1
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Yoshioka J, Ito Y, Fukao K. Morphogenesis of a chiral liquid crystalline droplet with topological reconnection and Lehmann rotation. Sci Rep 2024; 14:7597. [PMID: 38556534 DOI: 10.1038/s41598-024-58054-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 03/25/2024] [Indexed: 04/02/2024] Open
Abstract
Morphogenesis is a hierarchical phenomenon that produces various macroscopic structures in living organisms, with high reproducibility. This study demonstrates that such structural formation can also be observed in a chiral liquid crystalline droplet under a temperature gradient. Through specific control of the temperature change process, we were able to switch the final structure obtained as a result of the formation via the appearance and reconnection of loop defects in the transient state during structure formation. Simultaneously, the existence of the gradient resulted in a characteristic rotational phenomenon called Lehmann rotation, which was prominently induced in the transient state. By demonstrating three-dimensional measurements of the flow field, we revealed the existence of Marangoni convection in the state. Consequently, it is indicated that the convection results in high-speed Lehmann rotation and large structural deformation with topological changes, thereby playing a significant role in the structure formation.
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Affiliation(s)
- Jun Yoshioka
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga, 525-8577, Japan.
| | - Yuki Ito
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga, 525-8577, Japan
| | - Koji Fukao
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga, 525-8577, Japan
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2
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Money J, Munguia-Fernández JG, Norouzi S, Esmaeili M, Martínez-González JA, Sadati M. Photonic features of blue phase liquid crystals under curved confinement. Chem Commun (Camb) 2023; 59:12231-12247. [PMID: 37750291 DOI: 10.1039/d3cc03284a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Blue phase (BP) liquid crystals represent a fascinating state of soft matter that showcases unique optical and electro-optical properties. Existing between chiral nematic and isotropic phases, BPs are characterized by a three-dimensional cubic lattice structure resulting in selective Bragg reflections of light and consequent vivid structural colors. However, the practical realization of these material systems is hampered by their narrow thermal stability and multi-domain crystalline nature. This feature article provides an overview of the efforts devoted to stabilizing these phases and creating monodomain structures. In particular, it delves into the complex relationship between geometrical confinement, induced curvature, and the structural stability and photonic features of BPs. Understanding the interaction of curved confinement and structural stability of BPs proves crucially important for the integration of these materials into flexible and miniaturized devices. By shedding light on these critical aspects, this feature review aims to highlight the significance of understanding the coupling effects of physical and mechanical forces on the structural stability of these systems, which can pave the way for the development of efficient and practical devices based on BP liquid crystals.
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Affiliation(s)
- Jeremy Money
- Department of Chemical Engineering, College of Engineering and Computing, University of South Carolina, Columbia, SC, 29208, USA.
| | - Juan G Munguia-Fernández
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Av. Parque Chapultepec 1570, San Luis Potosí 78210, SLP, México
| | - Sepideh Norouzi
- Department of Chemical Engineering, College of Engineering and Computing, University of South Carolina, Columbia, SC, 29208, USA.
| | - Mohsen Esmaeili
- Department of Chemical Engineering, College of Engineering and Computing, University of South Carolina, Columbia, SC, 29208, USA.
| | - José A Martínez-González
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Av. Parque Chapultepec 1570, San Luis Potosí 78210, SLP, México
| | - Monirosadat Sadati
- Department of Chemical Engineering, College of Engineering and Computing, University of South Carolina, Columbia, SC, 29208, USA.
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3
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Intercalation or external binding: How to torque chromonic Sunset Yellow. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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4
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Rudyak VY, Krakhalev MN, Gardymova AP, Abdullaev AS, Alekseev AA, Zyryanov VY. Effect of elastic constants on electrically induced transition in twisted radial cholesteric droplets. Sci Rep 2022; 12:9565. [PMID: 35688866 PMCID: PMC9187752 DOI: 10.1038/s41598-022-13612-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 05/10/2022] [Indexed: 11/09/2022] Open
Abstract
In this work, we investigated the behavior of cholesteric droplets with homeotropic boundary conditions experimentally and by computer simulations. Small droplets forming twisted radial structures were studied. We obtained two different paths of structural transformations under electric field in such droplets. The choice between these paths has probabilistic nature. The ratio between the two transition types was found to be sensitive to the elastic constants of LC forming the droplet. We suggest the principal approach for in situ estimation of ratios between elastic constants in cholesteric LCs deposited in polymer-dispersed LC material and discuss its strong and weak sides.
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Affiliation(s)
- Vladimir Yu Rudyak
- Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia, 119991.
| | - Mikhail N Krakhalev
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia, 660036.,Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russia, 660041
| | - Anna P Gardymova
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russia, 660041
| | - Abylgazy S Abdullaev
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia, 660036.,Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russia, 660041
| | - Andrey A Alekseev
- Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Victor Ya Zyryanov
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia, 660036
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5
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Polymer-Dispersed Cholesteric Liquid Crystal under Homeotropic Anchoring: Electrically Induced Structures with λ1/2-Disclination. Polymers (Basel) 2022; 14:polym14071454. [PMID: 35406327 PMCID: PMC9002932 DOI: 10.3390/polym14071454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/25/2022] [Accepted: 03/31/2022] [Indexed: 11/30/2022] Open
Abstract
Orientational structures of polymer-dispersed cholesteric liquid crystal under homeotropic anchoring and their transformations under the action of an electric field are studied. The switching of cholesteric droplets between different topological states are experimentally and theoretically demonstrated. Structures with λ+1/2-disclination are found and considered. These structures are formed during the transformation of a twisted toroidal configuration induced by a decrease in the electric field when a relative chiral parameter N0>6.3. The transformation of the initial structure with a bipolar distribution of the helix axis into a twisted toroidal configuration and then into a structure with λ+1/2-disclination is investigated in detail. The behavior of these structures under the influence of an external electric field, as well as the appearance of structures with λ−1/2-disclination, are studied. Obtained results are promising for the development of optical materials with programmable properties.
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6
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Yang Y, Palacio-Betancur V, Wang X, de Pablo JJ, Abbott NL. Strongly Chiral Liquid Crystals in Nanoemulsions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2105835. [PMID: 35023609 DOI: 10.1002/smll.202105835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/22/2021] [Indexed: 06/14/2023]
Abstract
Liquid crystal (LC) emulsions represent a class of confined soft matter that exhibit exotic internal organizations and size-dependent properties, including responses to chemical and physical stimuli. Past studies have explored micrometer-scale LC emulsion droplets but little is known about LC ordering within submicrometer-sized droplets. This paper reports experiments and simulations that unmask the consequences of confinement in nanoemulsions on strongly chiral LCs that form bulk cholesteric and blue phases (BPs). A method based on light scattering is developed to characterize phase transitions of LCs within the nanodroplets. For droplets with a radius to the pitch ratio (Rv /p0 ) as small as 2/3, the BP-to-cholesteric transition is substantially suppressed, leading to a threefold increase of the BP temperature interval relative to bulk behavior. Complementary simulations align with experimental findings and reveal the dominant role of chiral elastic energy. For Rv /p0 ≈ 1/3, a single LC phase forms below the clearing point, with simulations revealing the new configuration to contain a τ-1/2 disclination that extends across the nanodroplet. These findings are discussed in the context of mechanisms by which polymer networks stabilize BPs and, more broadly, for the design of nanoconfined soft matter.
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Affiliation(s)
- Yu Yang
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14853, USA
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI, 53706, USA
| | | | - Xin Wang
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14853, USA
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637, USA
- Center for Molecular Engineering, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Nicholas L Abbott
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14853, USA
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7
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Sadati M, Martinez-Gonzalez JA, Cohen A, Norouzi S, Guzmán O, de Pablo JJ. Control of Monodomain Polymer-Stabilized Cuboidal Nanocrystals of Chiral Nematics by Confinement. ACS NANO 2021; 15:15972-15981. [PMID: 34597503 DOI: 10.1021/acsnano.1c04231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Liquid crystals are important components of optical technologies. Cuboidal crystals consisting of chiral liquid crystals-the so-called blue phases (BPs), are of particular interest due to their crystalline structures and fast response times, but it is critical that control be gained over their phase behavior as well as the underlying dislocations and grain boundaries that arise in such systems. Blue phases exhibit cubic crystalline symmetries with lattice parameters in the 100 nm range and a network of disclination lines that can be polymerized to widen the range of temperatures over which they occur. Here, we introduce the concept of strain-controlled polymerization of BPs under confinement, which enables formation of strain-correlated stabilized morphologies that, under some circumstances, can adopt perfect single-crystal monodomain structures and undergo reversible crystal-to-crystal transformations, even if their disclination lines are polymerized. We have used super-resolution laser confocal microscopy to reveal the periodic structure and the lattice planes of the strain and polymerization stabilized BPs in 3D real space. Our experimental observations are supported and interpreted by relying on theory and computational simulations in terms of a free energy functional for a tensorial order parameter. Simulations are used to determine the orientation of the lattice planes unambiguously. The findings presented here offer opportunities for engineering optical devices based on single-crystal, polymer-stabilized BPs whose inherent liquid nature, fast dynamics, and long-range crystalline order can be fully exploited.
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Affiliation(s)
- Monirosadat Sadati
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
- Department of Chemical Engineering, Swearingen Engineering Center, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Jose A Martinez-Gonzalez
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Av. Parque Chapultepec 1570, San Luis Potosí 78295, SLP, Mexico
| | - Alexander Cohen
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Sepideh Norouzi
- Department of Chemical Engineering, Swearingen Engineering Center, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Orlando Guzmán
- Departamento de Física, Universidad Autonóma Metropolitana, Av. San Rafael Atlixco 186, Ciudad de México 09340, Mexico
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
- Argonne National Laboratory, 9700 Cass Avenue Lemont, Illinois 60439, United States
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8
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Zhang YS, Ma CL, Rudyak VY, Jiang SA, Shvetsov SA, Lin JD, Lee CR. Thermal and optical manipulation of morphology in cholesteric liquid crystal microdroplets constrained on microfibers. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115383] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Shvetsov SA, Rudyak VY, Gruzdenko AA, Emelyanenko AV. Axisymmetric skyrmion-like structures in spherical-cap droplets of chiral nematic liquid crystal. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Sadati M, Martinez-Gonzalez JA, Zhou Y, Qazvini NT, Kurtenbach K, Li X, Bukusoglu E, Zhang R, Abbott NL, Hernandez-Ortiz JP, de Pablo JJ. Prolate and oblate chiral liquid crystal spheroids. SCIENCE ADVANCES 2020; 6:eaba6728. [PMID: 32832603 PMCID: PMC7439570 DOI: 10.1126/sciadv.aba6728] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 05/28/2020] [Indexed: 05/15/2023]
Abstract
Liquid crystals are known to exhibit intriguing textures and color patterns, with applications in display and optical technologies. This work focuses on chiral materials and examines the palette of morphologies that arises when microdroplets are deformed into nonspherical shapes in a controllable manner. Specifically, geometrical confinement and mechanical strain are used to manipulate orientational order, phase transitions, and topological defects that arise in chiral liquid crystal droplets. Inspired by processes encountered in nature, where insects and animals often rely on strain and temperature to alter the optical appearance of dispersed liquid crystalline elements, chiral droplets are dispersed in polymer films and deformation induced by uniaxial or biaxial stretching. Our measurements are interpreted by resorting to simulations of the corresponding systems, thereby providing an in-depth understanding of the morphologies that arise in these materials. The reported structures and assemblies offer potential for applications in smart coatings, smart fabrics, and wearable sensors.
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Affiliation(s)
- Monirosadat Sadati
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Department of Chemical Engineering, Swearingen Engineering Center, University of South Carolina, Columbia, SC 29208, USA
| | - Jose A. Martinez-Gonzalez
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Av. Parque Chapultepec 1570, San Luis Potosí 78295, SLP, México
| | - Ye Zhou
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Nader Taheri Qazvini
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Department of Chemical Engineering, Swearingen Engineering Center, University of South Carolina, Columbia, SC 29208, USA
| | - Khia Kurtenbach
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Xiao Li
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA
| | - Emre Bukusoglu
- Chemical Engineering Department, Middle East Technical University, Ankara 06800, Turkey
| | - Rui Zhang
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Nicholas L. Abbott
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Juan Pablo Hernandez-Ortiz
- Departamento de Materiales y Minerales, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Calle 75 # 79A-51, Bloque M17, Medellín, Colombia
| | - Juan J. de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Argonne National Laboratory, 9700 Cass Avenue, Lemont, IL 60439, USA
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11
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Yoshioka J, Fukao K. Self-excited oscillation of the director field in cholesteric liquid crystalline droplets under a temperature gradient. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:325102. [PMID: 32213682 DOI: 10.1088/1361-648x/ab83b1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 03/26/2020] [Indexed: 06/10/2023]
Abstract
In this study, we demonstrate a self-excited oscillation induced in cholesteric liquid crystalline droplets under a temperature gradient. At equilibrium, a winding Maltese cross pattern with a point defect was observed via polarised microscopy in the droplets dispersed in an isotropic solvent. When the temperature gradient was applied, the pattern was deformed owing to the Marangoni convection induced by the gradient. Here, when both the droplet size and temperature gradient were sufficiently large, the periodic movement of the defect together with the pattern deformation was observed, which demonstrated the self-excited oscillation of the director field. To describe this phenomenon, we theoretically analysed the flow and director fields by using Onsager's variational principle. This principle enabled the simplified description of the phenomenon; consequently, the time evolution of the director field could be expressed by the phenomenological equations for the two parameters characterising the field. These equations represented the van der Pol equation, which well expressed the mechanism of the self-excited oscillation.
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Affiliation(s)
- Jun Yoshioka
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan
| | - Koji Fukao
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan
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12
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Gardymova AP, Krakhalev MN, Zyryanov VY. Optical Textures and Orientational Structures in Cholesteric Droplets with Conical Boundary Conditions. Molecules 2020; 25:molecules25071740. [PMID: 32290090 PMCID: PMC7181251 DOI: 10.3390/molecules25071740] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/03/2020] [Accepted: 04/03/2020] [Indexed: 12/02/2022] Open
Abstract
Cholesteric droplets dispersed in polymer with conical boundary conditions have been studied. The director configurations are identified by the polarising microscopy technique. The axisymmetric twisted axial-bipolar configuration with the surface circular defect at the droplet’s equator is formed at the relative chirality parameter N0≤2.9. The intermediate director configuration with the deformed circular defect is realised at 2.9<N0<3.95, and the layer-like structure with the twisted surface defect loop is observed at N0≥3.95. The cholesteric layers in the layer-like structure are slightly distorted although the cholesteric helix is untwisted.
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Affiliation(s)
- Anna P. Gardymova
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660041 Krasnoyarsk, Russia;
- Correspondence: ; Tel.: +7-391-249-4510
| | - Mikhail N. Krakhalev
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660041 Krasnoyarsk, Russia;
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk, Russia;
| | - Victor Ya. Zyryanov
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk, Russia;
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13
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Belmonte A, Ussembayev YY, Bus T, Nys I, Neyts K, Schenning APHJ. Dual Light and Temperature Responsive Micrometer-Sized Structural Color Actuators. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1905219. [PMID: 31793728 DOI: 10.1002/smll.201905219] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 10/28/2019] [Indexed: 05/15/2023]
Abstract
Externally induced color- and shape-changes in micrometer-sized objects are of great interest in novel application fields such as optofluidics and microrobotics. In this work, light and temperature responsive micrometer-sized structural color actuators based on cholesteric liquid-crystalline (CLC) polymer particles are presented. The particles are synthesized by suspension polymerization using a reactive CLC monomer mixture having a light responsive azobenzene dye. The particles exhibit anisotropic spot-like and arc-like reflective colored domains ranging from red to blue. Electron microscopy reveals a multidirectional asymmetric arrangement of the cholesteric layers in the particles and numerical simulations elucidate the anisotropic optical properties. Upon light exposure, the particles show reversible asymmetric shape deformations combined with structural color changes. When the temperature is increased above the liquid crystal-isotropic phase transition temperature of the particles, the deformation is followed by a reduction or disappearance of the reflection. Such dual light and temperature responsive structural color actuators are interesting for a variety of micrometer-sized devices.
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Affiliation(s)
- Alberto Belmonte
- Stimuli-Responsive Functional Materials and Devices, Department of Chemical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- SCNU-TUE Joint Laboratory of Device Integrated Responsive Materials (DIRM), South China Normal University, Guangzhou Higher Education Mega Center, 510006, Guangzhou, China
| | - Yera Ye Ussembayev
- Liquid Crystals and Photonics Group, Department of Electronics and Information Systems, Ghent University, Tech Lane Ghent Science Park - Campus A 126, 9052, Ghent, Belgium
| | - Tom Bus
- Stimuli-Responsive Functional Materials and Devices, Department of Chemical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- SCNU-TUE Joint Laboratory of Device Integrated Responsive Materials (DIRM), South China Normal University, Guangzhou Higher Education Mega Center, 510006, Guangzhou, China
| | - Inge Nys
- Liquid Crystals and Photonics Group, Department of Electronics and Information Systems, Ghent University, Tech Lane Ghent Science Park - Campus A 126, 9052, Ghent, Belgium
| | - Kristiaan Neyts
- Liquid Crystals and Photonics Group, Department of Electronics and Information Systems, Ghent University, Tech Lane Ghent Science Park - Campus A 126, 9052, Ghent, Belgium
| | - Albertus P H J Schenning
- Stimuli-Responsive Functional Materials and Devices, Department of Chemical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- SCNU-TUE Joint Laboratory of Device Integrated Responsive Materials (DIRM), South China Normal University, Guangzhou Higher Education Mega Center, 510006, Guangzhou, China
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Den Dolech 2, 5600 MB, Eindhoven, The Netherlands
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14
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Sofi JA, Barthakur A, Dhara S. Whispering gallery mode lasing in mesomorphic liquid crystal microdroplets. SOFT MATTER 2019; 15:7832-7837. [PMID: 31528973 DOI: 10.1039/c9sm01132c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In recent years, investigation on the non-display applications of liquid crystals has increased considerably. One of the emerging applications is whispering gallery mode (WGM) lasing. Here, we report experimental studies on the morphology and WGM lasing in nematic (N), smectic-A (SmA) and smectic-C (SmC) microdroplets dispersed in a highly transparent and low refractive index perfluopolymer. The mesomorphic microdroplets, obtained by varying the temperature, exhibit radial director configuration. The SmA microdroplets are found to be highly stable and robust against mechanical stress compared to the N and SmC microdroplets. We study lasing properties such as intensity, threshold pump energy and linewidth, and show that overall the SmA microdroplets are superior to the N and SmC microdroplets. The experimental results are discussed based on the orientation of the dye molecules, director fluctuations and tilting at the interface.
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Affiliation(s)
- Junaid Ahmad Sofi
- School of Physics, University of Hyderabad, Hyderabad-500046, India.
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15
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Krakhalev MN, Rudyak VY, Prishchepa OO, Gardymova AP, Emelyanenko AV, Liu JH, Zyryanov VY. Orientational structures in cholesteric droplets with homeotropic surface anchoring. SOFT MATTER 2019; 15:5554-5561. [PMID: 31243424 DOI: 10.1039/c9sm00384c] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The dependency of orientational structures in cholesteric droplets with homeotropic surface anchoring on the helicity parameter has been studied by experiment and simulations. We have observed a sequence of structures, in which the director configurations and topological defects were identified by comparison of polarized microscopy pictures with simulated textures. A toron-like and low-symmetry intermediate layer-like structures have been revealed and studied in detail. The ranges of stability of the observed structures have been summarized in a general diagram and explained by the helicity parameter dependence of the free energy terms.
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Affiliation(s)
- Mikhail N Krakhalev
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia and Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk 660041, Russia
| | - Vladimir Yu Rudyak
- Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Oxana O Prishchepa
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia and Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk 660041, Russia
| | - Anna P Gardymova
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk 660041, Russia
| | | | | | - Victor Ya Zyryanov
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia
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16
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Yoshioka J, Fukao K. Horizontal transportation of a Maltese cross pattern in nematic liquid crystalline droplets under a temperature gradient. Phys Rev E 2019; 99:022702. [PMID: 30934222 DOI: 10.1103/physreve.99.022702] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Indexed: 11/07/2022]
Abstract
Flow and director fields strongly couple with each other in liquid crystalline systems, and herein we discuss the coupling effect in cylindrical and spherical-cap droplets formed by nematic liquid crystal. Applying a temperature gradient to droplets dispersed in a liquid solvent, we observed a crosslike texture in the droplets moved toward the high-temperature side, indicating that the director field was deformed from equilibrium. Additionally, measurement of the flow field revealed that a convective flow was induced in the droplets under temperature gradient. These results suggested that the director deformation in the droplet was induced by convection. By designing a simplified model based on this, we theoretically analyzed the above phenomenon based on Onsager's variational principle. The results show that the phenomenon was well described by a balance of surface energy gradient with viscous and elastic forces.
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Affiliation(s)
- Jun Yoshioka
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-0058, Japan
| | - Koji Fukao
- Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-0058, Japan
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Oswald P, Ignés-Mullol J, Dequidt A. Lehmann rotation of cholesteric droplets driven by Marangoni convection. SOFT MATTER 2019; 15:2591-2604. [PMID: 30816902 DOI: 10.1039/c8sm02574f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We show experimentally and theoretically that the Lehmann effect recently observed by Yoshioka and Araoka (Nat. Commun., 2018, 9, 432) in emulsified cholesteric liquid crystal droplets under temperature gradients is due to Marangoni flows rather than to the thermomechanical or chemomechanical couplings often invoked to explain the phenomenon. Using colloidal tracers we visualize convection rolls surrounding stationary cholesteric droplets in vertical temperature gradients, while a shift in the position of internal point defects reveals the corresponding inner convection in nematic droplets thermomigrating in a horizontal temperature gradient. We attribute these phenomena to the temperature dependence of the surface tension at the interface between these partially-miscible liquids, and justify their absence in the usual case of purely lyophobic emulsions. We perform a theoretical analysis to help validate this hypothesis, demonstrating the strong dependence of the precession velocity on the configuration of the cholesteric director field.
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Affiliation(s)
- P Oswald
- Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France.
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Yoshioka J, Salamon P, Paterson DA, Storey JMD, Imrie CT, Jákli A, Araoka F, Buka A. Spherical-cap droplets of a photo-responsive bent liquid crystal dimer. SOFT MATTER 2019; 15:989-998. [PMID: 30657150 DOI: 10.1039/c8sm01751d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Using a photo-responsive dimer exhibiting the transition between nematic (N) and twist-bend nematic (NTB) phases, we prepared spherical cap-shaped droplets on solid substrates exposed to air. The internal director structures of these droplets vary depending on the phase and on the imposed boundary conditions. The structural switching between the N and NTB phases was successfully performed either by temperature control or by UV light-irradiation. The N phase is characterized by an extremely small bend elastic constant K3, and surprisingly, we found that the droplet-air interface induces a planar alignment, in contrast to that seen for typical calamitic liquid crystals. As a consequence, the director configuration was stabilized in a structure substantially different from that normally found in conventional nematic liquid crystalline droplets. In the twist-bend nematic droplets characteristic structures with macroscopic length scales were formed, and they were well controlled by the droplet size. These results indicated that a continuum theory is effective in describing the stabilization mechanism of the macroscopic structure even in the twist-bend nematic liquid crystal droplets exhibiting director modulations on a scale of several molecular lengths.
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Affiliation(s)
- Jun Yoshioka
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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