Liquid Crystals In Biotribology

This book summarizes the theoretical and experimental studies confirming the concept of the liquid-crystalline nature of boundary lubrication in synovial joints. It is shown that cholesteric liquid crystals in the synovial liquid play a significant role in the mechanism of intra-articular friction reduction. The results of structural, rheological and tribological research of the creation of artificial synovial liquids containing cholesteric liquid crystals in natural synovial liquids are described. These liquid crystals reproduce the lubrication properties of natural synovia and provide a high chondroprotective efficiency. They were tested in osteoarthritis models and in clinical practice.

This volume is oriented toward industrial applications of liquid crystals in the friction-lubrication area. Broad techniques are stressed, leaving the path open for varied applications. Individual topics discussed include the lubricating properties of liquid crystals, numerical analysis of layered liquid crystals in a thin wedge, spectral changes of liquid crystals undergoing shear in a simulated bearing, temperature effects on the tribological properties of thermotropic liquid crystals, the effect of liquid-crystalline structures on lubrication of aluminum surfaces, the basis of the use of lyotropic liquid crystals in lubrication, and film thickness and frictional behavior in concentrated point contacts.

This book discusses the tribological, rheological and optical properties of liquid-crystal nanomaterials as well as lubricant media. It also describes the formation of liquid-crystal materials and the application of cholesteric liquid-crystal compounds in technical friction units and in human and animal joints. Further, it shows the connection between the tribological and other physical properties of liquid-crystal cholesterol compounds and develops a lubricity conceptual model of cholesteric–nematic, liquid-crystalline nanostructures on the basis of physical and energetic interpretations. This general model is valid for all surfaces and friction pairs, including biopolymers, and could lead to applications of cholesteric liquid-crystalline nanomaterials in different friction units and tribosystems as well as in the treatment of joint diseases.

1. Liquid crystals: a unique phase of matter -- 2. Medical displays -- 3. Liquid crystals in spectroscopy, microscopy and hyperspectral imaging -- 4. Liquid crystal biosensors -- 5. Liquid crystak lasers -- 6. Biomimicking with liquid crystals -- 7. Actuators and delivery systems

Over the past ten years liquid crystals have attracted much interest and considerable progress has been made with respect to our knowledge in this field. The recent development was initiated mainly by the work of J. L. Fergason and G. H. Heilmeier, who pointed out the importance of liquid crystals for thermographic and electro optic applications. The first part of this book is a brief introduction to the physics of liquid crystals. The structures and properties of the three basic types of liquid crystals are discussed. A special paragraph is devoted to electric-field effects, which are important in display applications. The chapter on Scientific Applications gives an insight into the potential applications of liquid crystals in fundamental research, with special emphasis on explaining the principles involved. Two groups of potential applications are discussed in detail: 1. the use of liquid crystals as anisotropic solvent for the determination of molecular properties by means of spectroscopy, and 2. their use in analytical chemistry, particularly in gas chromatography. The reverse process involves the use of the dissolved molecules as microscopic probes in the investigation of the dynamical molecular structure of anisotropic fluid systems (e.g. biological membranes). This extremely important technique is also described.

The liquid crystalline state may be identified as a distinct and unique state of matter which is characterised by properties which resembles those of both solids and liquids. It was first recognised in the middle of the last century through the study of nerve myelin and derivatives of cholesterol. The research in the area really gathered momentum, however, when as a result of the pioneering work of Gray in the early 1970's organic compounds showing liquid crystalline properties were shown to be suitable to form the basis of display devices in the electronic products. The study of liquid crystals is truly multidisciplinary and has attached the attention of physicists, biologists, chemists, mathematicians and electronics engineers. It is therefore impossible to cover all these aspects fully in two small volumes and therefore it was decided in view of the overall title of the series to concentrate on the structural and bonding aspects of the subject. The Chapters presented in these two volumes have been organised to cover the following fundamental aspects of the subject. The calculation of the structures of liquid crystals, an account of their dynamical properties and a discussion of computer simulations of liquid crystalline phases formed by Gay Berne mesogens. The relationships between molecular conformation and packing are analysed in some detail. The crystal structures of liquid crystal mesogens and the importance of their X ray scattering properties for characterisational purposes are discussed.

Polymer-dispersed liquid crystal (PDLC) materials are of interest both for their potential in display technology and the fascinating science found in liquid crystals confined to small cavities. Liquid Crystal Dispersions is a comprehensive overview of the science and technology of this new class of materials. Topics covered include formation of PDLC devices, a catalog of droplet structures and transformations, device electro-optical properties, and applications. Liquid Crystal Dispersions will be of value to the nonspecialists keen on gaining an overview of this new field, as well as to specialists interested in a comprehensive review of work in this area. Contents:Introduction:The PDLC ParadigmRecipes:Emulsion Methods for PDLC FilmsPhase Separation Methods for PDLC FilmsNematic Configurations within Droplets:Factors Controlling Nematic AlignmentCatalog of Droplet StructuresTransformations between Droplet StructuresElectro-Optical Effects:Light ScatteringDichroic Effects in PDLC FilmsHysteresis and Memory EffectsPDLC Electrical PropertiesApplications:Projection DisplaysDirect-View Scattering-Mode Displaysand other papers Readership: Liquid crystal research scientists and people interested in display technology. keywords: “It is difficult to think of a better author to provide an overview of Liquid Crystal Dispersions than Paul Drzaic … a most welcome addition to his contributions … wholeheartedly recommending this book to both beginners and specialists. It is very well researched and clearly written for all levels of expertise.” Liquid Crystals Today