Special Issue "Selected Papers from "3rd Asian Conference on Liquid Crystals, ACLC 2017""

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (31 May 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Wei Lee

Institute of Imaging and Biomedical Photonics, College of Photonics, National Chiao Tung University, 301 Gaofa 3rd Road, Guiren Dist., Tainan 71150, Taiwan
Website | E-Mail
Interests: liquid crystal photonics; dielectric spectroscopy; photonic crystals; biosensors; energy-saving devices

Special Issue Information

Dear Colleagues,

On behalf of the Taiwan Liquid Crystal Society, we are pleased to welcome you to the third Asian Conference on Liquid Crystals (ACLC 2017) to be held at the National Cheng Kung University in Tainan, Taiwan, 13–15 February, 2017. (http://aclc2017.conf.tw/site/Page.aspx?pid=901&sid=1102&lang=en).

Following the first ACLC, held in Japan, and the second in Korea, the conference continuously aims to foster the growth of research in liquid crystal science and technology and its benefits to the community at large. We hope that ACLC 2017 will provide a great platform for academic and industry professionals to have fruitful discussions and to exchange new ideas of recent developments and latest advances in the interdisciplinary field. It is our pleasure to announce the supportive participation of leading academics and researchers, in their respective areas of focus, from various countries, not only in, but also beyond Asia. We invite you to participate in this conference by submitting a paper reflecting your current research and to excel in liquid-crystal-related R&D worldwide.

Participants of the conference are cordially invited to contribute original research papers or reviews to this Special Issue of Crystals.

Prof. Dr. Wei Lee
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 papers will be 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 1000 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

  • thermotropic liquid crystals
  • lyotropic liquid crystals
  • polymeric liquid crystals
  • colloidal liquid crystals

Published Papers (9 papers)

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Research

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Open AccessArticle Electro-optical Effect of Gold Nanoparticle Dispersed in Nematic Liquid Crystals
Crystals 2017, 7(10), 287; doi:10.3390/cryst7100287
Received: 13 July 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 23 September 2017
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Abstract
The electro-optical performance of nematic liquid crystals (NLCs) dispersed with gold nanoparticles (GNPs) was investigated in this study. The addition of a small amount of GNP dopant decreased the threshold voltage for LC reorientation due to the decreased elastic constant and increased dielectric
[...] Read more.
The electro-optical performance of nematic liquid crystals (NLCs) dispersed with gold nanoparticles (GNPs) was investigated in this study. The addition of a small amount of GNP dopant decreased the threshold voltage for LC reorientation due to the decreased elastic constant and increased dielectric anisotropy of the LC mixture. The response time of the LC cell was decreased with the addition of tiny amounts of GNPs because of decrease in rotational viscosity of LCs. The doped GNPs also shorten LC reorientation angle during voltage switching, further decreasing the response time of the LC cell. The addition of high amounts of GNPs slowed down the response time of the LC cell, because excess GNPs aggregated and formed networks in the cell, thus disturbing LC alignment and hindering LC reorientation. The measured dielectric spectra of the GNP-LC mixture revealed that the addition of GNPs decreased the relaxation time constant of the LCs. This result confirmed that the GNP dopant decreased the rotational viscosity and elastic constant of the LCs. Full article
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Open AccessCommunication Electrohydrodynamics-Induced Abnormal Electro-Optic Characteristics in a Polymer-Dispersed Liquid Crystal Film
Crystals 2017, 7(7), 227; doi:10.3390/cryst7070227
Received: 14 June 2017 / Revised: 17 July 2017 / Accepted: 18 July 2017 / Published: 21 July 2017
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Abstract
This study demonstrates for the first time abnormal electro-optic (EO) characteristics induced by electrohydrodynamics (EHD) in a polymer-dispersed liquid crystal (PDLC) film in the presence of a low-frequency (1 kHz) AC voltage. Large LC droplets (20−40 µm) buried in the film can be
[...] Read more.
This study demonstrates for the first time abnormal electro-optic (EO) characteristics induced by electrohydrodynamics (EHD) in a polymer-dispersed liquid crystal (PDLC) film in the presence of a low-frequency (1 kHz) AC voltage. Large LC droplets (20−40 µm) buried in the film can be obtained after the illumination of one UV light with a weak intensity (~0.96 mW/cm2) for 12 h. This film exhibits abnormal EO features, including the transmittance’s decay at a high voltage regime at normal incidence and the conversion between polarization independence and polarization dependence for the transmittance-voltage curve at normal and oblique incidences, respectively, of which properties are different from those shown in traditional PDLC films with small droplets. The abnormal EO characteristics of the large-droplet PDLC at the high voltage regime are attributed to a strong scattering effect associated with the formation of the foggy LC droplets in the cell. This effect is induced by a vortex-like LC director field with a rotational axis normal to the cell substrates in each dome-like droplet of the cell at the high voltage regime. The vortex-like director field is induced by a vortex-like turbulence of charged impurity generated by the EHD effect under the action of the AC electric field along the cell normal and the confinement of the dome-like boundary of the droplet on the charged impurities in each droplet. The scattering is decided by the degrees of mismatch between the refractive indices of the LC droplet and polymer, and the local fluctuation of the vortex-like director field in the droplet, resulting in the abnormal EO behaviors of the large-droplet PDLC. This investigation provides novel insight into the EHD effect in three dimensional (3D) microdroplets with anisotropic fluid. Such a large-droplet PDLC has potential in photonic applications, such as electrically controlled polarization-based optical components or optical converters between polarization independence and polarization dependence. Full article
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Open AccessArticle An Electrically Tunable Liquid Crystal Lens with Coaxial Bi-Focus and Single Focus Switching Modes
Crystals 2017, 7(7), 209; doi:10.3390/cryst7070209
Received: 30 May 2017 / Revised: 3 July 2017 / Accepted: 4 July 2017 / Published: 7 July 2017
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Abstract
A hole-patterned electrode liquid crystal (LC) lens with electrically switching coaxial bi-focus and single focus modes of tuning is demonstrated. The proposed LC lens mainly consists of a two LC layer (TLCL) structure with different thicknesses to achieve higher focusing power than the
[...] Read more.
A hole-patterned electrode liquid crystal (LC) lens with electrically switching coaxial bi-focus and single focus modes of tuning is demonstrated. The proposed LC lens mainly consists of a two LC layer (TLCL) structure with different thicknesses to achieve higher focusing power than the conventional hole-patterned electrode LC lens with the same aperture size. In the TLCL structure, one LC layer, doped with 3 wt % RM257, was photopolymerized to achieve a fixed focusing power of 18.5 Diopter. Due to polarization dependence in TLCL lenses, an additional 90° twisted nematic (TN) cell was used to change the incident polarization in order to switch lens functions on or off. As a result, a fixed focusing power of 18.5 Diopter was achieved when voltages of 10 Vrms were applied to the 90° TN cell. In addition, the switching capabilities of the bi-focus and single focus modes were achieved when operating individually with applied voltages from 20 Vrms to 90 Vrms, and higher voltages of over 90 Vrms, respectively. The maximum focusing power in the fabricated TLCL lens is 30.9 Diopter. Full article
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Open AccessArticle Doping Liquid Crystal Cells with Photocurable Monomer via Holographic Exposure to Realize Optical-Scattering-Free Infrared Phase Modulators with Fast Response Time
Crystals 2017, 7(7), 208; doi:10.3390/cryst7070208
Received: 30 May 2017 / Revised: 3 July 2017 / Accepted: 4 July 2017 / Published: 7 July 2017
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Abstract
Photocurable monomer-doped liquid crystal (LC) cells were processed via holographic exposure using a low-power He–Ne laser to generate holographic polymer networks. The polymer network LC (PNLC) cells are used to fabricate infrared phase modulators at 1550 nm wavelength possessing favorable electro-optical performance. Compared
[...] Read more.
Photocurable monomer-doped liquid crystal (LC) cells were processed via holographic exposure using a low-power He–Ne laser to generate holographic polymer networks. The polymer network LC (PNLC) cells are used to fabricate infrared phase modulators at 1550 nm wavelength possessing favorable electro-optical performance. Compared with our previous work, the percentages of ingredients in the LC mixture filled in PNLC cells underwent a slight change. The 2 wt% concentration of anisotropic monomer RM257 were in place of isotropic monomer N–vinyl–2–pyrrolidinone (NVP). As a result, the fabricated phase modulators also maintained well homogeneous LC alignments and optical-scattering-free characteristics. Furthermore, NVP dopant successfully reduced the operating voltages from 95 Vrms to 79 Vrms to prevent polymer network deformation when electrically operating with higher voltages. The fabricated infrared phase modulators had a good average response time (i.e., rising time of 0.88 ms and falling time of 0.40 ms). Full article
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Open AccessCommunication External-Voltage-Free Dielectrophoresis of Liquid Crystal Droplets
Crystals 2017, 7(7), 202; doi:10.3390/cryst7070202
Received: 12 May 2017 / Revised: 26 June 2017 / Accepted: 30 June 2017 / Published: 3 July 2017
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Abstract
This work reports, for the first time, a dielectrophoresis (DEP) effect-induced motion of liquid crystal (LC) droplets in an LC/monomer mixture sample with a poly-(N-vinyl carbazole) PVK-coated substrate without an external voltage. With the UV pre-irradiation of the PVK layer through
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This work reports, for the first time, a dielectrophoresis (DEP) effect-induced motion of liquid crystal (LC) droplets in an LC/monomer mixture sample with a poly-(N-vinyl carbazole) PVK-coated substrate without an external voltage. With the UV pre-irradiation of the PVK layer through a binary mask, a laterally non-uniform electric field can be induced between the pre-illuminated regions and the neighboring non-pre-illuminated PVK regions near the borders of the two regions. The phase separation occurs once the temperature is lower than 50 °C and the LC droplets can form in the sample. The pre-formed non-uniform field provides a DEP-like force to manipulate the small LC microdroplets in the pre-illuminated regions to effectively migrate to the adjacent non-pre-illuminated regions. The continuous supply of the LC from the pre-illuminated regions to the adjacent non-pre-illuminated regions significantly increases the diffraction efficiency of the grating sample. This study provides an insight into developing new external-voltage-free DEP-based devices that can be applied on various fields, such as photonics, displays, and biomedicines. Full article
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Open AccessArticle Fast Turn-Off Switching of Vertically-Aligned Negative Liquid Crystals by Fine Patterning of Pixel Electrodes
Crystals 2017, 7(7), 201; doi:10.3390/cryst7070201
Received: 25 May 2017 / Revised: 29 June 2017 / Accepted: 30 June 2017 / Published: 3 July 2017
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Abstract
We investigated the two-dimensional (2D) confinement effect on the switching of vertically-aligned negative liquid crystals (LCs) by an electric field applied between the top and bottom patterned electrodes. When an electric field is applied to a patterned vertical alignment (PVA) cell, virtual walls
[...] Read more.
We investigated the two-dimensional (2D) confinement effect on the switching of vertically-aligned negative liquid crystals (LCs) by an electric field applied between the top and bottom patterned electrodes. When an electric field is applied to a patterned vertical alignment (PVA) cell, virtual walls form in the middle of the gaps between and at the center of the patterned electrodes. These virtual walls formed in a PVA cell results in the turn-off time being dependent on the pitch of the patterned electrodes as well as the cell gap. We found that a short response time can be achieved by the fine patterning of pixel electrodes with little decrease in the transmittance. The obtained numerical results agree well with the model based on the 2D confinement effect of LCs. Full article
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Open AccessArticle Photonic Bandgap–Cholesteric Device with Electrical Tunability and Optical Tristability in Its Defect Modes
Crystals 2017, 7(7), 184; doi:10.3390/cryst7070184
Received: 14 May 2017 / Revised: 15 June 2017 / Accepted: 20 June 2017 / Published: 23 June 2017
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Abstract
This study proposes a hybrid structure for a one-dimensional (1D) photonic crystal (PC) comprising a tristable cholesteric liquid crystal (CLC) as the defect layer. The CLC exhibits three optically stable states: the Grandjean planar (P), focal conic (FC), and uniform lying helix (ULH)
[...] Read more.
This study proposes a hybrid structure for a one-dimensional (1D) photonic crystal (PC) comprising a tristable cholesteric liquid crystal (CLC) as the defect layer. The CLC exhibits three optically stable states: the Grandjean planar (P), focal conic (FC), and uniform lying helix (ULH) configurations. Specifically, the reflection band of the CLC is set within the photonic bandgap (PBG) of the 1D PC. While the ULH and the FC states can be regarded as the light-on and light-off states for defect-mode peaks in the visible spectrum, respectively, switching the device from the ULH to the P state enables suppression of the transmission of partial defect modes within the PBG. This device possesses many alluring features, such as optical tristability at null applied voltage and transmission tunability of the defect modes, providing a new pathway for the design of multifunctional and energy-efficient optical switches, light shutters, multichannels, and wavelength selectors. Full article
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Open AccessArticle Chiral Optical Tamm States: Temporal Coupled-Mode Theory
Crystals 2017, 7(4), 113; doi:10.3390/cryst7040113
Received: 28 February 2017 / Revised: 4 April 2017 / Accepted: 8 April 2017 / Published: 17 April 2017
Cited by 2 | PDF Full-text (1983 KB) | HTML Full-text | XML Full-text
Abstract
The chiral optical Tamm state (COTS) is a special localized state at the interface of a handedness-preserving mirror and a structurally chiral medium such as a cholesteric liquid crystal or a chiral sculptured thin film. The spectral behavior of COTS, observed as reflection
[...] Read more.
The chiral optical Tamm state (COTS) is a special localized state at the interface of a handedness-preserving mirror and a structurally chiral medium such as a cholesteric liquid crystal or a chiral sculptured thin film. The spectral behavior of COTS, observed as reflection resonances, is described by the temporal coupled-mode theory. Mode coupling is different for two circular light polarizations because COTS has a helical structure replicating that of the cholesteric. The mode coupling for co-handed circularly polarized light exponentially attenuates with the cholesteric layer thickness since the COTS frequency falls into the stop band. Cross-handed circularly polarized light freely goes through the cholesteric layer and can excite COTS when reflected from the handedness-preserving mirror. The coupling in this case is proportional to anisotropy of the cholesteric and theoretically only anisotropy in magnetic permittivity can ultimately cancel this coupling. These two couplings being equal result in a polarization crossover (the Kopp–Genack effect) for which a linear polarization is optimal to excite COTS. The corresponding cholesteric thickness and scattering matrix for COTS are generally described by simple expressions. Full article
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Open AccessLetter Switchable Two-Dimensional Liquid Crystal Grating in Blue Phase
Crystals 2017, 7(6), 182; doi:10.3390/cryst7060182
Received: 11 May 2017 / Revised: 18 June 2017 / Accepted: 19 June 2017 / Published: 21 June 2017
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Abstract
We demonstrate a switchable two-dimensional phase grating in blue phase liquid crystal (BPLC), which is fabricated by sawtooth in-plane-switch (IPS) electrodes. They are used to generate the horizontal electric field on a single indium-tin-oxide (ITO) glass substrate and, as a result, the 1-D
[...] Read more.
We demonstrate a switchable two-dimensional phase grating in blue phase liquid crystal (BPLC), which is fabricated by sawtooth in-plane-switch (IPS) electrodes. They are used to generate the horizontal electric field on a single indium-tin-oxide (ITO) glass substrate and, as a result, the 1-D and 2-D phase gratings can be mutual switched via different polarizations of incident light with an applied voltage. The first-order diffraction efficiency is up to 20% and 10% for the 1-D and 2-D phase grating at V = 150 V, respectively. Moreover, the rise and decay time is 0.9 and 1.1 ms, respectively, which is suitable for wide applications of high-speed optical manipulations. Full article
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