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2 pages, 166 KiB

Open AccessEditorial

Patterned-Liquid-Crystal for Novel Displays

by Kun Yin, Guanjun Tan, Shuxin Liu, Artur Geivandov and Gaurav P. Shrivastav

Crystals 2022, 12(2), 185; https://doi.org/10.3390/cryst12020185 - 27 Jan 2022

Viewed by 2250

Abstract

The “Patterned-Liquid-Crystal for Novel Displays” is a Special Issue focused on new insights and explorations in the field of liquid crystals arranged in a periodic patterned way [...] Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

Research

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11 pages, 6843 KiB

Open AccessArticle

Self-Assembly of an Equimolar Mixture of Liquid Crystals and Magnetic Nanoparticles

by Gaurav P. Shrivastav

Crystals 2021, 11(7), 834; https://doi.org/10.3390/cryst11070834 - 19 Jul 2021

Cited by 3 | Viewed by 2232

Abstract

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found [...] Read more.

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found that the LCs show isotropic, nematic, and smectic phases when the mixture is compressed at a fixed temperature. The DSS form chain-like structures, which remain randomly oriented at low densities where the LCs are in the isotropic phase. At intermediate and high densities, the DSS chains align along the nematic and smectic directors of LCs. We found that the DSS inside a chain follow a ferromagnetic ordering. However, the mixture does not show a significant macroscopic magnetization. The extent of nematic order in the DSS remains very similar to the LCs in intermediate densities. At high densities, the DSS have a lower extent of nematic order than the LCs. The structure of the LC–DSS mixture was further analyzed via projected pair correlation functions for distances parallel and perpendicular to directors in the nematic and smectic phases. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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8 pages, 2986 KiB

Open AccessEditor’s ChoiceArticle

Enlarging the Eyebox of Maxwellian Displays with a Customized Liquid Crystal Dammann Grating

by Ziqian He, Kun Yin, Kuan-Hsu Fan-Chiang and Shin-Tson Wu

Crystals 2021, 11(2), 195; https://doi.org/10.3390/cryst11020195 - 17 Feb 2021

Cited by 15 | Viewed by 3659

Abstract

The Maxwellian view offers a promising approach to overcome the vergence-accommodation conflict in near-eye displays, however, its pinhole-like imaging naturally limits the eyebox size. Here, a liquid crystal polymer-based Dammann grating with evenly distributed energy among different diffraction orders is developed to enlarge [...] Read more.

The Maxwellian view offers a promising approach to overcome the vergence-accommodation conflict in near-eye displays, however, its pinhole-like imaging naturally limits the eyebox size. Here, a liquid crystal polymer-based Dammann grating with evenly distributed energy among different diffraction orders is developed to enlarge the eyebox of Maxwellian view displays via pupil replication. In the experiment, a 3-by-3 Dammann grating is designed and fabricated, which exhibits good efficiency and high brightness uniformity. We further construct a proof-of-concept Maxwellian view display breadboard by inserting the Dammann grating into the optical system. The prototype successfully demonstrates the enlarged eyebox and full-color operation. Our work provides a promising route of eyebox expansion in Maxwellian view displays while maintaining full-color operation, simple system configuration, compactness, and lightweight. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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17 pages, 10616 KiB

Open AccessArticle

Textures of Nematic Liquid Crystal Cylindric-Section Droplets Confined by Chemically Patterned Surfaces

by Peng Bao, Daniel A. Paterson, Sally A. Peyman, J. Cliff Jones, Jonathan A. T. Sandoe, Richard J. Bushby, Stephen D. Evans and Helen F. Gleeson

Crystals 2021, 11(1), 65; https://doi.org/10.3390/cryst11010065 - 15 Jan 2021

Cited by 6 | Viewed by 3286

Abstract

The director fields adopted by nematic liquid crystals (LCs) that are confined by the surface to form long, thin droplets are investigated using polarising optical microscopy. Samples are produced by de-wetting of the LC on a surface patterned with alternating high-surface energy and [...] Read more.

The director fields adopted by nematic liquid crystals (LCs) that are confined by the surface to form long, thin droplets are investigated using polarising optical microscopy. Samples are produced by de-wetting of the LC on a surface patterned with alternating high-surface energy and low-surface energy stripes of 10–30 μm width. The droplets obtained are expected to adopt a profile which is that of a longitudinal section of a cylinder and, as this suggests, the director fields observed are variants in the case where the LC is constrained in a cylindrical capillary or fibre. Hence, when there is normal anchoring at the air interface, the textures observed are related to the well-known escaped radial texture (for the nematic LC mixture E7) or plane polar texture (for the LC mixture MLC6609). More surprising is the observation that the nematic LC mixture MLC7023, which is anchored in a planar or tilted manner at the air interface, also gives what appears to be an escaped radial director field. As an exploration of the possibility of using these systems in creating sensors, the effects of adding a chiral dopant and of adding water to the substrates are also investigated. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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17 pages, 6895 KiB

Open AccessArticle

Mueller Matrix Polarimetric Imaging Analysis of Optical Components for the Generation of Cylindrical Vector Beams

by Guadalupe López-Morales, María del Mar Sánchez-López, Ángel Lizana, Ignacio Moreno and Juan Campos

Crystals 2020, 10(12), 1155; https://doi.org/10.3390/cryst10121155 - 18 Dec 2020

Cited by 17 | Viewed by 3778

Abstract

In this work, we performed a Mueller matrix imaging analysis of two commercial optical components usually employed to generate and manipulate vector beams—a radial polarizer and a liquid-crystal q-plate. These two elements generate vector beams by different polarization mechanisms—polarizance and retardance, respectively. [...] Read more.

In this work, we performed a Mueller matrix imaging analysis of two commercial optical components usually employed to generate and manipulate vector beams—a radial polarizer and a liquid-crystal q-plate. These two elements generate vector beams by different polarization mechanisms—polarizance and retardance, respectively. The quality of the vector beams relies on the quality of the device that generates them. Therefore, it is of interest to apply the well-established polarimetric imaging techniques to evaluate these optical components by identifying their spatial homogeneity in diattenuation, polarizance, depolarization, and retardance, as well as the spatial variation of the angles of polarizance and retardance vectors. For this purpose, we applied a customized imaging Mueller matrix polarimeter based on liquid-crystal retarders and a polarization camera. Experimental results were compared to the numerical simulations, considering the theoretical Mueller matrix. This kind of polarimetric characterization could be very helpful to the manufacturers and users of these devices. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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14 pages, 2400 KiB

Open AccessArticle

Engineering Aspheric Liquid Crystal Lenses by Using the Transmission Electrode Technique

by José Francisco Algorri, Dimitrios C. Zografopoulos, Luis Rodríguez-Cobo, José Manuel Sánchez-Pena and José Miguel López-Higuera

Crystals 2020, 10(9), 835; https://doi.org/10.3390/cryst10090835 - 18 Sep 2020

Cited by 15 | Viewed by 2540

Abstract

The transmission electrode technique has been recently proposed as a versatile method to obtain various types of liquid-crystal (LC) lenses. In this work, an equivalent electric circuit and new analytical expressions based on this technique are developed. In addition, novel electrode shapes are [...] Read more.

The transmission electrode technique has been recently proposed as a versatile method to obtain various types of liquid-crystal (LC) lenses. In this work, an equivalent electric circuit and new analytical expressions based on this technique are developed. In addition, novel electrode shapes are proposed in order to generate different phase profiles. The analytical expressions depend on manufacturing parameters that have been optimized by using the least squares method. Thanks to the proposed design equations and the associated optimization, the feasibility of engineering any kind of aspheric LC lenses is demonstrated, which is key to obtain aberration-free lenses. The results are compared to numerical simulations validating the proposed equations. This novel technique, in combination with the proposed design equations, opens a new path for the design and fabrication of LC lenses and even other types of adaptive-focus lenses based on voltage control. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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9 pages, 1894 KiB

Open AccessArticle

Fast-Response Liquid Crystal Phase Modulators with an Excellent Photostability

by Qian Yang, Junyu Zou, Yannanqi Li and Shin-Tson Wu

Crystals 2020, 10(9), 765; https://doi.org/10.3390/cryst10090765 - 29 Aug 2020

Cited by 24 | Viewed by 3012

Abstract

We report a new mixture, which is modified from Merck TL-216, for liquid-crystal-on-silicon spatial light modulators (SLMs). To achieve 2π phase change at λ = 633 nm with 5 V operation voltage, the measured response time is about 3 ms at 50 °C. [...] Read more.

We report a new mixture, which is modified from Merck TL-216, for liquid-crystal-on-silicon spatial light modulators (SLMs). To achieve 2π phase change at λ = 633 nm with 5 V operation voltage, the measured response time is about 3 ms at 50 °C. Meanwhile, our mixture exhibits no sign of photodegradation and even the total dosage has exceeded 400 MJ/cm² at a blue laser wavelength λ = 465 nm. In comparison, E7 died at about 30 MJ/cm². Widespread applications of this material for high brightness SLMs, near-eye displays, and head-up displays are foreseeable. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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13 pages, 2955 KiB

Open AccessArticle

Stable and Metastable Patterns in Chromonic Nematic Liquid Crystal Droplets Forced with Static and Dynamic Magnetic Fields

by Jordi Ignés-Mullol, Marc Mora, Berta Martínez-Prat, Ignasi Vélez-Cerón, R. Santiago Herrera and Francesc Sagués

Crystals 2020, 10(2), 138; https://doi.org/10.3390/cryst10020138 - 24 Feb 2020

Cited by 6 | Viewed by 4147

Abstract

Spherical confinement of nematic liquid crystals leads to the formation of equilibrium director field configurations that include point and line defects. Driving these materials with flows or dynamic fields often results in the formation of alternative metastable states. In this article, we study [...] Read more.

Spherical confinement of nematic liquid crystals leads to the formation of equilibrium director field configurations that include point and line defects. Driving these materials with flows or dynamic fields often results in the formation of alternative metastable states. In this article, we study the effect of magnetic field alignment, both under static and dynamic conditions, of nematic gems (nematic droplets in coexistence with the isotropic phase) and emulsified nematic droplets of a lyotropic chromonic liquid crystal. We use a custom polarizing optical microscopy assembly that incorporates a permanent magnet whose strength and orientation can be dynamically changed. By comparing simulated optical patterns with microscopy images, we measure an equilibrium twisted bipolar pattern within nematic gems that is only marginally different from the one reported for emulsified droplets. Both systems evolve to concentric configurations upon application of a static magnetic field, but behave very differently when the field is rotated. While the concentric texture within the emulsified droplets is preserved and only displays asynchronous oscillations for high rotating speeds, the nematic gems transform into a metastable untwisted bipolar configuration that is memorized by the system when the field is removed. Our results demonstrate the importance of boundary conditions in determining the dynamic behavior of confined liquid crystals even for configurations that share similar equilibrium bulk structures. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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11 pages, 11078 KiB

Open AccessCommunication

Electro-Optical Effects of a Color Polymer-Dispersed Liquid Crystal Device by Micro-Encapsulation with a Pigment-Doped Shell

by Chao Ping Chen, Dae Soo Kim and Chul Gyu Jhun

Crystals 2019, 9(7), 364; https://doi.org/10.3390/cryst9070364 - 17 Jul 2019

Cited by 14 | Viewed by 5469

Abstract

Polymer-dispersed liquid crystals (PDLCs) refer to nematic liquid crystals, which are embedded in a polymer matrix. A conventional PDLC device is fabricated by phase separation. However, this method leads to non-uniform electro-optical characteristics of the device due to the non-uniform size distribution of [...] Read more.

Polymer-dispersed liquid crystals (PDLCs) refer to nematic liquid crystals, which are embedded in a polymer matrix. A conventional PDLC device is fabricated by phase separation. However, this method leads to non-uniform electro-optical characteristics of the device due to the non-uniform size distribution of the liquid crystal droplets. Moreover, the PDLC device is switched between the transparent state and the scattering state so that a full color scheme is intrinsically impossible without a color filter. In this paper, a fabrication method for a color PDLC device with uniform size and shape for liquid crystal droplets is proposed. Droplets of a fairly uniform size in large quantities can be obtained by means of membrane emulsification. Microcapsules are fabricated by complex coacervation with gelatin and gum arabic. By adding red, green, and blue pigments, color microcapsules are obtained. The electro-optical effects of the fabricated color PDLC devices are also demonstrated. The driving voltage of the device is 90 V, and the switching time is 8.3 ms. In the turn-on state, the measured hazes of red, green, and blue PDLC devices are 16.89%, 15.82%, and 18.55%, respectively, while in the turn-off state, the measured hazes of those devices are 65.21%, 67.32%, and 70.76%, respectively. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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Review

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20 pages, 2332 KiB

Open AccessReview

Dynamics of Dislocations in Smectic A Liquid Crystals Doped with Nanoparticles

by Patrick Oswald

Crystals 2019, 9(8), 400; https://doi.org/10.3390/cryst9080400 - 02 Aug 2019

Cited by 7 | Viewed by 4367

Abstract

Edge dislocations are linear defects that locally break the positional order of the layers in smectic A liquid crystals. As in usual solids, these defects play a central role for explaining the plastic properties of the smectic A phase. This work focuses on [...] Read more.

Edge dislocations are linear defects that locally break the positional order of the layers in smectic A liquid crystals. As in usual solids, these defects play a central role for explaining the plastic properties of the smectic A phase. This work focuses on the dynamical properties of dislocations in bulk samples prepared between two glass plates and in free-standing films. The emphasis will be put on the measurement of the mobility of edge dislocations in liquid crystals either pure or doped with nanoparticles. The experimental results will be compared to the existing models. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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