Liquid Crystals

Identification of flow pattern during the simultaneous flow of two immiscible liquids requires knowledge of the flow rate of each fluid as well as knowledge of other physical parameters like conduit inclination, pipe material, pipe diameter, viscosity of the oil, wetting characteristics of the pipe, design of the entry mixer, and fluid-fluid interfacial tension. This article presents an artificial neural

Photonic crystal fiber is glass or polymer fiber with array of microscopic air holes running along length of the fiber. Waveguide properties of such fiber can be controlled by introducing additional materials into the air holes. Liquid crystals (LC) are very suitable for that purpose because its refractive index can be easily tuned by electric field or temperature. Alignment of LC in photonic holes determines mostly the optical properties of the fiber. In this paper, we have developed the technique of photo-configurable alignment of LC in glass micro-tubes and in photonic crystal fiber. The order parameter of LC has been obtained from FTIR spectroscopy data and has demonstrated good alignment quality. Presented technique can be used as non-contact method of LC alignment in complex photonic crystal structure.

Intrinsic evolution in evolvable hardware research has hitherto been limited to using standard electronic components as the media for problem solving. However, recently it has been argued that because such components are human designed and intentionally has predictable responses; they may not be the optimal medium to use when trying to get a naturally inspired search technique to solve a problem. Evolution has been demonstrated as capable of exploiting the physical properties of material to form solutions; however, by giving evolution only conventional components, we may be placing arbitrary constraints on our ability to solve certain problems. We have shown for the first time, that liquid crystal can be used as the physical substrate for evolution. We demonstrate that it is possible to evolve various functions, including a tone discriminator, in materio.

Series of 4-(4-substituted benzylideneamino)-5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazole-3-thiols were synthesized and their structures were confirmed. The synthesized Schiff bases were used as photostabilizers for polystyrene against photodegradation. Polystyrene polymeric films containing synthesized Schiff bases (0.5% by weight) were irradiated (λ max = 365 nm and light intensity = 6.43 × 10 −9 ein·dm −3 ·s −1) at room temperature. The photostabilization effect of 1,2,4-triazole-3-thiols Schiff bases was determined using various methods. All the additives used enhanced the photostability of polystyrene films against irradiation compared with the result obtained in the absence of Schiff base. The Schiff bases can act as photostabilizers for polystyrene through the direct absorption of UV radiation and/or radical scavengers.

We report highly efficient red phosphorescent organic light-emitting diodes with a triplet p-i-n single quantum well (QW) structure. This p-i-n single QW structure is realized using p-doped and n-doped wide band-gap hole and electron injection and transporting layers with narrow band-gap host and dopant materials. The maximum current and power efficiencies of 11.1 cd/A and 14.4 lm/W, respectively, are demonstrated by a good carrier confinement effect of QW. Very low driving voltage characteristics of 3.7 ∼ 3.9 V at 1000 cd/m2 are realized by almost no injection barrier with high conductivity configuration in our p-i-n structure.

—We review recent advances in quantum dot (QD)-enhanced liquid crystal displays (LCDs), including material formulation , device configuration, and system integration. For the LCD system, we first compare the color gamut difference between the commonly used Gaussian fitting method and that using real emission spectra. Next, we investigate the Helmholtz–Kohlrausch effect. Our simulation results indicate that QD-enhanced LCD appears 1.26X more efficient than organic light-emitting diode (OLED) display due to its wider color gamut. Finally, two new trends for QD-LCDs are discussed: 1) replacing conventional color filters with a QD array, and 2) emerging quantum rod (QR)-enhanced backlight. Their inherent advantages, technical challenges, and potential solutions are presented. We believe the prime time for QD-enhanced LCDs is around the corner. Index Terms—Color gamut, Quantum dot (QD), Quantum rod (QR), liquid crystal display (LCD).

Gel Polymer Electrolytes (GPE) based on agar and containing LiClO4 have been prepared, characterized and applied to electrochromic devices. The ionic conductivity revealed the best result of 6.5 × 10−5 S/cm for the sample with 17 wt.% of LiClO4, which increased to 5.4 × 10−4 S/cm at 72°C. The GPE have been used in electrochromic devices (ECD) with K-glass/WO3/GPE/CeO2-TiO2/K-glass configuration. The ECD changed transmittance values up to 30% between the colored and transparent states. The charge density measurements revealed an increase of 5.5 to 7.5 mC/cm2 from the first to 500th cycles and then a decrease to 4.4 mC/cm2 during the next 4500 cycles. Coloration efficiency (η) of 25 cm2/C was obtained.

We proposed a switchable beam steering device with cycloidal diffractive waveplate (CDW) for eye tracking in a virtual reality (VR) or augmented reality (AR) display system. Such a CDW diffracts the incident circularly polarized light to the first order with over 95% efficiency. To convert the input linearly polarized light to right-handed or left-handed circular polarization, we developed a broadband polarization switch consisting of a twisted nematic liquid crystal cell and an achromatic quarter-wave retardation film. By cascading 2-3 CDWs together, multiple diffraction angles can be achieved. To suppress the color dispersion, we proposed two approaches to obtain the same diffraction angle for red, green, and blue LEDs-based full color displays. Our device exhibits several advantages, such as high diffraction efficiency, fast response time, low power consumption, and low cost. It holds promise for the emerging VR/AR displays.

Four series of new [1]benzothieno[3,2- b][1]benzothiophene derivatives have been synthesized. In the non-chiral series a SmA phase occurs, while the chiral series exhibits a rather wide antiferroelectric SmC* phase just below the SmA phase. The SmA-SmC* phase transition has been studied using DSC and dielectric spectroscopy. In the SmC* phase the spontaneous quantities have been measured. The tilt angle shows

— We have proposed a compact, yet high ambient contrast ratio augmented reality (AR) system by incorporating a tunable transmittance liquid crystal (LC) cell and a thin functional reflective polarizer. The broadband polarization-independent guest–host LC cell can change the transmittance from ~73% to ~26% with merely 8 V. Its response time (~50 ms) is at least 10× faster than that of photochromic materials used in commercial transition glasses. Combining the LC cell with a light sensor, the tunable trans-mittance LC cell can efficiently improve the ambient contrast ratio of the AR system under different lighting conditions. Meanwhile, the functional reflective polarizer works similarly to a polarizing beam splitter, except that it is much more compact and lighter weight. With some modification, we also designed a functional reflective polarizer to help people with color vision deficiency.

Les cristaux liquides sont des substances qui lorsqu'on les chauffe, passent par des structures intermédiaires entre le cristal à réseau périodique bien ordonné dans trois directions et le liquide complètement désordonné. Dans ces états, ils tiennent à la fois du liquide et du cristal. Ces structures résultent de la forme non-sphérique de leurs molécules qui s'empilent comme des allumettes, des assiettes, les cartes d'un jeu de cartes ou encore des hélices. Ce sont ces mêmes cristaux liquides qui se cachent dans les écrans numériques sous le sigle LCD. Les cristaux plastiques ont par contre des molécules quasi-sphériques et ils représentent une autre façon d'inventer un ordre intermédiaire, dû à la mobilité rotationnelle de leurs molécules.

We briefly review studies of liquid crystal films suspended in submillimeter size grids for biosensing applications and beyond. Due to intense recent research, the sensitivity of liquid crystal films to targeted biologically relevant agents can be increased, and the LC surface can be functionalized to be sensitive only to pre-assigned pathogens. Beyond sensor applications, we show that novel liquid crystal defect structures can be used to manipulate separation and deposition of lipids. Finally, we demonstrate that not only the nematic liquid crystal phase, but also chiral nematic (cholesteric and blue phase) and smectic liquid crystals can be used for sensing and may extend the sensitivity and/or the selection of biomaterials, which can be sensed.

Here, a novel method of immobilizing proteins with well-defined orientation directly on liquid crystal surfaces that allow subsequent real-time imaging of specific protein–protein binding events on these surfaces is reported. Self-assembly of nitrilotriacetic acid terminated amphiphiles loaded with Ni2+ ions at aqueous-liquid crystal interface creates a surface capable of immobilizing histidine-tagged ubiquitin through complex formation between Ni2+ and histidine. When these surfaces containing immobilized histidine-tagged ubiquitin are exposed to anti-ubiquitin antibody, the spatial and temporal of specific protein–protein binding events trigger orientational transitions of liquid crystals. As a result, sharp liquid crystal optical switching from dark to bright can readily be observed under polarized lighting. The protein–protein binding can be observed within seconds and only requires nanogram quantities of proteins. This work demonstrates a simple strategy to immobilize proteins with well-defined orientation on liquid crystal surfaces for real-time and label-free detection of specific protein–protein binding events, which may find use in biomedical diagnostics.

The effect of QDs on the dielectric and electro-optical (E-O) properties of different
ferroelectric liquid crystal matrices has been studied in the SmC∗ phase. A substantial
change in the different parameters like tilt angle, spontaneous polarization and relative
permittivity has been observed for the doped system. For the better understanding of the
effect of QDs on FLC relaxation process another quantum dot CdSe has been dispersed
in two other FLC systems 16/100 and DOBAMBC. The effect of QDs on the three FLC
systems on relaxation behavior attributes to the alteration of tilt angle in different way
in different doped system. This difference in relaxation behavior is observed due to the
dissimilar composition and structure of FLC mixture and FLC molecule.

This dissertation mainly focuses on the delicate phenomena that happen at liquid interfaces. In the introduction, I start by defining the interface and discuss its structure and the relevant interfacial forces. I then introduce the general characteristics of biosensors and, in particular, describe the design of biosensors that employ liquid crystal/aqueous solution interfaces. I further describe the basic properties of liquid crystal materials that are relevant for liquid crystal-based biosensing applications.