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- 摘要
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- 实验方案
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A blue-phase liquid crystal lens array based on dual square ring-patterned electrodes
摘要： We propose a blue-phase liquid crystal (BPLC) lens array based on dual square ring-patterned electrodes. A high dielectric constant layer is used to smoothen out the horizontal electric field and reduce the operating voltage. By creating a potential difference between the dual square ring-patterned electrodes, gradient electric fields are generated and lens-like phase profile is obtained. Besides, the focal length of the BPLC lens is adjustable with voltage changes and all simulation results indicate that the BPLC lens array is polarisation-insensitive.
关键词： polarisation-insensitive,lens array,Blue phase,liquid crystal
更新于2025-09-23 15:21:01
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An apparatus for measuring a material's photomechanical response
摘要： This paper describes a simple and inexpensive apparatus for measuring the light-induced shape change of a material, which can be implemented in a high school or undergraduate laboratory. The key components of the apparatus are a laser pointer to actuate the material, a force sensor from an inexpensive jeweler’s balance to measure the response, an Arduino for data acquisition, and a means for mechanically mounting the setup. The apparatus described here was used by high school students and teachers in a summer program to characterize liquid crystal elastomer samples. The theory of photomechanical response is used to interpret the gathered data, from which material parameters related to this theory are determined.
关键词： photomechanical effect,liquid crystal elastomers,Arduino,laser pointer,force sensor
更新于2025-09-23 15:21:01
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Mosaics of topological defects in micropatterned liquid crystal textures
摘要： Topological defects in the orientational order that appear in thin slabs of a nematic liquid crystal, as seen in the standard schlieren texture, behave as a random quasi–two-dimensional system with strong optical birefringence. We present an approach to creating and controlling the defects using air pillars, trapped by micropatterned holes in the silicon substrate. The defects are stabilized and positioned by the arrayed air pillars into regular two-dimensional lattices. We explore the effects of hole shape, lattice symmetry, and surface treatment on the resulting lattices of defects and explain their arrangements by application of topological rules. Last, we show the formation of detailed kaleidoscopic textures after the system is cooled down across the nematic–smectic A phase transition, frustrating the defects and surrounding structures with the equal-layer spacing condition of the smectic phase.
关键词： smectic A,nematic,birefringence,micropatterned,topological defects,liquid crystal
更新于2025-09-23 15:21:01
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Thermodynamic Analysis of the Transition of Liquid Crystals from Lamellar to Vesicular Phase
摘要： Here, we report the results of thermodynamic analyses on the lamellar-vesicular transition for a cationic amphiphilic species, namely 2-hydroxyethyl di(alkanol)oxyethyl methylammonium methylsulfate (DEAE). Previously, we have shown that spontaneous vesicle formation from a Lα-lamellar liquid crystal (LC) phase only occurs on the addition of a quantitative amount of additives to the DEAE LC at certain temperatures and that this change occurs without the input of any extra mechanical energy. These lamellar-vesicular transitions occur in two steps: the first step is the formation of an excited state, caused by the solubilization of organic substances in the bilayer structure. The second step, induced by the addition of a small amount of inorganic salt to the excited LC state, is the transition from lamellar to vesicular phase. From our experimental data, the change in the Gibbs free energy was estimated by assuming an ideal electrical chemical potential. As a result, the thermodynamic parameters at 303 K for the lamellar-vesicular transition from the initial state (lamellar) to the final state (vesicle) were found to be approximately －2.7 kJ/mol for the Gibbs free energy, －14.6 kJ/mol for the enthalpy change, and －11.9 kJ/mol for the entropy change. Each state change was due to structural changes not only in the LC bilayers but also in the hydration structure of the surrounding water. Moreover, the most significant finding is that the free energy change in lamellar-vesicular transition is negative, which may be explained based on the stabilization of solubilized vesicles with respect to the unsolubilized lamellar phases.
关键词： electrochemical potential,lamellar liquid crystal,chemical potential,vesicle,transition energy
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Liquid Crystal Alignment on the Patterns Produced by Nonlinear Laser Lithography
摘要： Liquid crystal (LC) based devices such as displays, spatial light modulators (SLM) and different switchable phase masks constitute the main part of the graphic information display and light control. Mechanical rubbing and photo-alignment are the most widely used industrial technologies to create anisotropic surfaces for these devices. Recently, nonlinear laser lithography (NLL) was introduced as a fast, cost effective method for large area nano-grating fabrication based on laser-induced periodic surface structuring [1]. Here we report on alignment of nematic LC on NLL treated Ti film deposited on glass for the first time. We demonstrate controllable changes of azimuthal anchoring energy (AAE) depending on processing and additional coating parameters. To create the large area of structured Ti layers we used the experimental scheme of the NLL method, as described in [2]. The setup consists of a home-made femtosecond fiber laser system (up to 1.8 μJ pulse energy at 1 MHz repetition rate), galvanometer-scanner and motorized 3D–translation stage. The samples were 300 nm Ti films deposited on glass. 5x5 mm2 zones were structured by raster scanning of the laser beam over the surface with different parameters. To measure the twist angle and further calculate the AAE we have made combined twist LC cells. LC cells consisted of the tested and reference substrates where the last one was a glass substrate coated with a polyimide PI2555 and processed by the rubbing technique. The first type of the tested substrate was coated with Ti layer and further processed by the NLL method. The second type of the tested substrate was additionally coated with ODAPI. The twist angle was measured by using the combined twist LC cell method. Later, the AAE was calculated from the obtained twist angles of different samples. Fig. 1 (a-c) demonstrates dependencies of the measured twist angles and calculated AAE for different samples. We obtain controllable changes of the anchoring energy in the range between 2x10-6 J/m2 to 10-4 J/m2. The highest AAE 10-4 J/m2 is obtained for the samples which are processed by NLL with post-coating by ODAPI.
关键词： Azimuthal anchoring energy,Liquid crystal alignment,Nonlinear laser lithography,Nematic LC,Ti film
更新于2025-09-23 15:19:57
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Silicon Containing Hybrid Copolymers || Construction of Organic Optoelectronic Materials by Using Polyhedral Oligomeric Silsesquioxanes ( <scp>POSS</scp> )
摘要： Organic optoelectronic materials can be generally divided into small molecular weight semiconductors and conjugated polymers with high opto/electronic performance. This interesting electroluminescence and conducting properties were first discovered in the 1970s, but the real surge of the interest occurred in the past 20 years with significant improvements in material performance through creative material design and high material purification. Small molecular weight semiconductors are interesting because of their high purity, ordered structures, and ideal model for fundamental mechanism studies of excitons and charge carriers. Conjugated polymers are mainly used for device fabrication for their advantages of large‐area device fabrication, high performance, and multiple functions. Currently, organic materials receive considerable attention because of their successful applications in organic light‐emitting diodes (OLEDs), solar cell, liquid crystal display (LCD), thin film transistors, sensors, electrochromic devices, and many others. Thanks to the extensive academic and industrial efforts, the mechanism and the relationship between the molecular structure and optoelectronic properties have been illustrated, and various device structures have been developed. Although organic optoelectronic materials have experienced tremendous progress over the past 10 years in fundamental physics and real applications, more work is necessary such as theoretical descriptions in charge generation and transport, distinction in the contributions of various interactions, thermal stability improvement, and commercialization of existing applications. Various new phenomena are still being discovered every day and device performance is continuing to rise. Among these efforts, the incorporation of polyhedral oligomeric silsesquioxanes (POSSs) into organic optoelectronic materials to achieve improved performances has been attracting attention particularly because of the unique and interesting hybrid structures of POSS.
关键词： Electroluminescence,Organic optoelectronic materials,Polyhedral oligomeric silsesquioxanes (POSS),Liquid crystal display (LCD),Electrochromic materials
更新于2025-09-23 15:19:57
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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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Dielectric and electro-optic properties of cybotactic nematic phase in hydrogen-bonded liquid crystals
摘要： The new compounds 4-decyloxy-2-fluorobenzoic acid and 4-dodecyloxy-2-fluorobenzoic acid display hydrogen-bonded liquid crystals (HBLC) of smectic and nematic phases. Their phase behavior established using polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) consistently occurs as the sequence upon cooling: Isotropic liquid – Nematic – SmC – crystalline solid. The dielectric study in the nematic phase shows a single relaxation process at low frequency characteristic of a cybotactic nematic phase. The optical properties of the nematic phase show a decrease of birefringence as alkyl chain length increases in the high-temperature part of the nematic domain, which reveals a decrease of order parameter for longer chains.
关键词： Polarized optical microscopy,Dielectric spectroscopy,Nematic,Hydrogen-bonded liquid crystal
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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Electrically controlled white laser emission through liquid crystal/polymer multiphases
摘要： White lasers are becoming increasingly relevant in various fields since they exhibit unprecedented properties in terms of beam brightness and intensity modulation. Here we introduce a white laser based on a polymer matrix encompassing liquid crystals and multiple organic chromophores in a multifunctional phase-separation system. The separation of the hydrophilic matrix and the hydrophobic liquid crystals leads to the formation of a complex optically active layer, featuring lasing emission tuneable from blue to red. White laser emission is found with an optical excitation threshold of approximately 12 mJ/cm2. Importantly, an external electric field can be used to control the device emission intensity. White lasers with low-voltage (≤10 V) controllable emission might pave the way for a new generation of broadband light sources for analytical, computational, and communication applications.
关键词： polymer matrix,electrically controlled,liquid crystal,organic chromophores,white laser
更新于2025-09-23 15:19:57