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Crystals
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Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume...
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Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II)

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Liquid Crystals".

Deadline for manuscript submissions: closed (31 August 2020) | Viewed by 22905

Special Issue Editor

Prof. Dr. Vladimir Chigrinov

E-Mail Website
Guest Editor
Department of Electronic, Computer Engineering, Hong Kong University of Science and Technology, Hong Kong, China
Interests: liquid crystals; electrooptics; displays; photonics; photoalignment; photopatterning
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A new Liquid Crystals section has been established in the open access journal Crystals (https://www.mdpi.com/journal/crystals/sections/liquid_crystals). Because of the many advances in recent years, we are dedicating the first Special Issue of the Liquid Crystals section to the topic “Micro and Nano Patterned Substrates for Liquid Crystal Alignment”. The Special Issue will explore techniques and challenges for micro- and nanopatterned substrates, scientific consequences of the patterns, and technological outcomes. It is intended that both extant and novel methods will be covered, ranging from traditional mechanical techniques adapted to small patterns, to optical techniques, to methods involving non-traditional alignment layers, such as graphene. The goal is to facilitate dissemination of information on methods and outcomes that will benefit the broader community involved in control of liquid crystal alignment.

Prof. Dr. Vladimir Chigrinov
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • alignment layer materials
  • patterned photoalignment
  • mechanically-generated patterns
  • electron and ion beam patterning
  • novel materials and approaches
  • scientific and technological outcomes

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Related Special Issue

Published Papers (6 papers)

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Research

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7 pages, 3448 KiB  
Article
Broadband Multichannel Optical Vortex Generators via Patterned Double-Layer Reverse-Twist Liquid Crystal Polymer
by Hanqing Zhang, Wei Duan, Ting Wei, Chunting Xu and Wei Hu
Crystals 2020, 10(10), 882; https://doi.org/10.3390/cryst10100882 - 29 Sep 2020
Cited by 10 | Viewed by 3484
Abstract
The capacity of an optical communication system can be greatly increased by using separate orbital angular momentum (OAM) modes as independent channels for signal transmission and encryption. At present, a transmissive OAM mode generator compatible with wavelength division multiplexing is being highly pursued. [...] Read more.
The capacity of an optical communication system can be greatly increased by using separate orbital angular momentum (OAM) modes as independent channels for signal transmission and encryption. At present, a transmissive OAM mode generator compatible with wavelength division multiplexing is being highly pursued. Here, we introduce a specific double-layer reverse-twist configuration into liquid crystal polymer (LCP) to overcome wavelength dependency. With this design, broadband-applicable OAM array generators are proposed and demonstrated. A Damman vortex grating and a Damman q-plate were encoded via photopatterning two subsequent LCP layers adopted with oppositely handed chiral dopants. Rectangular and hexagonal OAM arrays with mode conversion efficiencies exceeding 40.1% and 51.0% in the ranges of 530 to 930 nm, respectively, are presented. This provides a simple and broadband efficient strategy for beam shaping. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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7 pages, 2374 KiB  
Article
Shear Induced TiO2 Nano Structure Using Brush-Coating for Liquid Crystal Alignment
by Jong In Jang and Hae-Chang Jeong
Crystals 2020, 10(10), 860; https://doi.org/10.3390/cryst10100860 - 24 Sep 2020
Cited by 4 | Viewed by 2950
Abstract
We have developed a very useful and cost-effective liquid crystal (LC) alignment layer of brush-coated TiO2 that is solution-processable for twisted nematic (TN) LC cells. TiO2 was prepared via the sol-gel method. The TiO2 solution was brush-coated on the substrate, [...] Read more.
We have developed a very useful and cost-effective liquid crystal (LC) alignment layer of brush-coated TiO2 that is solution-processable for twisted nematic (TN) LC cells. TiO2 was prepared via the sol-gel method. The TiO2 solution was brush-coated on the substrate, followed by an annealing process. During the brush-coating process, a retracting force is generated on the deposited TiO solutions along the coating direction. The annealing process hardens the TiO2 and generates shearing stress arising from the retracting force along the brush-coating direction. The shearing stress created highly oriented nano/microstructure and uniformly aligned LCs with a stable pretilt angle of 0.6°. TN mode LC cells based on brush-coated TiO2 exhibited a performance of 12.5 ms of response and a threshold voltage of 1.8 V. Our brush-coated TiO2 incorporates two steps of the film deposition and alignment process into one step. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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17 pages, 8472 KiB  
Article
Surface Stabilized Topological Solitons in Nematic Liquid Crystals
by Inge Nys, Brecht Berteloot and Guilhem Poy
Crystals 2020, 10(9), 840; https://doi.org/10.3390/cryst10090840 - 19 Sep 2020
Cited by 21 | Viewed by 3932
Abstract
Photo-alignment is a versatile tool to pattern the alignment at the confining substrates in a liquid crystal (LC) cell. Arbitrary alignment patterns can be created by using projection with a spatial light modulator (SLM) for the illumination. We demonstrate that a careful design [...] Read more.
Photo-alignment is a versatile tool to pattern the alignment at the confining substrates in a liquid crystal (LC) cell. Arbitrary alignment patterns can be created by using projection with a spatial light modulator (SLM) for the illumination. We demonstrate that a careful design of the alignment patterns allows the stabilization of topological solitons in nematic liquid crystal (NLC) cells, without the need for chirality or strong confinement. The created LC configurations are stabilized by the anchoring conditions imposed at the substrates. The photo-aligned background at both substrates is uniformly planar aligned, and ring-shaped regions with a 180° azimuthal rotation are patterned with an opposite sense of rotation at the top and bottom substrate. A disclination-free structure containing a closed ring of vertically oriented directors is formed when the patterned rings at the top and bottom substrate overlap. Thanks to the topological stability, a vertical director orientation in the bulk is observed even when the centra of both patterned rings are shifted over relatively large distances. The combination of numerical simulations with experimental measurements allows identification of the 3D director configuration in the bulk. A finite element (FE) Q-tensor simulation model is applied to find the equilibrium director configuration and optical simulations are used to confirm the correspondence with experimental microscopy measurements. The created LC configurations offer opportunities in the field of optical devices, light guiding and switching, particle trapping and studies of topological LC structures. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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Graphical abstract

11 pages, 4070 KiB  
Article
Spectral Properties of Photo-Aligned Photonic Crystal Fibers Infiltrated with Gold Nanoparticle-Doped Ferroelectric Liquid Crystals
by Daniel Budaszewski, Kaja Wolińska, Bartłomiej Jankiewicz, Bartosz Bartosewicz and Tomasz Ryszard Woliński
Crystals 2020, 10(9), 785; https://doi.org/10.3390/cryst10090785 - 4 Sep 2020
Cited by 6 | Viewed by 2826
Abstract
This paper describes our recent results on light propagation in photonic crystal fibers (PCFs) partially infiltrated with W212 ferroelectric liquid crystal (FLC) doped with 1–3 nm gold nanoparticles (NPs) with a concentration in the range of 0.1–0.5% wt. Based on our previous results [...] Read more.
This paper describes our recent results on light propagation in photonic crystal fibers (PCFs) partially infiltrated with W212 ferroelectric liquid crystal (FLC) doped with 1–3 nm gold nanoparticles (NPs) with a concentration in the range of 0.1–0.5% wt. Based on our previous results devoted to PCFs infiltrated with nematic liquid crystals (NLCs) doped with gold NPs (GNPs), we extend our research line with FLCs doped with these NPs. To enhance the proper alignment of the NP-FLC nanocomposites inside PCFs, we applied an additional photo-aligning layer of SD-1 azo-dye material (DIC, Japan). Electro-optical response times and thermal tuning were studied in detail. We observed an improvement in response times for NP-FLC nanocomposites in comparison to the undoped FLC. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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7 pages, 1659 KiB  
Article
The Effect of Operating Temperature on the Response Time of Optically Driven Liquid Crystal Displays
by Vladimir Chigrinov, Jiatong Sun, Mikhail M. Kuznetsov, Victor Belyaev and Denis Chausov
Crystals 2020, 10(7), 626; https://doi.org/10.3390/cryst10070626 - 20 Jul 2020
Cited by 10 | Viewed by 2893
Abstract
Optically driven liquid crystal displays (ODLCDs) realizes their display function by tuning the easy axis of liquid crystal (LC) molecules under polarized blue light, which has been utilized in some optical devices due to its advantages of ultra-low power consumption. However, a big [...] Read more.
Optically driven liquid crystal displays (ODLCDs) realizes their display function by tuning the easy axis of liquid crystal (LC) molecules under polarized blue light, which has been utilized in some optical devices due to its advantages of ultra-low power consumption. However, a big issue arises in response time, i.e., the rewriting time of the ODLCD. The rewriting time of ODLCD samples was studied. Rotational viscosity plays a very important role for decreasing the rewriting time of the ODLCD. The operating temperature was changed from room temperature to nearly clearing point, the rewriting time decreased a lot as the rotational viscosity decreased for the five different kinds of the LCs. The rewriting time can be decreased from 5.2 s to 0.2 s around 25 times for the LC N4. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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Review

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15 pages, 7684 KiB  
Review
Photoaligning and Photopatterning: New LC Technology
by Vladimir Chigrinov, Jiatong Sun and Xiaoqian Wang
Crystals 2020, 10(4), 323; https://doi.org/10.3390/cryst10040323 - 20 Apr 2020
Cited by 42 | Viewed by 6119
Abstract
We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC [...] Read more.
We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC E-paper on flexible substrates as 3D E-paper, as well as optically rewritable technology for photonics devices; (ii) photonics LC devices, such as LC Switches, polarization controllers and polarization rotators, variable optical attenuators, LC filled photonic crystal fiber, switchable diffraction grating; (iii) patterned micro-polarizer array using photo-alignment technology for image sensor; (iv) electrically tunable liquid crystal q-plates; (v) electrically switchable liquid crystal Fresnel lens; (vi) liquid crystal optical elements with integrated Pancharatnam-Berry phases. We are sure, that in the field of (LC), the main point is no longer display research, but new photonic applications of LC are emerging in telecommunication, fiber optical communication systems, sensors, switchable lenses, LC light converters and other LC photonics devices. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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