Alignment Materials Research Articles

Electrically tunable metasurface in TN LC configuration with enhanced quality factor and metaatom-induced alignment.

Dynamic metasurface with subwavelength dimensions has emerged as a key optical technology in recent years. Although various active tuning mechanisms are being proposed, liquid crystal-based dynamic metasurface remains attractive due to its large index variation, electrical tunability, reliability, and mass fabricability. In this work, we report a dynamic metasurface for amplitude modulation in reflection, with twisted nematic liquid crystal configuration to reduce broadband reflection in the off state. The metasurface consists of coupled subwavelength grating fingers, which provide alignment for the liquid crystal without the need for an additional alignment material or process. The alignment of liquid crystal materials was examined between crossed polarizers, and the twist of nematic liquid crystal was confirmed. The coupled grating fingers exhibit a resonance quality factor of 27 at telecommunication wavelength and an amplitude modulation depth of 8 times of the minimum at 1630 nm. This work highlights the potential of liquid crystal-based tunable metasurface, combining polarization control via liquid crystal and spectrum control via metasurface. Furthermore, it also shows a way in which the interaction between liquid crystal and metasurface is used for an alignment layer-free cell assembly process.

P‐92: Photo‐sensitive Vertical Alignment Material with Room Temperature Dipcoating Technique

Using a room‐temperature dip‐coating technique, we propose a cinnamate‐unit‐phosphonic‐acid‐based surfactant alignment material that can be orientated by linear polarized light. Using the technique, we can treat a substrate simply and quickly, achieving a uniform pretilt angle of approximately 86° with a low dose of polarized UV light. We examined the optical and electrical properties of the alignment material under different conditions, including pretilt angles under different irradiation doses, voltage holding ratio (VHR) and residual direct circuit (RDC) when using different solvents, stability, etc. The results show that the material has acceptable performance. Since the phosphonic acid series photosensitive materials still have much room for optimization, we believe it is a potential new generation of photosensitive surfactant alignment materials.

Q&A of liquid crystal alignment: theory and practice

We selected and summarized the most important aspects of liquid crystal alignment. Alignment by the surface profile and flat surface alignment are discussed as the main factors leading to the high-quality orientation of liquid crystals. The advanced level of understanding and formulation allows linking the alignment layer properties to the molecular structure of the alignment material. The paper reviews and combines the latest knowledge about liquid crystal alignment, dwells upon the relationship between the polar and azimuthal anchoring energy, explains the major particularities regarding anchoring measurements in the case of birefringent alignment materials with truly high azimuthal anchoring energy, and observes the current trends of water-friendly alignment materials and their application in geometrical phase device fabrication.

Full-angle chip scale package of mini LEDs with a V-shape packaging structure.

The light distribution of light-emitting diodes (LEDs) generally resembles that of a Lambertian light source. When used as large-area light sources, the light distribution angle of LEDs must be modified through secondary optics design to achieve uniformity and minimize the number of light sources. However, secondary optical components pose several challenges such as demanding alignment accuracy, material aging, detachment, and lower reliability. Therefore, this paper proposes a primary optical design approach to achieve full-angle emission in LEDs without the need for lenses. The design employs a flip-chip as the light source and incorporates a V-shaped packaged structure, including a white wall layer, optical structure layers, and a V-shaped diffuse structure. With this design, the LEDs achieve full-angle emission without relying on lenses. Our experimental results demonstrated a peak intensity angle of 77.7°, a 20.3% decrease in the intensity of the central point ratio, and a full width at half maximum (FWHM) of the light distribution of 175.5°. This design is particularly suitable for thin, large-area, and flexible backlight light sources. Moreover, the absence of secondary optical components allows for a thinner light source module.

Multiscale Control of Nanofiber-Composite Hydrogel for Complex 3D Cell Culture by Extracellular Matrix Composition and Nanofiber Alignment.

In order to manipulate the complex behavior of cells in a 3-dimensional (3D) environment, it is important to provide the microenvironment that can accurately portray the complexity of highly anisotropic tissue structures. However, it is technically challenging to generate a complex microenvironment using conventional biomaterials that are mostly isotropic with limited bioactivity. In this study, the gelatin-hyaluronic acid hydrogel incorporated with aqueous-dispersible, short nanofibers capable of insitu alignment is developed to emulate the native heterogeneous extracellular matrix consisting of fibrous and non-fibrous components. The gelatin nanofibers containing magnetic nanoparticles, which could be aligned by external magnetic field, are dispersed and embedded in gelatin-hyaluronic acid hydrogel encapsulated with dermal fibroblasts. The aligned nanofibers via magnetic field could be safely integrated into the hydrogel, and the process could be repeated to generate larger 3D hydrogels with variable nanofiber alignments. The aligned nanofibers in the hydrogel can more effectively guide the anisotropic morphology (e.g., elongation) of dermal fibroblasts than random nanofibers, whereas myofibroblastic differentiation is more prominent in random nanofibers. At a given nanofiber configuration, the hydrogel composition having intermediate hyaluronic acid content induces myofibroblastic differentiation. These results indicate that modulating the degree of nanofiber alignment and the hyaluronic acid content of the hydrogel are crucial factors that critically influence the fibroblast phenotypes. The nanofiber-composite hydrogel capable of directional nanofiber alignment and tunable material composition can effectively induce a wide array of phenotypic plasticity in 3D cell culture.

Cost-effective photolithography-based dual liquid crystal alignment for versatile electro-optic applications

Nematic liquid crystals (NLCs) containing rod-shaped molecules exhibit remarkable birefringence and tunability. Therefore, they are of high interest for numerous electro-optic applications. Uniform molecular orientation is of utmost importance for their effective use. Current techniques for LC alignment, such as mechanical rubbing or photo-alignment, have limitations in creating specifically complex LC orientation patterns. To address this issue, we have developed a cost-effective photolithography-based technique for dual LC alignment which combines planar and vertical alignments. Our process involves inexpensive exposure systems and a lift-off process and employs commercially-available alignment materials, thereby reducing production costs. We utilized this process to generate a tunable phase grating with diffraction efficiencies which can be varied through voltage application, thus demonstrating the potential of dual alignment. Furthermore, we investigated smart windows that are insensitive to polarization, utilizing a two-dimensional grating structure, achieving high haze values and dynamic shading without relying on incident polarization.

Recent progress in liquid crystal devices and materials of TFT-LCDs

Thin-film-transistor-liquid crystal displays (TFT-LCDs) still dominate most of the display markets due to a big leap in image quality while keeping low cost and superior reliability, and its evolution is continuing to compete with emerging emissive displays. In this paper, recent progress in liquid crystal technologies mainly focusing on fringe-field switching (FFS) and polymer-stabilized vertical alignment (PS-VA) modes and materials for improving electro-optic performances is reviewed.

Load Carrying Capacity Enhancing Design and Lubrication Investigation of the Magnetic-Water Double Suspension Elastic Support Thrust Bearing

Aiming at the problem that the traditional water-lubricated bearing cannot carry the heavy load and adapt to the constantly changing operating conditions for the high-power Rim Driven Thruster (RDT), the principle structure of the Magnetic Water-double-suspension Elastic-support Thrust Bearing (MWETB) is designed and the optimal structure parameters of the bearing are selected using simulation. To demonstrate the reliability of the MWETB under the RDTs’ actual working conditions, performance tests, which include the magnetic flux density, magnetic force, and lubrication performance, are carried out. The simulation and experimental results indicate that the optimal offset ratios are in two intervals, and the magnetic alignment and sheath materials have a great effect on the load reduction. The load-carrying force has obvious zoning characteristics with the change in bearing clearance. Besides, compared with the water-lubricated thrust bearings, the MWETB has advantages in terms of minimum film thickness and friction coefficient.

High contrast ratio and fast response ferroelectric liquid crystal displays based on alignment optimization

There are a series of polyimide material synthesized and studied with different dianhydride and diamine structures. By exploring the structural variations of these materials and their surface energy characteristics, we successfully obtained ferroelectric liquid crystal devices exhibiting exceptional optical and electrical properties. Notably, our findings highlight that a specific polyimide material comprised of dianhydride with a benzene ring structure and diamine with a long-chain amino structure demonstrates remarkable achievements, including a maximum contrast of 872 and a rapid response speed of less than 0.1 ms. These results establish the superiority of this particular polyimide material over its commercially available counterparts. Additionally, the optical characteristics of various polyimide materials were examined by establishing a correlation between these properties and the surface energy of the materials. This research presents a novel approach to developing alignment materials suitable for ferroelectric liquid crystal applications. The implications of our findings are of great significance in driving advancements in field-sequential-color display devices with high pixels per inch in the ferroelectric liquid crystal field.

Angular Dependence of Guest–Host Liquid Crystal Devices with High Pretilt Angle Using Mixture of Vertical and Horizontal Alignment Materials

To date, devices exhibiting incidence-angle-dependent transmittance have been fabricated by imparting an angle to a bulk liquid crystal (LC) by aligning the LC in the vicinity of one substrate horizontally (with respect to the substrate) while aligning the LC in the vicinity of another substrate vertically. Another approach has been to control LC angles near substrates by blending or layering horizontal and vertical alignment films. In this study, we control LC angles near substrates by controlling the pretilt angles of blended alignment films; for specific angles, we use dichroic dyes to characterize the incidence angle dependence of these LC devices. Using a guest/host LC device with a pretilt angle near 45°, we successfully construct an LC element with a transmittance peak near a polar angle of 45°.

Design of Virtual Lab Geometry Using Virtual to Supplement Learning In Mathematics Classes

In learning the geometry of the parallels, there is a misconception between the position of the two lines and the position of the two angles. One way by which students can learn this material better is by virtual reality-based virtual lab media that is able to display objects like in the real world. The purpose of this research is to design the learning media, Virtual Laboratory Geometry Based on Virtual Reality so that students of the mathematics education study program at the Universitas PGRI Semarang are able to understand the alignment material accurately. This study uses ADDIE model development research with five steps that are carried out systematically. Virtual reality-based geometry lab application products have been validated by learning materials experts and learning media experts with scores of 91 and 92, which are categorized as very suitable for use in learning geometry in the classroom.
 Keywords: Design; Virtual Geometry Lab; Supplements; Learning Media

Monomolecular vertical alignment layer with room temperature processibility for flexible liquid crystal displays

In this article, we disclose a vertical alignment material using alkylphosphonic acid for liquid crystals that only requires simple room temperature treatments to secure good vertical alignment for liquid crystals. Alkylphosphonic acid forms a monomolecular layer on the substrate providing strong vertical alignment. The proposed alignment layer shows decent electro-optical properties, such as high voltage holding ratio, low residual direct current voltage, low image sticking parameter, etc. Later, we combine the alkylphosphonic acid with photo-rewritable azo-dye to fabricate a hybrid alignment of nematic cells and study its stability and anchoring energy. The material shows great compatibility with flexible substrates. Thus, the proposed alignment layer of alkylphosphonic acid can potentially find application as the alignment layer for flexible liquid crystal displays.

54.3: Invited Paper: Surface Control of LC Alignment for Creation of Liquid Crystal Lenses Arrays

New photosensitive alignment materials, capable to obtain pretilt angle from 90 to 0 degree in single technological process of UV exposure, are developed. The novel technological method for fabrication LC lens and LC lenses arrays has been developed based on new pretilt angle gradient alignment materials. Laboratory samples of voltage tunable LC lens and LC lenses arrays are obtained and characterized. The developed low cost fabrication technology of tunable micro‐lenses arrays based on photosensitive alignment materials has low complexity and is perspective for light field technology applications.

56.2: Invited Paper: Novel Bistable Liquid Crystal Materials for AR/VR Technology, Vehicle and Flexible Display

The object of study is chiral-nematic and smectic A liquid crystals. The aim of the work is to develop new bistable materials with improved physico-chemical and electro-optical properties for various applications. Chiral liquid-crystalline compounds and compounds characterized by the presence of the smectic A phase over a wide temperature range were synthesized during the studies. The influence of the viscoelastic properties of liquid crystals, the anchoring energy of the alignment material, and the helical twisting power of chiral dopants on the memory effect in chiral-nematic liquid crystals was investigated. In order to clarify the possible mechanism of bistability in highly twisted nematics, we performed a numerical simulation of the reorientation of liquid crystal molecules in an electric field. It was also necessary to find out which parameters of the liquid crystal material have the greatest effect on the bistability. Based on the synthesized smectic compounds, mixtures with different values of optical anisotropy and viscosity were developed. The influence of the compounds structure (bridge fragments, polar groups, alkyl chains) on mesomorphic and basic physico-chemical characteristics was determined. Electrically and electrochemically stable ion dopants were also synthesized with a number of organic cations and organic/inorganic anions. The composition of mixtures has been optimized for long-term operation, especially in the upper operating temperature range.

47.2: A New Generation of LCD's Based on Ferroelectric Liquid Crystals Showing Uniform and Stable Orientation

The object of the research is new ferroelectric liquid crystal (FLC) compositions with a wide temperature range of SmC* phase and the fabrication of a fast switching mechanically stable display with improved electro-optical properties. The aim of the work is to synthesize new highly viscous non-chiral compounds and to develop on their basis in combination with known ferroelectric compounds with a large value of spontaneous polarization of mixtures stable to mechanical deformations. As a result, the influence of the length of nonchiral molecules and the viscosity of the compositions on the mechanical stability of the alignment was investigated. The relationship between the surface anchoring energy of the alignment materials and the viscoelastic properties of ferroelectric liquid crystals is described. For our investigation we synthesized new non-chiral smectic C compounds containing four or five attached phenyl rings, so called 4,4'-di-substituted quaterphenyls 4,4'-di-substituted-pentaphenyls which have in series-connected benzene rings, but not separated by bridging fragments. We found that the switching of FLC mixtures with such compounds is much faster compared to mixtures containing compounds with the same quaterphenyl or pentaphenyl fragment in chiral molecules. New ferroelectric liquid crystal compositions with optimized parameters have been designed. The possibility to develop FLC displays with switching time less than 10 μs and stable against mechanical deformations and independent of the type of alignment material and pretilt angle was shown.

Multi-stakeholder Engagement for the Sustainable Development Goals: Introduction to the Special Issue

The world is not on track to achieve Agenda 2030—the approach chosen in 2015 by all UN member states to engage multiple stakeholders for the common goal of sustainable development. The creation of the 17 Sustainable Development Goals (SDGs) arguably offered a new take on sustainable development by adopting hybrid and principle-based governance approaches, where public, private, not for profit and knowledge-institutions were invited to engage around achieving common medium-term targets. Cross-sector partnerships and multi-stakeholder engagement for sustainability have consequently taken shape. But the call for collaboration has also come with fundamental challenges to meaningful engagement strategies—when private enterprises try to establish elaborate multi-stakeholder configurations. How can the purpose of businesses be mitigated through multi-stakeholder principle-based partnerships to effectively serve the purpose of a common sustainability agenda? In selecting nine scholarly contributions, this special issue aims at advancing this discourse. To stimulate further progress in business studies, this introductory essay, furthermore, identifies three pathways for research on multi-stakeholder engagement processes in support of the Decade of Action along three coupling lines: multi-sector alignment (relational coupling), operational perception alignment (cognitive coupling) and goal and strategic alignment (material coupling).

A new generation of ferroelectric liquid crystals with homogeneous and shock-stable orientation

ABSTRACT This research is focused on ferroelectric liquid crystal compositions with a wide temperature range of the SmC* phase and the design of mechanically stable, fast switching surface-stabilised ferroelectric liquid crystal display with improved electro-optical properties. The work involves the synthesis of high-viscosity achiral compounds and the creation of mixtures based on them that are resistant to mechanical shocks. For this reason, the viscosity of the compositions and the length of achiral molecules were investigated for their impact on mechanical stability of the alignment. For our investigation we synthesised new achiral smectic C compounds containing four or five attached phenyl rings, so called 4,4’-di-substituted quaterphenyls 4,4’-di-substituted-pentaphenyls which have in series-connected benzene rings, but not separated by bridging fragments. We found that the switching of FLCs with such compounds is much faster compared to mixtures containing compounds with the same quaterphenyl or pentaphenyl fragment in chiral molecules. New ferroelectric liquid crystal compositions with optimised parameters have been devised. This work demonstrated that surface-stabilised ferroelectric liquid crystal display could be developed that had switching times less than 10 μs, was stable against mechanical deformations and was independent of alignment material and pre-tilt angle.

P‐116: Student Poster: Transparent Displays Using Vertically Aligned Polyimide‐Free Liquid Crystal‐Polymer Composite

In this work, we propose a normally transparent polymer‐networked liquid crystal (PNLC) mode to use as a transparent display with energy saving, high contrast ratio, easy manufacturing process (Polyimide‐free). In this system, we adopt a homeotropic alignment material (HAM), which serves as both vertical alignment inducer and photopolymerizable reactive mesogen (RM). With no polarizers, the ground state shows clear transparency, and applying voltage induces an opaque scattering state successfully. By using double‐sided UV irradiation strategy, we can minimize hysteresis on voltage‐dependent transmittance. we believe the proposed concept will open a way to reach a novel transparent display with high transparency.

Investigation of the thermomechanical performance of hybrid polymer composite using micro bamboo powder and graphite flakes

AbstractThe current research project is dedicated to tackling the issue of fiber alignment and composite material delamination. Alkali treatment is performed to enhance the bamboo filler reinforced composite's mechanical performance as well as interfacial bonding strength. The hybrid composite is developed with varied bamboo powder content from 2.5 to 12.5 wt% and graphite nanoplatelets (GN) are reinforced in the polymer matrix. The hybrid composite is manufactured with bamboo powder approximately 65 μm sized and GN for electrical and electronics packaging, heat sink, conductive paste, light back cover for thermal management, automobile parts, and packaging goods. The developed material is investigated experimentally through the tensile test, modulus of elasticity, storage modulus, thermal conductivity, corrosion and tribological analysis. Results revealed that 5 and 7.5 wt% bamboo filler with 1 wt% GN gives the best property among others.

PLANNING AND DESIGNING STANDARD OF RURAL ROAD CONSTRUCTION - AN EXPLORATORY STUDY: A CASE OF LUSAKA PROVINCE IN ZAMBIA

The state of rural roads in Zambia is very poor and in a deplorable condition. Drainages are missing, or where they exist, they are narrow, inadequate and not constructed correctly. Bridges are missing, old, inadequate or wrongly constructed and usually very poorly maintained. In most roads, the shoulders are not stable. From reviewed literature, several gaps in the planning, design, specifications, funding and general roads management in Zambia were identified as being the root causes of poor-quality rural roads. An in-depth literature review was carried out as secondary sources using journals, rural road construction handbook, peer reviewed articles, dissertations and the internet. In-depth interviews were further carried out with the staff at Ministry of Finance, Road Development Agency (RDA), National Road Fund Agency (NRFA), National Council for Construction (NCC), Rural Road Unit and also the Royal Highnesses and their subjects in Chongwe and Lusaka North areas. The results show that the planning is adequate but the problem lies with the planning personnel who are not adequately trained to undertake the tasks. Designs and specifications needed to consider the alignment requirements, technical performance, pavement solutions, material requirements and structures that are specific to an area. Results indicate that planners use a one-size fits all approach kind of designing resulting in the quality deficiency in some areas. The research assist government in developing and disseminating improved policies that assists in better planning, constructing and maintenance of rural roads. It introduces mitigatory actions and recommendations which the government can utilize in coming up with sustainable and reliable quality rural roads