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High-density Azobenzene Side Chain Polymer Brush for Azimuthal and Zenithal Orientation Photoswitching of Nematic Liquid Crystal
摘要： The azimuthal and zenithal orientation switching of nematic liquid crystals (NLCs) can be performed by photoresponsive azobenzene alignment layers called command surfaces. Such photoresponsive layers have been prepared by molecular assembly methods or spincast of polymer materials. This work reports on the photo-switching orientation behavior of NLC on a high-density brush of an azobenzene-containing side chain liquid crystalline polymer. On the high-density polymer brush surface, the zenithal homeotropic/planar photoalignment switching modes triggered by UV/visible light irradiation are reversed from those observed for traditional command surface systems, reflecting the azobenzene side chain orientation directing parallel with the substrate surface. Because the thermally stable trans-azobenzene provides the in-plane orientation of NLC, irradiation with linearly polarized visible light readily switches the azimuthal direction to an arbitrary direction, and the resulting orientation is retained persistently. This paper discusses the features of the architecture of high-density polymer brush as the command surface for NLC orientation.
关键词： azobenzene,photoalignment,photoresponsive surface,nematic liquid crystal,polymer brush
更新于2025-09-23 15:23:52
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Incompressible limit for compressible nematic liquid crystal flows in a bounded domain
摘要： In this paper, we consider the incompressible limit of strong solution for the compressible nematic liquid crystal flows in a 3D bounded domain (cid:2) ? R3 where the the velocity field satisfies the Dirichlet boundary condition. We establish the uniform estimates with respect to the Mach number for the strong solutions with large initial data in a short time interval. Consequently, we obtain the convergence of the compressible nematic liquid crystal system to the incompressible nematic liquid crystals system as the Mach number tends to zero.
关键词： Incompressible limit,Dirichlet boundary condition,compressible nematic liquid crystal equations
更新于2025-09-23 15:23:52
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Zirconia Nanocolloids Having a Nanospace of Poly(cyclodextrin): Preparation and Application to Liquid Crystal Devices
摘要： Poly(β-cyclodextrin) (PβCyD)-protected ZrO2 nanocolloids were prepared by using a microwave reactor equipped with ultrasonic nozzle mixing at 240 °C for 30 min in a tetraethylene glycol solution of zirconium (IV) ethoxide in the presence of poly(β-cyclodextrin). Particles in PβCyD-protected ZrO2 nanocolloids have an average diameter of 7.2 nm and mainly distribute within the range of about 3 to 10 nm. The nanocolloids were dispersed in 4'-pentylbiphenyl-4-carbonitrile (5CB) and practical liquid crystal to construct novel twisted nematic liquid crystal devices (TN-LCDs). The response time of this TN-LCDs in the presence of PβCyD-protected ZrO2 nanocolloids was faster than that in the absence. The threshold voltage of TN-LCDs by doping PβCyD-protected ZrO2 nanocolloids decreased. The decrease of threshold voltage can reduce power consumption, which may meet the demands of future power-saving LCDs.
关键词： Twisted Nematic Liquid Crystal Devices,Zirconia Nanocolloids,Poly(cyclodextrin),Nanospace,4'-Pentylbiphenyl-4-Carbonitrile
更新于2025-09-23 15:22:29
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Textural and electro-optical study of a room temperature nematic liquid crystal 4ì?-pentyl-4-biphenylcarbonitrile doped with metal oxide nanowires in planar and in-plane switching cell configurations
摘要： This work shows the doping effect of metal oxide nanowires (alumina nanowires) on the textural and electro-optical characteristics of nematic liquid crystal (5CB) in planar and in-plane switching (IPS) cell configurations. Results indicate the increase in nematic to isotropic phase transition temperature after doping in both planar and IPS cells. A decrease in threshold voltage in addition to increase in contrast ratio, birefringence, and band gap energy was observed after doping with alumina nanowires in both types of cells. Overall analysis shows that IPS cell configuration has more improved threshold voltage and contrast ratio in addition to decrease in birefringence and transmission intensity, as compared to planar cell configuration. No effect of cell configuration was observed on energy band gap and found same value for both planar and IPS cell configurations, as energy band gap is a material specific property.
关键词： threshold voltage,Nematic liquid crystal,energy band gap,In-plane switching,nanowires
更新于2025-09-23 15:21:01
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Electronically controlled beam steering leaky wave antenna in nematic liquid crystal technology
摘要： A novel nematic liquid crystal (LC) technology-based electronically controlled leaky wave antenna (LWA) with microstrip-waveguide conversion working mechanism and wide beam steering range is presented in this article. The LWA is a combination of an inverted microstrip structure and rectangular waveguide. According to the characteristics of LC materials in microwave band, a broadband microstrip-waveguide conversion device is proposed. The gradient slot leaky wave structure is combined with the microstrip-waveguide conversion device to form an electronically controlled LWA with continuous tunable beam. Simulation and experiment results show that the LWA proposed in this article has a 32° beam scanning range at 12 GHz and good impedance matching and stable gain, suggesting the great potential of nematic LC materials for extensive applications in microwave band in the future.
关键词： leaky wave antenna (LWA),microstrip-waveguide conversion,beam steering,nematic,liquid crystal (LC)
更新于2025-09-23 15:19:57
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Optical properties and zeta potential of carbon quantum dots (CQDs) dispersed nematic liquid crystal 4a?2- heptyl-4-biphenylcarbonitrile (7CB)
摘要： In this work, carbon quantum dots (CQDS) of three concentrations 0.1, 0.2 and 0.5 wt% have been dispersed in nematic liquid crystal 4-Heptyl-4-biphenylcarbonitrile (7CB). The results on the optical properties and zeta potential of pure and CQDs dispersed nematic 7CB have been reported. It has been observed that the dispersion of CQDs in host nematic matrix induces quenching of photoluminescence and reduces the Ultra-Violet-Visible (UV–Vis) absorbance of pure nematic at a lower wavelength. From the result of fluorescence decay profile, the fluorescence life time of pristine and dispersed nematic systems have been obtained. No remarkable changes in nematic lifetime in the presence of CQDs have been observed, which confirm that no energy is transferred from nematic to CQDs. Further, it has been found that due to dispersion of CQDs the numerical values of zeta potential are increased for the dispersed systems with 0.1 and 0.2 wt% concentrations of CQDs as compared to pure 7 CB. This result demonstrates that the study of zeta potential provides useful information on the stability and aggregation of the CQDs dispersed nematic systems.
关键词： Carbon quantum dots,UV–Vis absorbance,Zeta potential,Nematic liquid crystal,Time resolved fluorescence
更新于2025-09-23 15:19:57
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Curvature-Induced Twist in Homeotropic Nematic Tori
摘要： We confine a nematic liquid crystal with homeotropic anchoring to stable toroidal droplets and study how geometry affects the equilibrium director configuration. In contrast to the case of cylindrical confinement, we find that the equilibrium state is chiral—a twisted and escaped radial director configuration. Furthermore, we find that the magnitude of the twist distortion increases as the ratio of the ring radius to the tube radius decreases; we confirm this with computer simulations of optically polarized microscopy textures. In addition, numerical calculations also indicate that the local geometry indeed affects the magnitude of the twist distortion. We further confirm this curvature-induced twisting using bent cylindrical capillaries.
关键词： twist distortion,nematic liquid crystal,curvature-induced twisting,chiral,toroidal droplets,homeotropic anchoring
更新于2025-09-23 15:19:57
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Measuring of nonlinear properties of spatial light modulator with different wavelengths
摘要： The non-linear optical properties of Spatial Light Modulator(SLM) represented by Nonlinear Refractive Index (NLR) and nonlinear Absorption coefficient has been measured in this work using highly sensitive method known as Z-scan technique for different wavelengths (red and green). The capability to do instant measurements of different nonlinear optical parameters lead to consider these techniques as a one of the most desired and effective methods that could apply for different materials. The results showed that the NLR were in the same power for the different wavelengths while the nonlinear absorption is higher in case of green laser.
关键词： Z-scan technique,Nematic Liquid Crystal,SLM
更新于2025-09-19 17:15:36
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Microwave CSIW Filter Based on The High Anisotropy Electro-Optic Nematic Liquid Crystal
摘要： In this work, for the research of novel waveguide filters, we propose a microwave corrugated substrate integrated waveguide CSIW filter based on the high anisotropy electro-optic nematic liquid crystal. Metallic vias of the substrate integrated waveguide (SIW) is replaced by quarter microstrip stubs of the CSIW, which solves the problem of shorting the upper and lower planes of the waveguide due to metalized vias when the SIW is biased. Using the electromagnetic scattering complementary open-loop resonance type anisotropic medium structure, the enhanced scattering characteristics can amplify the cutoff mode. In combination with the dielectric anisotropy of the liquid crystal and the high modulation efficiency of the inverted microstrip line, the waveguide filter has advantages such as high modulation efficiency, high Q value, and low transmission loss.
关键词： nematic liquid crystal,CSRR,CSIW,tunable,microwave
更新于2025-09-19 17:13:59
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Influences of nickel plated multi-walled carbon-nanotube on the electro-optical properties of nematic liquid crystal
摘要： Some enhanced performances can be obtained by doping multi-walled carbon-nanotube (MWCNT) into self-organized nematic liquid crystal (NLC). However, the dispersion of MWCNT in NLC is very few, thus the enhancement is restricted. In this work, a nickel plated MWCNT (MWCNT@Ni) is synthesized to obtain a relatively high dispersion. The morphology, element and chemical bond differences between MWCNT and MWCNT@Ni are characterized. For MWCNT@Ni, there is a layer of coaxial nickel coated on the surface of MWCNT, which weakens the interaction energy between the adjacent MWCNTs and further results in a relatively high dispersion. Moreover, MWCNT@Ni has a more orderly arrangement in NLC compared with MWCNT. The results suggest that the dielectric anisotropy of MWCNT@Ni/NLC with mass fraction of 0.01 wt% is increased by ～3.6%, and the saturation voltage is reduced by ～7.3%. Besides, the rise time is decreased by ～9.5% at 5 V and 1 kHz. These performances have been improved compared with MWCNT/NLC under the same mass fraction. The effect of mass fraction of MWCNT@Ni on rise time is further investigated. As a result, the rise time is decreased by ～16.7% as MWCNT@Ni with mass fraction of 0.10 wt% is added into NLC. In general, the method to increase dispersion of dopant in NLC is proposed, which can serve as a reference to improve the performances of NLC composites.
关键词： dispersion,nematic liquid crystal,nickel plated multi-walled carbon-nanotube
更新于2025-09-19 17:13:59