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Orr ACJ, Qiu X, Kamal W, Sykes TC, Elston SJ, Yeomans JM, Morris SM, Castrejón-Pita AA. Topologically frustrated structures in inkjet printed chiral nematic liquid crystal droplets - experiments and simulations. SOFT MATTER 2024. [PMID: 39263712 DOI: 10.1039/d4sm00541d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/13/2024]
Abstract
Director field alignment in inkjet printed droplets of chiral nematic liquid crystalline materials is investigated using both experiments and numerical simulations. Experimental investigations are performed by depositing droplets of varying sizes and pitches on homeotropic alignment layers. The competition between the bulk behaviour of the chiral nematic liquid crystal and the boundary conditions imposed by the droplet surface leads to the formation of a range of possible internal director configurations. Numerical investigations are performed using a free energy minimisation approach, and the resultant simulated polarising optical microscope images are found to agree well with experimental observations.
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Affiliation(s)
- Alva C J Orr
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
| | - Xuke Qiu
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
| | - Waqas Kamal
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
| | - Thomas C Sykes
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
- School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Steve J Elston
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
| | - Julia M Yeomans
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - Stephen M Morris
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
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2
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Oh HS, Kim KJ, Lee J, Kim JB, Ku KH. Unveiling the structural influence of nematic mesogens on customizable temperature and spectral responses. J Colloid Interface Sci 2024; 677:250-258. [PMID: 39146813 DOI: 10.1016/j.jcis.2024.08.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Revised: 08/05/2024] [Accepted: 08/07/2024] [Indexed: 08/17/2024]
Abstract
Rapid and accurate detection and visualization of temperature variations near the human body hold significant importance. This study presents thermochromic colloids capable of adjusting the detectable temperature range and reflection wavelength over a wide spectrum. The systematic investigation focuses on understanding the influence of the molecular structure of nematic mesogens on the morphological dynamics of cholesteric liquid crystal droplets and their associated thermochromic behaviors. A tunable colorimetric temperature range (i.e., from 10 to 40 °C) and high sensitivity (i.e., Δλ ΔT-1 > 100nm °C-1) are realized through precise modulation of the alkyl chain lengths in cyanobiphenyls molecules, combined with a cholesteryl oleyl carbonate as a chiral dopant. We demonstrate the efficiency of a binary mixture of different mesogens, enabling customized structural colors with desired temperature responses. Finally, inspired by the ability of the octopus to camouflage through the elongation or contraction of its pigment cells, thermochromic droplets are embedded within a polymer matrix, resulting in a portable skin patch that offers quick, reversible, and direct temperature visualization of the human body.
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Affiliation(s)
- Hyeong Seok Oh
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Kyeong Jin Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Juyoung Lee
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jong Bin Kim
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Kang Hee Ku
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
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3
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Akman A, Bukusoglu E. Understanding directed assembly of concentrated nanoparticles at energetically heterogeneous interfaces of cholesteric liquid crystal droplets. J Colloid Interface Sci 2023; 649:772-784. [PMID: 37385042 DOI: 10.1016/j.jcis.2023.06.143] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 05/13/2023] [Accepted: 06/19/2023] [Indexed: 07/01/2023]
Abstract
Colloidal self-assembly has gained significant interest in scientific and technological advances. We investigated the self-assembly of the colloids at fluidic interfaces that mediate elastic interactions. Whereas past studies have reported the assembly of micrometer- or molecular-sized species at aqueous interfaces of liquid crystals (LCs), herein we study the assembly of intermediate-sized nanoparticles. Specifically, surface-modified silica nanoparticles (50 to 500 nm) were adsorbed at the liquid crystal-water interfaces and their positioning was investigated using electron microscopy after polymerization. The study revealed that the electric double layer forces and the elastic forces caused by LC strain are dominant in the assembly of nanoparticles and their contributions can be tuned to direct the self-assembly guided by the sub-interface symmetry of confined cholesteric LCs. At high ionic strengths, we observed a strong localization of nanoparticles at the defects, whereas intermediate strengths resulted in their partial enrichment into cholesteric fingerprint patterns with an interaction energy of ≈3 kBT. This result is comparable with the calculations based on the strength of the binary interactions of the nanoparticles. The findings also support the role of ion partitioning at the LC-aqueous interfaces on the formation of the assemblies. The results can be utilized for applications in sensors, microelectronics, and photonics.
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Affiliation(s)
- Ali Akman
- Department of Chemical Engineering, Middle East Technical University, Dumlupınar Bulvarı No.1 Çankaya, Ankara 06800, Turkey
| | - Emre Bukusoglu
- Department of Chemical Engineering, Middle East Technical University, Dumlupınar Bulvarı No.1 Çankaya, Ankara 06800, Turkey.
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4
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Saito K, Kimura Y. Optically driven liquid crystal droplet rotator. Sci Rep 2022; 12:16623. [PMID: 36198748 PMCID: PMC9534986 DOI: 10.1038/s41598-022-21146-y] [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: 05/27/2022] [Accepted: 09/22/2022] [Indexed: 11/30/2022] Open
Abstract
In this study, the rotation of liquid crystal droplets induced by elliptically polarized laser light was investigated using optical tweezers. The rotation mechanism was analyzed based on the arrangement of liquid crystal molecules within the droplets. The change in the rotation behavior of nematic liquid crystal (NLC) droplets was evaluated by varying the droplet size. The experimental results were analyzed based on the waveplate effect and light-scattering process. The rotation behavior of cholesteric liquid crystal droplets was examined by varying the droplet size and helical pitch, which was controlled by the chiral dopant concentration. The results are discussed in terms of the selective reflection of the incident beam by the helical structure. The dependence of the rotation frequency on the ellipticity of the incident beam was also studied. The main contribution to the rotation gradually changes from light transmission to reflection with increasing chirality of the droplet. An NLC rotator system was constructed using holographic optical tweezers. Such an optically controllable rotator is a typical micro-optomechanical device. Complex flow fields, including multiple vortex and localized shear fields, were realized at the micron scale.
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Affiliation(s)
- Keita Saito
- Department of Physics, School of Science, Kyushu University, Fukuoka, 819-0395, Japan
| | - Yasuyuki Kimura
- Department of Physics, School of Science, Kyushu University, Fukuoka, 819-0395, Japan.
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5
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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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6
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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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7
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Norouzi S, Martinez Gonzalez JA, Sadati M. Chiral Liquid Crystal Microdroplets for Sensing Phospholipid Amphiphiles. BIOSENSORS 2022; 12:313. [PMID: 35624614 PMCID: PMC9139120 DOI: 10.3390/bios12050313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 12/17/2022]
Abstract
Designing simple, sensitive, fast, and inexpensive readout devices to detect biological molecules and biomarkers is crucial for early diagnosis and treatments. Here, we have studied the interaction of the chiral liquid crystal (CLC) and biomolecules at the liquid crystal (LC)-droplet interface. CLC droplets with high and low chirality were prepared using a microfluidic device. We explored the reconfiguration of the CLC molecules confined in droplets in the presence of 1,2-diauroyl-sn-glycero3-phosphatidylcholine (DLPC) phospholipid. Cross-polarized optical microscopy and spectrometry techniques were employed to monitor the effect of droplet size and DLPC concentration on the structural reorganization of the CLC molecules. Our results showed that in the presence of DLPC, the chiral LC droplets transition from planar to homeotropic ordering through a multistage molecular reorientation. However, this reconfiguration process in the low-chirality droplets happened three times faster than in high-chirality ones. Applying spectrometry and image analysis, we found that the change in the chiral droplets' Bragg reflection can be correlated with the CLC-DLPC interactions.
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Affiliation(s)
- Sepideh Norouzi
- Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA;
| | - Jose A. Martinez Gonzalez
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Av. Parque Chapultepec 1570, San Luis Potosí 78210 SLP, Mexico;
| | - Monirosadat Sadati
- Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA;
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8
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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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9
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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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10
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Spherical Confinement of Chromonics: Effects of a Chiral Aminoacid. NANOMATERIALS 2022; 12:nano12040619. [PMID: 35214948 PMCID: PMC8878752 DOI: 10.3390/nano12040619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 01/31/2022] [Accepted: 02/08/2022] [Indexed: 11/17/2022]
Abstract
Induced or spontaneous chirality in natural systems is an intriguing issue. In recent years, a lot of attention has been focused on chirality of chromonic liquid crystals, a class of materials that is able to self-assemble in columnar structures. However, the mechanism involved in the arising of chirality in these materials, that starts at the molecular level and controls the supramolecular structure, is poorly understood; however, it is certainly affected by ionic strength. In this work we present the results obtained doping Cromolyn, a chromonic material, with a strong helical-twisting-power peptide, and confining it in a spherical geometry. We demonstrate, by means of optical polarized microscopy and structural analysis, that both the geometrical constraint and the presence of the chiral dopant enhance the chiral effect; we also demonstrate that they favor the rise of a highly ordered helical superstructure, that may be optimized upon adding an ionic dye to the system. Finally, we report a procedure for the preparation of free-standing polymeric films, embedding and preserving the microspheres, and paving the way for the creation of biocompatible and eco-friendly optical devices to be used in the sensor and anticounterfeiting fields.
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11
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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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12
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Gardymova AP, Krakhalev MN, Zyryanov VY, Gruzdenko AA, Alekseev AA, Rudyak VY. Polymer Dispersed Cholesteric Liquid Crystals With a Toroidal Director Configuration under an Electric Field. Polymers (Basel) 2021; 13:732. [PMID: 33673505 PMCID: PMC7956821 DOI: 10.3390/polym13050732] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 02/16/2021] [Accepted: 02/22/2021] [Indexed: 01/12/2023] Open
Abstract
The electro-optical properties of polymer dispersed liquid crystal (PDLC) films are highly dependent on the features of the contained liquid crystal (LC) droplets. Cholesteric LC droplets with homeotropic boundaries can form several topologically different orientational structures, including ones with single and more point defects, layer-like, and axisymmetric twisted toroidal structures. These structures are very sensitive to an applied electric field. In this work, we have demonstrated experimentally and by computer simulations that twisted toroidal droplets reveal strong structural response to the electric field. In turn, this leads to vivid changes in the optical texture in crossed polarizers. The response of droplets of different sizes were found to be equivalent in terms of dimensionless parameters. In addition, the explanation of this phenomenon showed a comparison of theoretical and experimental structural response curves aids to determine the shape of the droplet. Finally, we demonstrated that the addition of a dichroic dye allows such films to be used as optical filters with adjustable color even without polarizers.
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Affiliation(s)
- Anna P. Gardymova
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660041 Krasnoyarsk, Russia; (A.P.G.); (M.N.K.)
| | - Mikhail N. Krakhalev
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660041 Krasnoyarsk, Russia; (A.P.G.); (M.N.K.)
- 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;
| | - Alexandra A. Gruzdenko
- Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia; (A.A.G.); (A.A.A.)
| | - Andrey A. Alekseev
- Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia; (A.A.G.); (A.A.A.)
| | - Vladimir Yu. Rudyak
- Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia; (A.A.G.); (A.A.A.)
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13
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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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14
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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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15
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Durey G, Sohn HRO, Ackerman PJ, Brasselet E, Smalyukh II, Lopez-Leon T. Topological solitons, cholesteric fingers and singular defect lines in Janus liquid crystal shells. SOFT MATTER 2020; 16:2669-2682. [PMID: 31898713 DOI: 10.1039/c9sm02033k] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Topological solitons are non-singular but topologically nontrivial structures in fields, which have fundamental significance across various areas of physics, similar to singular defects. Production and observation of singular and solitonic topological structures remain a complex undertaking in most branches of science - but in soft matter physics, they can be realized within the director field of a liquid crystal. Additionally, it has been shown that confining liquid crystals to spherical shells using microfluidics resulted in a versatile experimental platform for the dynamical study of topological transformations between director configurations. In this work, we demonstrate the triggered formation of topological solitons, cholesteric fingers, singular defect lines and related structures in liquid crystal shells. We show that to accommodate these objects, shells must possess a Janus nature, featuring both twisted and untwisted domains. We report the formation of linear and axisymmetric objects, which we identify as cholesteric fingers and skyrmions or elementary torons, respectively. We then take advantage of the sensitivity of shells to numerous external stimuli to induce dynamical transitions between various types of structures, allowing for a richer phenomenology than traditional liquid crystal cells with solid flat walls. Using gradually more refined experimental techniques, we induce the targeted transformation of cholesteric twist walls and fingers into skyrmions and elementary torons. We capture the different stages of these director transformations using numerical simulations. Finally, we uncover an experimental mechanism to nucleate arrays of axisymmetric structures on shells, thereby creating a system of potential interest for tackling crystallography studies on curved spaces.
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Affiliation(s)
- Guillaume Durey
- Laboratoire Gulliver, UMR CNRS 7083, ESPCI Paris, Université PSL, 10 rue Vauquelin, 75005 Paris, France.
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16
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Reorientation behavior in the helical motility of light-responsive spiral droplets. Nat Commun 2019; 10:5238. [PMID: 31748502 PMCID: PMC6868138 DOI: 10.1038/s41467-019-13201-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 10/25/2019] [Indexed: 01/07/2023] Open
Abstract
The physico-chemical processes supporting life's purposeful movement remain essentially unknown. Self-propelling chiral droplets offer a minimalistic model of swimming cells and, in surfactant-rich water, droplets of chiral nematic liquid crystals follow the threads of a screw. We demonstrate that the geometry of their trajectory is determined by both the number of turns in, and the handedness of, their spiral organization. Using molecular motors as photo-invertible chiral dopants allows converting between right-handed and left-handed trajectories dynamically, and droplets subjected to such an inversion reorient in a direction that is also encoded by the number of spiral turns. This motile behavior stems from dynamic transmission of chirality, from the artificial molecular motors to the liquid crystal in confinement and eventually to the helical trajectory, in analogy with the chirality-operated motion and reorientation of swimming cells and unicellular organisms.
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17
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Thermo-Optical Generation of Particle-Like Structures in Frustrated Chiral Nematic Film. CRYSTALS 2019. [DOI: 10.3390/cryst9110574] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The creation of metastable particle-like structures in frustrated (unwound) chiral nematic film containing light-absorbing additive is studied. It is shown that such localized structures can be generated by the thermo-optical action of a focused laser beam or arise spontaneously at a phase transition from an isotropic to a liquid crystal state. Observed axisymmetric patterns resemble cholesteric spherulites with toroidal double-twisted director-field configuration.
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