Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chemistry communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, we review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymerizations resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymerization are all reviewed.

Thiol–Ene Click Chemistry

Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.

Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip

Polymers for flexible displays: From material selection to device applications

An overview is given of theory and experiments on liquid crystal phases which appear in solutions of elongated colloidal particles or stiff polymers. The Onsager (1949) virial thecry for the isotropionematic transition of thin rodlike particles is treated comprehensively along with extensions to polydisperse solutions and soft interactions. Computer simulations of liquid crystal phases in hard particle fluids are summarized and used to assess the quality of statistical mechanical thwries for stiff panicles at higher dume haion-like the inclusion of higher Virial coefficients, yexpansion, scaled particle theory and density functional theory. Both computer simulations and density functional theory indicate formation of more highly ordered smectic phases. The range of experimental applicability h strongly widened by the extension of the viriai theory to wormlike chains by Khokhlov and Semenov (1981, 1982). Fmally, experimental results for a number of carefully studied, charged and uncharged colloids and polymers are summarized and wmpared to theoretical results. IE many cases the agreement is semi-quantitative.

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Phase transitions in lyotropic colloidal and polymer liquid crystals

The English-language dictionary defines wrinkles as "small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking". In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (e.g., wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.

Soft matter with hard skin : From skin wrinkles to templating and material characterization

A liquid crystal display has a pair of transparent electrodes, an anti-ferroelectric liquid crystal therebetween, a polarizer and an analyzer attached to the electrodes. The smectic layers are perpendicular to the electrodes and the liquid crystal has a twisted structure. The directors on the surfaces on the two electrodes are symmetrically aligned with respect to the polarization axis of the polarizer so that the average optical axis of the liquid crystal coincides with the polarization axis of the polarizer. In absence of applied electric field, the incident light through the polarizer passes through the liquid crystal slab with maintaining its polarization. However, when an electric field is applied, the liquid crystal molecules experiences some degree of distortion and the average optical axis rotates. Therefore, the incident light passes through the liquid crystal slab with rotating the polarization.

Anti-ferroelectric liquid crystal display

The concept of the azimuthal surface layer anchoring (ASLA) is introduced to describe the field-induced layer reorientation in a short pitch ferroelectric liquid crystal (FLC). It was found that for the larger ASLA, the smaller layer reorientation occurs and saturates in the high field regime, especially near both surfaces. The ASLA tends to renormalize the surface interactions which produce the asymmetric director switching. It is suggested that the ASLA acts as a hindered restoring force for the layer reorientation.

Effect of azimuthal surface layer anchoring on field-induced layer reorientation in a short pitch ferroelectric liquid crystal

on a flexible liquid crystal display (LCD) fabricated using self-aligned microstructures of the photopolymer/spacer composite material through a wettability patterning process. The microstructures confined on the patterned alignment layer provide spacers for the uniform cell gap as well as the mechanical stability. No structural change of the substrates was observed during the fabrication process. Our flexible LCD provides good flexibility, durability, and excellent electro-optic performances. This method can be applicable to the fabrication of large plastic LCDs using a roll-to-roll process. 1. Introduction flexible display(1) is one of the most promising display devices in the ubiquitous era due to several advantages such as higher portability and better durability than existing displays. The design scheme of the flexible display has potential for realizing future applications such as wearable computers, smart cards, and display systems in small packages with totally new concepts. Among a number of flexible display technologies under development, liquid crystal displays(2,3) (LCDs) are well established compared to organic light emitting devices(4) and electrophoretic displays(5). The use of flexible substrates, however, brings various issues on the reliability of the LCD. Flexible devices might be bent or rolled up with an elastic deformation of the substrates, which results in irregular thickness of the liquid crystal (LC) layer. In addition, the accompanying flow of the in-between LC significantly affects the optical properties of the LCD. From the viewpoint of improving both the mechanical stability between the top and bottom substrates and the electro-optic (EO) properties under the bent environment, a variety of techniques have been proposed and demonstrated. Recently, polymer wall formation techniques using the isotropic/anisotropic phase separation of photopolymer and liquid crystal (LC) composite systems have been proposed and successfully demonstrated(6-12). However, these systems suffer from inevitable drawbacks that are inappropriate for large size panel and mass production. Moreover, high image quality is not guaranteed due to the deterioration of contrast ratio by the residual polymer after the phase separation process. In addiction, the fabrication of the flexible LCD needs to be carried out with no chemical etching process to avoid structural changes and damages of the substrates. Therefore, a new technology applicable for a simple process and providing better EO properties should be developed. In this work, we demonstrate a new method of improving the mechanical stability of the flexible LCDs by spontaneously forming microstructures of a photopolymer/spacer composite. The wettability patterning technique used here confines the composite in patterned array regions prepared on the LC alignment layer without the chemical etching process. The microstructures serve as columnar spacers for the uniform cell gap as well as an adhesion layer that allows for mechanical stability and reproducibility against the bending deformations after ultraviolet irradiation. The EO measurements show the fast response time of about 7 ms, and the contrast ratio of 150 : 1 in the normally white mode. Our flexible LCD provides better electro-optic properties than the polymer/ LC composite system.

P‐121: Direct Formation of Polymer Walls by Wettability Patterning for Flexible Liquid Crystal Displays

In recent years, augmented/virtual reality (AR/VR) has been attracting attention and investment in both the tech and academic communities, kickstarting a new wave of innovations. In the wake of this momentum, this feature issue was launched to cover the latest advances in this burgeoning field that pertains to optics and photonics. Alongside the 31 research articles being published, this introduction is appended to share with readers the behind-the-issue stories, submission statistics, reading guides, author biographies, and editors' perspectives.

Introduction to the feature issue on augmented/virtual reality: optics & photonics.

A transflective display with high speed and gray scale capability is demonstrated using a vertically aligned deformed helix ferroelectric liquid crystal (VA-DHFLC) mode in a single gap geometry. In order to compensate the optical path difference between transmissive (T) and reflective (R) regions, dual types of transverse electric fields are produced from in-plane electrodes prepared on two substrates in T regions and on only one substrate in R regions. The VA-DHFLC mode employed in such electrode configuration provides several unique features such as defect-free alignment over large area, fast response, and gray scale capability without hysteresis.

Sin-Doo Lee

Papers

Anti-ferroelectric liquid crystal display

Effect of azimuthal surface layer anchoring on field-induced layer reorientation in a short pitch ferroelectric liquid crystal

P‐121: Direct Formation of Polymer Walls by Wettability Patterning for Flexible Liquid Crystal Displays

Introduction to the feature issue on augmented/virtual reality: optics & photonics.

A Fast Transflective Ferroelectric Liquid Crystal Display with Gray Scales in a Single Gap Geometry with Dual Transverse Electric Fields