Download or read book Flexoelectricity in Liquid Crystals written by Agnes Buka and published by World Scientific. This book was released on 2013 with total page 299 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book intends to give a state-of-the-art overview of flexoelectricity, a linear physical coupling between mechanical (orientational) deformations and electric polarization, which is specific to systems with orientational order, such as liquid crystals. Chapters written by experts in the field shed light on theoretical as well as experimental aspects of research carried out since the discovery of flexoelectricity. Besides a common macroscopic (continuum) description the microscopic theory of flexoelectricity is also addressed. Electro-optic effects due to or modified by flexoelectricity as well as various (direct and indirect) measurement methods are discussed. Special emphasis is given to the role of flexoelectricity in pattern-forming instabilities. While the main focus of the book lies in flexoelectricity in nematic liquid crystals, peculiarities of other mesophases (bent-core systems, cholesterics, and smectics) are also reviewed. Flexoelectricity has relevance to biological (living) systems and can also offer possibilities for technical applications. The basics of these two interdisciplinary fields are also summarized.
Download or read book Flexoelectric Liquid Crystals and Their Applications written by Yingfei Jiang and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid crystals are widely used in flat panel displays and smart windows. In flat panel display application, one way to improve the efficiency is to decrease the driving frequency when static images are displayed. As the driving frequency is decreased, the transmittance of the display may vary with time, a phenomenon known as flickering. We carried out both experimental and simulation studies to investigate the origins that cause the flickering problem. Our results show that flexoelectric effect and ions in the liquid crystal are the main factors responsible for the flickering. We quantitatively analyzed the flickering caused by the two factors. The ionic effect can be eliminated by using the fluorinated liquid crystals with high resistivity. The flexoelectric effect is attributed to the intrinsic flexoelectric coefficient of the liquid crystal and nonuniformity of the liquid crystal director configurations. We demonstrated that polymer stabilization can smooth the spatial variation of the liquid crystal orientation, while doping a liquid crystal dimer can reduce the flexoelectric coefficient of the liquid crystal. Using these methods we are able to reduce the flickering significantly. Radiant energy-flow control and privacy control are two important features for smart windows (or glass). Current smart window technologies can, however, only control one of them: radiant energy flow or privacy. Therefore, a dual-mode smart window is highly desirable. We developed a dual-mode switchable liquid-crystal window that can control both radiant energy flow and privacy. The switchable liquid-crystal window makes use of dielectric and flexoelectric effects. In the absence of an applied voltage, the window is clear and transparent, and radiant energy can flow through it and the scenery behind the window can be seen. When a low-frequency (50 Hz) voltage is applied, the window is switched to an optical scattering and absorbing state by a flexoelectric effect, and thus, privacy is protected. When a high-frequency (1 kHz) voltage is applied, the window is switched to an optical absorbing but nonscattering state through a dielectric effect, and thus, radiant energy flow is controlled. Smart windows can be categorized mainly into two types according to the operation principle: electrical switchable window and thermal switchable windows. In the electric switchable window, voltage must be applied to switch the window, which consumes energy and is not environmentally friendly. Therefore, a power-free smart window is highly demanded. We developed a thermal switchable smart window that is sensitive to ambient temperature. The window is based on a liquid crystal whose orientation imposed by an alignment layer varies with temperature. The liquid crystal layer is sandwiched between two parallel polarizers to make the window. At high temperature, the liquid crystal is aligned parallel to the cell substrate and rotates the polarization of the incident light after the first polarizer by 90o such that incident light is completely absorbed by the second polarizer, and the transmittance of the window is 0. When temperature is decreased, the liquid crystal is tilted toward the cell substrate normal and rotates the polarization of the incident light less so that some light can pass the second polarizer, and the transmittance of the window increases. When temperature is decreased below a critical value, the liquid crystal is aligned perpendicular to the cell substrate and does not rotate the polarization of the incident light such that all light passes the second polarizer, and the transmittance reaches a maximum.
Download or read book Flexoelectricity in Nematic Liquid Crystals written by Claudius Kischka and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Flexoelectricity in liquid crystals is thought to be due to a coupling between dielectric properties and shape anisotropy of the molecules and described by the fiexoelectric coefficients el and e3. Two experiments are needed to measure el and e3 and it is usual to measure the difference (el - e3) and the sum (el + e3) and then calculate el and e3· The first experiment to measure the difference (el - e3) uses a TN structure with an in-plane applied electric field. Due to the dielectric coupling, the director aligns with the electric field and due to the fiexoelectric effect, the director tilts out of plane. This tilt is measured optically using two laser beams at oblique incidence, e.g. 45°. Using a theoretical model the experimental data is fitted and the difference (el - e3) extracted. The second experiment to measure the sum (el + e3) uses a Pi cell. Applying an ac voltage the transmission through the device is a repeating oscillating signal which contains 1st and 2nd harmonics. The 1st harmonic corresponds to the fiexoelectric effect and the 2nd harmonic to the dielectric effect. Using a lock-in amplifier, the harmonics were measured and the sum (el + e3) extracted using a theoretical model to fit the experimental data. Unfortunately, the data proved the experiment to be unreliable and another method was developed, which uses a BAN cell. The third experiment uses simple pulses in a BAN cell and also measures the sum (el + e3). The big disadvantage of the BAN cell is an internal voltage, which is created by the homeotropic alignment layer and the fiexoelectric polarisation. The internal voltage has the same effect on the director profile as the fiexoelectric effect, which is a big problem in measuring fiexoelectricity. Using a material, which is non ionic and has no fiexoelectricity, the internal bias could be measured and taken into account. Applying short de pulses of opposite sign, the fiexoelectric effect can be observed by the optical response and can be measured. Using these experiments, a number of investigation are being carried out such as the correlation between fiexoelectricity and the molecular structure, ions, elastic properties, molecular orientation, dielectric anisotropy 6E, and order parameter S. The results showed that fiexoelectricity only depends on ions and dielectric properties which was very interesting and surprising at the same time.
Download or read book Flexoelectricity in Ceramics and their Application written by Satyanarayan Patel and published by Elsevier. This book was released on 2023-08-29 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flexoelectricity is the ability of materials to generate a voltage when they are bent or, conversely, to bend under voltage. Flexoelectricity can be present in all materials; however, the magnitude of the flexoelectric coefficients is so small that flexoelectricity is virtually imperceptible on the human scale. The book's objective is to look at the flexoelectric effect in ceramics for various applications point of view such as sensor, actuator and energy harvesting etc. It briefly discusses the flexoelectric effect theories and models with the latest development in this field. Several methods are discussed to increase the flexoelectric effect in ferroelectric and other ceramics. It focused on the latest development in various possible applications such as flexopyroelectric, flexocaloric and nano energy generators. Apart from these, it will also discuss the inverse flexoelectric effect, flexoelectric effect in 2D materials, ambiguities and controversies in this field. This book resolved many questions related to flexoelectricity and made significant discoveries with profound implications beyond flexoelectricity, in such diverse areas as caloric or MEMS devices, etc. It covers the most recent breakthroughs in nano-generator, composite-based ceramics to maximize energy harvesting and storage. Therefore, this book will be handy for a researcher working in this direction of ceramics and can be a reference book for allied specializations. It will open a new approach to using the flexoelectric effect in various ceramics and varieties of applications. Provides an in-depth study of the flexoelectric effect of a broad range of ceramic materials It updates the state of art progress that has been done in the area of flexoelectric-based energy harvesting via nano-generator or nanocomposites of ceramics Provides most recent advancement in the area of lead-free, lead-based ceramics, 2D material, flexocaloric and flexopyroelectric applications The inverse flexoelectric effect is discussed in detail, which helps newcomers and expert researchers, scientists, and engineers working in this field Includes an evaluation of ambiguities and controversies about the flexoelectric effect
Download or read book Bent Shaped Liquid Crystals written by Hideo Takezoe and published by CRC Press. This book was released on 2017-07-20 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bent-Shaped Liquid Crystals: Structures and Physical Properties provides insight into the latest developments in the research on liquid crystals formed by bent-shaped mesogens. After a historical introduction, the expert authors discuss different kinds of mesophase structures formed by bent-shaped molecules. This book devotes the majority of its pages to physical properties such as polar switching, optics and non-linear optics, and behavior in restricted geometries. However, as chemistry is often highly relevant to the emergence of new phases, particularly with reflection symmetry breaking, it also involves a broad spectrum of interesting chemistry viewpoints.
Download or read book Photorefractive Organic Materials and Applications written by Pierre-Alexandre Blanche and published by Springer. This book was released on 2016-06-10 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides comprehensive, state-of-the art coverage of photorefractive organic compounds, a class of material with the ability to change their index of refraction upon illumination. The change is both dynamic and reversible. Dynamic because no external processing is required for the index modulation to be revealed, and reversible because the index change can be modified or suppressed by altering the illumination pattern. These properties make photorefractive materials very attractive candidates for many applications such as image restoration, correlation, beam conjugation, non-destructive testing, data storage, imaging through scattering media, holographic imaging and display. The field of photorefractive organic material is also closely related to organic photovoltaic and light emitting diode (OLED), which makes new discoveries in one field applicable to others.
Download or read book Electro optic studies of the flexoelectric effect in chiral nematic liquid crystals written by Bronje Musgrave and published by . This book was released on 2000 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advances in Liquid Crystal Research and Applications written by Lajos Bata and published by Elsevier. This book was released on 2013-10-22 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Liquid Crystal Research and Applications, Volume 1 is a collection of papers presented at the Third Liquid Crystal Conference of the Socialist Countries, held in Budapest on August 27-31, 1979. This volume is comprised of three parts. The first part deals with the phases and structures of liquid crystals through methods employing synthesis, X-ray studies, electron diffraction, and calorimetric determination. The second part discusses molecular dynamics and dynamical methods where mostly dielectric investigations into liquid crystal properties are emphasized. This part includes the developments in the study of molecular dynamics in liquid crystals. Other topics presented in this part are the acousto-optical and ultrasonic relaxation methods. The third part covers the continual properties of liquid crystals: their properties and behavior when exposed to different testing methods and variables. For example, a correlation between viscosity coefficients of starting components and those of their mixtures is attempted, resulting when MBBA and EBBA in different percentages are mixed, that none of their coefficients is found to obey any pronounced law. However, the viscosity coefficients given in the table may serve as reference data for further studies. Physicists; process engineers; and graduate students in physics, chemistry, and materials science fields; and university professors and lecturers related to studies in the field of liquid crystals will find this collection of papers highly informative and rewarding.
Download or read book Ferroic Materials Based Technologies written by Inamuddin and published by John Wiley & Sons. This book was released on 2024-05-29 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: FERROIC MATERIALS-BASED TECHNOLOGIES The book addresses the prospective, relevant, and original research developments in the ferroelectric, magnetic, and multiferroic fields. Ferroic materials have sparked widespread attention because they represent a broad spectrum of elementary physics and are employed in a plethora of fields, including flexible memory, enormous energy harvesting/storage, spintronic functionalities, spin caloritronics, and a large range of other multi-functional devices. With the application of new ferroic materials, strong room-temperature ferroelectricity with high saturation polarization may be established in ferroelectric materials, and magnetism with significant magnetization can be accomplished in magnetic materials. Furthermore, magnetoelectric interaction between ferroelectric and magnetic orderings is high in multiferroic materials, which could enable a wide range of innovative devices. Magnetic, ferroelectric, and multiferroic 2D materials with ultrathin characteristics above ambient temperature are often expected to enable future miniaturization of electronics beyond Moore’s law for energy-efficient nanodevices. This book addresses the prospective, relevant, and original research developments in the ferroelectric, magnetic, and multiferroic fields. Audience The book will interest materials scientists, physicists, and engineers working in ferroic and multiferroic materials.
Download or read book Ferroelectric Materials for Energy Harvesting and Storage written by Deepam Maurya and published by Woodhead Publishing. This book was released on 2020-10-14 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need to more efficiently harvest energy for electronics has spurred investigation into materials that can harvest energy from locally abundant sources. Ferroelectric Materials for Energy Harvesting and Storage is the first book to bring together fundamental mechanisms for harvesting various abundant energy sources using ferroelectric and piezoelectric materials. The authors discuss strategies of designing materials for efficiently harvesting energy sources like solar, wind, wave, temperature fluctuations, mechanical vibrations, biomechanical motion, and stray magnetic fields. In addition, concepts of the high density energy storage using ferroelectric materials is explored. Ferroelectric Materials for Energy Harvesting and Storage is appropriate for those working in materials science and engineering, physics, chemistry and electrical engineering disciplines. Reviews wide range of energy harvesting including solar, wind, biomechanical and more Discusses ferroelectric materials and their application to high energy density capacitors Includes review of fundamental mechanisms of energy harvesting and energy solutions, their design and current applications, and future trends and challenges
Download or read book Flexoelectricity In Solids From Theory To Applications written by Alexander K Tagantsev and published by World Scientific. This book was released on 2016-08-11 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique compendium is devoted to flexoelectricity — the response of polarization to a strain gradient. The effect is analogous to piezoelectricity which is the response of polarization to strain itself. In contrast to piezoelectricity, which appears only in non-centrosymmetric materials, flexoelectric effect is allowed by symmetry in any materials. It becomes appreciable in nano-scale systems, where large strain gradients arise. The book discusses different nano-scale manifestations of the effect ranging from repulsion of acoustic and optic branches of materials to flexoelectricity in domain walls. It mainly caters for scientists, engineers and students.
Download or read book An Elementary Course On The Continuum Theory For Nematic Liquid Crystals written by Giovanni Barbero and published by World Scientific Publishing Company. This book was released on 2000-10-27 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book was written to enable physicists and engineers to learn, within a single course, some topics in variational calculus, theory of elasticity, molecular models, and surface properties of nematic materials. It prepares graduate students for studies that require a simple knowledge in the physics of nematic liquid crystals.With this consideration in mind, the authors have formulated the problems concerning the continuum theory of liquid crystals into a precise form. In working out the solutions, they have analyzed, systematically and naturally, the techniques and methods of variational calculus. Special attention is dedicated to the analysis of well-posed and ill-posed variational problems. The presence of sub-surface discontinuity in the nematic orientation is analyzed using different techniques. A full chapter is devoted to this aspect of the theory of elasticity of nematic media.
Download or read book Fundamentals of Liquid Crystal Devices written by Deng-Ke Yang and published by John Wiley & Sons. This book was released on 2014-12-03 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid Crystal Devices are crucial and ubiquitous components of an ever-increasing number of technologies. They are used in everything from cellular phones, eBook readers, GPS devices, computer monitors and automotive displays to projectors and TVs, to name but a few. This second edition continues to serve as an introductory guide to the fundamental properties of liquid crystals and their technical application, while explicating the recent advancements within LCD technology. This edition includes important new chapters on blue-phase display technology, advancements in LCD research significantly contributed to by the authors themselves. This title is of particular interest to engineers and researchers involved in display technology and graduate students involved in display technology research. Key features: Updated throughout to reflect the latest technical state-of-the-art in LCD research and development, including new chapters and material on topics such as the properties of blue-phase liquid crystal displays and 3D liquid crystal displays; Explains the link between the fundamental scientific principles behind liquid crystal technology and their application to photonic devices and displays, providing a thorough understanding of the physics, optics, electro-optics and material aspects of Liquid Crystal Devices; Revised material reflecting developments in LCD technology, including updates on optical modelling methods, transmissive LCDs and tunable liquid crystal photonic devices; Chapters conclude with detailed homework problems to further cement an understanding of the topic.
Download or read book Electrooptic Effects in Liquid Crystal Materials written by L.M. Blinov and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 477 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrooptic effects provide the basis for much liquid-crystal display technology. This book, by two of the leaders in liquid-crystal research in Russia, presents a complete and accessible treatment of virtually all known phenomena occurring in liquid crystals under the influence of electric fields.
Download or read book Statistical Mechanics of Polar Biaxial and Chiral Order in Liquid Crystals written by Subas Dhakal and published by . This book was released on 2010 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation addresses three distinct problems in liquid crystal: phase transitions among different SmCP phases of bent-core liquid crystal, flexoelectric effect in nematic liquid crystal and interplay between chirality and biaxiality in cholesteric liquid crystal. These problems are studied with computer simulations and analytical calculations. The first part of this dissertation is about chiral switching in smectic phases of bent-core liquid crystals. The phenomenon is investigated with a lattice Monte Carlo simulation and a phenomenological theory. Both methods show that the antiferroelectric (AFE) ground state switches into a ferroelectric state (FE) at sufficiently large electric field. In this transition, the chirality of the phase could change or not. In the case of weak inter-layer chiral coupling, anticlinic order of molecules from layer to layer could remain through the transition -thus changing the chirality of the phase. However, for a large value of chiral coupling, the anticlinic state could change to a synclinic state in the transition -thus preserving the chirality of the phase. Another area of focus is on flexoelectric effect in nematic liquid crystal. Recent experiments have shown that bent-core liquid crystals have a surprisingly large bend flexoelectric coefficient, up to 35 nC/m, roughly three orders of magnitude larger than the typical value. With this large bend flexoelectric coefficient, bent-core liquid crystals may be practical materials for converting mechanical into electrical energy. One of the focal points of this dissertation is to explain the large flexoelectric effect found in bent-core liquid crystals. Theoretical models of splay and bend flexoelectric effect are developed that incorporates the coupling between the director distortion (either splay or bend) and polarization. Through these models the flexoelectric response as a function of interaction parameters, temperature, and applied electric field is studied. Simulations and analytical calculations show that there is a large flexoelectric effect in the nematic phase, which diverges as the system approaches the transition to the polar phase. This observation demonstrated that flexoelectricity is not just a molecular effect but could be a statistical phenomenon associated with the response of correlated volumes of molecules, which increases as one approaches the polar phase. Finally, we investigate the statistical mechanics of chirality and biaxiality in liquid crystals through a variety of theoretical approaches, including Monte Carlo simulations, lattice mean-field theory, and Landau theory. All of these calculations show that there is an important interaction between cholesteric twist and biaxial order: The twist acts as a field on the biaxial order, and conversely, the biaxial order increases the twist, i.e. reduces the pitch. We model the behavior of chiral biaxial liquid crystals as a function of temperature, and discuss how the predictions can be tested in experiments.
Download or read book Geometric Methods in the Elastic Theory of Membranes in Liquid Crystal Phases written by Zhong-Can Ou-Yang and published by World Scientific. This book was released on 1999 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a comprehensive description of the mechanical equilibrium and deformation of membranes as a surface problem in differential geometry. Following the pioneering work by W Helfrich, the fluid membrane is seen as a nematic or smectic ? A liquid crystal film and its elastic energy form is deduced exactly from the curvature elastic theory of the liquid crystals. With surface variation the minimization of the energy at fixed osmotical pressure and surface tension gives a completely new surface equation in geometry that involves potential interest in mathematics. The investigations of the rigorous solution of the equation that have been carried out in recent years by the authors and their co-workers are presented here, among which the torus and the discocyte (the normal shape of the human red blood cell) may attract attention in cell biology. Within the framework of our mathematical model by analogy with cholesteric liquid crystals, an extensive investigation is made of the formation of the helical structures in a tilted chiral lipid bilayer, which has now become a hot topic in the fields of soft matter and biomembranes.
Download or read book Nuclear Magnetic Resonance Spectroscopy of Liquid Crystals written by Ronald Y. Dong and published by World Scientific. This book was released on 2010 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: This edited volume provides an extensive overview of how nuclear magnetic resonance can be an indispensable tool to investigate molecular ordering, phase structure, and dynamics in complex anisotropic phases formed by liquid crystalline materials. The chapters, written by prominent scientists in their field of expertise, provide a state-of-the-art scene of developments in liquid crystal research. The fantastic assortment of shape anisotropy in organic molecules leads to The discoveries of interesting new soft materials made at a rapid rate which not only inject impetus to address the fundamental physical and chemical phenomena, but also the potential applications in memory, sensor and display devices. The review volume also covers topics ranging from solute studies of molecules in nematics and biologically ordered fluids to theoretical approaches in treating elastic and viscous properties of liquid crystals. This volume is aimed at graduate students, novices and experts alike, and provides an excellent reference material for readers interested in the liquid crystal research. it is, indeed, a reference book for every science library to have.
