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Subject: search.filters.subject.liquid crystals

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Now showing 1 - 10 of 30
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    A biosensor of high-density lipoprotein of human serum on a liquid crystal and polymer composite film
    (2013-01-01)
    Lin, Yi-Hsin
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    Chang, Kai-Han
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    Chu, Wei-Lin
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    Tsou, Yu-Shih
    ;
    Wu, Li-Ching
    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.
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    Electro-optically and all optically addressed spatial light modulator devices based on organic-inorganic hybrid structures
    (2017-01-01)
    Marinova, Vera
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    Lin, Shiuan Huei
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    Hsu, Ken Yuh
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    電子物理學系
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    光電工程學系
    The paper reviews two types of organic-inorganic hybrid structures: electro-optically addressed and all optically addressed that can be used as spatial light modulator devices, operating in a transmission mode. Both hybrid devices are assembled by inorganic Bi12SiO20 (BSO) crystals and organic liquid crystals (LC). The electro-optically controlled device demonstrates very high beam-amplification values at Raman-Nath regime of diffraction whereas all optically controlled device operates at Bragg matched regime of diffraction allowing sub-micron spatial resolution. Phase modulation ability has been demonstrated supporting possibilities for applications in adaptive optics, information processing and display technologies.
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    Liquid-Crystal Terahertz Quarter-Wave Plate Using Chemical-Vapor-Deposited Graphene Electrodes
    (2015-12-01)
    Yang, Chan-Shan
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    Kuo, Chun
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    Tang, Chiu-Chun
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    Chen, J. C.
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    Pan, Ru-Pin
    Quarter-wave operation or a phase shift of more than pi/2, which is approximately ten times greater than that reported in previous works using liquid crystals (LCs) and graphene electrodes, was demonstrated. The device is transparent to the terahertz (THz) wave, and the driving voltage required was as low as approximately 2.2 V (rms), which is also unprecedented. Experimental results supported a theoretical formalism adapted for LC cells with THz wavelength-scale thickness. The scattering rate, DC mobility, and carrier mean free path of bilayer graphene were also determined using THz spectroscopic techniques; the parameters were inferior to those of monolayer graphene. This observation can be attributed to the higher density of charged impurities in the bilayer graphene. The device performances of LC phase shifters using monolayer and bilayer graphene as electrodes were essentially identical.
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    Recent advances in liquid-crystal THz filters
    (2018-01-01)
    Huang, Chia-Yi
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    Chen, Wei-Yuan
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    Chiu, Jing-Ya
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    Chang, Hsiao-Shan
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    Liu, Jia-Kai
    Liquid crystal polymer (LCP) films are rolled into hollow cylinders. The hollow cylinders are measured by a terahertz spectrometer. Experimental results reveal that the transmittance spectra of the hollow cylinders have peaks at specific frequencies due to Fabry-Perot resonance, and the frequencies of the peaks can be tuned by changing the thicknesses and rolled layers of the LCP films. Therefore, the rolled LCP films can be used to develop terahertz filters.
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    Unique Supramolecular Liquid-Crystal Phases with Different Two-Dimensional Crystal Layers
    (2018-10-08)
    Hu, Yi
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    Wu, Kuan-Yi
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    Zhu, Tiantian
    ;
    Shen, Peng
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    Zhou, Yi
    We report herein a series of tetrablock-mimic azobenzene-containing [60]fullerene dyads that form supramolecular liquid crystals (LCs) from phase-segregated two-dimensional (2D) crystals. The unique double-, triple-, and quadruple-layer packing structure of fullerenes in the 2D crystals leads to different smectic supramolecular LC phases, and novel LC phase transitions were observed upon changes in the fullerene packing layer number in the 2D crystals. Interestingly, by combining the LC properties with 2D crystals, these materials show excellent electron mobility in the order of 10(-3) cm(2) V-1 s(-1), despite their relatively low fullerene content. Our results provide a novel method to manipulate 2D crystal layer thickness, with promising applications in optoelectronic devices.
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    Three-dimensional/two-dimensional convertible display based on computer-generated holograms and an amplitude-modulated spatial light modulator
    (2018-06-01)
    Matoba, Osamu
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    Lin, Wen-Kai
    ;
    Hsiao, Fu-Li
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    Huang, Chi-Yen
    ;
    Lin, Bor-Shyh
    A three-dimensional/two-dimensional (3-D/2-D) convertible display was proposed. The display system offers 2-D images via the traditional display technology and offers 3-D images via the computer-generated hologram (CGH) technology. In this system, 2-D and 3-D images are generated from the same amplitude-modulated spatial light modulator (SLM). In the 2-D display mode, the panel displays an amplitude-modulated image and the 2-D image is projected on a polarization-dependent diffuser (PD) screen. In the 3-D display mode, the SLM panel displays CGHs to generate 3-D images. The zero-order diffraction of the amplitude-type CGH will be blocked by a spatial filter (SF), which is designed by a polarizer. Furthermore, a liquid crystal element was employed to modulate the polarization state of the reconstructed light to let the 3-D image quality not to be reduced by the PD. Finally, the proposed system can offer 2-D and 3-D images both clearly. The system suppresses the zero-order diffraction noise of the amplitude-type CGH system successfully. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    Twisted Nematic Liquid-Crystal-Based Terahertz Phase Shifter using Pristine PEDOT: PSS Transparent Conducting Electrodes
    (2019-02-02)
    Sahoo, Anup Kumar
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    Yang, Chan-Shan
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    Yen, Chun-Ling
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    Lin, Hung-Chun
    ;
    Wang, Yu-Jen
    For this study, we demonstrated three different types of twisted nematic (TN) liquid crystal (LC) terahertz (THz) phase shifters using pristine poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) thin films as transparent conducting electrodes (TCEs). The transmittance of spin-coated pristine PEDOT: PSS thin film was as high as 92% in the frequency range of 0.2-1.2 THz. This is among the highest reported. Several TN-LC cells were constructed in a comparative study, which confirmed the reliability of pristine PEDOT: PSS as a TCE layer for THz phase shifter applications. The highest phase shift, required root-mean-square (RMS) driving voltage, and threshold voltage achieved by devices tested were 95.2 degrees at 1 THz, 7.2 V-RMS, and 0.5 V-RMS, respectively. The thickness of the LC layer for the phase shifter was 250 mu m, approximately half as thick as previous designs. In addition, the pristine PEDOT: PSS-based TN-LC phase shifter exhibited a figure-of-merit (FOM) value of approximately 6.65 degree.dB(-1).V-1. This compared favorably with previously reported homogeneously aligned phase shifters with an FOM of 2.19 degree.dB(-1).V-1. Our results indicated that a twisted nematic LC cell with pristine PEDOT: PSS thin films as electrodes is a good combination for a THz phase shifter and wave plates as well as other LC-based THz devices.
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    High-Transmittance 2 Electrically Tunable Terahertz Phase Shifter with CMOS-Compatible Driving Voltage Enabled by Liquid Crystals
    (2019-01-02)
    Yang, Chan-Shan
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    Kuo, Chun
    ;
    Chen, Po-Han
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    Wu, Wei-Ta
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    Pan, Ru-Pin
    We have investigated tunable terahertz (THz) phase shifters that are based on a sandwiched liquid crystal (LC) cell with indium-tin-oxide (ITO) nanowhiskers (NWhs) as transparent electrodes. More than 360 degrees of phase shift at 1.0 THz was achieved at a driving voltage as low as similar to 2.6 V (rms). This is approximately 40 times smaller than that reported in previous works using an electrically tuned LC device. Significance of the NWhs in reducing the required voltage is demonstrated. Overall transmittance of the device is as high as 30%, which is accountable by absorption losses of ITO NWhs, quartz substrate and LC. Experimental results are in good agreement with a theoretical formulism while taking into account super-thick LC cells (similar to 1 mm) and pretilt angles. We also propose and demonstrate a novel THz technique for measuring pretilt angles of liquid crystals.
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    Synthesis and characterisation of liquid crystal molecules based on thieno [3,2-b] thiophene and their application in organic field-effect transistors
    (2017-02-01)
    Liau, Wei-Lung
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    Su, Yi-Jen
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    Tseng, Hsiao-Fan
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    Chen, Jiun-Tai
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    Hsu, Chain-Shu
    A thieno [3,2-b] thiophene-based planar liquid crystal molecule, C-12-PTTT, which possesses the characteristics of an organic field-effect transistor (OFET), was synthesised and its mesomorphic properties were studied by polarising optical microscopy and differential scanning calorimetry. A wide temperature range for a highly oriented smectic phase was observed. OFET devices made under various conditions, such as self-assembled monolayer treatment and alignment treatment, and with micro-channel structures, were fabricated to measure the electrical properties. Among different OFET device conditions, the best electric carrier mobility for C-12-PTTT was 0.038 cm(2)V(-1)s(-1). [GRAPHICS]
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    Three-dimensional coating flow of nematic liquid crystal on an inclined substrate
    (2015-10-01)
    Lam, M. A.
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    Cummings, L. J.
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    Lin, T. -S.
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    Kondic, L.
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    應用數學系
    We consider a coating flow of nematic liquid crystal (NLC) fluid film on an inclined substrate. Exploiting the small aspect ratio in the geometry of interest, a fourth-order nonlinear partial differential equation is used to model the free surface evolution. Particular attention is paid to the interplay between the bulk elasticity and the anchoring conditions at the substrate and free surface. Previous results have shown that there exist two-dimensional travelling wave solutions that translate down the substrate. In contrast to the analogous Newtonian flow, such solutions may be unstable to streamwise perturbations. Extending well-known results for Newtonian flow, we analyse the stability of the front with respect to transverse perturbations. Using full numerical simulations, we validate the linear stability theory and present examples of downslope flow of nematic liquid crystal in the presence of both transverse and streamwise instabilities.