Research

9 pages, 4001 KiB

Open AccessArticle

Flexible Optically Rewritable Electronic Paper

by Vladimir Chigrinov, Aleksey Kudreyko and Jiatong Sun

Crystals 2023, 13(8), 1283; https://doi.org/10.3390/cryst13081283 - 20 Aug 2023

Cited by 2 | Viewed by 835

In this article, we present the procedure of preparation of flexible electronic paper with a photosensitive azo dye layer as the key element for changing the orientation of the polarization plane. The main steps of the technology for the fabrication of flexible e-paper [...] Read more.

In this article, we present the procedure of preparation of flexible electronic paper with a photosensitive azo dye layer as the key element for changing the orientation of the polarization plane. The main steps of the technology for the fabrication of flexible e-paper are reported. The possible production of Digital Mirror Devices and the roll-to-roll process is discussed. Images on flexible e-paper are demonstrated, including bank card options. The advantages of optically rewritable e-paper technology in comparison with the e-ink usually used for this purpose are highlighted. Potential applications of flexible optically rewritable e-paper include price tags for supermarkets, indoor and outdoor advertisements, smart card labels, etc. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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10 pages, 2732 KiB

Open AccessArticle

Electrically Tunable Liquid Crystal Phase Grating with Double Period Based on the VIS Mode

by Zhou Guo, Yao Li, Yu-Meng Zeng, Le Yu and Li-Lan Tian

Crystals 2023, 13(8), 1235; https://doi.org/10.3390/cryst13081235 - 10 Aug 2023

Viewed by 685

Abstract

A tunable liquid crystal (LC) phase grating based on vertical-field in-plane electrical switching (VIS) is proposed. The tunable LC phase grating is composed of four parts: an LC layer, the top-plane and bottom-plane electrodes, the polyimide (PI) layer, and the top and bottom [...] Read more.

A tunable liquid crystal (LC) phase grating based on vertical-field in-plane electrical switching (VIS) is proposed. The tunable LC phase grating is composed of four parts: an LC layer, the top-plane and bottom-plane electrodes, the polyimide (PI) layer, and the top and bottom periodical strip electrodes. On the one hand, a large period LC phase grating can be obtained by applying voltage to the upper plane electrode and the lower periodic strip electrodes. On the other hand, a small period LC phase grating can be obtained by applying voltage to the lower plane electrode and the upper period electrodes. As a result, two kinds of LC phase grating with different periods can be realized by changing the driving scheme. Naturally, the diffraction angle can be adjusted by controlling different LC phase grating periods. The simulation results show that this tunable LC phase grating based on the VIS mode has a relatively short response time and low operating voltage (5.4 V). These characteristics make the tunable LC phase grating have good application prospects in holographic 3D or augmented reality (AR) display. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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9 pages, 2578 KiB

Open AccessArticle

Laser Processing of Liquid Crystal Droplets with Diverse Internal Structures

by Jin-Kun Guo, Jinzhong Ling, Ying Yuan, Fengjiao Chang, Xiaorui Wang and Jang-Kun Song

Crystals 2023, 13(4), 683; https://doi.org/10.3390/cryst13040683 - 16 Apr 2023

Cited by 3 | Viewed by 1827

Abstract

To control the spatial placement and organize micro/nanodroplets (NDs) has fundamental importance both in science and engineering. Cholesteric liquid crystal (CLC) droplets with topological diversity can offer many self-assembly modalities to arrange guest NDs in their spherical confinement; however, limited progress has been [...] Read more.

To control the spatial placement and organize micro/nanodroplets (NDs) has fundamental importance both in science and engineering. Cholesteric liquid crystal (CLC) droplets with topological diversity can offer many self-assembly modalities to arrange guest NDs in their spherical confinement; however, limited progress has been achieved due to difficulties of loading NDs into stabilized host droplets. Here, a laser injection technique is introduced, through which a controlled number of NDs were injected from a pre-selected location onto the surface of the host droplet. The sequentially injected NDs spontaneously drifted toward areas with topological defects and self-assembled along its geometry or local director field into a predefined shape. Within CLC droplets with different topological structures, guest NDs self-assembled near areas with defect points as twisting radial chains and quill-like assembly structures, and along defect lines as discrete beads and helical threads, respectively. The injection speed of the NDs, controlled by laser power, was found to play a key role in the assembly geometry of NDs as well as the internal structure of the CLC droplet processed. This study expands our abilities to precisely organize NDs in a spherical confinement and such droplet-based microsystems have potential applications for sensors, photonic devices, pharmaceuticals, and biotechnology. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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12 pages, 2470 KiB

Open AccessArticle

Customized Design of Aperiodic Liquid Crystal Grating for Generation of Multiple Optical Patterns

by Chen Liu, Zhenghao Guo, Jun Wu, Dong Yuan, Guofu Zhou, Biao Tang and Huapeng Ye

Crystals 2023, 13(2), 300; https://doi.org/10.3390/cryst13020300 - 11 Feb 2023

Cited by 1 | Viewed by 1563

Abstract

Liquid crystal (LC) grating has drawn extensive attention due to its merits, including tunability, easy preparation process, cost effectiveness, and high diffraction efficiency. However, limited efforts have been made to explore LC grating for the generation of customized diffraction patterns, despite the fact [...] Read more.

Liquid crystal (LC) grating has drawn extensive attention due to its merits, including tunability, easy preparation process, cost effectiveness, and high diffraction efficiency. However, limited efforts have been made to explore LC grating for the generation of customized diffraction patterns, despite the fact that the patterning size of LC molecular director orientation has been tremendously reduced even to subwavelength scale via high-precision photoalignment techniques. Here, we propose a versatile method based on the binary particle swarm optimization algorithm to efficiently design aperiodic LC gratings for customized optical patterns generation, including needle beam, multi-foci, and hollow beam. The optical performance of the LC gratings was simulated using both the vectorial Rayleigh–Sommerfeld method (with discrete zero or π phase, in this article) and the actual director orientations. These results matched each other well, which proves the effectiveness of the optimization method based on discrete phase. This study paves the way for designing LC gratings with engineered functionalities, which may find applications in optical tweezers, laser delivery systems, and laser scanning imaging. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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11 pages, 2857 KiB

Open AccessArticle

Influence of Goethite Nanorods on Structural Changes and Transitions in Nematic Liquid Crystal E7

by Peter Bury, Marek Veveričík, František Černobila, Natália Tomašovičová, Milan Timko, Peter Kopčanský, Filippo Agresti and Simona Barison

Crystals 2023, 13(2), 162; https://doi.org/10.3390/cryst13020162 - 17 Jan 2023

Cited by 2 | Viewed by 1001

Abstract

A composite ferronematic system based on the nematic liquid crystal E7, doped with lath-like goethite magnetic nanoparticles of volume concentrations 10⁻³, 5 × 10⁻⁴, and 10⁻⁵, was investigated. Both surface acoustic waves (SAWs) and the magneto-optical effect [...] Read more.

A composite ferronematic system based on the nematic liquid crystal E7, doped with lath-like goethite magnetic nanoparticles of volume concentrations 10⁻³, 5 × 10⁻⁴, and 10⁻⁵, was investigated. Both surface acoustic waves (SAWs) and the magneto-optical effect were used to study the influence of magnetic nanoparticles on ferronematic liquid crystals’ structural changes, focused above all on structural transitions. The responses of SAW attenuation and light transmission to external magnetic fields were investigated experimentally under linearly increasing/decreasing or jumped (time influence) magnetic fields, respectively. An investigation of temperature on structural changes was performed, as well. The experimental results validated the decrease in the threshold field of the ferronematic composites in comparison with the pure E7, as well as an increase in the transition temperature with the increasing volume fraction of nanoparticles. The effect of the nanoparticles’ concentration on both total structural changes and residual attenuations at the vanishing magnetic field was also registered. The light transmission measurements confirmed the effect of the concentration of goethite nanoparticles on the resultant magneto-optical behavior, concerning both its stability and switching time. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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11 pages, 7230 KiB

Open AccessArticle

Full Stokes Polarization Imaging Based on Broadband Liquid Crystal Polarization Gratings

by Yan Xuan, Qi Guo, Huijie Zhao and Hao Zhang

Crystals 2023, 13(1), 38; https://doi.org/10.3390/cryst13010038 - 26 Dec 2022

Cited by 3 | Viewed by 1788

Abstract

A method for full Stokes polarization imaging based on broadband liquid crystal polarization grating (LCPG) is presented. Firstly, the properties of the LCPG-based polarization detection module, which consists of a phase retarder and a broadband polarization grating in series, were investigated by means [...] Read more.

A method for full Stokes polarization imaging based on broadband liquid crystal polarization grating (LCPG) is presented. Firstly, the properties of the LCPG-based polarization detection module, which consists of a phase retarder and a broadband polarization grating in series, were investigated by means of Stokes calculus. The relationship between the polarization state of the incidence and the efficiencies of the diffractions was derived. Then, the azimuth parameters of the polarization detection module were optimized by using an equally weighted variance (EWV) evaluation criterion. Finally, the detection of the linearly and arbitrarily polarized laser beam and a linearly polarized broadband object were experimentally verified. The proposed method provides the design of polarization imaging systems based on LCPGs and has the advantages of compact structure, and broad wavelength coverage, therefore offering potential applications for image polarization information acquisition. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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8 pages, 2492 KiB

Open AccessArticle

Electro-Optical Characteristics of Solution-Derived Zinc Oxide Film According to Number of Rubbing Iterations for Liquid Crystal Alignment

by Hong-Gyu Park, Jin-Ah Kim and Bong-Jin Ko

Crystals 2022, 12(12), 1711; https://doi.org/10.3390/cryst12121711 - 25 Nov 2022

Cited by 2 | Viewed by 1421

Abstract

Zinc oxide (ZnO) films reportedly exhibit a rubbing effect for liquid crystal (LC) alignment. In this study, we investigated the LC alignment characteristics of solution-derived ZnO films according to the number of rubbing iterations. Uniform and homogeneous LC alignments were achieved on the [...] Read more.

Zinc oxide (ZnO) films reportedly exhibit a rubbing effect for liquid crystal (LC) alignment. In this study, we investigated the LC alignment characteristics of solution-derived ZnO films according to the number of rubbing iterations. Uniform and homogeneous LC alignments were achieved on the rubbed ZnO films, regardless of the number of rubbing iterations. As the number of rubbing iterations increased, the surface energies of the rubbed ZnO films were similar to 42.20 mJ/m², but the polar energy increased from 4.288 mJ/m² to 6.470 mJ/m². Additionally, the electro-optical characteristics of the twisted-nematic (TN) LC cells fabricated by rubbed ZnO films showed the best performance when the number of rubbing iterations was at five. By confirming that the ZnO film with improved physical, chemical, and electro-optical characteristics compared to the polyimide film achieved a perfect LC alignment through the conventional rubbing process, it indicates that the ZnO film can be an excellent substitute for the LC alignment film. In addition, it is expected that it can be applied to an LC-based virtual reality (VR)/augmented reality (AR) display system that requires a very fast response time through the excellent EO characteristics of the TN LC cell of the solution-derived ZnO film through the rubbing process. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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8 pages, 881 KiB

Open AccessArticle

Novel and Classical Materials Used in the Plane of Polarization of Light Rotation: Liquid Crystal with WS₂ Nanotubes

by Natalia Kamanina, Andrey Toikka and Svetlana Likhomanova

Crystals 2022, 12(9), 1185; https://doi.org/10.3390/cryst12091185 - 23 Aug 2022

Viewed by 1039

Abstract

It is well known that among the materials used in the daily lives of individuals and also in industrial applications, the specific structures applied in biomedicine occupy a special place. It is connected with the possibility to expand our basic physical-chemical knowledge and [...] Read more.

It is well known that among the materials used in the daily lives of individuals and also in industrial applications, the specific structures applied in biomedicine occupy a special place. It is connected with the possibility to expand our basic physical-chemical knowledge and regarded to the real application of novel structures in the interdisciplinary arena. In this paper, a comparative study is conducted on the influence of different materials: sugar, DNA, WS₂ nanoparticles, dyes—on the rotation of the plane of polarization of light. Firstly, this effect is shown namely for a liquid crystal mixture doped with WS₂ nanotubes. On the one hand, it is shown that the new materials are quite suitable for use in sugar-meters and polarimeter devices instead of sugar solutions. On the other hand, the rotation of the plane of polarization of light in solutions with DNA and WS₂ nanoparticles in water or in the liquid crystal mixture can predict a larger angle of the rotation of the polarization plane of the light and can find a better design than in volumetric classical sugar solutions. This makes it possible to expand the application of these materials to the technical devices. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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10 pages, 2669 KiB

Open AccessArticle

Structural and Optical Characteristics of Flexible Optically Rewritable Electronic Paper

by Aleksey Kudreyko and Vladimir Chigrinov

Crystals 2022, 12(8), 1149; https://doi.org/10.3390/cryst12081149 - 16 Aug 2022

Cited by 6 | Viewed by 1225

Abstract

A comprehensive theory of light-reflective characteristics and experimental technique of liquid crystal layer thickness control for flexible optically rewritable electronic paper is presented. Cylindrical pillars were used to control the gap between flexible substrates. The introduced prototype of optically rewritable electronic paper has [...] Read more.

A comprehensive theory of light-reflective characteristics and experimental technique of liquid crystal layer thickness control for flexible optically rewritable electronic paper is presented. Cylindrical pillars were used to control the gap between flexible substrates. The introduced prototype of optically rewritable electronic paper has shown very promising performance. In this regard, we report theoretical results of structural photosensitive alignment of nematic liquid crystals on flexible substrate. The focus of theoretical study is on understanding the self-assembled complex structure, governed by the interplay between surface anchoring and liquid crystal elasticity. Mueller matrix spectroscopic ellipsometry was used to study light-reflecting characteristics and polarization properties of the twisted nematic film. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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10 pages, 1851 KiB

Open AccessArticle

A Mesoporous Silica Nanoparticle-Doped Photo-Alignment Layer and Liquid Crystal Layer for Optimizing the Rewriting Speed and the Response Time of Optically Driving Liquid Crystal Displays

by Jingxin Sang, Yujian Lai, Jiatong Sun, Jianhua Shang and Shuguang Zhao

Crystals 2022, 12(8), 1088; https://doi.org/10.3390/cryst12081088 - 04 Aug 2022

Cited by 3 | Viewed by 1484

Abstract

Optically driving liquid crystal displays (ODLCDs) are widely applied in display and optical devices due to their long axis of liquid crystal (LC) molecules that can be tuned by a photo-alignment layer under exposure polarized light. However, their use remains challenging due to [...] Read more.

Optically driving liquid crystal displays (ODLCDs) are widely applied in display and optical devices due to their long axis of liquid crystal (LC) molecules that can be tuned by a photo-alignment layer under exposure polarized light. However, their use remains challenging due to their long rewriting time and response time. In this work, the rewriting time and the response time of an ODLCD depending on mesoporous silica nanoparticles (MSNs) doped in azo-dye (SD1) and LC 5CB were studied. Among the different concentration ratios of SD1-MSNs (1-0 to 1-0.1), a ratio of 1-0.07 was optimal, decreasing the rewriting time by 40 s (from 69.1 to 29.6 s). Meanwhile, the response time was improved 10 times with MSNs doped into 5CB. Full article

(This article belongs to the Special Issue Liquid Crystals and Their Advanced Applications)

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