optical performance comparable to that of TN cells with conventional polyimide layers was achieved, with almost no capacitance-voltage hysteresis. Moreover, LC cells based on IB-irradiated HfYGaO films had a high thermal budget. The proposed IB-irradiated solution-derived HfYGaO films have considerable potential for use in advanced LC applications. PMID:26191738

  9. 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.

  10. Comparison of transferred freely-suspended films and LB-films of liquid crystals

    SciTech Connect

    Decher, G.; Reibel, J.; Sohling, U.

    1993-12-31

    Amphiphilic liquid crystalline (LC) compounds offer the possibility to obtain similar layered structures such as LB mono- and multilayers, freely suspended and transferred freely-suspended films or bulk LC-phases from a single compound. This way a structural comparison of all types of assemblies can be achieved, combining the experience from both the LB-and the LC-fields. There is a remarkable similarity of the structures of the transferred freely-suspended (TFS) and LB-films. Nevertheless both types of multilayer assemblies, prepared from the same substance (ethyl-4`-n-octyloxybiphenyl-4-carboxylate), show a different thermal behavior. Whereas the TFS-films undergo reversible phase transitions and are stable up to the clearing point of the bulk material (110{degrees}C), the LB-films show only one irreversible phase transition and start to melt already 30{degrees}C below the clearing point of the bulk material.

  11. 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.

  12. 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

  13. Microfluidic sensing devices employing in situ-formed liquid crystal thin film for detection of biochemical interactions.

    PubMed

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

    2012-10-01

    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 A(2) (PLA(2)). PMID:22842797

  14. Near-zero pretilt alignment of liquid crystals using polyimide films doped with UV-curable polymer.

    PubMed

    Oh, Seung-Won; Park, Jun-Hee; Yoon, Tae-Hoon

    2015-01-26

    We propose an alignment method for the near-zero pretilt angle of liquid crystals (LCs) using polyimide films doped with a UV-curable polymer. The near-zero pretilt angle can be obtained by UV curing of reactive mesogen monomers mixed with planar alignment material while a vertical electric field is applied to an LC cell assembled after the rubbing process. We demonstrated that the pretilt angle can be decreased from 2.390° to 0.082° by employing the proposed method. PMID:25835864

  15. 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.

  16. Phase Determination of Second-Order Surface Susceptibility Tensor of Liquid Crystal Monolayer Using Ultra-Thin Film Local Oscillator

    NASA Astrophysics Data System (ADS)

    Sei, Masaki; Nagayama, Kohei; Kajikawa, Kotaro; Ishii, Hisao; Seki, Kazuhiko; Kondo, Katsumi; Matsumoto, Yoshiyasu; Ouchi, Yukio

    1998-04-01

    We demonstrated full determination of second-order nonlinear susceptibility of a 4‧-n-octyl-4-cyanobiphenyl (8CB) liquid crystal (LC) monolayer adsorbed on a second-harmonic (SH) active polyimide (PI) substrate. In order to separate the SH signal of the LC film from that of the PI film, we adopted an interferometry technique of second-harmonic generation (SHG) using an ultra-thin film local oscillator. We have found a variety of phases in the components of susceptibility: those of χzii and χizi are almost the same but the phase of χzzz differs by 80° from the other two. The phases of the components of the surface susceptibility tensor are not always identical. This fact indicates that the surface SH response is more complicated than what we expected.

  17. Selective liquid crystal molecule orientation on ion beam irradiated tantalum oxide ultrathin films

    SciTech Connect

    Lim, Ji-Hun; Oh, Byeong-Yun; Lee, Won-Kyu; Lee, Kang-Min; Na, Hyun-Jae; Kim, Byoung-Yong; Seo, Dae-Shik; Han, Jeong-Min; Hwang, Jeong-Yeon

    2009-09-21

    We recently achieved the homogeneous alignment of liquid crystal (LC) on amorphous Ta{sub 2}O{sub 5} layers. This study demonstrates that LC layers could be aligned either homogeneously or vertically by increasing the growth temperature of rf magnetron sputtering device and the irradiation time of the DuoPIGatron type Ar ion beam device causing uniform and dense plasma. We attained two LC orientations by observing Ta 4f and O 1s peak shifts with x-ray photoelectron spectroscopy. Moreover, the decreased thickness of layers with high-k dielectric constants helped to decrease driving LC voltages and in turn to achieve low power consumption.

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

    PubMed

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

    2010-12-01

    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. PMID:21164982

  19. 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.

  20. 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.

  1. Smectic C liquid crystal growth through surface orientation by ZnxCd1-xSe thin films

    NASA Astrophysics Data System (ADS)

    Katranchev, B.; Petrov, M.; Bineva, I.; Levi, Z.; Mineva, M.

    2012-12-01

    A smectic C liquid crystal (LC) texture, consisting of distinct local single crystals (DLSCs) was grown using predefined orientation of ternary nanocrystalline thin films of ZnxCd1-xSe. The surface morphology and orientation features of the ZnxCd1-xSe films were investigated by AFM measurements and micro-texture polarization analysis. The ZnxCd1-xSe surface causes a substantial enlargement of the smectic C DLSCs and induction of a surface bistable state. The specific character of the morphology of this coating leads to the decrease of the corresponding anchoring energy. Two new chiral states, not typical for this LC were indicated. The physical mechanism providing these new effects is presented.

  2. 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)

  3. 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)

  4. Computational studies of optical textures of twist disclination loops in liquid-crystal films by using the finite-difference time-domain method

    NASA Astrophysics Data System (ADS)

    Hwang, Dae Kun; Rey, Alejandro D.

    2006-02-01

    Optical images of textured liquid-crystal films containing various types of twist disclination loops are computed using an approximate matrix method and a direct numerical simulation based on the finite-difference time-domain (FDTD) method. The selected defects introduce large multidirectional spatial gradients in the optic axis, mimicking the orientation textures that arise in the construction and use of biosensors based on liquid-crystal vision. It is shown that under these experimentally relevant conditions, the matrix method fails to capture important signatures in the transmitted light intensity under crossed polarizers. The differences between the predictions by the two methods are analyzed with respect to gradients in the optic axis. We show that the FDTD method is a useful tool to perform computational optics of textured liquid-crystal films.

  5. 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.

  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. 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%. PMID:25399759

  8. Application of Commercially Available Liquid Crystal Polymer Films for the Improvement of Color and Viewing Angle Performance of Twisted Nematic Devices

    NASA Astrophysics Data System (ADS)

    Tatiana A. Sergan,; Marina D. Lavrentovich,; Jack R. Kelly,; Tadayuki Kameyama,

    2010-06-01

    In our work we analyzed the optical performance of liquid crystal polymer films by Nippon Mitsubishi Oil and by Fuji Film. We applied the films for twisted nematic (TN) display compensation and found several non-traditional display configurations. One display configuration employs flipped Nippon Mitsubishi Oil films mounted on polarizers, the second one, a combination of both types of films on one TN side and two crossed uniaxial films on the other. The compensated devices demonstrate greatly improved optical characteristics that surpass all those previously known, utilize the commercially available films, and are experimentally verified.

  9. [Comparison of detectability of liquid crystal displays (LCDs) and film using phantoms of small adenocarcinomas as abnormalities].

    PubMed

    Mochizuki, Yasuo; Abe, Shinji; Monma, Masahiko; Yamaguchi, Kojirou; Adachi, Toshiki

    2011-01-01

    Following the trend of the digitalization of the modalities used for diagnostic imaging, the devices for such imaging have increasingly included monitors. The present study was undertaken to evaluate the usefulness of soft-copy (liquid crystal display; LCD) images of phantoms of small adenocarcinomas using receiver operating characteristic (ROC) analysis of two different display systems: LCD and hard copy (film). A two-tailed paired t-test and the jackknife method (parametric methods) were performed, and no significant differences were found in the area under the ROC curve (AUC) for the pulmonary fields, lungs, ribs, or mediastinum between the film and LCD display systems, and the detectability did not differ between the film and LCD monitors. A Mann-Whitney U test, which is a non-parametric method that applies to the analysis of a small sample, also showed no significant differences in the AUC. The results of this study suggest that LCDs can replace hard-copy film as a display system if the signals. PMID:21532242

  10. Ultra fast polymer network blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Hussain, Zakir; Masutani, Akira; Danner, David; Pleis, Frank; Hollfelder, Nadine; Nelles, Gabriele; Kilickiran, Pinar

    2011-06-01

    Polymer-stabilization of blue phase liquid crystal systems within a host polymer network are reported, which enables ultrafast switching flexible displays. Our newly developed method to stabilize the blue phase in an existing polymer network (e.g., that of a polymer network liquid crystal; PNLC) has shown wide temperature stability and fast response speeds. Systems where the blue phase is stabilized in an already existing polymer network are attractive candidates for ultrafast LCDs. The technology also promises to be applied to flexible PNLC and/or polymer dispersed liquid crystal (PDLC) displays using plastic substrate such as polyethylene terephthalate (PET).

  11. 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. PMID:27070511

  12. Circular flow formation triggered by Marangoni convection in nematic liquid crystal films with a free surface.

    PubMed

    Choi, Hyunhee; Takezoe, Hideo

    2016-01-14

    We demonstrate circular flow formation at a surface in homeotropically oriented nematic liquid crystals with a free surface using focused laser beam irradiation. Under a weak laser power, a pit together with an associated circular bulge is formed: the Marangoni effect. Here a diverging molecular flow from the pit (thermocapillary flow) also induces director tilt in the radial direction. Upon increasing the laser power, the pit becomes deeper, and eventually evolves into a circular flow associated with a deeper pit and a subsidiary circular bulge or valley structure. This phenomenon is induced by escaping from excess deformation energy due to a bend deformation of the director. Actually, we confirmed that the circular flow is never formed in the isotropic phase. The handedness of the vortex cannot be controlled by circular polarisation, but is controllable by doping with chiral molecules. This rotational motion (a nematic micro-rotor) is a unique phenomenon only exhibited by anisotropic liquids, and is expected to be applied for novel devices. PMID:26482229

  13. Photochemical manipulation of microparticles on azobenzene-doped liquid-crystal films with homogeneous or homeotropic alignment structures

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takahiro; Yoshida, Masaru

    2012-10-01

    In this study, we investigated self-organized structures and photoinduced motions of microparticles on azobenzenedoped liquid crystal (LC) films with homogeneous or homeotropic alignment structures. In the case of homogeneous alignment, the microparticles formed linear chains oriented along the direction of the bulk LC alignment at air-LC interface in the initial state. Upon irradiation with ultra-violet (UV) light, the linear chains gathered into the irradiated area and formed closely-packed aggregates. The assembled chains diffused outside the irradiated area to reform the chains upon irradiation with visible light. In contrast, on the homeotropically aligned LC films, pseudo-hexagonal lattice structures of microparticles with long interparticle distances have been organized in the initial state. The particles exhibited photoinduced motions in directions opposite to those observed on the homogeneously aligned LC films. Upon irradiation with UV light, lattice structures were expanded by a particle motion away from the photoirradiated area. Irradiation with visible light then induced contraction of lattice structures based on a particle motion toward the irradiated area. The photoinduced particle motions depending on LC alignments would be explained by macroscopic convective flow or deformation of LC surface induced by cis-trans photoisomerization of azobenzene dopant.

  14. High-optical-quality ferroelectric film wet-processed from a ferroelectric columnar liquid crystal as observed by non-linear-optical microscopy.

    PubMed

    Araoka, Fumito; Masuko, Shiori; Kogure, Akinori; Miyajima, Daigo; Aida, Takuzo; Takezoe, Hideo

    2013-08-01

    The self-organization of ferroelectric columnar liquid crystals (FCLCs) is demonstrated. Columnar order is spontaneously formed in thin films made by the wet-process due to its liquid crystallinity. Electric-field application results in high optical quality and uniform spontaneous polarization. Such good processability and controllability of the wet-processed FCLC films provide us with potential organic ferroelectric materials for device applications. PMID:23740767

  15. Evaluation of photoinduced change in refractive index of a polymer film doped with an azobenzene liquid crystal by means of a prism-coupling method

    SciTech Connect

    Kurihara, Hideo; Shishido, Atsushi; Ikeda, Tomiki

    2005-10-15

    The photoinduced change in refractive index of poly(methyl methacrylate) films doped with an azobenzene liquid crystal was measured by the prism-coupling method. Upon irradiation of the film with a high-pressure mercury lamp at 366 nm, the coupling angles shifted and then recovered to the initial position by turning off the light. The change in refractive index was found to be 2x10{sup -3}, which is attributed to the reversible photoisomerization of the azobenzene moieties.

  16. 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.

  17. Thin liquid crystal films on liquids in the nematic range of temperatures.

    PubMed

    Delabre, Ulysse; Richard, Céline; Sang, Yann Yip Cheung; Cazabat, Anne-Marie

    2010-08-17

    Hybrid nematic films deposited on liquid substrates reveal a complex behavior, which is not fully understood. Here, the behavior of the n-cyanobiphenyl series on water and glycerol has been studied in a wide temperature range, including the vicinity of the nematic-isotropic (NI) transition. Wettability, allowed film thicknesses, and line tension of nematic domains have been investigated. The study provides a coherent picture of hybrid nematic films, allowing us to account for lower thickness threshold, structure of the film edge, and line tension of domains in the whole nematic range of temperatures. PMID:20695580

  18. Thin Films of a Main Chain Columnar Liquid Crystal: Studies of Structure, Phase Transitions and Alignment

    SciTech Connect

    Defaux, M.; DiMasi, E.; Vidal, Loic; Moller, Martin; Gearba, Raluca; Ivanov, Dimitri

    2009-03-22

    The structure of thin films of poly(di-n-propylsiloxane), PDPS, was studied with a combination of optical and atomic force microscopy, electron diffraction, and grazing incidence X-ray diffraction. Two different morphological features are observed in the mesomorphic films. The lamellar ribbons are composed of the chains oriented parallel to the plane of the substrate in which the reciprocal space 10 vector is vertical. The other feature with a circular symmetry, the cylindrite, contains the chains parallel to the substrate normal. The cylindrites and needles are essentially the same mesomorphic lamellae that develop differently under the conditions of confinement. The crystallization of PDPS films does not change the gross morphological features developed during the mesophase formation and mainly proceeds via epitaxial growth of the {alpha}-crystal on the parent mesophase. Spontaneous alignment of the mesomorphic PDPS films on the PTFE-rubbed substrates allows fabricating highly crystalline inorganic polymer surfaces oriented on the scale of centimeters.

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

    PubMed

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

    2014-04-01

    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. PMID:24584886

  20. 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.

  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. Combined photocatalysis and membrane bioreactor for the treatment of feedwater containing thin film transistor-liquid crystal display discharge.

    PubMed

    You, Sheng-Jie; Semblante, Galilee Uy; Chen, Yu-Pu; Chang, Tien-Chin

    2015-01-01

    The nitrogen content of waste water generated by the thin film transistor-liquid crystal display (TFT-LCD) industry is not satisfactorily removed through the conventional aerobic-activated sludge process. In this study, the performance of three reactors – suspended type TiO2 membrane photoreactor (MPR), anoxic/oxic membrane bioreactor (AOMBR), and their combination (MPR-AOMBR) – was evaluated using feedwater containing TFT-LCD discharge. The parameters that maximized monoethanolamine (MEA) removal in the MPR were continuous ultraviolet (UV) irradiation and pH 11. Among the tested loadings, 0.1 g/l of TiO2 promoted MEA removal but degradation rate may further increase with photocatalyst concentration. The nitrified sludge recycle ratio R of the AOMBR was adjusted to 1.5 to minimize the amount of nitrate in the effluent. The AOMBR greatly decreased chemical oxygen demand and MEA, but removed only 32.7% of tetramethyl ammonium hydroxide (TMAH). The MPR was configured as the pre-treatment unit for AOMBR, and the combined MPR-AOMBR has improved TMAH removal by 80.1%. The MPR bolstered performance by decomposing slowly biodegradable compounds, and had no negative effects on denitrification and carbon removal. PMID:25952015

  3. 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. PMID:20227824

  4. 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.

  5. Shear-Sensitive Monomer/Polymer Liquid Crystal System

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  6. 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.

  7. 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. PMID:23859140

  8. Liquid crystal light valve structures

    NASA Technical Reports Server (NTRS)

    Koda, N. J. (Inventor)

    1985-01-01

    An improved photosensor film and liquid crystal light valves embodying said film is provided. The photosensor film and liquid crystal light valve is characterized by a significant lower image retention time while maintaining acceptable photosensitivity. The photosensor film is produced by sputter depositing CdS onto an ITO substrate in an atmosphere of argon/H2S gas while maintaining the substrate at a temperature in the range of about 130 C to about 200 C and while introducing nitrogen gas into the system to the extent of not more than about 1% of plasma mixture. Following sputter deposition of the CdS, the film is annealed in an inert gas at temperatures ranging from about 300 C to about 425 C.

  9. 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.

  10. Vertical alignment of liquid crystal through ion beam exposure on oxygen-doped SiC films deposited at room temperature

    SciTech Connect

    Son, Phil Kook; Park, Jeung Hun; Kim, Jae Chang; Yoon, Tae-Hoon; Rho, Soon Joon; Jeon, Back Kyun; Shin, Sung Tae; Kim, Jang Sub; Lim, Soon Kwon

    2007-09-03

    The authors report the vertical alignment of liquid crystal (LC) through the ion beam exposure on amorphous oxygen-doped SiC (SiOC) film surfaces deposited at room temperature. The optical transmittance of these films was similar to that of polyimide layers, but much higher than that of SiO{sub x} films. The light leakage of a LC cell aligned vertically on SiOC films was much lower than those of a LC cell aligned on polyimide layers or other inorganic films. They found that LC molecules align vertically on ion beam treated SiOC film when the roughness of the electrostatic force microscopy (EFM) data is high on the SiOC film surface, while they align homogeneously when the roughness of the EFM data is low.

  11. Temperature and orientation dependence of surface relief gratings based on dye-doped polymer film with the interface of nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Huang, Shuan-Yu; Huang, Bing-Yau; Hung, Wen-Chi; Yu, Kai-Yu; Cheng, Wen-Shou; Kuo, Chie-Tong

    2011-02-01

    The formation of surface relief grating on dye-doped polymer film with the interface of nematic liquid crystals has been investigated by means of the holographic technique. The first-order diffraction efficiency of surface relief grating depends on the temperature and the orientation of molecular director in the interface of nematic liquid crystals. The diffraction efficiency is roughly independent of thermal fluctuations of molecular director in the most part of nematic temperature range and apparently drops near the transition temperature. The morphology of surface relief grating demonstrates that the surface modulation is larger for molecular director parallel to the groove direction. The experimental result also shows that the first-order diffraction efficiency is dependent on the surface modulation of surface relief grating.

  12. Fast response liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Wu, Yung-Hsun

    LC-based VOA. In Chapter 7, we report a new device called axially-symmetric sheared polymer network liquid crystals (AS-SPNLC) and use it as LC devices. Through analyzing the structure of this axially-symmetric SPNLC, we construct a 3-D model to explain the observed phenomena. An axially-symmetric sheared polymer network liquid crystal has several attractive features: (1) it is polarization independent, (2) it has gradient phase change, and (3) its response time is fast. It can be used for polarization converter and divergent LC lens. In addition, a new method for simultaneously measuring the phase retardation and optic axis of a compensation film is demonstrated using an axially-symmetric sheared polymer network liquid crystal. By overlaying a tested compensation film with a calibrated SPNLC cell between crossed polarizers, the optic axis and phase retardation value of the compensation film can be determined. This simple technique can be used for simultaneously measuring the optic axis and phase retardations of both A- and C-plates. These compensation films have been used extensively in wide-view LCD industry. Therefore, this method will make an important impact to the LCD industry.

  13. 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.

  14. 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.

  15. Investigaction of Switching Behavior in a Ferroelectric Liquid Crystal Aligned on Obliquely Deposited SiO Films

    NASA Astrophysics Data System (ADS)

    Yamada, Yuichiro; Yamamoto, Norio; Inoue, Tetsuya; Orihara, Hiroshi; Ishibashi, Yoshihiro

    1989-01-01

    The effect of oblique evaporation of SiO on the chevron structure and the switching behavior in a ferroelectric liquid crystal have been investigated by means of the X-ray diffraction and the stroboscopic micrographs. It is found experimentally that the chevron direction and the domain structure appearing during the switching are determined by the direction of incidence of evaporated SiO. On the basis of the experimental results, it is clarified that the bow and the stern of the boat-shaped domain correspond to {+}2π and {-}2π internal disclinations, respectively. The structure of the zig-zag defect is determined.

  16. Excitability in liquid crystal.

    PubMed

    Coullet, P.; Frisch, T.; Gilli, J. M.; Rica, S.

    1994-09-01

    The spiral waves observed in a liquid crystal submitted to a vertical electric field and a horizontal rotating magnetic field are explained in the framework of a purely mechanical description of the liquid crystal. The originality of the experiment described in this paper is the presence of the vertical electric field which allows us to analyze the spiral waves in the framework of a weakly nonlinear theory. PMID:12780124

  17. 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.

  18. 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.

  19. 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.

  20. Process Techniques of 15-inch Full-Color High-Resolution Liquid Crystal Displays Addressed by a-Si Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Fujii, Kenichi; Tanaka, Yasuo; Honda, Kouichi; Tsutsu, Hiroshi; Koseki, Hideo; Hotta, Sadayoshi

    1992-12-01

    A 15 inch-diagonal-size full-color liquid crystal display (LCD) with 1152(× 3)× 900 pixels has been fabricated which enables a portable workstation with improved display performances. The process techniques used for this development are described, with special reference to metallization and dry etching. In multilevel metallization, Cr/Al interconnection is metallurgically undesirable. By contrast, the Cr/Ti/Al metal system provides excellent properties of contact resistivity and thermodynamical stability. Dry etching processes are developed for multilayered insulating films and metallization-related bilayers, namely SiO2/TaOx/SiNx/(i/n+)a-Si and a-Si/Ti, respectively. Fine patterning and easier stepcoverage of subsequently deposited layers are achieved.

  1. Tunable liquid crystal photonic devices

    NASA Astrophysics Data System (ADS)

    Fan, Yun-Hsing

    2005-07-01

    Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices. In Chap. 3, we demonstrate a novel electrically tunable-efficiency Fresnel lens which is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. The nanoscale LC devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated tunable Fresnel lens using polymer-network liquid crystal (PNLC) and phase-separated composite film (PSCOF). The operating voltage is below 12 Vrms. The PNLC and PSCOF devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. Using PNLC, we also demonstrated LC blazed grating. The diffraction efficiency of these devices is continuously controlled by the electric field. We also develop a system with continuously tunable focal length. A conventional mechanical zooming system is bulky and power hungry. In Chap. 4, we developed an electrically tunable-focus flat LC spherical lens and microlens array. A huge tunable range from 0.6 m to infinity is achieved by the applied voltage. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative by the applied voltage. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. In

  2. Semiconductor nanorod liquid crystals

    SciTech Connect

    Li, Liang-shi; Walda, Joost; Manna, Liberato; Alivisatos, A. Paul

    2002-01-28

    Rodlike molecules form liquid crystalline phases with orientational order and positional disorder. The great majority of materials in which liquid crystalline phases have been observed are comprised of organic molecules or polymers, even though there has been continuing and growing interest in inorganic liquid crystals. Recent advances in the control of the sizes and shapes of inorganic nanocrystals allow for the formation of a broad class of new inorganic liquid crystals. Here we show the formation of liquid crystalline phases of CdSe semiconductor nanorods. These new liquid crystalline phases may have great importance for both application and fundamental study.

  3. Liquid crystal polyester thermosets

    SciTech Connect

    Benicewicz, B.C.; Hoyt, A.E.

    1990-01-01

    The present invention relates to the field of curable liquid crystal polyester monomers and to thermoset liquid crystalline polyester compositions prepared therefrom. It is an object of this invention to provide curable liquid crystalline polyester materials. Another object of this invention is to provide a process of preparing curable liquid crystal polyester monomers. Yet another object of this invention is to provide liquid crystalline blends of polyester materials. It is a further object of this invention to provide thermoset liquid crystalline polyester compositions. It is a still further object of this invention to provide thermoset liquid crystalline polyester compositions having a high heat resistance. 1 fig.

  4. Liquid crystal polyester thermosets

    SciTech Connect

    Benicewicz, B.C.; Hoyt, A.E.

    1990-12-31

    The present invention relates to the field of curable liquid crystal polyester monomers and to thermoset liquid crystalline polyester compositions prepared therefrom. It is an object of this invention to provide curable liquid crystalline polyester materials. Another object of this invention is to provide a process of preparing curable liquid crystal polyester monomers. Yet another object of this invention is to provide liquid crystalline blends of polyester materials. It is a further object of this invention to provide thermoset liquid crystalline polyester compositions. It is a still further object of this invention to provide thermoset liquid crystalline polyester compositions having a high heat resistance. 1 fig.

  5. Pretilt Angle of Liquid Crystals on Polyimide Films Photo-Aligned by Single Oblique Angle Irradiation with Un-polarized Light

    NASA Astrophysics Data System (ADS)

    Sakamoto, Kenji; Usami, Kiyoaki; Sasaki, Toru; Uehara, Yoichi; Ushioda, Sukekatsu

    2006-04-01

    We have investigated the pretilt angle of liquid crystal (LC) molecules induced by photo-aligned films of polyimide containing azobenzene in the backbone structure (Azo-PI). The photo-alignment treatment was single oblique-angle irradiation with un-polarized light (UP-L) at an incidence angle of 45°. It was performed on films of polyamic acid (Azo-PAA) using a light source of wavelength 340-500 nm. The photo-treated films of Azo-PAA were converted into Azo-PI by thermal imidization. The pretilt angle of LC molecules was determined by a crystal rotation method. The pretilt angle increased with the UP-L exposure, reaching ˜3° at 880 J/cm2. For UP-L exposures above 440 J/cm2 the LC alignment was uniform and defect-free, while marbled textures were observed below 220 J/cm2. This is due to the small in-plane anisotropy of the photo-aligned Azo-PI films.

  6. 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.

  7. 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

  8. The effect of salt on ion adsorption on a SiOx alignment film and reduced conductivity of a liquid crystal host

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    It is shown that the addition of salt to liquid crystal cells, using a SiOx alignment layer, can actually reduce the ion concentration. This seeming contradiction may be explained by the ability of salt to complex with water and to aid the drying of the liquid crystal material. The results show a pathway to purifying liquid crystal devices to the extent needed for low-power low-refresh rate displays for e-book applications.

  9. Control of liquid crystal molecular orientation using ultrasound vibration

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  10. Thermoelectricity in liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  11. Band-tunable color cone lasing emission based on a dye-doped cholesteric liquid crystal film

    NASA Astrophysics Data System (ADS)

    Lee, Chia-Rong; Lin, S.-H.; Yeh, H.-C.; Ji, T.-D.; Liu, J.-H.; Yang, P.-C.; Mo, T.-S.; Huang, S.-Y.; Kuo, C.-T.; Lo, K.-Y.; Fuh, Andy Y.

    2010-02-01

    This investigation reports for the first time a novel phenomenon, called band-tunable color cone lasing emission (CCLE), based on a single-pitched one-dimensional photonic crystal-like dye-doped cholesteric liquid crystal (DDCLC) cell. The lasing wavelength in the CCLE pattern is distributed continuously at 676.7-595.6 nm as the oblique angle increases continuously from 0° to 50° relative to the helical axis. The variation of the lasing wavelength in the CCLE with the oblique angle is consistent with that of the wavelength at the long-wavelength edge (LWE) of the CLC reflection band (CLCRB) with the oblique angle. Simulation results obtained utilizing Berreman's 4×4 matrix method show that, at each oblique angle, the associated group velocity and density of photonic state (DOS) are near zero and large at the shortwavelength edge (SWE) and LWE of the CLCRB, respectively, and are in good agreement with experimental results. The particularly strong lasing ring emission at a cone angle of ~35° can be explained to be likely due to a special effect that, under the condition of overlap between the LWE of the CLCRB measured at 35° and the SWE of the CLCRB measured at 0°, the LWE and SWE fluorescence propagating along 35° and 0°, respectively, may indirectly enhance each other due to individual enhanced rate of spontaneous emission. Furthermore, the lasing band of the CCLE can be tuned from long-wavelength (deep red~orange) to short-wavelength (orange~green) regions by changing the concentration of the chiral or by the photo-irradiation on a DDCLC cell with a photoisoemerizable chiral dopant.

  12. Liquid crystal orientation control in photonic liquid crystal fibers

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  13. Topographic-pattern-induced homeotropic alignment of liquid crystals.

    PubMed

    Yi, Youngwoo; Lombardo, Giuseppe; Ashby, Neil; Barberi, Riccardo; Maclennan, Joseph E; Clark, Noel A

    2009-04-01

    Polymer films nanoimprinted with checkerboard patterns of square wells align calamitic (rodlike) liquid crystals vertically, horizontally, or tilted depending on the depth/width ratio of the wells. The liquid crystal prefers planar orientation on polymer films that are smooth but when the films are topographically patterned, the increasing elastic energy density as the wells become narrower eventually overcomes the surface anchoring of the polymer and the liquid crystal director field makes a transition from planar to homeotropic. Similar effects have been demonstrated in both nematics and smectics, and the behavior is confirmed by theory and computer simulation. PMID:19518244

  14. Experimental investigation of the effects of compound angle holes on film cooling effectiveness and heat transfer performance using a transient liquid crystal thermometry technique

    NASA Astrophysics Data System (ADS)

    Seager, David J.; Liburdy, James A.

    1997-11-01

    To further understand the effect of both compound angle holes and hole shaping on film cooling, detailed heat transfer measurements were obtained using hue based thermochromic liquid crystal method. The data were analyzed to measure both the full surface adiabatic effectiveness and heat transfer coefficient. The compound angles that were evaluated consist of holes that were aligned 0 degrees, 45 degrees, 60 degrees and 90 degrees to the main cross flow direction. Hole shaping variations from the traditional cylindrical shaped hole include forward diffused and laterally diffused hole geometries. Geometric parameters that were selected were the length to diameter ratio of 3.0, and the inclination angle 35 degrees. A density ratio of 1.55 was obtained for all teste. For each set of conditions the blowing ratio was varied to be 0.88, 1.25, and 1.88. Adiabatic effectiveness was obtained using a steady state test, while an active heating surface was used to determine the heat transfer coefficient using a transient method. The experimental method provides a unique method of analyzing a three-temperature heat transfer problem by providing detailed surface transport properties. Based on these results for the different hole geometries at each blowing ratio conclusions are drawn relative to the effects of compound angle holes on the overall film cooling performance.

  15. Chromonic liquid crystals and their dispersion in polymers

    NASA Astrophysics Data System (ADS)

    Park, Jung; Yao, Xuxia; Srinivasarao, Mohan

    2010-03-01

    Chromonic liquid crystals can self-assemble into an ordered complex fluid, potentially applicable for biosensor, polarizers, optical compensetors and organic solar cells. Different from common amphiphilic lyotropic mesophases, aggregation of the chromonic liquid crystals is thought to be isodesmic and without optimum aggregation size. We studied the aggregation behavior by Vis-spectroscopy, and the phase behavior by polarizing optical microscopy and differential scanning calorimetry. We also used capillary flow to achieve uniform planar alignment in a flat capillary, and measured polarized Raman scattering, from which the temperature and concentration dependence of order parameters, both and , and the orientation distribution were deduced. Order parameters increase as concentration increases and decrease as temperature increases. Polymer dispersed chromonic droplets with different director configurations were obtained by using different water soluble polymers and those anchoring phenomena were compared.

  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. 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.

  18. Living liquid crystals.

    PubMed

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

    2014-01-28

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

  19. Living liquid crystals

    PubMed Central

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

    2014-01-01

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

  20. 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).

  1. 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. PMID:23005436

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

    PubMed

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

    2010-09-01

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

  3. Short channel amorphous In-Ga-Zn-O thin-film transistor arrays for ultra-high definition active matrix liquid crystal displays: Electrical properties and stability

    NASA Astrophysics Data System (ADS)

    Kim, Soo Chang; Kim, Young Sun; Yu, Eric Kai-Hsiang; Kanicki, Jerzy

    2015-09-01

    The electrical properties and stability of ultra-high definition (UHD) amorphous In-Ga-Zn-O (a-IGZO) thin-film transistor (TFT) arrays with short channel (width/length = 12/3 μm) were examined. A-IGZO TFT arrays have a mobility of ∼6 cm2/V s, subthreshold swing (S.S.) of 0.34 V/decade, threshold voltage of 3.32 V, and drain current (Id) on/off ratio of <109 with Ioff below 10-13 A. Overall these devices showed slightly different electrical characteristics as compared to the long channel devices; non-saturation of output curve at high drain-to-source voltage (Vds), negative shift of threshold voltage with increasing Vds, and the mobility reduction at high gate voltage (Vgs) were observed. The second derivative method adopting Tikhonov's regularization theory is suggested for the robust threshold voltage extraction. The temperature dependency of γ-value was established after taking into consideration the impact of source/drain contact resistances. The AC bias-temperature stress was used to simulate the actual operation of active matrix liquid crystal displays (AM-LCDs). The threshold voltage shift had a dependency on the magnitude of drain bias stress, frequency, and duty cycle due to the impact ionization accelerated at high temperature. This study demonstrates that the short channel effects, source/drain contact resistances and impact ionization have to be taken into account during optimization of UHD AM-LCDs.

  4. Photoalignment of liquid crystals and development of novel glassy liquid crystals

    NASA Astrophysics Data System (ADS)

    Kim, Chunki

    This thesis consists of two parts: (i) photoalignment of liquid crystals, including a nematic fluid, a glassy-namtic pentafluorene, and a cholesteric glassy liquid crystal; and (ii) development of cholesteric glassy liquid crystals comprising a hybrid chiral-nematic mesogen and of photochromic glassy liquid crystals with dithienylethene cores. Photoalignment behaviors were interpreted in terms of the kinetics of axis-selective photodimerization, the rotational mobility of pendant coumarin monomers, and the coumarin monomer's and dimer's absorption dipoles located by computational chemistry. Coumarin-containing polymethacrylate films were employed to elucidate the roles played by coumarin monomer's and dimer's orientational order, their relative abundance, and the energetics of their interactions with overlying liquid crystals. Under favorable conditions, photoalignment was shown to be comparable to rubbing polymimide film in the ability to orient liquid crystals. A hole-conducting copolymer film comprising triphenylamine and coumarin was used to unravel how the dilution of coumarin monomers, polarization ratio of UV-irradiation to induce dimerization of coumarin, and triplet energy transfer from triphenylamine to coumarin moieties affect the quality of photoalignment and its cross-over behavior. Cholesteric glassy liquid crystals are comprised of a helical stack of quasi-nematic layers frozen in the solid state capable of selective wavelength reflection with simultaneous circular polarization. Potentially applications of this material class include robust non-absorbing circular polarizers, optical notch filters and reflectors, and polarized light-emitters and lasers. To facilitate material synthesis over prior arts, hybrid chiral-nematic mesogens were chemically bonded to benzene via enantiomeric 2-methylpropylene spacers, exhibiting a broad cholesteric fluid temperature range. Phase transition temperatures, glass-forming ability, morphological stability against

  5. Simultaneous measurements of molecular forces and electro-optical properties of a confined 5CB liquid crystal film using a surface forces apparatus.

    PubMed

    Kristiansen, Kai; Zeng, Hongbo; Zappone, Bruno; Israelachvili, Jacob N

    2015-04-01

    Using a surface forces apparatus (SFA), we studied the forces associated with the reorientation of molecules of a common nematic thermotropic liquid crystal, 4'-n-pentyl-4-cyanobiphenyl (5CB), confined between two conducting (silver) surfaces and its optical behavior under the influence of electric fields with varying magnitudes and field directions. A transient attractive force was observed due to partial reorientations of the liquid crystal molecules and the flow of free ions, in addition to a stronger constant capacitance attraction between the silver surfaces. At the same time, the optical properties of the liquid crystals were observed perpendicular to the silver surfaces. Observations of shifts and fluctuations of the extraordinary wave of the (multiple beam) interference fringes measure the refractive index of the director component parallel to the surface, which is sensitive to tilt motion (or reorientation) of the liquid crystal molecules that provided details of the anisotropic orientations of the molecules and domains. Any lateral differential refractive index change is easily observed by optical microscopy. The optical microscope imaging showed that the changes in the optical properties are due to convective flow at domain boundaries of the liquid crystal molecules (and possible free ions) between the two charged surfaces. At low electric fields, propagation of domain boundaries was observed, while at higher electric fields, hexagonal patterns of flowing molecules were observed. The interplay of the force measurements and optical observations reveal a complex dynamic behavior of liquid crystals subjected to varying electric fields in confined spaces. PMID:25774432

  6. Enhancement of third-harmonic generation in a polymer-dispersed liquid-crystal grating

    NASA Astrophysics Data System (ADS)

    Markowicz, Przemyslaw P.; Hsiao, Vincent K. S.; Tiryaki, Hanifi; Cartwright, Alexander N.; Prasad, Paras N.; Dolgaleva, Ksenia; Lepeshkin, Nick N.; Boyd, Robert W.

    2005-08-01

    We report the observation of significant enhancement of one-step third-harmonic generation in a one-dimensional photonic crystal pumped by a near-infrared laser beam tuned to the low-frequency edge of the first photonic band gap. The third-harmonic phase matching can be controlled by changing the angle of incidence of the fundamental radiation, allowing tunability of the third-harmonic wavelength. The observed phenomenon was modeled theoretically using the transfer-matrix method. The enhancement is attributed to the combined action of phase-matching between the pump and harmonic waves and pump-field localization within the photonic crystal.

  7. 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

  8. Wetting of cholesteric liquid crystals.

    PubMed

    Silvestre, Nuno M; Figueirinhas Pereira, Maria Carolina; Bernardino, Nelson R; Telo da Gama, Margarida M

    2016-02-01

    We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted, the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal. PMID:26920516

  9. 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.

  10. 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.

  11. Liquid crystal photoalignment material based on chloromethylated polyimide

    SciTech Connect

    Zhong Zhenxin; Li Xiangdan; Lee, Seung Hee; Lee, Myong-Hoon

    2004-09-27

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

  12. 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.

  13. Optical modeling of liquid crystal biosensors

    NASA Astrophysics Data System (ADS)

    Hwang, Dae Kun; Rey, Alejandro D.

    2006-11-01

    Optical simulations of a liquid crystal biosensor device are performed using an integrated optical/textural model based on the equations of nematodynamics and two optical methods: the Berreman optical matrix method [J. Opt. Soc. Am. 62, 502 (1972)] and the discretization of the Maxwell equations based on the finite difference time domain (FDTD) method. Testing the two optical methods with liquid crystal films of different degrees of orientational heterogeneities demonstrates that only the FDTD method is suitable to model this device. Basic substrate-induced texturing process due to protein adsorption gives rise to an orientation correlation function that is nearly linear with the transmitted light intensity, providing a basis to calibrate the device. The sensitivity of transmitted light to film thickness, protein surface coverage, and wavelength is established. A crossover incident light wavelength close to λco≈500nm is found, such that when λ >λco thinner films are more sensitive to the amount of protein surface coverage, while for λ <λco the reverse holds. In addition it is found that for all wavelengths the sensitivity increases with the amount of protein coverage. The integrated device model based on FDTD optical simulations in conjunction with the Landau-de Gennes nematodynamics model provides a rational basis for further progress in liquid crystal biosensor devices.

  14. Instability of liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    An, Ning; Li, Meie; Zhou, Jinxiong

    2016-01-01

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

  15. Liquid crystal filled diffraction gratings

    NASA Astrophysics Data System (ADS)

    Jepsen, Mary Lou

    1997-12-01

    Liquid crystal technology is becoming increasingly important for flat displays in electronics, computers and TV. Most liquid crystal displays currently made have as their basic unit, two flat surfaces each coated with a transparent, conductive layer, between which a thin layer of liquid crystals is sandwiched. The work detailed in this dissertation is based on a modification of the basic liquid crystal unit and studies the properties of structures which consist of certain anisotropic liquid crystals confined between a flat substrate and a corrugated one, each substrate being transparent and having a thin trans-parent conductive coating. Without an applied electric field, the refractive indices of the liquid crystal and corrugated substrate do not match, and thus strong diffraction occurs. When an electric field is applied to the device, the liquid crystals are re-oriented so that the refractive indices now match, and the device behaves as a uniform slab of homogeneous material producing no diffraction. Rigorous coupled wave analysis was developed to design the ideal devices and analyze the performance of our experimental ones. 99% diffraction efficiencies in single wavelength polarized illumination are shown to be possible with this class of devices. The best device we fabricated showed a 62% distraction efficiency, as our fabrication process roughened the top surface of the device so that (≃30%) of the incident light was lost to scatter. Several new fabrication processes are proposed to eliminate this scatter problem, and that details of fabrication processes thus far attempted are outlined.

  16. Magnetoactive Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Winkler, Moritz; Kaiser, Andreas; Krause, Simon; Finkelmann, Heino; Schmidt, Annette

    2008-03-01

    Liquid crystal elastomers (LCEs) offer an interesting spectrum of properties, including temperature induced, fully reversible shape changes connected with considerable development of pulling force, and synthetic diversity. In order to take advantage of LCEs for an extended number of viable devices, it is desirable to trigger such shape changes with electromagnetic fields rather than temperature changes. Magnetoactive LCEs are accessible by the incorporation of superparamagnetic Fe3O4 nanoparticles into oriented nematic side-chain LCEs and offer a contactless activation pathway to activate the nematic-to-isotrope transition by local magnetic heating in external fields due to relaxational processes. In magnetomechanical measurements at 300 kHz and 43 kA.m-1, a sample contraction of up to 30 % is observed under field influence, that is fully released when the field is switched off. The load evolved reaches 60 kPa and more. The materials' ability to respond to a contactless electromagnetic stimulus with a well-defined contraction can be of use for various actuator applications.

  17. Planarization of amorphous silicon thin film transistors for high-aperture-ratio and large-area active-matrix liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Lan, Je-Hsiung

    The reduction of the backlight power consumption and the improvement of the display image uniformity for future large-area and high-resolution active-matrix liquid- crystal displays (AM-LCDs) are very important. One possible method to achieve the former goal is to increase the pixel electrode aperture-ratio. This can be realized by overlapping the pixel electrode with both gate/data buslines. While for the latter, reduction of the RC-delay by using a low resistance gate metal line is the key. Both of these approaches can be realized by using planarization technology. In this dissertation, the planarization technology based on low dielectric constant organic polymer, benzocyclobutene (BCB), is demonstrated, and this technology has been successfully applied to hydrogenated amorphous-silicon (a-Si:H) thin-film transistor (TFT) arrays and thick metal gate buslines/electrodes. Through the planarization technology, a high-aperture-ratio (HAR) pixel electrode structure has been fabricated. The parasitic capacitance and crosstalk issues in the HAR pixel electrode have been studied through interconnect analysis and circuit simulation. The impact of the parasitic capacitance on display performances, such as feedthrough voltage, vertical crosstalk, pixel electrode aperture-ratio, pixel charging behavior, and gate busline RC-delay issues, has been thoroughly discussed. Some key issues during the process integration of the HAR pixel electrode structure have been addressed. These include the BCB contact via formation, the patterning of the ITO pixel electrodes on BCB layer, the selection of Ar plasma treatment conditions for BCB surface, and the optical transmittance evaluation of the ITO/BCB double-layer structure. In addition, the BCB passivation effects on back-channel etched type a-Si:H TFTs have been investigated. It is found that there is no degradation in the TFT electrical performance and reliability after the BCB passivation. Finally, the planarization technology is

  18. Thermotropic liquid crystals from biomacromolecules

    PubMed Central

    Liu, Kai; Chen, Dong; Marcozzi, Alessio; Zheng, Lifei; Su, Juanjuan; Pesce, Diego; Zajaczkowski, Wojciech; Kolbe, Anke; Pisula, Wojciech; Müllen, Klaus; Clark, Noel A.; Herrmann, Andreas

    2014-01-01

    Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components. PMID:25512508

  19. 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.

  20. Liquid crystal nanodroplets in solution

    NASA Astrophysics Data System (ADS)

    Brown, W. Michael; Petersen, Matt K.; Plimpton, Steven J.; Grest, Gary S.

    2009-01-01

    The aggregation of liquid crystal nanodroplets from a homogeneous solution is studied by molecular dynamics simulations. The liquid crystal particles are modeled as elongated ellipsoidal Gay-Berne particles while the solvent is modeled as spherical Lennard-Jones particles. Extending previous studies of Berardi et al. [J. Chem. Phys. 126, 044905 (2007)], we find that liquid crystal nanodroplets are not stable and that after sufficiently long times the nanodroplets always aggregate into a single large droplet. Results describing the droplet shape and orientation for different temperatures and shear rates are presented. The implementation of the Gay-Berne potential for biaxial ellipsoidal particles in a parallel molecular dynamics code is also briefly discussed.

  1. Liquid crystal nanodroplets in solution.

    PubMed

    Brown, W Michael; Petersen, Matt K; Plimpton, Steven J; Grest, Gary S

    2009-01-28

    The aggregation of liquid crystal nanodroplets from a homogeneous solution is studied by molecular dynamics simulations. The liquid crystal particles are modeled as elongated ellipsoidal Gay-Berne particles while the solvent is modeled as spherical Lennard-Jones particles. Extending previous studies of Berardi et al. [J. Chem. Phys. 126, 044905 (2007)], we find that liquid crystal nanodroplets are not stable and that after sufficiently long times the nanodroplets always aggregate into a single large droplet. Results describing the droplet shape and orientation for different temperatures and shear rates are presented. The implementation of the Gay-Berne potential for biaxial ellipsoidal particles in a parallel molecular dynamics code is also briefly discussed. PMID:19191407

  2. Liquid crystal assisted optical fibres.

    PubMed

    Wahle, M; Kitzerow, H-S

    2014-01-13

    Microstructured fibres which consist of a circular step index core and a liquid crystal inclusion running parallel to this core are investigated. The attenuation and electro-optic effects of light coupled into the core are measured. Coupled mode theory is used to study the interaction of core modes with the liquid crystal inclusion. The experimental and theoretical results show that these fibres can exhibit attenuation below 0.16 dB cm(-1) in off-resonant wavelength regions and still have significant electro-optic effects which can lead to a polarisation extinction of 6 dB cm(-1). PMID:24514987

  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. 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.

  5. 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

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

    2014-06-01

    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

  6. 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

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2000-10-01

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

  10. Detection of harmful vapors and biological agents by means of liquid crystals

    NASA Astrophysics Data System (ADS)

    Gustafson, Jon; Shibaev, Petr

    2014-03-01

    Orientation of liquid crystals is determined by surface energy and molecular orientation at the surface. This opens a possibility of exploring liquid crystals as gas sensors. In this work the simple model that takes into account gas concentration, absorption rate and material characteristics of liquid crystals (MBBA and pentylcyanobiphenyl) is experimentally tested in order to determine the sensitivity of the method. Thin films and droplets of chiral and non-chiral liquid crystals were used to detect vapors of volatile organic solvents. It was found that sensitivity of the method depends on the chemical nature of gas and structure of liquid crystal. Modification of liquid crystalline composition by means of additions of specifically tailored compounds (for example, hydrogen bonded acids) can lead to significant increase in sensitivity of liquid crystal to harmful vapors. The method was also tested for detection of biological molecules.

  11. 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.

  12. 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.…

  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. Cooperative liquid-crystal alignment generated by overlaid topography

    NASA Astrophysics Data System (ADS)

    Yi, Youngwoo; Maclennan, Joseph E.; Clark, Noel A.

    2011-05-01

    Nematic and smectic liquid crystals were introduced into μm-scale gaps between plates coated with polymer films nanoimprinted with parallel arrays of rectangular channels. Overlaying the channels on the two plates close enough at a slight angle produces a mosaic of alternating planar and homeotropic alignments and hybrid alignment, showing that complex liquid-crystal orientation patterns can be achieved by combining two simple topographic patterns. These alignment patterns are attributed to spatial variation of surface roughness and 3D topographic structure created by a sufficient proximity of the two patterns.

  15. Cooperative liquid-crystal alignment generated by overlaid topography.

    PubMed

    Yi, Youngwoo; Maclennan, Joseph E; Clark, Noel A

    2011-05-01

    Nematic and smectic liquid crystals were introduced into μm-scale gaps between plates coated with polymer films nanoimprinted with parallel arrays of rectangular channels. Overlaying the channels on the two plates close enough at a slight angle produces a mosaic of alternating planar and homeotropic alignments and hybrid alignment, showing that complex liquid-crystal orientation patterns can be achieved by combining two simple topographic patterns. These alignment patterns are attributed to spatial variation of surface roughness and 3D topographic structure created by a sufficient proximity of the two patterns. PMID:21728557

  16. Structural studies of tubular discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Mindyuk, Oksana Yaroslavovna

    1999-11-01

    Discotic liquid crystals based on the rigid ring-shaped phenylacetylene macrocycle molecule (PAM) are of great interest due to their potential organization into supramolecular channels. We have used high resolution X-ray diffraction to study the structure of pure and doped PAM and to demonstrate that PAM forms a tubular columnar liquid crystal with an unexpected distortion and doubling of the underlying hexagonal lattice. We have doped PAM with different percentages of silver ions and determined that doping did not change peak positions on the powder diffraction data but significantly altered the intensity of the peaks. This implies that the silver ions were most likely intercalated within the channels formed by the PAM molecules, thus leaving the lattice parameters unaffected. We have also used grazing incidence X-ray diffraction and X-ray reflectivity to study Langmuir films of PAM. PAM adopts an "edge-on" molecular arrangement at the air-water interface. We will discuss the direct observation of the structural reorganization within macromolecular Langmuir films of disc-shaped ionophoric molecules arising from interactions with potassium and cesium ions in the subphase. The columnar order is disrupted by CsCl in the subphase and strongly enhanced by KCl in the subphase, thus effectively tailoring the structural properties of the Langmuir films for potential applications. We have also used X-ray reflectivity (XR) and grazing incidence x-ray diffraction (GID) to study Langmuir films of another macrocyclic ionophore: torand (tributyldodecahydrohexaazakekulene, "TBDK") molecules. TBDK is a rigid, triangular molecule; it has been investigated as a potential surface-active complexing agent. The system forms a stable monolayer at the air-water interface and exhibits two distinct structural phases at lower and higher pressures.

  17. Electro- and nonlinear optics of liquid crystals with nano-dopants and nano-structures

    NASA Astrophysics Data System (ADS)

    Williams, Yana Zhang

    Nano materials are useful materials with interesting optical and electronic properties. When combined with liquid crystals, they can improve the optical performance of liquid crystals. On the other hand, liquid crystals are very versatile materials which can be easily incorporated with nanoscale materials, or encapsulated inside nanoscale structures. Combining nano materials with liquid crystals, and studying the optical properties of these composites for the purpose of discovering new materials for low optical power, high resolution, and fast response, is the driving force behind our research. The motivation of this work is presented in Chapter 1 and a brief introduction of liquid crystals and nano materials is presented in Chapter 2. In Chapter 3, we blended photosensitive cadmium selenide (CdSe) nanorods (7nm in diameter, 40nm in length) inside a nematic liquid crystal system. The effective intensity dependent refractive index coefficients are on the order of 10-2 (cm2/ Watt). This is at least 10 times larger than that of undoped liquid crystals. Most importantly, it is a transient process. We also observed one of the lowest electro-optical (E-O) switching threshold voltages from this doped system Vth = 0.78 ( Volts). It is postulated that the photosensitive CdSe nanorods improved the charge generation and charge transportation, as well as permittivity and conductivity anisotropy, of the liquid crystal system. In Chapter 4, a unique 4-beam holographic method in an umbrella configuration is used to successfully fabricate three dimensional photonic structures within polymer dispersed liquid crystals. The resultant 3D structures exhibit multicolor reflection, and are optically characterized by taking transmission spectrum, as well as Bragg diffraction. An electro-optical switching time of tens of milliseconds is obtained from the structures. This tuning ability is achieved by the encapsulated liquid crystal droplets at the nodes of the structures. The fabrication

  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. PMID:27088310

  19. Deformations in chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Shibaev, Petr; Reddy, Kathryn; Bateman, Daniel; Iljin, Andrey

    2014-03-01

    Deformations and their relaxation in chiral liquid crystals are studied experimentally and theoretically in planar geometry for liquid crystalline mixtures of varying viscosities. It is shown by both methods that shear deformation in liquid crystals results in the inclination and extension of cholesteric helix in samples with high viscosity. Stretching deformation results in shrinking cholesteric helix. This leads to a possibility of detecting deformations on a nanometer scale by observing changes in selective reflection spectra. Theoretical model takes into account elastic strain of physical network formed by the entanglements between components of liquid crystalline mixture, viscosity of the matrix and elasticity of the liquid crystalline subsystem. This allows to model mechanical response of the matrix with different viscosities to stretching and shear of various amplitudes. It is shown that relaxation of the cholesteric helix takes much shorter time than mechanical relaxation of the mixtures. The model perfectly agrees with experimental data. The model is compared with theoretical model describing behavior of elastomers.

  20. Bent core liquid crystal elastomers

    SciTech Connect

    Verduzco, R.; DiMasi, E.; Luchette, P.; Ho Hong, S.; Harden, J.; Palffy-Muhoray, P.; Kilbey II, S.M.; Sprunt, S.; Gleeson, G.T. Jakli, A.

    2010-07-28

    Liquid crystal (LC) elastomers with bent-core side-groups incorporate the properties of bent-core liquid crystals in a flexible and self-supporting polymer network. Bent-core liquid crystal elastomers (BCEs) with uniform alignment were prepared by attaching a reactive bent-core LC to poly(hydrogenmethylsiloxane) and crosslinking with a divinyl crosslinker. Phase behavior studies indicate a nematic phase over a wide temperature range that approaches room temperature, and thermoelastic measurements show that these BCEs can reversibly change their length by more than a factor of two upon heating and cooling. Small-angle X-ray scattering studies reveal multiple, broad low-angle peaks consistent with short-range smectic C order of the bent-core side groups. A comparison of these patterns with predictions of a Landau model for short-range smectic C order shows that the length scale for smectic ordering in BCEs is similar to that seen in pure bent-core LCs. The combination of rubber elasticity and smectic ordering of the bent-core side groups suggests that BCEs may be promising materials for sensing, actuating, and other advanced applications.

  1. Optical trapping in liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  2. 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.

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

    DOEpatents

    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.

  4. 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.

  5. 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

  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. 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.

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

    PubMed

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

    2014-03-18

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

  9. Computer simulations of liquid crystals

    NASA Astrophysics Data System (ADS)

    Smondyrev, Alexander M.

    Liquid crystal physics is an exciting interdisciplinary field of research with important practical applications. Their complexity and the presence of strong translational and orientational fluctuations require a computational approach, especially in the studies of nonequlibrium phenomena. In this dissertation we present the results of computer simulation studies of liquid crystals using the molecular dynamics technique. We employed the Gay-Berne phenomenological model of liquid crystals to describe the interaction between the molecules. Both equilibrium and non-equilibrium phenomena were studied. In the first case we studied the flow properties of the liquid crystal system in equilibrium as well as the dynamics of the director. We measured the viscosities of the Gay-Berne model in the nematic and isotropic phases. The temperature-dependence of the rotational and shear viscosities, including the nonmonotonic behavior of one shear viscosity, are in good agreement with experimental data. The bulk viscosities are significantly larger than the shear viscosities, again in agreement with experiment. The director motion was found to be ballistic at short times and diffusive at longer times. The second class of problems we focused on is the properties of the system which was rapidly quenched to very low temperatures from the nematic phase. We find a glass transition to a metastable phase with nematic order and frozen translational and orientational degrees of freedom. For fast quench rates the local structure is nematic-like, while for slower quench rates smectic order is present as well. Finally, we considered a system in the isotropic phase which is then cooled to temperatures below the isotropic-nematic transition temperature. We expect topological defects to play a central role in the subsequent equilibration of the system. To identify and study these defects we require a simulation of a system with several thousand particles. We present the results of large

  10. 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.

  11. Multifunctional Glassy Liquid Crystal for Photonics

    SciTech Connect

    Chen,S.H.

    2004-11-05

    As an emerging class of photonic materials, morphologically stable glassy liquid crystals, were developed following a versatile molecular design approach. Glassy cholesteric liquid crystals with elevated phase-transition temperatures and capability for selective-wavelength reflection and circular polarization were synthesized via determinstic synthesis strategies. Potential applications of glassy cholesteric liquid crystals include high-performance polarizers, optical notch filters and reflectors, and circularly polarized photoluminescence. A glassy nematic liquid crystal comprising a dithienylethene core was also synthesized for the demonstration of nondestructive rewritable optical memory and photonic switching in the sollid state.

  12. 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.

  13. Accurate Optical Detection of Amphiphiles at Liquid-Crystal-Water Interfaces

    NASA Astrophysics Data System (ADS)

    Popov, Piotr; Mann, Elizabeth K.; Jákli, Antal

    2014-04-01

    Liquid-crystal-based biosensors utilize the high sensitivity of liquid-crystal alignment to the presence of amphiphiles adsorbed to one of the liquid-crystal surfaces from water. They offer inexpensive, easy optical detection of biologically relevant molecules such as lipids, proteins, and cells. Present techniques use linear polarizers to analyze the alignment of the liquid crystal. The resulting images contain information not only about the liquid-crystal tilt with respect to the surface normal, the quantity which is controlled by surface adsorption, but also on the uncontrolled in-plane liquid-crystal alignment, thus making the detection largely qualitative. Here we show that detecting the liquid-crystal alignment between circular polarizers, which are only sensitive to the liquid-crystal tilt with respect to the interface normal, makes possible quantitative detection by measuring the transmitted light intensity with a spectrophotometer. Following a new procedure, not only the concentration dependence of the optical path difference but also the film thickness and the effective birefringence can be determined accurately. We also introduce a new "dynamic" mode of sensing, where (instead of the conventional "steady" mode, which detects the concentration dependence of the steady-state texture) we increase the concentration at a constant rate.

  14. Mesomorphism and electrochemistry of thienoviologen liquid crystals.

    PubMed

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

    2015-07-21

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

  15. 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.

  16. 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…

  17. 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…

  18. 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.

  19. RAPID COMMUNICATION: Simultaneous determination of anisotropic thermal conductivities of liquid crystals by means of a photothermal self-diffracting technique

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Shibata, Kazuaki

    2000-11-01

    Anisotropic thermal conductivities of liquid crystals were simultaneously determined by means of a photothermal self-diffracting technique. A single-mode laser beam with Gaussian profile excited refractive index distribution due to the photothermal effect in homogeneously-aligned liquid-crystal films. The refractive index distribution, which is affected by thermal conductivities of liquid crystals, transformed the incident Gaussian beam. The laser beam was self-diffracted and thermal conductivities of liquid crystals were determined by characterizing the beam profile by both Kirchhoff's diffraction theory and heat conduction analysis.

  20. Photoalignment of an azobenzene-based chromonic liquid crystal dispersed in triacetyl cellulose: single-layer alignment films with an exceptionally high order parameter.

    PubMed

    Matsumori, Masaki; Takahashi, Ayami; Tomioka, Yasushi; Hikima, Takaaki; Takata, Masaki; Kajitani, Takashi; Fukushima, Takanori

    2015-06-01

    Single-layer thin alignment films of dye molecules are of growing importance, particularly for state-of-the-art LCD technology. Here we show that a sequential process involving the photoalignment and humidification of a chromonic liquid crystalline azobenzene (brilliant yellow; BY) dispersed in a triacetyl cellulose (TAC) matrix gives a thin alignment film with an exceptionally high order parameter (0.81). Spectroscopic and X-ray diffraction analyses of a BY/TAC composite film in each alignment process revealed that brief humidification triggers restructuring of the BY assembly from 1D nematic-like order to anisotropic 2D columnar order, resulting in the dramatic increase in the order parameter. PMID:25984633

  1. Analog optical phase modulator based on chiral smectic and polymer cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Stockley, Jay E.; Sharp, Gary D.; Serati, Steven A.; Johnson, Kristina M.

    1995-12-01

    A high-speed analog optical phase modulator based on chiral smectic and cholesteric liquid crystals is discussed. The chiral smectic liquid-crystal device functions as a variable-orientation half-wave retarder, whereas the polymer cholesteric liquid-crystal film acts as a polarization-preserving mirror. We use circular Jones calculus to describe optical phase modulation, using a half-wave retarder of variable orientation acting on circularly polarized light. The phase induced by this modulator is achromatic. Analog phase modulation of nearly 360deg is demonstrated with a device switching time of 200 mu s at 25degC .

  2. Liquid crystal device and method thereof

    SciTech Connect

    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.

  3. Generation of fluorescent nanodroplets of liquid crystal utilizing electrospray deposition

    NASA Astrophysics Data System (ADS)

    Ohdaira, Yasuo; Oka, Hisaki; Shinbo, Kazunari; Baba, Akira; Kato, Keizo; Kaneko, Futao

    2016-02-01

    Fluorescent nanodroplets of liquid crystal (LC) were generated by the electrospray deposition of LC solvent containing rhodamine 6G (Rh6G) dye molecules. The shape and density of the nanodroplets strongly depended on the concentration of LC diluted with ethanol solution. The fluorescent spectra from the Rh6G molecules in LC nanodroplets were obviously blue-shifted compared with the LC films of the bulk state. Furthermore, the LC nanodroplets were dispersed on a metallic nanograting formed by optically modifying an azobenzene thin-film layer under the metallic film. The nanodroplets were size-selectively aligned on the metallic nanograting.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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.

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

    PubMed Central

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

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface. PMID:23965955

  12. Domain structures in nematic liquid crystals on a polycarbonate surface.

    PubMed

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

    2013-01-01

    Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface. PMID:23965955

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

    PubMed

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

    2005-01-14

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

  14. Advancements of vertically aligned liquid crystal displays.

    PubMed

    Kumar, Pankaj; Jaggi, Chinky; Sharma, Vandna; Raina, Kuldeep Kumar

    2016-02-01

    This review describes the recent advancements in the field of the vertical aligned (VA) liquid crystal displays. The process and formation of different vertical alignment modes such as conventional VA, patterned VA, multi-domain VA, and polymer stabilised VA etc are widely discussed. Vertical alignment of liquid crystal due to nano particle dispersion in LC host, bifunctional PR-SAM formed by silane coupling reaction to oxide surfaces, azo dye etc., are also highlighted and discussed. Overall, the article highlights the advances in the research of vertical aligned liquid crystal in terms of their scientific and technological aspects. PMID:26800482

  15. Liquid Crystal Cells Based on Photovoltaic Substrates

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  16. 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.

  17. 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.

  18. 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.

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

    PubMed Central

    Mushenheim, Peter C.

    2014-01-01

    We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4′-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field director of the DSCG phase. We determine that this coupling of orientations does not result from either anisometric LC droplet shape or interfacial ionic phenomena but rather is consistent with the influence of van der Waals interactions that arise from the anisotropic polarizabilities of nematic 5CB (Δn = + 0.18) and DSCG (Δn = − 0.02) phases. We also find that it is possible to rotate and uniformly align the nematic droplets by using a weak magnetic field (B ∼ 0.3 T). An analysis of the dynamics of relaxation of the orientations of the 5CB droplets following removal of the magnetic field reveals the DSCG and 5CB droplets to be coupled by energies of ∼104kT, consistent with a simple theoretical estimate of the influence of anisotropic van der Waals interactions. We also observed the nematic 5CB droplets to form dimers and larger assemblies mediated by the elasticity of the nematic DSCG. Overall, these results reveal that LC-in-LC emulsions define a new class of hierarchically ordered soft matter in which both thermotropic and lyotropic LCs are coupled in their ordering. PMID:25278032

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

    PubMed

    Mushenheim, Peter C; Abbott, Nicholas L

    2014-11-21

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

  1. Hybrid graphene nematic liquid crystal light scattering device.

    PubMed

    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

    2015-09-01

    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. PMID:26243047

  2. Graphene-based liquid crystal microlens arrays

    NASA Astrophysics Data System (ADS)

    Hu, Wei; Chen, Cheng; Wu, Yong; Luo, Jun; Lei, Yu; Tong, Qing; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2015-12-01

    In this paper, we design and fabricate a kind of liquid crystal microlens arrays (LCMAs) with patterned electrodes made of monolayer graphene, which is grown on copper sheet by chemical vapor deposition (CVD). Graphene is the first two-dimensional atomic crystal. It uniquely combines extreme mechanical strength, high optically transmittance from visible light to infrared spectrum, and excellent electrical conductivity. These properties make it highly attractive for various applications in photonic devices that require conductive but transparent thin films. The graphene-based LCMAs have shown excellent optical performances in the tests. By adjusting the voltage signal loaded over the graphene-based LCMAs, the point spread functions (PSF) and focusing images of incident laser beams with different wavelengths, could be obtained. At the same time, we also get the focusing images of the common ITO-based LCMAs under the same experimental conditions to discuss the advantages and disadvantages between them. Further, the graphene-based LCMAs are also used in visible imaging. During the imaging tests, the graphene electrodes in the LCMAs work well.

  3. The solution structure of liquid-crystal polymers with small liquid-crystal thermoset maleimides and nadimides

    SciTech Connect

    Hjelm, R.P.; Douglas, E.P.; Benicewicz, B.C.

    1995-03-01

    The solution structure of the deuterated liquid-crystal polyamide polymer (LCP) poly(p-phenylene-2-nitroterephthalamide), alone and mixed with small, rodlike, amide, liquid-crystal molecules (LCT) in N-methyl-2-pyrrolidinone (NMP), is studied using small-angle neutron scattering. Measurements were made as a function of LCP concentration using different LCTs mixed at 20 and 40 wt% relative to LCP. Our motivation for studying this system comes from a need to connect solution structure with film morphology in processing these materials for high-performance molecular composites. Our analysis shows that LCP in NMP forms large domain-like structures. The presence of LCT breaks up the LCP domains into smaller structures, some of which are filamentous LCP-LCT aggregates. This result suggests that the simple entropic description of the solution behavior of mixtures of long and short rods is not adequate in describing systems of this type.

  4. REVIEW ARTICLE: Effects of light on molecular orientation of liquid crystals

    NASA Astrophysics Data System (ADS)

    Simoni, F.; Francescangeli, O.

    1999-10-01

    A review of basic physical phenomena underlying the light-induced molecular reorientation in nematic liquid crystals is presented. A detailed description of the mechanisms of direct optical torque, photoisomerization and photorefractivity and of their effect on the macroscopic order of liquid crystals is reported. The first part of the article deals with the study of reorientation effects in transparent liquid crystalline materials. Here, the effects of photo-induced molecular reorientation are fully interpreted within the framework of classical electrodynamics and standard continuum theory of liquid crystals. We investigate the peculiar properties related to the macroscopic anisotropy and the collective behaviour of liquid crystals that result in extraordinarily large nonlinear optical response. Afterwards, the behaviour of liquid crystals in the presence of light absorption is considered and the related reorientation effects are discussed. We give a review of the wide phenomenology which is met in liquid crystals when doped with absorbing azo-dye molecules. The photoisomerization process that in this case drives the evolution of the dye-liquid crystal mixture consequent to the interaction with the light is discussed in detail. Finally, the relatively new field of photorefractivity in liquid crystals as a source of molecular reorientation is considered. We describe the different mechanisms contributing to the creation of a space-charge field such as conductivity anisotropy, dielectric anisotropy and photocharge production. A theoretical discussion of the fundamental mechanisms regulating the dc-field-assisted optically induced space-charge fields and the optical molecular reorientation in nematic liquid crystal films is also given.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Guided-wave liquid-crystal photonics.

    PubMed

    Zografopoulos, D C; Asquini, R; Kriezis, E E; d'Alessandro, A; Beccherelli, R

    2012-10-01

    In this paper we review the state of the art in the field of liquid-crystal tunable guided-wave photonic devices, a unique type of fill-once, molecular-level actuated, optofluidic systems. These have recently attracted significant research interest as potential candidates for low-cost, highly functional photonic elements. We cover a full range of structures, which span from micromachined liquid-crystal on silicon devices to periodic structures and liquid-crystal infiltrated photonic crystal fibers, with focus on key-applications for photonics. Various approaches on the control of the LC molecular orientation are assessed, including electro-, thermo- and all-optical switching. Special attention is paid to practical issues regarding liquid-crystal infiltration, molecular alignment and actuation, low-power operation, as well as their integrability in chip-scale or fiber-based devices. PMID:22842818

  10. 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)

  11. Multidimensional optics and dynamics of liquid crystals

    NASA Astrophysics Data System (ADS)

    Tang, Shouping

    2007-12-01

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

  12. 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

  13. Electric field generation of Skyrmion-like structures in a nematic liquid crystal.

    PubMed

    Cattaneo, Laura; Kos, Žiga; Savoini, Matteo; Kouwer, Paul; Rowan, Alan; Ravnik, Miha; Muševič, Igor; Rasing, Theo

    2016-01-21

    Skyrmions are particle-like topological objects that are increasingly drawing attention in condensed matter physics, where they are connected to inversion symmetry breaking and chirality. Here we report the generation of stable Skyrmion-like structures in a thin nematic liquid crystal film on chemically patterned patchy surfaces. Using the interplay of material elasticity and surface boundary conditions, we use a strong electric field to quench the nematic liquid crystal from a fully aligned phase to vortex-like nematic liquid crystal structures, centered on patterned patches, which carry two different sorts of topological defects. Numerical calculations reveal that these are Skyrmion-like structures, seeded from the surface boojum topological defects and swirling towards the second confining surface. These observations, supported by numerical methods, demonstrate the possibility to generate, manipulate and study Skyrmion-like objects in nematic liquid crystals on patterned surfaces. PMID:26549212

  14. Molecular Interactions in Monolayers οf Azo Dye/Liquid Crystal Mixtures at Interfaces

    NASA Astrophysics Data System (ADS)

    Bauman, D.; Płóciennik, A.; Inglot, K.

    2009-08-01

    Full Text PDF A study of azo dye/liquid crystal mixtures in monolayers formed at an air-water interface (the Langmuir films) and at a solid surface (the Langmuir-Blodgett films) has been performed. Five azo dyes with various molecular structure and the liquid crystal 4-octyl-4' cyanobiphenyl (8CB) have been used. The dyes have been added to the liquid crystal at various molar fractions. Surface pressure and surface potential versus mean molecular area isotherms for the Langmuir films have been recorded and information about intermolecular interactions at the air-water interface has been obtained. On the basis of electronic absorption measurements for the Langmuir and Langmuir-Blodgett films the conclusions about the ability of dyes molecules to form self aggregates at the interfaces have been drawn. The influence of the dye molecular structure and its concentration on aggregates' geometry has been found.

  15. Optical vortex arrays from smectic liquid crystals.

    PubMed

    Son, Baeksik; Kim, Sejeong; Kim, Yun Ho; Käläntär, K; Kim, Hwi-Min; Jeong, Hyeon-Su; Choi, Siyoung Q; Shin, Jonghwa; Jung, Hee-Tae; Lee, Yong-Hee

    2014-02-24

    We demonstrate large-area, closely-packed optical vortex arrays using self-assembled defects in smectic liquid crystals. Self-assembled smectic liquid crystals in a three-dimensional torus structure are called focal conic domains. Each FCD, having a micro-scale feature size, produces an optical vortex with consistent topological charge of 2. The spiral profile in the interferometry confirms the formation of an optical vortex, which is predicted by Jones matrix calculations. PMID:24663788

  16. Liquid crystals under the spotlight: light based measurements of electrical and flow properties of liquid crystals

    NASA Astrophysics Data System (ADS)

    Bennett, Thomas P.; Proctor, Matthew B.; Kaczmarek, Malgosia; D'Alessandro, Giampaolo

    2015-09-01

    Optical light modulation in photorefractive liquid crystal cells depends strongly on the relative voltage drop across the photoconductive and liquid crystal layers. This quantity can be estimated using the Voltage Transfer Function, a generalization of the standard cross polarized intensity measurements. Another advantage of this new measurement technique is that we can use it to estimate dynamical parameters of the liquid crystal and of the device, either through simple black-box models or using a full Ericksen-Leslie theory. In this latter case we can obtain estimates of some of the viscosities of the liquid crystal.

  17. 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

  18. 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.

  19. Biosensing using smectic and cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Popov, Piotr; Mann, Elizabeth; Jakli, Antal

    2015-03-01

    Liquid-crystal-based biosensors utilize liquid crystal alignment's high sensitivity to the presence of lipids and proteins self-assembled at the liquid crystal/aqueous solution interface. The optical response of the bulk liquid crystal to the interface offers inexpensive, easy optical detection of such biologically relevant molecules. Present technique uses nematic liquid crystal phase state that typically has a planar-to-homeotropic response only. Here we show that smectic and cholesteric phase states of liquid crystals can be used as new sensing modes that can provide additional information or improve the characteristics of a potential biosensor device. Smectic-A phase extends the detection range both toward the lower and higher concentration. Cholesteric phase (nematic with a chiral dopant) may be sensitive to the chirality of biological surface-active molecules such as phospholipids. Additionally, the ``finger-print'' texture of a cholesteric phase may show the differences between biomolecule homologues, thus providing a promising way of distinguishing between subtle differences of hydrocarbon chain or head-group size and structure.

  20. 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)....

  1. 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)....

  2. 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)....

  3. 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)....

  4. 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)....

  5. 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.

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

    PubMed

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

    2015-08-01

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

  7. 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

  8. Nanostructured hybrid materials from aqueous polymer dispersions.

    PubMed

    Castelvetro, Valter; De Vita, Cinzia

    2004-05-20

    Organic-inorganic (O-I) hybrids with well-defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials both for their use as biomimetic composites and because of their potential use in a wide range of technologically advanced as well as more conventional application fields. Their unique features can be exploited or their role envisaged as components of electronic and optoelectronic devices, in controlled release and bioencapsulation, as active substrates for chromatographic separation and catalysis, as nanofillers for composite films in packaging and coating, in nanowriting and nanolithography, etc. A synergistic combination or totally new properties with respect to the two components of the hybrid can arise from nanostructuration, achieved by surface modification of nanostructures, self-assembling or simply heterophase dispersion. In fact, owing to the extremely large total surface area associated with the resulting morphologies, the interfacial interactions can deeply modify the bulk properties of each component. A wide range of starting materials and of production processes have been studied in recent years for the controlled synthesis and characterization of hybrid nanostructures, from nanoparticle or lamellar dispersions to mesoporous materials obtained from templating nanoparticle dispersions in a continuous, e.g. ceramic precursor, matrix. This review is aimed at giving some basic definitions of what is intended as a hybrid (O-I) material and what are the main synthetic routes available. The various methods for preparing hybrid nanostructures and, among them, inorganic-organic or O-I core-shell nanoparticles, are critically analyzed and classified based on the reaction medium (aqueous, non-aqueous), and on the role it plays in directing the final morphology. Particular attention is devoted to aqueous systems and water-borne dispersions which, in addition to being environmentally more acceptable or even a

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

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Nose, Toshiaki

    2016-04-01

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

  10. 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

  11. 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.

  12. Reversible switching of liquid crystal micro-particles in a nematic liquid crystal.

    PubMed

    Imamura, Koki; Yoshida, Hiroyuki; Ozaki, Masanori

    2016-01-21

    Liquid crystal micro-particles are functional materials possessing optical and dielectric anisotropies originating from the arrangement of rod-like molecules within the particles. Although they can be switched by an electric field, particles dispersed in isotropic hosts usually cannot return to their original state, because there is no restoration force acting on the particles. Here, we describe reversible switching of liquid crystal micro-particles by dispersing them in a nematic liquid crystal host. We fabricate square micro-particles with unidirectional molecular alignment and investigate their static and dynamic electro-optic properties by applying an in-plane electric field. The behavior of the micro-particles is well-described by the theoretical model we construct, making this study potentially useful for the development of liquid crystal-liquid crystal particle composites with engineered properties. PMID:26514389

  13. Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip; Tsai, Yun-Yen; Lin, Chi-Wen; Shieh, Han-Ping David

    2006-08-01

    A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 μm pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.

  14. Optical characterization of lyotropic chromonic liquid crystals

    NASA Astrophysics Data System (ADS)

    Liu, Hui

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

  15. Molecular Orientation of Liquid Crystals on Topographic Nanopatterns.

    PubMed

    Ryu, Seong Ho; Yoon, Dong Ki

    2016-07-13

    Controlling the orientation of building blocks in soft matter on the substrate has been a big challenge in material sciences. We have controlled the molecular orientation of liquid crystal (LC) materials on the porous anodic aluminum oxide (AAO) film having hexagonal pore arrays on the top surface. In our method, anchoring conditions can be varied by changing the pore size (Dp) and the porosity (P). As a proof-of-concept, the orientation of smectic A (SmA) structure at different anchoring conditions was successfully controlled in a sandwich cell consisting of AAO and a glass substrate, which has not been successfully controlled by conventional methods. PMID:27322013

  16. 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.

  17. 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.

  18. 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

  19. Liquid-crystal fiber-optic switch.

    PubMed

    Soref, R A

    1979-05-01

    An adjustable access coupler for multimode fiber-optic networks has been constructed, based on the voltage-tunable total-internal-reflection effect in nematic liquid crystals. Fibers are coupled via graded-index rod lenses at normal incidence to flint-glass prisms in contact with a 6-microm liquid-crystal layer. The achromatic four-port switch has a 1.6-dB optical insertion loss, a tap ratio controllable from -4.6 to -48 dB, a directionality of 44 dB, and an operating voltage of 5 to 20 V rms. PMID:19687832

  20. Dynamic Theory of Polydomain Liquid Crystal Elastomers.

    PubMed

    Duzgun, Ayhan; Selinger, Jonathan V

    2015-10-30

    When liquid crystal elastomers are prepared without any alignment, disordered polydomain structures emerge as the materials are cooled into the nematic phase. These polydomain structures are often attributed to quenched disorder in the cross-linked polymer network. As an alternative explanation, we develop a theory for the dynamics of the isotropic-nematic transition in liquid crystal elastomers, and show that the dynamics can induce a polydomain structure with a characteristic length scale, through a mechanism analogous to the Cahn-Hilliard equation for phase separation. PMID:26565497

  1. Electro-osmosis in nematic liquid crystals.

    PubMed

    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. PMID:27575193

  2. 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.

  3. Phase behavior of ionic liquid crystals

    NASA Astrophysics Data System (ADS)

    Kondrat, S.; Bier, M.; Harnau, L.

    2010-05-01

    Bulk properties of ionic liquid crystals are investigated using density functional theory. The liquid crystal molecules are represented by ellipsoidal particles with charges located in their center or at their tails. Attractive interactions are taken into account in terms of the Gay-Berne pair potential. Rich phase diagrams involving vapor, isotropic and nematic liquid, as well as smectic phases are found. The dependence of the phase behavior on various parameters such as the length of the particles and the location of charges on the particles is studied.

  4. Topology and bistability in liquid crystal devices

    SciTech Connect

    Majumdar, A.; Newton, C. J. P.; Robbins, J. M.; Zyskin, M.

    2007-05-15

    We study nematic liquid crystal configurations in a prototype bistable device--the post aligned bistable nematic (PABN) cell. Working within the Oseen-Frank continuum model, we describe the liquid crystal configuration by a unit-vector field n, in a model version of the PABN cell. First, we identify four distinct topologies in this geometry. We explicitly construct trial configurations with these topologies which are used as initial conditions for a numerical solver, based on the finite-element method. The morphologies and energetics of the corresponding numerical solutions qualitatively agree with experimental observations and suggest a topological mechanism for bistability in the PABN cell geometry.

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

    SciTech Connect

    Li Jinhui Gao Song; Duan Huabo; Liu Lili

    2009-07-15

    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 deg. 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{sub 3}:H{sub 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 deg. C.

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

    PubMed

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

    2009-11-26

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

  7. Angular velocity response of nanoparticles dispersed in liquid crystal

    NASA Astrophysics Data System (ADS)

    Huang, Pin-Chun; Shih, Wen-Pin

    2013-06-01

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

  8. 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.

  9. 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.

  10. 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.

  11. 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…

  12. 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.

  13. Annihilation of defects in liquid crystals

    NASA Astrophysics Data System (ADS)

    Svetec, M.; Ambrožič, M.; Kralj, S.

    The annihilation of defect is studied theoretically in liquid crystals (LCs). We consider the annihilation of point disclinations in nematic and line edge dislocations in smectic A LC phase, respectively. We stress qualitative similarities in these processes. The whole annihilation regime is taken into account, consisting of the pre-collision, collision, and post-collision stage.

  14. The Langmuir-Blodgett technique as a tool for homeotropic alignment of fluorinated liquid crystals mixed with arachidic acid.

    PubMed

    Modlińska, Anna; Bauman, Danuta

    2011-01-01

    Some fluoro-substituted liquid crystals mixed with arachidic acid in monolayers formed at air-liquid (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces were investigated. Molecular organization in Langmuir films was determined on the basis of the analysis of the shape of the surface pressure-mean molecular area isotherm and observations made by means of a Brewster angle microscope. It was found that in the compression process the liquid crystal molecules are pushed out towards the top of the first monolayer being in direct contact with the subphase. Langmuir films were transferred onto the quartz substrates at various surface pressures and mono- and multilayered Langmuir-Blodgett films were obtained. The films were characterized using electronic absorption measurements. The conditions for obtaining the homeotropic orientation of the liquid crystal molecules were determined. PMID:21954335

  15. The Langmuir-Blodgett Technique as a Tool for Homeotropic Alignment of Fluorinated Liquid Crystals Mixed with Arachidic Acid

    PubMed Central

    Modlińska, Anna; Bauman, Danuta

    2011-01-01

    Some fluoro-substituted liquid crystals mixed with arachidic acid in monolayers formed at air-liquid (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces were investigated. Molecular organization in Langmuir films was determined on the basis of the analysis of the shape of the surface pressure-mean molecular area isotherm and observations made by means of a Brewster angle microscope. It was found that in the compression process the liquid crystal molecules are pushed out towards the top of the first monolayer being in direct contact with the subphase. Langmuir films were transferred onto the quartz substrates at various surface pressures and mono- and multilayered Langmuir-Blodgett films were obtained. The films were characterized using electronic absorption measurements. The conditions for obtaining the homeotropic orientation of the liquid crystal molecules were determined. PMID:21954335

  16. Electric heating effects in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Yin, Y.; Shiyanovskii, S. V.; Lavrentovich, O. D.

    2006-07-01

    Electric heating effects in the nematic liquid crystal change the liquid crystal physical properties and dynamics. We propose a model to quantitatively describe the heating effects caused by dielectric dispersion and ionic conductivity in the nematic liquid crystals upon the application of an ac electric field. The temperature increase of the liquid crystal cell is related to the properties of the liquid crystal such as the imaginary part of the dielectric permittivity, thermal properties of the bounding plates, and the surrounding medium as well as frequency and amplitude of the electric field. To study the temperature dynamics experimentally, we use a small thermocouple inserted directly into the nematic bulk; we assure that the thermocouple does not alter the thermal behavior of the system by comparing the results to those obtained by a noncontact birefringent probing technique recently proposed by Wen and Wu [Appl. Phys. Lett. 86, 231104 (2005)]. We determine how the temperature dynamics and the stationary value of the temperature increase depend on the parameters of the materials and the applied field. We used different surrounding media, from extremely good heat conductors such as aluminum cooling device to extremely poor conductor, Styrofoam; these two provide two limiting cases as compared to typical conditions of nematic cell exploitation in a laboratory or in commercial devices. The experiments confirm the theoretical predictions, namely, that the temperature rise is controlled not only by the heat transfer coefficient of the surrounding medium (as in the previous model) but also by the thickness and the thermal conductivity coefficient of the bounding plates enclosing the nematic layer. The temperature increase strongly depends on the director orientation and can change nonmonotonously with the frequency of the applied field.

  17. Liquid Crystals: Graphene Oxide Liquid Crystals: Discovery, Evolution and Applications (Adv. Mater. 16/2016).

    PubMed

    Narayan, Rekha; Kim, Ji Eun; Kim, Ju Young; Lee, Kyung Eun; Kim, Sang Ouk

    2016-04-01

    Graphene-oxide liquid crystals (GOLCs) have recently been discovered as a novel 2D material with remarkable properties. On page 3045, S. O. Kim and co-workers review the discovery of different GOLC mesophases and recent progress on fundamental studies and applications. The image displays the nematic schlieren texture (in the background) formed by flowing domains of graphene-oxide liquid crystals and their potential applications in energy storage, optoelectronics and wet-spun fibers. PMID:27105812

  18. 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.

  19. Chiral oily streaks in a smectic-A liquid crystal.

    PubMed

    Nemitz, Ian R; Ferris, Andrew J; Lacaze, Emmanuelle; Rosenblatt, Charles

    2016-08-21

    The liquid crystal octylcyanobiphenyl (8CB) was doped with the chiral agent CB15 and spin-coated onto a substrate treated for planar alignment of the director, resulting in a film of thickness several hundred nm in the smectic-A phase. In both doped and undoped samples, the competing boundary conditions - planar alignment at the substrate and vertical alignment at the free surface - cause the liquid crystal to break into a series of flattened hemicylinders to satisfy the boundary conditions. When viewed under an optical microscope with crossed polarizers, this structure results in a series of dark and light stripes ("oily streaks") of period ∼1 μm. In the absence of chiral dopant the stripes run perpendicular to the substrate's easy axis. However, when doped with chiral CB15 at concentrations up to c = 4 wt%, the stripe orientation rotates by a temperature-dependent angle φ with respect to the c = 0 stripe orientation, where φ increases monotonically with c. φ is largest just below the nematic - smectic-A transition temperature TNA and decreases with decreasing temperature. As the temperature is lowered, φ relaxes to a steady-state orientation close to zero within ∼1 °C of TNA. We suggest that the rotation phenomenon is a manifestation of the surface electroclinic effect: The rotation is due to the weak smectic order parameter and resulting large director tilt susceptibility with respect to the smectic layer normal near TNA, in conjunction with an effective surface electric field due to polar interactions between the liquid crystal and substrate. PMID:27426740

  20. 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.

  1. Development of an Ion Beam Irradiation System for Liquid Crystal Alignment Layer Production

    SciTech Connect

    Matsumoto, Takeshi; Kinoshita, Yuko; Tanii, Masahiro; Tatemichi, Junichi; Konishi, Masashi; Naito, Masao

    2008-11-03

    Ion beam irradiation was employed to produce alignment layers for liquid crystal (LC) displays. The alignment characteristics were compared with those by the conventional rubbing method. Ion incident angle to the films played an important role in LC sample optical qualities. A new ion irradiation method to realize a multi-domain structure for a wide viewing angle was demonstrated.

  2. Self-assembling of molecular nanowires for enhancing the conducting properties of discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Park, Ji Hyun; Kim, Kyung Ho; Takanishi, Yoichi; Yamamoto, Jun; Park, Yung Woo; Kim, Youn Sang; Scalia, Giusy

    2015-08-01

    The self-organization of discotic liquid crystal molecules in columns has enormous interest for soft nanoelectronic applications. A great advantage of discotic liquid crystal is that defects can be self-annealed in contrast to typical organic materials. Through the overlap of molecular orbitals, the aromatic cores assemble into long range ordered one-dimensional structures. Very thin structured films can be obtained by spin-coating from solution and the resulting morphologies are strongly dependent on the interaction between discotics and solvent molecules. Toluene produces films formed by very long nanowires, spontaneously aligned along a common direction and over fairly large areas. These nanostructured films are a result of the interplay between liquid crystal self-organization and solvent driven assembly. The ordered nanowire structures exhibit improvement in the electrical properties compared to misaligned structures and even to pristine HAT5, deposited without the aid of solvent. In this study we show that the toluene-based deposition of discotic liquid crystals is advantageous because it allows a uniform coverage of the substrate, unlike pristine HAT5 but also thanks to the type of induced structures exhibiting one order of magnitude higher conductivity, in the aligned nanowire films, compared to bare HAT5 ones.

  3. 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

  4. Cholesteric liquid crystal photonic crystal lasers and photonic devices

    NASA Astrophysics Data System (ADS)

    Zhou, Ying

    emission is further demonstrated in a hybrid photonic band edge - Fabry-Perot (FP) type structure by sandwiching the CLC active layer within a circular polarized resonator consisting of two CLC reflectors. The resonator generates multiple FP modes while preserving the PBE mode from the active layer. More importantly this band edge mode can be greatly enhanced by the external resonator under some conditions. Theoretical analysis is conducted based on 4x4 transfer matrix and scattering matrix and the results are consistent with our experimental observations. To make the CLC laser more compact and miniaturized, we have developed a flexible polymer laser using dye-doped cholesteric polymeric films. By stacking the mirror reflecting layer, the active layer and the CLC reflecting layer, enhanced laser emission was observed in opposite-handed circular polarization state, because of the light recycling effect. On the other hand, we use the stacked cholesteric liquid crystal films, or the cholesteric liquid crystals and polymer composite films to demonstrate the single film broadband circular polarizers, which are helpful for converting a randomly polarized light into linear polarization. New fabrication methods are proposed and the circular polarizers cover ˜280 nm in the visible spectral range. Both theoretical simulation and experimental results are presented with a good match.

  5. 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)

  6. Orientation of nematic liquid crystal in open glass microstructures

    NASA Astrophysics Data System (ADS)

    Azarinia, H.; Beeckman, J.; Neyts, K.; Schacht, E.; Gironès, J.; James, R.; Fernandez, F. A.

    2009-09-01

    Liquid crystal materials can have bulk reorientation due to surface interaction and are therefore of interest for biosensing applications. We present a setup, with holes etched in a substrate, filled with liquid crystal and covered by a sample fluid. The influence of the depth of the microcavities and the type of liquid on the liquid crystal orientation is investigated by experiments and simulations.

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. Titanium dioxide surface modification via ion-beam bombardment for vertical alignment of nematic liquid crystal.

    PubMed

    Na, Hyun-Jae; Lee, Jin-Woo; Lee, Won-Kyu; Lim, Ji-Hun; Park, Hong-Gyu; Kim, Byoung-Yong; Hwang, Jeong-Yeon; Han, Jeong-Min; Seo, Dae-Shik

    2010-04-15

    We introduce the characteristics of the titanium dioxide (TiO(2)) inorganic film deposited by rf magnetron sputtering for liquid crystal display applications. The TiO(2) films demonstrated vertical alignment (VA) of the liquid crystals (LCs) obtained by using ion-beam (IB) bombardment. As observed by using x-ray photoelectron spectroscopy, the chemical structure of the TiO(2) was changed by IB bombardment, altering the Ti-O bonding of the Ti 2p spectra to lower intensity levels. Breaking Ti-O bonding by IB bombardment created pretilt angles between the TiO(2) film and LC molecules. The better voltage-transmittance characteristics of the VA LCDs based on TiO(2) film were measured and compared with the same characteristics of polyimide film. PMID:20410949

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

    PubMed

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

    2009-06-01

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

  14. 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.

  15. 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.

  16. 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.

  17. Influence of 4-cyano-4'-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces.

    PubMed

    Park, Joon-Seo; Jang, Chang-Hyun; Tingey, Matthew L; Lowe, Aaron M; Abbott, Nicholas L

    2006-12-15

    We report two methods that involve tailoring of the chemical composition of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl to achieve control over the orientational ordering of the liquid crystal on chemically functionalized surfaces. The first method involves the direct addition of 4-cyano-4'-biphenylcarboxylic acid to 4-cyano-4'-pentylbiphenyl. The second method involves exposure of 4-cyano-4'-pentylbiphenyl to ultraviolet light and photochemical generation of a range of products, including 4-cyano-4'-biphenylcarboxylic acid. The addition of the acid or exposure to ultraviolet light accelerated the rate at which the liquid crystal exhibited an orientational transition from planar to perpendicular (homeotropic) alignment on surfaces presenting ammonium groups. The appearance of the homeotropic orientation of the UV-treated 4-cyano-4'-pentylbiphenyl on ammonium-terminated surfaces was dependent on the thickness of the film of liquid crystal (13-50 mum), consistent with a dipolar coupling between the liquid crystal and the electric field associated with an electrical double layer generated at the ammonium surface. Although the addition of 4-cyano-4'-biphenylcarboxylic acid or UV treatment of the liquid crystal also promoted homeotropic orientations on surfaces presenting hydroxyl groups, the orientations of the UV-treated liquid crystal on the hydroxyl-terminated surface did not change with thickness of the film of liquid crystal in the manner observed on the ammonium-terminated surfaces. The latter result indicates that the mechanism leading to homeotropic anchoring on hydroxyl-terminated surfaces is distinct from that on ammonium-terminated surfaces. Measurements performed using polarization modulation infrared reflection-absorption spectroscopy suggest that hydrogen bonding between the 4-cyano-4'-biphenylcarboxylic acid and the hydroxyl-terminated surface is responsible for the homeotropic anchoring on the surface. Finally, the orientation of the liquid

  18. 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.

  19. 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.

  20. Modal liquid crystal array of optical elements.

    PubMed

    Algorri, J F; Love, G D; Urruchi, V

    2013-10-21

    In this study, a novel liquid crystal array based on modal control principle is proposed and demonstrated. The advanced device comprises a six striped electrode structure that forms a configurable 2D matrix of optical elements. A simulation program based on the Frank-Oseen equations and modal control theory has been developed to predict the device electrooptic response, that is, voltage distribution, interference pattern and unwrapped phase. A low-power electronics circuit, that generates complex waveforms, has been built for driving the device. A combined variation of the waveform amplitude and phase has provided a high tuning versatility to the device. Thus, the simulations have demonstrated the generation of a liquid crystal prism array with tunable slope. The proposed device has also been configured as an axicon array. Test measurements have allowed us to demonstrate that electrooptic responses, simulated and empirical, are fairly in agreement. PMID:24150324

  1. Macroscopic dynamics of polar nematic liquid crystals.

    PubMed

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

    2006-08-01

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

  2. Colloidal cholesteric liquid crystal in spherical confinement.

    PubMed

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

    2016-01-01

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

  3. Colloidal cholesteric liquid crystal in spherical confinement

    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

  4. Photoinduced molecular reorientation of absorbing liquid crystals

    NASA Astrophysics Data System (ADS)

    Marrucci, L.; Paparo, D.

    1997-08-01

    The phenomenon of photoinduced molecular reorientation of absorbing nematic liquid crystals is analyzed in a macroscopic general framework and with a specific molecular model. The photoinduced torque responsible for the reorientation is shown to describe a transfer of angular momentum from the molecule center-of-mass degrees of freedom to the rotational ones, mediated by molecular friction. As a consequence, a photoinduced stress tensor is predicted to develop together with the torque in the illuminated fluid. A molecular expression of the photoinduced torque is derived with a rigorous procedure, valid both for a pure material and for a dye-liquid-crystal mixture. This torque expression corrects those reported in previous works on the same subject. The photoinduced torque is evaluated analytically in a simple approximate limit.

  5. 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.

  6. 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.

  7. 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.

  8. 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. PMID:17982514

  9. 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

  10. Liquid crystal phase shifters for space applications

    NASA Astrophysics Data System (ADS)

    Woehrle, Christopher D.

    Space communication satellites have historically relied heavily on high gain gimbal dish antennas for performing communications. Reflector dish antennas lack flexibility in anti-jamming capabilities, and they tend to have a high risk associated to them given the need for mechanical mechanisms to beam steer. In recent years, a great amount of investment has been made into phased array antenna technologies. Phased arrays offer increased signal flexibility at reduced financial cost and in system risk. The problem with traditional phased arrays is the significant program cost and overall complexity added to the satellite by integrating antenna elements that require many dedicated components to properly perform adaptive beam steering. Several unique methods have been proposed to address the issues that plague traditional phase shifters slated for space applications. Proposed approaches range from complex mechanical switches (MEMS) and ferroelectric devices to more robust molecular changes. Nematic liquid crystals offer adaptive beam steering capabilities that traditional phased arrays have; however, with the added benefit of reduced system cost, complexity, and increased resilience to space environmental factors. The objective of the work presented is to investigate the feasibility of using nematic liquid crystals as a means of phase shifting individual phased array elements slated for space applications. Significant attention is paid to the survivability and performance of liquid crystal and associated materials in the space environment. Performance regarding thermal extremes and interactions with charged particles are the primary factors addressed.

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

    PubMed

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

    2016-04-01

    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

  12. 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

  13. 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.

  14. 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.

  15. Liquid-Crystal Photoalignment by Super Thin Azo Dye Layer

    NASA Astrophysics Data System (ADS)

    Li, Xihua; Kozenkov, Vladimir M.; Yeung, Fion Sze-Yan; Xu, Peizhi; Chigrinov, Vladimir G.; Kwok, Hoi-Sing

    2006-01-01

    A novel liquid crystal (LC) photoalignment method, based on a super thin azo dye molecular layer is proposed. The basic idea of this method is to form a very neat textile knitwear and uniform alignment by azo dye layer without spin coating and rubbing processes. The thickness of the alignment layer is smaller than 3 nm, which is much thinner than traditional PI alignment film. In addition to the advantages of a conventional photoalignment method, the use of super thin layer simplifies the alignment procedure, making possible a high electrooptical performance, good photo-tolerance and thermal stability, better adhesion on indium tin oxide (ITO) surface and compatibility with roll-to-roll process.

  16. Effect of nanoconfinement on liquid-crystal polymer chains

    NASA Astrophysics Data System (ADS)

    Micheletti, Davide; Muccioli, Luca; Berardi, Roberto; Ricci, Matteo; Zannoni, Claudio

    2005-12-01

    We apply a Monte Carlo polymerization model for Gay-Berne [J. Chem. Phys. 74, 3316 (1981)] monomers that we have recently introduced [J. Chem. Phys. 121, 9123 (2004)] to investigate with computer simulations the effects of nanoconfinement and anchoring type on the structure of the main-chain liquid-crystal polymers formed in thin films, in the presence of several types of surface alignment: parallel to the interface (random and uniform) or perpendicular to it (homeotropic). We perform first a study of the confined monomers and then we examine the features of the polymer chains obtained from an isotropic or nematic sample. We find a significant effect of the anchoring conditions on the characteristics of the chains and particularly striking differences between planar and homeotropic boundaries. Furthermore, our results indicate that the choice of different anchorings could be used to tune the linearity and degree of polymerization of the chains.

  17. Effect of nanoconfinement on liquid-crystal polymer chains.

    PubMed

    Micheletti, Davide; Muccioli, Luca; Berardi, Roberto; Ricci, Matteo; Zannoni, Claudio

    2005-12-01

    We apply a Monte Carlo polymerization model for Gay-Berne [J. Chem. Phys. 74, 3316 (1981)] monomers that we have recently introduced [J. Chem. Phys. 121, 9123 (2004)] to investigate with computer simulations the effects of nanoconfinement and anchoring type on the structure of the main-chain liquid-crystal polymers formed in thin films, in the presence of several types of surface alignment: parallel to the interface (random and uniform) or perpendicular to it (homeotropic). We perform first a study of the confined monomers and then we examine the features of the polymer chains obtained from an isotropic or nematic sample. We find a significant effect of the anchoring conditions on the characteristics of the chains and particularly striking differences between planar and homeotropic boundaries. Furthermore, our results indicate that the choice of different anchorings could be used to tune the linearity and degree of polymerization of the chains. PMID:16375493

  18. 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.

  19. 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. PMID:23293743

  20. 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

  1. 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.

  2. 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.

  3. Narrowband multispectral liquid crystal tunable filter.

    PubMed

    Abuleil, Marwan; Abdulhalim, Ibrahim

    2016-05-01

    Multispectral tunable filters with high performance are desirable components in various biomedical and industrial applications. In this Letter, we present a new narrowband multispectral tunable filter with high throughput over a wide dynamic range. It is composed from a wideband large dynamic range liquid crystal tunable filter combined with a multiple narrowbands spectral filter made of two stacks of photonic crystals and cavity layer in between. The filter tunes between nine spectral bands covering the range 450-1000 nm with bandwidth <10  nm and throughput >80%. PMID:27128048

  4. 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%.

  5. Liquid crystal alignment in cylindrical microcapillaries

    NASA Astrophysics Data System (ADS)

    Chychłowski, M.; Yaroshchuk, O.; Kravchuk, R.; Woliński, T.

    2011-09-01

    A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

  6. Liquid crystal alignment in cylindrical microcapillaries

    NASA Astrophysics Data System (ADS)

    Chychłowski, M.; Yaroshchuk, O.; Kravchuk, R.; Woliński, T.

    2012-03-01

    A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

  7. Thermal diode made by nematic liquid crystal

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  8. Phase Behavior of Perturbed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Kralj, S.; Kutnjak, Z.; Lahajnar, G.; Svetec, M.

    We study theoretically the combined effect of confinement and randomness on LC phase transitions in orientational (isotropic-nematic) and translational (nematic-smectic A) degrees of ordering. We focus to cases where these transitions are of (very) weakly 1st order. An adequate experimental realisation is, e.g., 8CB liquid crystal confined to a Controlled-Pore Glass matrix. Based on universal responses of "hard" and "soft" continuum fields to distortions we derive how different mechanisms influence qualitative and quantitative characteristics of phase transitions under consideration.

  9. 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.

  10. Molecular reorientation of a nematic liquid crystal by thermal expansion

    PubMed Central

    Kim, Young-Ki; Senyuk, Bohdan; Lavrentovich, Oleg D.

    2012-01-01

    A unique feature of nematic liquid crystals is orientational order of molecules that can be controlled by electromagnetic fields, surface modifications and pressure gradients. Here we demonstrate a new effect in which the orientation of nematic liquid crystal molecules is altered by thermal expansion. Thermal expansion (or contraction) causes the nematic liquid crystal to flow; the flow imposes a realigning torque on the nematic liquid crystal molecules and the optic axis. The optical and mechanical responses activated by a simple temperature change can be used in sensing, photonics, microfluidic, optofluidic and lab-on-a-chip applications as they do not require externally imposed gradients of temperature, pressure, surface realignment, nor electromagnetic fields. The effect has important ramifications for the current search of the biaxial nematic phase as the optical features of thermally induced structural changes in the uniaxial nematic liquid crystal mimic the features expected of the biaxial nematic liquid crystal. PMID:23072803

  11. Diffraction properties of highly birefringent liquid-crystal composite gratings.

    PubMed

    Butler, J J; Malcuit, M S

    2000-03-15

    We have fabricated electrically switchable holographic gratings, using Polaroid Corporation's DMP-128 photopolymer filled with the nematic liquid crystal E7. It is shown that a coupled-wave theory that includes the effects of the birefringence of the liquid crystal must be used to explain the diffraction properties of these anisotropic volume gratings. Furthermore, a detailed comparison of theory and experiment provides information about the alignment of the liquid crystal within the polymer host. PMID:18059899

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

    PubMed

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

    2013-04-01

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

  13. Electrically Tilted Liquid Crystal Display Mode for High Speed Operation

    NASA Astrophysics Data System (ADS)

    Gwag, Jin Seog; Kim, Jae Chang; Yoon, Tae-Hoon

    2006-09-01

    To develop liquid crystal displays suitable for moving picture, a liquid crystal display mode having an electrically tilted phase is proposed. This is realized by initially having a tilted liquid crystal with low bias voltage. We found that its measured response time is in good agreement with numerical calculation obtained using the Erickson-Leslie equation. The falling times were smaller than 10 ms with conventional driving and 6 ms with overdriving.

  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. 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.

  16. Photorefractive conjugated polymer-liquid crystal composites

    SciTech Connect

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

    2000-05-15

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

  17. Liquid crystal-carbon nanotubes mixtures

    NASA Astrophysics Data System (ADS)

    Popa-Nita, V.; Kralj, S.

    2010-01-01

    The self-organizing properties of nematic liquid crystals (LCs) can be used to align carbon nanotubes (CNTs) dispersed in them. In the previous paper [P. van der Schoot, V. Popa-Nita, and S. Kralj, J. Phys. Chem. B 112, 4512 (2008)], we have considered the weak anchoring limit of the nematic LC molecules at the nanotube's surface, where the CNT alignment is caused by the anisotropic interfacial tension of the nanotubes in the nematic host fluid. In this paper, we present the theoretical results obtained for strong enough anchoring at the CNT-LC interface for which the nematic ordering around nanotube is apparently distorted. Consequently, relatively strong long-range and anisotropic interactions can emerge within the system. In order to get insight into the impact of LC ordering on the alignment of nanotubes we treat the two mixture components on the same footing and combine Landau-de Gennes free energy for the thermotropic ordering of the liquid crystal and Doi free energy for lyotropic nematic ordering of carbon nanotubes caused by their mutually excluded volume. The phase ordering of the binary mixture is analyzed as a function of the volume fraction of the carbon nanotubes, the strength of coupling, and the temperature. We find that the degree of ordering of the nanorods can be tuned by raising or lowering the temperature or by increasing or decreasing their concentration.

  18. Nanoscale viscoplastic behavior of smectic liquid crystals and its application in nanolithography

    NASA Astrophysics Data System (ADS)

    Schulz, Benjamin; Steffen, Paul; Bahr, Christian

    2014-02-01

    We report a unique combination of properties of smectic liquid crystal films that can be described as a viscoplastic behavior on the nanoscale: On the one hand, the films preserve imprinted surface patterns despite being permeated by a directed molecular flow of the film material. On the other hand, their surface morphology can easily be manipulated using an atomic force microscopy tip. Our results demonstrate a controlled molecular-scale deposition of material on the film surface, thereby enabling nanolithographic surface modification of a fluid material.

  19. Nanoscale viscoplastic behavior of smectic liquid crystals and its application in nanolithography

    SciTech Connect

    Schulz, Benjamin Steffen, Paul Bahr, Christian

    2014-02-21

    We report a unique combination of properties of smectic liquid crystal films that can be described as a viscoplastic behavior on the nanoscale: On the one hand, the films preserve imprinted surface patterns despite being permeated by a directed molecular flow of the film material. On the other hand, their surface morphology can easily be manipulated using an atomic force microscopy tip. Our results demonstrate a controlled molecular-scale deposition of material on the film surface, thereby enabling nanolithographic surface modification of a fluid material.

  20. 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

  1. Nonlinear optical studies of liquid crystals and polymers

    NASA Astrophysics Data System (ADS)

    Hong, Seok-Cheol

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

  2. Photoinduced extrinsic electrical conduction of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Dedov, O. V.; Krivoschekov, V. A.

    1996-05-01

    During recent years the interest in media with strong nonlinear response is growing. These media allow the user to observe different nonlinear optic effects using small intensities of light. It is well known that liquid crystals are rather promising media for this research. This paper is devoted to the experimental research of the photoinduced conduction of a mixture of a nematic liquid crystal and a dye. Dependence of the conduction on the intensity of light was studied for different concentrations of a dye added to the nematic crystal. Also the problem of the optimum type of a dye for observing the photorefractive nonlinearity using Ar+- ion laser was considered. We made the experiments using the following available laser dyes: rhodamine '6G,' rhodamine 'G,' rhodamine 'C' and two ocsasine-type dyes also. The mixture of the nematic crystal 5CB and a dye was placed in a cell of 100 micrometer width, with the plates filmed with the transparent electrodes of SnO2. The dc voltage on the order of magnitude 1 V was applied to decrease the influence of the cell capacity on the conduction measurements of the samples. We used the light of two wavelengths: lambda1 equals 488 nm, lambda2 equals 514.5 nm. The best dyes for these wavelengths were the rhodamine- type dyes. Taking the other two dyes we observed much smaller effect of influence of the laser radiation on conduction of the samples. Maybe the reason was that the pump wavelength of ocsasine dyes is too far way from the wavelength of the radiation used. So the optimum dye must have the wavelength of the pump near to the wavelength used. Using rhodamine 'C' we obtained the dependencies of the induced conduction on laser light intensity for three different concentrations of the dye.

  3. 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'.

  4. Interfacial study of cell adhesion to liquid crystals using widefield surface plasmon resonance microscopy.

    PubMed

    Soon, Chin Fhong; Khaghani, Seyed Ali; Youseffi, Mansour; Nayan, Nafarizal; Saim, Hashim; Britland, Stephen; Blagden, Nick; Denyer, Morgan Clive Thomas

    2013-10-01

    Widefield surface plasmon resonance (WSPR) microscopy provides high resolution imaging of interfacial interactions. We report the application of the WSPR imaging system in the study of the interaction between keratinocytes and liquid crystals (LC). Imaging of fixed keratinocytes cultured on gold coated surface plasmon substrates functionalized with a thin film of liquid crystals was performed in air using a 1.45NA objective based system. Focal adhesion of the cells adhered to glass and LC were further studied using immunofluorescence staining of the vinculin. The imaging system was also simulated with 2×2 scattering matrix to investigate the optical reflection of the resonant plasmonic wave via the glass/gold/cell and glass/gold/LC/cell layers. WSPR imaging indicated that keratinocytes are less spread and formed distinct topography of cell-liquid crystal couplings when cultured on liquid crystal coated substrates. The simulation indicates that glass/LC shifted the surface plasmon excitation angle to 75.39° as compared to glass/air interface at 44°. The WSPR microcopy reveals that the cells remodelled their topography of adhesion at different interfaces. PMID:23711786

  5. Ultraweak azimuthal anchoring of a nematic liquid crystal on a planar orienting photopolymer

    SciTech Connect

    Nespoulous, Mathieu; Blanc, Christophe; Nobili, Maurizio

    2007-10-01

    The search of weak anchoring is an important issue for a whole class of liquid crystal displays. In this paper we present an orienting layer showing unreached weak planar azimuthal anchoring for 4-n-pentyl-4{sup '}-cyanobiphenyl nematic liquid crystal (5CB). Azimuthal extrapolation lengths as large as 80 {mu}m are easily obtained. Our layers are made with the commercial photocurable polymer Norland optical adhesive 60. The anisotropy of the film is induced by the adsorption of oriented liquid crystal molecules under a 2 T magnetic field applied parallel to the surfaces. We use the width of surface {pi}-walls and a high-field electro-optical method to measure, respectively, the azimuthal and the zenithal anchorings. The azimuthal anchoring is extremely sensitive to the ultraviolet (UV) dose and it also depends on the magnetic field application duration. On the opposite, the zenithal anchoring is only slightly sensitive to the preparation parameters. All these results are discussed in terms of the adsorption/desorption mechanisms of the liquid crystal molecules on the polymer layer and of the flexibility of the polymer network.

  6. 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.

  7. Microscopic theory of liquid crystal rheology

    NASA Astrophysics Data System (ADS)

    Sarman, Sten

    1995-07-01

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

  8. 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

  9. Helical motion of chiral liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takaki; Sano, Masaki

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

  10. Nanoparticles induced multiferroicity in liquid crystal

    NASA Astrophysics Data System (ADS)

    Ganguly, Prasun; Kumar, Ajay; Muralidhar, K.; Biradar, A. M.

    2016-05-01

    Soft multiferroic character has been observed in a ferroelectric liquid crystal (FLC) dispersed with nickel nanoparticles (Ni NPs). A suitable amount of ferromagnetic Ni NPs has been added into FLC material, and the co-existence of ferroelectric and ferromagnetic ordering is examined using P-E and M-H hysteresis measurements. The magnitude of ferromagnetic order is found to depend strongly on the concentration of Ni NPs. Our theoretical approach indicated a strong dependence of helical pitch of FLC on the doping concentration of Ni NPs. We proposed that the intrinsic magnetic field of Ni NPs has been coupled with that of director field of the FLC molecules to result in the observed multiferroic behavior.

  11. Adaptive lens using liquid crystal concentration redistribution

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

  12. Tuning fluidic resistance via liquid crystal microfluidics.

    PubMed

    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

  13. Localized soft elasticity in liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  14. 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).

  15. Cholesteric liquid crystal devices with nanoparticle aggregation.

    PubMed

    Jeng, Shie-Chang; Hwang, Shug-June; Hung, Yu-Hsiang; Chen, Sheng-Chieh

    2010-10-11

    A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. PMID:20941154

  16. 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

  17. 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

  18. 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. PMID:27136779

  19. 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.

  20. 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.

  1. Dendritic Growth in Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Martin, Joshua; Garg, Shila

    2000-03-01

    The experimental study of the onset of electrohydrodynamic convection (EHC) through a dendritic growth is reported. If a magnetic Freedericksz-distorted liquid crystal of negative dielectric anisotropy is subjected to an electric field parallel to the magnetic field, EHC sets in through the nucleation of dendrites [1,2]. Measurements of tip speeds of the dendrites as a function of applied voltage at a fixed magnetic field are made. The goal is to explore the effect of the magnetic and electric fields on the dendritic growth. In addition, pattern dynamics is monitored once the final state of spatio-temporal chaos is reached by the system. [1] J. T. Gleeson, Nature 385, 511 (1997). [2] J. T. Gleeson, Physica A 239, 211 (1997). This research was supported by NSF grants DMR 9704579 and DMR 9619406.

  2. Pseudo-casimir structural force drives spinodal dewetting in nematic liquid crystals

    PubMed

    Ziherl; Podgornik; Zumer

    2000-02-01

    We analyze theoretically the fluctuation-induced force in thin nematic films subject to competing surface interactions, and we find that the force is attractive at small distances and repulsive otherwise. The results provide a consistent interpretation of a recent study of spinodal dewetting of 5CB on a silicon wafer [F. Vandenbrouck et al., Phys. Rev. Lett. 82, 2693 (1999)], implying that this experiment can be regarded as the first observation of the pseudo-Casimir effect in liquid crystals. PMID:11017485

  3. Multiple chiral topological states in liquid crystals from unstructured light beams

    SciTech Connect

    Loussert, Charles; Brasselet, Etienne

    2014-02-03

    It is shown experimentally that unstructured light beams can generate a wealth of distinct metastable defect structures in thin films of chiral liquid crystals. Various kinds of individual chiral topological states are obtained as well as dimers and trimers, which correspond to the entanglement of several topological unit cells. Self-assembled nested assemblies of several metastable particle-like topological states can also be formed. Finally, we propose and experimentally demonstrate an opto-electrical approach to generate tailor-made architectures.

  4. Highly anisotropic conductivity in organosiloxane liquid crystals

    NASA Astrophysics Data System (ADS)

    Gardiner, D. J.; Coles, H. J.

    2006-12-01

    In this paper, we present the conductivity and dielectric characterization of three homologous series of smectic A siloxane containing liquid crystals. The materials studied include one monomesogenic series, which consists of a 4-(ω-alkyloxy)-4'-cyanobiphenyl unit terminated by pentamethyldisiloxane, and two bimesogenic series, which consist of twin 4-(ω-alkyloxy)-4'-cyanobiphenyls joined via tetramethyldisiloxane or decamethylpentasiloxane. All of the compounds exhibit wide temperature range enantiotropic smectic A phases; the effect of the siloxane moiety is to suppress nematic morphology even in the short chain homologs. We find that these compounds exhibit a highly anisotropic conductivity: the value perpendicular to the director is to up to 200 times that parallel to the director. For the nonsiloxane analog 4-(ω-octyl)-4'-cyanobiphenyl (8CB), this value is approximately 2. It is also found that the dielectric anisotropy is reduced significantly; a typical value is ˜1 compared to 8.4 for 8CB. We propose that the origin of these unusual properties is in the smectic structure; the microphase separation of the bulky, globular siloxane moieties into liquidlike regions severely inhibits the mobility parallel to the director and across the smectic layers. Further, the inclusion of this unit acts to increase the antiparallel correlations of molecular dipoles in the aromatic and alkyloxy sublayers, reducing the dielectric anisotropy significantly compared to nonsiloxane analogs. The highly anisotropic conductivity suggests that these materials are particularly suitable for application in electro-optic effects which exploit this property, e.g., the bistable electro-optic effect in smectic A liquid crystals.

  5. Simulation of electrically controlled nematic liquid crystal Rochon prism

    NASA Astrophysics Data System (ADS)

    Buczkowska, M.; Derfel, G.

    2016-09-01

    Operation of an electrically controlled beam steering device based on Rochon prism made by use of nematic liquid crystal is modelled numerically. Deflection angles and angular distribution of light intensity in the deflected beam are calculated. Dynamics of the device is studied. Advantage of application of dual frequency nematic liquid crystal is demonstrated. Role of flexoelectric properties of the nematic is analyzed.

  6. Simulation of a Liquid Crystal at a Polymer Surface

    NASA Astrophysics Data System (ADS)

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

    2002-03-01

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

  7. Liquid-crystal prisms for tip-tilt adaptive optics.

    PubMed

    Love, G D; Major, J V; Purvis, A

    1994-08-01

    Results from an electrically addressed liquid-crystal cell producing continuous phase profiles are presented. The adaptive deflection of a beam of light for use in a tip-tilt adaptive optics system is demonstrated. We compare the optical performance of liquid-crystal prisms with experimental data on atmospheric seeing at the William Herschel Telescope. PMID:19844566

  8. 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.

  9. 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.

  10. 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.

  11. 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…

  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. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  16. Electrically tunable birefringence of a polymer composite with long-range orientational ordering of liquid crystals.

    PubMed

    Choi, Byeongdae; Song, Seongkyu; Jeong, Soon Moon; Chung, Seok-Hwan; Glushchenko, Anatoliy

    2014-07-28

    We report an optical film with electrically tunable birefringence in which the liquid crystals (LCs), mixed with the host polymer, form long-range ordering. The film was prepared through polymerization without phase separation between the LCs and polymers. Driving voltage below 30 V for full switching of birefringence is achieved in a 6 μm-thick film. Electro-optical investigations for the film suggest that the long-range ordering of the LCs mixed in the film caused by polymerization lead to rotations of the LCs as well as optical anisotropy in the film. These films with electrically tunable birefringence could have applications as flexible light modulators and phase retardation films for 2D-3D image switching. PMID:25089422

  17. Plasmonic Photopatterning of Complex Molecular Orientations in Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Guo, Yubing; Jiang, Miao; Peng, Chenhui; Sun, Kai; Yaroshchuk, Oleg; Lavrentovich, Oleg; Wei, Qi-Huo

    Aligning liquid crystal (LC) molecules in spatially non-uniform patterns are highly demanded for applications such as programmable origami and liquid crystal enabled nonlinear electrokinetics. We developed a high resolution projection photoalignment technique for patterning arbitrary LC alignment fields. The photoalignment is based on carefully engineered metasurfaces, or dubbed as plasmonic metamasks (PMMs). When illuminated by light, the PMMs generate patterns of both light intensity and polarization. By projecting the light transmitted through the PMMs onto liquid crystal cells coated with photosensitive materials, alignment patterns predesigned in polarization patterns of the PMMs can be imposed in liquid crystals. This technique makes the liquid crystal alignment a repeatable and scalable process similar to conventional photolithography, promising various applications. National Science Foundation CMMI-1436565.

  18. Insertion of liquid crystal molecules into hydrocarbon monolayers.

    PubMed

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

    2014-08-01

    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'-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. PMID:25106607

  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. 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.

  1. Flexible Nerve Stimulation Electrode with Iridium Oxide Sputtered on Liquid Crystal Polymer

    PubMed Central

    Wang, Kevin; Liu, Chung-Chiun; Durand, Dominique M.

    2009-01-01

    Current electrode designs require flexible substrates that absorb little moisture and provide large charge injection capability. Sputtered iridium oxide films have superior charge injection capabilities versus noble metals and can adhere to various substrates. Liquid crystal polymers (LCP) have very little water absorption compared to other flexible substrates. Therefore, the combination of sputtered iridium oxide film on liquid crystal polymer substrate was studied using 50Hz, 100μs duration, 10mA biphasic current waveforms for 700 hours at 67°C in bicarbonate buffer saline. Scanning electron micrograph (SEM) analysis showed no delamination and approximately 1% of electrode material was lost to the bicarbonate buffer. The charge injection limit and the cathodic charge storage capacity within the water window were 4.6 +/− 1.0mC/cm2 and 31.5 +/− 6.6mC/cm2 respectively. Additional electrochemical analysis revealed significant charge imbalance attributed to oxygen reduction within the water window. These results, along with the flexible, chemically inert, biocompatible substrate, indicate that sputtered iridium oxide films on liquid crystal polymer could become the method of choice for flexible substrate nerve electrodes. PMID:19224713

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

    PubMed

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

    2013-03-01

    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

  3. 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.

  4. Nematic liquid crystal interfaces for chemical and biological detection

    NASA Astrophysics Data System (ADS)

    Most, Darrin R.; VanTreeck, Heidi J.; Grinwald, Bart A.; Kupcho, Kurt A.; Sen, Avijit; Bonds, Michael D.; Anhalt, Karla; Israel, Barbara A.; Acharya, Bharat R.

    2011-03-01

    Nematic liquid crystals (NLCs) have traditionally been used in displays and other electro-optical applications where the orientation of NLC is manipulated by using an external electric field to display the information. In recent years, there have been significant advances in unconventional applications of NLCs in photonics, sensors, and diagnostics. In this paper, the application of NLCs for detection of vapor phase chemicals and biological entities is presented. When NLCs are in contact with another medium (solid, liquid or air) the delicate interplay between the properties of medium and NLCs determines the nature of the alignment assumed by NLCs at the interface. Interfaces functionalized with select chemical or biological entities promote alignment of NLCs in predetermined orientations (perpendicular or parallel to that interface) that are primarily dictated by local interactions at the interface. When these interfaces are exposed to target analytes, the interactions at the interfaces are perturbed and the NLC films undergo orientational transitions from perpendicular to parallel alignment, or vice versa. The orientational transition can be detected by viewing the film of NLCs between crossed polarizers (optical signal) or by measuring the differential capacitance associated with the change in alignment of NLCs (electrical signal). By engineering surfaces with different interfacial properties, sensors based on this principle have been demonstrated to selectively detect a wide variety of chemical and biological analytes that have relevance in industrial hygiene, environmental monitoring, homeland security, diagnostics, and biomedical applications.

  5. Optically and electrically controlled circularly polarized emission from cholesteric liquid crystal materials doped with semiconductor quantum dots.

    PubMed

    Bobrovsky, Alexey; Mochalov, Konstantin; Oleinikov, Vladimir; Sukhanova, Alyona; Prudnikau, Anatol; Artemyev, Mikhail; Shibaev, Valery; Nabiev, Igor

    2012-12-01

    Novel types of electro- and photoactive quantum dot-doped cholesteric materials have been engineered. UV-irradiation or electric field application allows one to control the degree of circular polarization and intensity of fluorescence emission by prepared quantum dot-doped liquid crystal films. PMID:22972420

  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. Achromatic wide-view circular polarizers for a high-transmittance vertically-aligned liquid crystal cell.

    PubMed

    Oh, Seung-Won; Yoon, Tae-Hoon

    2014-08-15

    We propose an optical compensation scheme through which we can eliminate the off-axis light leakage in a vertically-aligned liquid crystal cell with circular polarizers. In this scheme, four uniaxial films with complementary dispersion characteristics are used to compensate one another, resulting in achromatic effective phase retardation for off-axis angles. By using the proposed optical compensation, a contrast ratio higher than 2000:1 can be realized over the entire 55° viewing cone in a multi-domain vertical-alignment liquid crystal cell with circular polarizers. PMID:25121848

  8. 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)

  9. Surface mediated nonlinear optic effects in liquid crystals

    NASA Astrophysics Data System (ADS)

    Merlin, Jessica M.

    Liquid crystals have become a significant part of technology, mainly through their use in the display industry. This is due in part to the fact that the optical properties of liquid crystals are easily manipulated electronically. It has been recognized that the optical properties liquid crystals may also be controlled using light. Because of this, there are other various applications being explored for liquid crystals in photorefraction, optical limiting and switching, and in spatial light modulators. Although, the photorefractive effect was reported in liquid crystals over 10 years ago, there is still controversy over the exact mechanism for the reorientation of the liquid crystal director. This difficulty may be due in part to the fact that it is difficult to characterize the effect using photorefractive measurements and figures of merit. The optical and electronic control of liquid crystals will be studied here using a Friedericksz transition measurement in a twist cell geometry. This type of apparatus was chosen because it leads to a more direct demonstration of the surface effect. Namely, by studying changes in the Friedericksz transition threshold in a twist cell, a more direct observation of changes in the internal field may be observed. First a brief introduction to liquid crystals and their role in technology will be presented. This will be followed by a more rigorous discussion of the physics of liquid crystals and a review of the important literature. The experimental apparatus and the materials and cell geometry used will be described followed by the results of those measurements. Finally, the results will be considered in terms of a model involving interfacial charge and discussed in the context of previous work.

  10. 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.

  11. Helical nanofilaments of bent-core liquid crystals with a second twist.

    PubMed

    Zhang, C; Diorio, N; Lavrentovich, O D; Jákli, A

    2014-01-01

    The B4 phase of bent-core liquid crystals has been shown to be an assembly of twisted layers stacked to form helical nanofilaments. Interestingly, some of them have structural colours that cannot be explained by the nanofilaments alone. Here cryogenic-transmission electron microscopy observations on 40-120 nm films of four bent-core liquid crystal materials show that the filaments are present even in contact with a carbon substrate with only minor deformation, thus representing bulk properties. We find that the subsequent arrays of nanofilaments are not parallel to each other, but rotate by an angle of 35-40° with respect to each other. This doubly twisted structure can explain the structural colour. Being principally different from the packing of molecules in the twist grain boundary and blue phases, the double-twist structure of helical nanofilaments expands the rich word of nanostructured organic materials. PMID:24548912

  12. Experimental study of de Vries properties in antiferroelectric smectic liquid crystals.

    PubMed

    Sandhya, K L; Panarin, Yu P; Panov, V P; Vij, J K; Dabrowski, R

    2008-12-01

    Results of the experimental study on different antiferroelectric liquid crystal (AFLC) materials are presented using a number of techniques such as the optical birefringence, electro-optics and the measurements of optical thickness of free-standing films. Despite differences in the molecular structures of the various AFLC materials studied, these are found to exhibit a de Vries type of smecticA (SmA) properties in a temperature range higher than SmC. This correlation leads to the conclusion that these two classes of liquid crystals are related to each other. Furthermore, we suggest that these arise from the same physical mechanism, namely the existence of the weak synclinic (or reduced anticlinic) correlations between the neighbouring molecular tilt directions. PMID:19104855

  13. 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.

  14. Length Selection in Dendritic Growth of Electrohydrodynamic Convection in a Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Gheorghiu, Nadina; Gleeson, J. T.

    2001-03-01

    Dendritic growth of electrohydrodynamic convection (EHC) with parallel magnetic field in a nematic liquid crystal (NLC) has been already subjected to one important experiment (J.T.Gleeson, Nature, 385, 511 (1997)). Further exploration of this interesting pattern-forming system is presented here. The most important question is: What sets the length scale for the dendrite? In order to find this, we use two control parameters in our experiment: the thickness d of the liquid crystal film, and the intensity H of the magnetic field. The first one is proportional to the pattern wavelength in the traditional EHC experiment, while the second determines the distance of externally imposed anisotropy, the magnetic coherence length ξ_m. By systematically varying d and ξ_m, we relate these two imposed lengths to those that characterize the dendrite: the tip radius of curvature ρ and the interface width w. An estimate of the critical field HC for the subcritical bifurcation is also provided.

  15. Magneto-optic garnet and liquid crystal optical switches

    NASA Technical Reports Server (NTRS)

    Krawczak, J. A.; Torok, E. J.; Harvey, W. A.; Hewitt, F. G.; Nelson, G. L.

    1984-01-01

    Magnetic stripe domain and liquid crystal devices are being developed and evaluated as fiber optic switches that can be utilized for nonblocking type nxm optical matrix switches in networking and optical processing. Liquid crystal switches are characterized by very low insertion loss and crosstalk, while stripe domain switches commutate in less than one microsecond. Both switches operate on multimode, randomly polarized fiber light with potentially large values for (n,m). The applications of these magnetic stripe domain and liquid crystal devices are discussed.

  16. 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.

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

    DOEpatents

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

    1991-01-01

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

  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. Infrared cylindrical cloak in nanosphere dispersed liquid crystal metamaterial.

    PubMed

    Pawlik, G; Tarnowski, K; Walasik, W; Mitus, A C; Khoo, I C

    2012-06-01

    We present a design of an infrared cylindrical cloak using nanosphere dispersed nematic liquid crystal (NLC) metamaterial following the approach of Smith's group [Science 314, 977 (2006)]. Cloaking conditions require spatial distribution of liquid crystal birefringence with constant extraordinary index of refraction and radially dependent ordinary index of refraction. An approximate analytical formula for the latter is derived. Finite element (FE) simulations confirm the cloaking effect. Owing to the tunable birefringence of the liquid crystal component, such cloaking material offers the interesting possibilities of real-time control of invisibility. The possibility of experimental realization is briefly discussed. PMID:22660049

  20. Thermochromic liquid crystals in heat transfer research

    NASA Astrophysics Data System (ADS)

    Stasiek, Jan A.; Kowalewski, Tomasz A.

    2002-06-01

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

  1. Surface Dipole Control of Liquid Crystal Alignment.

    PubMed

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

    2016-05-11

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

  2. Blue-phase liquid crystal droplets

    PubMed Central

    Martínez-González, José A.; Zhou, Ye; Rahimi, Mohammad; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    Blue phases of liquid crystals represent unique ordered states of matter in which arrays of defects are organized into striking patterns. Most studies of blue phases to date have focused on bulk properties. In this work, we present a systematic study of blue phases confined into spherical droplets. It is found that, in addition to the so-called blue phases I and II, several new morphologies arise under confinement, with a complexity that increases with the chirality of the medium and with a nature that can be altered by surface anchoring. Through a combination of simulations and experiments, it is also found that one can control the wavelength at which blue-phase droplets absorb light by manipulating either their size or the strength of the anchoring, thereby providing a liquid–state analog of nanoparticles, where dimensions are used to control absorbance or emission. The results presented in this work also suggest that there are conditions where confinement increases the range of stability of blue phases, thereby providing intriguing prospects for applications. PMID:26460039

  3. Hydrogen-Bonded Liquid Crystal Nanocomposites.

    PubMed

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

    2016-08-23

    Nanoparticle-liquid crystal (NP-LC) composites based on hydrogen bonding were explored using a model system. The ligand shells of 3 nm diameter zirconium dioxide nanoparticles (ZrO2 NPs) were varied to control their interaction with 4-n-hexylbenzoic acid (6BA). The miscibility and effect of the NPs on the nematic order as a function of particle concentration was characterized by polarized optical microscopy (POM), fluorescence microscopy and (2)H NMR spectroscopy. Nonfunctionalized ZrO2 NPs have the lowest miscibility and strongest effect on the LC matrix due to irreversible binding of 6BA to the NPs via a strong zirconium carboxylate bond. The ZrO2 NPs were functionalized with 6-phosphonohexanoic acid (6PHA) or 4-(6-phosphonohexyloxy)benzoic acid (6BPHA) which selectively bind to the ZrO2 NP surface via the phosphonic acid groups. The miscibility was increased by controlling the concentration of the pendant CO2H groups by adding hexylphosphonic acid (HPA) to act as a spacer group. Fluorescence microscopy of lanthanide doped ZrO2 NPs showed no aggregates in the nematic phase below the NP concentration where aggregates are observed in the isotropic phase. The functionalized NPs preferably concentrate into LC defects and any remaining isotropic liquid but are still present throughout the nematic liquid at a lower concentration. PMID:27466705

  4. Liquid Crystal Phases of Semiflexible Polymers

    NASA Astrophysics Data System (ADS)

    Mackay, Ian; Sullivan, Don

    2012-02-01

    Liquid crystal polymers exhibit orientational order (nematic phase) and position order (smectic phase). Previous work on semiflexible polymers using self consistent field theory studied the isotropic-nematic and nematic-smectic transition for homogenous and diblock copolymers. The nematic phase is stabilized by excluded-volume effects between wormlike cylindrical segments. The smectic phase is further stabilized by excluded-volume effects between terminal end segments. Because models of semiflexible polymers include orientational degrees of freedom, in addition to the usual positional degrees of freedom, they are computationally more demanding to study. Spectral decomposition applied to segment orientations has previously been used to make computation feasible. However this method does not converge well for strongly ordered states, which arise in many real systems. I describe a Crank-Nicolson finite difference method applied to the orientations which is expected to converge well for highly ordered systems. This method also exhibits better numerical stability and accuracy and may thus serve as a better foundation for further studies of highly ordered systems. I also describe a modification to the spectral method which can compute the tilted Smectic C phase.

  5. Localized soft elasticity in liquid crystal elastomers.

    PubMed

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

    2016-01-01

    Synthetic approaches to prepare designer materials that localize deformation, by combining rigidity and compliance in a single material, have been widely sought. Bottom-up approaches, such as the self-organization of liquid crystals, offer potential advantages over top-down patterning methods such as photolithographic control of crosslink density, relating to the ease of preparation and fidelity of resolution. Here, we report on the directed self-assembly of materials with spatial and hierarchical variation in mechanical anisotropy. The highly nonlinear mechanical properties of the liquid crystalline elastomers examined here enables strain to be locally reduced >15-fold without introducing compositional variation or other heterogeneities. Each domain (⩾0.01 mm(2)) exhibits anisotropic nonlinear response to load based on the alignment of the molecular orientation with the loading axis. Accordingly, we design monoliths that localize deformation in uniaxial and biaxial tension, shear, bending and crack propagation, and subsequently demonstrate substrates for globally deformable yet locally stiff electronics. PMID:26902873

  6. Liquid Crystal Ordering of Random DNA Oligomers

    NASA Astrophysics Data System (ADS)

    Bellini, Tommaso; Zanchetta, Giuliano; Fraccia, Tommaso; Cerbino, Roberto; Tsai, Ethan; Moran, Mark; Smith, Gregory; Walba, David; Clark, Noel

    2012-02-01

    Concentrated solutions of DNA oligomers (6 to 20 base pairs) organize into chiral nematic (NEM) and columnar (COL) liquid crystal (LC) phases. When the oligomer duplexes are mixed with single strands, LC phase formation proceeds through macroscopic phase separation, as a consequence of the combination of various self-assembly processes including strand pairing, reversible linear aggregation, demixing and LC ordering. We extended our investigation to the case of LC ordering in oligonucleotides whose sequences are partially or entirely randomly chosen, and we observed LC phases even in entirely random 20mers, corresponding to a family of 4^20 10^12 different sequences. We have tracked the origin of this behaviour: random sequences pair into generally defected duplexes, a large fraction of them terminating with stretches of unpaired bases (overhangs); overhangs promote linear aggregation of duplexes, with a mean strength depending on the overhang length; LC formation is accompanied by a phase separation where the duplexes with longer overhangs aggregate to form COL LC domains that coexist with an isotropic fluid rich in duplexes whose structure cannot aggregate.

  7. Liquid crystal polyester-carbon fiber composites

    NASA Technical Reports Server (NTRS)

    Chung, T. S.

    1984-01-01

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

  8. Optically rewritable 3D liquid crystal displays.

    PubMed

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

    2014-11-01

    Optically rewritable liquid crystal display (ORWLCD) is a concept based on the optically addressed bi-stable display that does not need any power to hold the image after being uploaded. Recently, the demand for the 3D image display has increased enormously. Several attempts have been made to achieve 3D image on the ORWLCD, but all of them involve high complexity for image processing on both hardware and software levels. In this Letter, we disclose a concept for the 3D-ORWLCD by dividing the given image in three parts with different optic axis. A quarter-wave plate is placed on the top of the ORWLCD to modify the emerging light from different domains of the image in different manner. Thereafter, Polaroid glasses can be used to visualize the 3D image. The 3D image can be refreshed, on the 3D-ORWLCD, in one-step with proper ORWLCD printer and image processing, and therefore, with easy image refreshing and good image quality, such displays can be applied for many applications viz. 3D bi-stable display, security elements, etc. PMID:25361316

  9. Molecular wires from discotic liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  10. Structural Transitions in Cholesteric Liquid Crystal Droplets.

    PubMed

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A; Rahimi, Mohammad; Roberts, Tyler F; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L; de Pablo, Juan J

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates. PMID:27249186

  11. Localized soft elasticity in liquid crystal elastomers

    PubMed Central

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

    2016-01-01

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

  12. Colloidal particles embedded in liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Melchert, Drew; Sadati, Monirosadat; Zhou, Ye; de Pablo, Juan J.

    In this work, we encapsulate polystyrene and silica particles in nematic liquid crystal (LC) droplets dispersed in water using microfluidic glass capillary devices. While polystyrene particles induce planar anchoring on the surface, silica particles, treated with DMOAP, create homeotropic anchoring of the LC molecules at their surface. Sodium dodecyl sulfate (SDS) is added to the aqueous phase to stabilize LC droplets and promote a radial configuration with point defect in the center of LC droplet. Our experimental and computational studies show that, when trapped inside the LC droplets, particles with both anchoring types become mostly localized at the defect point (at the center) and interact with the radial configuration. Interestingly, a twisting structure is observed for polystyrene particle with strong planar anchoring. Although localization of the particles at the droplet center is the most stable state and with the lowest free energy, off-center positions also emerge, displacing the defect point from the center to near the surface of a radial droplet. - Corresponding author - Second affiliation: Argonne National Laboratory, Argonne, IL 60439, USA.

  13. Lenticular arrays based on liquid crystals

    NASA Astrophysics Data System (ADS)

    Urruchi Del Pozo, V.; Algorri Genaro, J. F.; Sánchez-Pena, J. M.; Geday, M. A.; Arregui, X. Q.; Bennis, N.

    2012-09-01

    Lenticular array products have experienced a growing interest in the last decade due to the very wide range of applications they can cover. Indeed, this kind of lenses can create different effects on a viewing image such as 3D, flips, zoom, etc. In this sense, lenticular based on liquid crystals (LC) technology is being developed with the aim of tuning the lens profiles simply by controlling the birefringence electrically. In this work, a LC lenticular lens array has been proposed to mimic a GRIN lenticular lens array but adding the capability of tuning their lens profiles. Comb control electrodes have been designed as pattern masks for the ITO on the upper substrate. Suitable high resistivity layers have been chosen to be deposited on the control electrode generating an electric field gradient between teeth of the same electrode. Test measurements have allowed us to demonstrate that values of phase retardations and focal lengths, for an optimal driving waveform, are fairly in agreement. In addition, results of focusing power of tuneable lenses were compared to those of conventional lenses. The behaviour of both kinds of lenses has revealed to be mutually similar for focusing collimated light and for refracting images.

  14. Liquid crystal filled surface plasmon resonance thermometer.

    PubMed

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

    2016-05-16

    A novel surface plasmon resonance (SPR) thermometer based on liquid crystal (LC) filled hollow fiber is demonstrated in this paper. A hollow fiber was internally coated with silver and then filled with LC. The SPR response to temperature was studied using modeling and verified experimentally. The results demonstrated that the refractive index of LC decreases with the increasing temperature and the variation can be detected by the resonance wavelength shift of the plasmon resonance. The temperature sensitivities were 4.72 nm/°C in the temperature range of 20 to 34.5 °C and 0.55 nm/°C in the temperature range of 36 to 50 °C, At the phase transition temperature between nematic and isotropic phases of the LC, the temperature sensitivity increased by one order of magnitude and a shift of more than 46 nm was observed with only a 1.5 °C temperature change. This sensor can be used for temperature monitoring and alarming, and can be extended for other physical parameter measurement. PMID:27409911

  15. Infrared shutter using cholesteric liquid crystal.

    PubMed

    Choi, Gyu Jin; Jung, Hye Min; Lee, Seung Hee; Gwag, Jin Seog

    2016-06-01

    In this paper, we propose an infrared light shutter device using cholesteric liquid crystals. The pitch of the device corresponds to the wavelengths of the infrared region with a strong thermal effect. This device is intended for use as a smart window to maintain an optimal indoor temperature by controlling the infrared radiation coming from the sun. The proposed cholesteric device switches between the planar state and the isotropic state by controlling the temperature using an electrically heated transparent electrode made of indium tin oxide. A window with a planar state that reflects infrared radiation would be used mainly in the summer, while the isotropic state that transmits infrared would be applied in the winter. The proposed device produced a variety of gray levels of transmittance based on the temperature, and thus it can provide the proper temperature for each user. The easy fabrication process gives it appeal as a functional device in the smart window market, and it compares favorably with previous light shutter devices. The infrared shutter is expected to be useful for next-generation window applications. PMID:27411200

  16. Liquid crystal elastomer strips as soft crawlers

    NASA Astrophysics Data System (ADS)

    DeSimone, Antonio; Gidoni, Paolo; Noselli, Giovanni

    2015-11-01

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

  17. Disassembly and characterization of liquid crystal screens.

    PubMed

    Juchneski, Nichele C F; Scherer, Janine; Grochau, Inês H; Veit, Hugo M

    2013-06-01

    The technology used in the manufacturing of televisions and monitors has been changing in recent years. Monitors with liquid crystal displays (LCD) emerged in the market with the aim of replacing cathode ray tube monitors. As a result, the disposal of this type of product, which is already very high, will increase. Thus, without accurate knowledge of the components and materials present in an LCD monitor, the recycling of materials, such as mercury, thermoplastic polymers, glasses, metals and precious metals amongst others, is not only performed, but allows contamination of soil, water and air with the liberation of toxic compounds present in this type of waste when disposed of improperly. Therefore, the objective of this study was to disassemble and characterize the materials in this type of waste, identify the composition, amount and form to enable, in further work, the development of recycling routes. After various tests and analyses, it was observed that an LCD display can be recycled, provided that precautions are taken. Levels of lead, fluoride and copper are above those permitted by the Brazilian law, characterizing this residue as having a high pollution potential. The materials present in printed circuit boards (base and precious metals)-thermoplastics, such as polyethylene terephthalate, acrylic, acrylonitrile butadiene styrene and polycarbonate and metals, such as steel and aluminum, and a layer of indium (in the internal face of the glass)-are components that make a point in terms of their potential for recycling. PMID:23615511

  18. Isotropization of nematic liquid crystals by TMDSC

    SciTech Connect

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

    1997-12-01

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

  19. Thermal Evaporation versus Spin-Coating: Electrical Performance in Columnar Liquid Crystal OLEDs.

    PubMed

    Eccher, Juliana; Zajaczkowski, Wojciech; Faria, Gregório C; Bock, Harald; von Seggern, Heinz; Pisula, Wojciech; Bechtold, Ivan H

    2015-08-01

    The electrical responses of a columnar liquid crystal (a diimidodiester derivative of benzo[ghi]perylene) deposited either by spin-coating or by thermal evaporation into a typical OLED device are compared. For the spin-coated film, homeotropic alignment was induced by thermal annealing, which enhanced the charge carrier mobility significantly. For the evaporated films, homeotropic alignment could not be obtained by annealing. However, a degree of rectification higher than 3 orders of magnitude was achieved, even without annealing, with an electrical response similar to the response of the aligned spin-coated film. A trap-limited space-charge-limited current model was used to extract the charge carrier mobility directly from the current-voltage curves. Grazing incidence wide-angle X-ray scattering confirmed the homeotropic alignment of the annealed spin-coated film, whereas the columns are mostly oriented parallel to the surface in the evaporated case. In a field-effect transistor with bottom-gate bottom-contact geometry, the evaporated film exhibited a typical behavior of an n-type transistor. The degree of intermolecular order is thereby strongly dependent on the deposition method where vacuum deposition leads to a higher order. This higher order, however, impedes reorientation by annealing of the evaporated film but leads to improved charge transport between the electrodes even without homeotropic alignment of columnar liquid crystal. PMID:26168313

  20. Surface-polymer stabilized liquid crystals with dual-frequency control.

    PubMed

    Minasyan, Amalya; Galstian, Tigran

    2013-08-01

    Dual-frequency control liquid crystal (LC) and thin reactive mesogen (RM) films, cast on internal surfaces of cell substrate, are used to build surface polymer stabilized structures. Electric field of high frequency is used to orient the LC molecules by the negative dielectric torque prior to the photopolymerization of RM films. Electro-optic characterization results show that the contrasts of light scatter modulation and polarization dependence are noticeably improved by the dual-frequency control. However, there is no significant shortening in the full cycle duration of excitation-relaxation-excitation. PMID:23913090