1
|
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.
Collapse
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
| |
Collapse
|
2
|
Kim J, Jeong J. Confinement twists achiral liquid crystals and causes chiral liquid crystals to twist in the opposite handedness: cases in and around sessile droplets. SOFT MATTER 2024; 20:1361-1368. [PMID: 38252544 DOI: 10.1039/d3sm01283b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
We study the chiral symmetry breaking and metastability of confined nematic lyotropic chromonic liquid crystals (LCLCs) with and without chiral dopants. The isotropic-nematic coexistence phase of the LCLC renders two confining geometries: sessile isotropic (I) droplets surrounded by the nematic (N) phase and sessile nematic droplets immersed in the isotropic background. In the achiral system with no dopants, LCLC's elastic anisotropy and topological defects induce a spontaneous twist deformation to lower the energetic penalty of splay deformation, resulting in spiral optical textures under crossed polarizers both in the I-in-N and N-in-I systems. While the achiral system exhibits both handednesses with an equal probability, a small amount of the chiral dopant breaks the balance. Notably, in contrast to the homochiral configuration of a chirally doped LCLC in the bulk, the spiral texture of the disfavored handedness appears with a finite probability both in the I-in-N and N-in-I systems. We propose director field models explaining how chiral symmetry breaking arises by the energetics and the opposite-twist configurations exist as meta-stable structures in the energy landscape. These findings help us create and control chiral structures using confined LCs with large elastic anisotropy.
Collapse
Affiliation(s)
- Jungmyung Kim
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
| | - Joonwoo Jeong
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
| |
Collapse
|
3
|
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.
Collapse
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.
| |
Collapse
|
4
|
Rotation and transportation of liquid crystal droplets for visualizing electric properties of microstructured electrodes. Sci Rep 2023; 13:4369. [PMID: 36927766 PMCID: PMC10020540 DOI: 10.1038/s41598-023-31026-8] [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: 12/15/2022] [Accepted: 03/06/2023] [Indexed: 03/18/2023] Open
Abstract
The spatial resolution of typical sensor probes is sufficient for measuring the average electric properties of microelectrical devices, but they are unable to measure the distribution with a spatial precision. Liquid crystal droplets (LCDs) are promising candidate for visualizing the distribution. When voltage is applied, the LCDs show rotational and translational behaviors which depend on the location of LCDs within the devices. We demonstrate that by comparing the experimental and numerical results, the electric field and electrostatic energy distribution are visualized by rotating and transporting LCDs, with a spatial resolution of 10 µm and a detection accuracy of 5 µV/µm. In addition, we produced an array of LCDs by designing periodic modulation of the electrostatic energy density in the model device. These findings show that the LCDs serve as a periodic modulator of the refractive index as well as a sensor for the observation of electric properties of microelectrical devices.
Collapse
|
5
|
Norouzi S, Tavera-Vazquez A, Ramirez-de Arellano J, Kim DS, Lopez-Leon T, de Pablo JJ, Martinez-Gonzalez JA, Sadati M. Elastic Instability of Cubic Blue Phase Nano Crystals in Curved Shells. ACS NANO 2022; 16:15894-15906. [PMID: 36166665 DOI: 10.1021/acsnano.2c02799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Many crystallization processes, including biomineralization and ice-freezing, occur in small and curved volumes, where surface curvature can strain the crystal, leading to unusual configurations and defect formation. The role of curvature on crystallization, however, remains poorly understood. Here, we study the crystallization of blue phase (BP) liquid crystals under curved confinement, which provides insights into the mechanism by which BPs reconfigure their three-dimensional lattice structure to adapt to curvature. BPs are a three-dimensional assembly of high-chirality liquid crystal molecules arranged into body-centered (BPI) or simple cubic (BPII) symmetries. BPs with submicrometer cubic-crystalline lattices exhibit tunable Bragg reflection and submillisecond response time to external stimuli such as an electric field, making them attractive for advanced photonic materials. In this work, we have systematically studied BPs confined in spherical shells with well-defined curvature and boundary conditions. The optical behavior of shells has also been examined at room temperature, where the cholesteric structure forms. In the cholesteric phase, perpendicular anchoring generates focal conic domains on the shell's surface, which transition into stripe patterns as the degree of curvature increases. Our results demonstrate that both higher degrees of curvature and strong spatial confinement destabilize BPI and reconfigure that phase to adopt the structure and optical features of BPII. We also show that the coupling of curvature and confinement nucleates skyrmions at greater thicknesses than those observed for a flat geometry. These findings are particularly important for integrating BPs into miniaturized and curved/flexible devices, including flexible displays, wearable sensors, and smart fabrics.
Collapse
Affiliation(s)
- Sepideh Norouzi
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Antonio Tavera-Vazquez
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Johanan Ramirez-de Arellano
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Avenida Parque Chapultepec 1570, San Luis Potosí 78210, San Luis Potosi México
| | - Dae Seok Kim
- Department of Polymer Engineering, Pukyong National University, Busan 48513, South Korea
| | - Teresa Lopez-Leon
- Laboratoire Gulliver, UMR CNRS 7083, ESPCI Paris, Université PSL, 10 rue Vauquelin, 75005 Paris, France
| | - 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
| | - Jose A Martinez-Gonzalez
- Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, Avenida Parque Chapultepec 1570, San Luis Potosí 78210, San Luis Potosi México
| | - Monirosadat Sadati
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, United States
| |
Collapse
|
6
|
Bono S, Konishi S. Temperature gradient sensing mechanism using liquid crystal droplets with 0.1-mK-level detection accuracy and high spatial resolution. Sci Rep 2022; 12:13733. [PMID: 35962134 PMCID: PMC9374739 DOI: 10.1038/s41598-022-18008-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: 04/12/2022] [Accepted: 08/03/2022] [Indexed: 11/15/2022] Open
Abstract
We proposed the detection mechanism of the micro-levels of temperature gradient in a micro-electromechanical system using the unidirectional rotation of cholesteric-liquid crystal (Ch-LC) droplets. Ch-LC droplets in the presence of an isotropic phase subjected to a heat flux rotate with a speed proportional to the magnitude of the temperature gradient. We further quantified the temperature gradient-to-torque conversion efficiency to apply the thermomechanical cross-correlation to the detection of temperature gradient. Then, we observed the rotational behavior of Ch-LC droplets after introducing them onto model devices containing patterned Au thin-film electrodes. Direct electric current applied to these Au electrodes results in unidirectional rotation of the Ch-LC droplets in response to heat flux generated from the Au electrodes. By evaluating the possible temperature gradient detection resolution using Ch-LC droplet rotation, we show that Ch-LC droplets can achieve both high spatial resolution (~ 10 µm) and high detection accuracy (~ 0.1 mK/µm).
Collapse
Affiliation(s)
- Shinji Bono
- Department of Mechanical Engineering, College of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan. .,Graduate Course of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan. .,Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, Kyoto, 604-8520, Japan.
| | - Satoshi Konishi
- Department of Mechanical Engineering, College of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan.,Graduate Course of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan.,Ritsumeikan Advanced Research Academy, Kyoto, 604-8520, Japan.,Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, Kyoto, 604-8520, Japan
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
Bono S, Maruyama Y, Nishiyama K, Tabe Y. Heat-Driven Rigid-Body Rotation of a Mixture of Cholesteric Liquid Crystal Droplets and Colloids. J Phys Chem B 2020; 124:6170-6174. [PMID: 32558576 DOI: 10.1021/acs.jpcb.0c04186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We show that cholesteric (Ch) liquid crystal droplets with cylindrically symmetric orientation dispersing in an isotropic (Iso) phase exhibited unidirectional rotation under a heat flux along the symmetry axis. By introducing colloidal particle adhesive to the Ch droplet surface, we traced the translational motion of the colloids and found that the colloids rotated unidirectionally around the center of each Ch droplet. The director configuration of the droplets was not distorted either spatially or temporally, while the colloids rotated constantly. The results suggest that the Ch droplets under the heat flux should rotate as a rigid body. Using this heat-driven rotation of the Ch droplets, we designed new geometries of various composites of Ch droplets and colloids and succeeded in driving intriguing complex dynamics.
Collapse
Affiliation(s)
- Shinji Bono
- Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
| | - Yuji Maruyama
- Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
| | - Katsu Nishiyama
- Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
| | - Yuka Tabe
- Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
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.
Collapse
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;
| |
Collapse
|
11
|
Bono S, Maruyama Y, Nishiyama K, Tabe Y. A thermomechanical coupling in cholesteric liquid crystals: Unidirectional rotation of double-twist cylinders driven by heat flux. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:99. [PMID: 31392491 DOI: 10.1140/epje/i2019-11867-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/16/2019] [Indexed: 06/10/2023]
Abstract
We made aggregates of cholesteric liquid crystalline Cylinders with Double-Twist orientational structure (DTC) and investigated their rigid-body rotation under a temperature gradient, focusing on how the rotational speed should depend on the cylinder size. The experimental results showed that the angular velocity of the DTC aggregates linearly increased with the height of the cylinders and was inversely proportional to the base area. With a phenomenological equation, we analyzed the torque caused by the heat flux and its balance with the viscous friction, and found that the simple analysis well explained the size-dependence of the rotation of the DTC aggregates. The coupling constant between the heat flux and the torque to drive the rigid-body rotation was in the same order of magnitude as that for the director rotation.
Collapse
Affiliation(s)
- Shinji Bono
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Yuji Maruyama
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Katsu Nishiyama
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Yuka Tabe
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan.
- Kagami Memorial Research Institute for Material Science and Technology, Waseda University, Tokyo, Japan.
| |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- Jun Yoshioka
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Bono S, Maruyama Y, Tabe Y. Formation and dynamics of the aggregates of cholesteric double-twist cylinders. SOFT MATTER 2018; 14:9798-9805. [PMID: 30398276 DOI: 10.1039/c8sm01565a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We succeeded in driving the unidirectional rigid-body rotation of cholesteric (Ch) double-twist cylinder (DTC) droplets under a heat flux along the cylindrical symmetry axis. To directly observe the rigid-body rotation of DTC droplets, in each of which the center of the rotation and the symmetry axis of the structure correspond, we fabricated DTC aggregates that comprise several DTCs with intact structures. Given a steady heat flux, the DTC aggregates metastabilized by the shape and the surface anchoring show a unidirectional rigid-body rotation with a constant angular velocity. The rotational direction is determined by the molecular chirality and the direction of the heat flux, and the rotational velocity increases with the temperature gradient and decreases with the aggregation number N of the DTCs as 1 + 2/sin2(π/N). The behavior agrees with a simple model based on the linear phenomenological equation.
Collapse
Affiliation(s)
- Shinji Bono
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan.
| | | | | |
Collapse
|
14
|
Bipolar configuration with twisted loop defect in chiral nematic droplets under homeotropic surface anchoring. Sci Rep 2017; 7:14582. [PMID: 29109533 PMCID: PMC5674080 DOI: 10.1038/s41598-017-15049-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 10/19/2017] [Indexed: 11/22/2022] Open
Abstract
Optical textures and appropriate orientational structures have been studied within droplets of chiral nematic dispersed in polymer assigning the homeotropic anchoring. The helix axis of the chiral structure inside droplets forms the bipolar configuration. The optical droplet textures were analysed in the unpolarised light, analyser switching-off scheme and in crossed polarisers. The twisted loop defect reveals itself convincingly in all schemes. Its appearance at the optical patterns of the chiral nematic droplets has been examined depending on their size and the aspect direction. The existence of the defect has been verified by the structural and optical calculations. The effect of an electric field on both the defect line shape and the orientational structure of chiral nematic has been studied.
Collapse
|
15
|
Poy G, Bunel F, Oswald P. Role of anchoring energy on the texture of cholesteric droplets: Finite-element simulations and experiments. Phys Rev E 2017; 96:012705. [PMID: 29347207 DOI: 10.1103/physreve.96.012705] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Indexed: 11/07/2022]
Abstract
We present a numerical method to compute defect-free textures inside cholesteric domains of arbitrary shape. This method has two interesting properties, namely a robust and fast quadratic convergence to a local minimum of the Frank free energy, thanks to a trust region strategy. We apply this algorithm to study the texture of cholesteric droplets in coexistence with their isotropic liquid in two cases: when the anchoring is planar and when it is tilted. In the first case, we show how to determine the anchoring energy at the cholesteric-isotropic interface from a study of the optical properties of droplets of different sizes oriented with an electric field. This method is applied to the case of the liquid crystal CCN-37. In the second case, we come back to the issue of the textural transition as a function of the droplet radius between the double-twist droplets and the banded droplets, observed for instance in cyanobiphenyl liquid crystals. We show that, even if this transition is dominated by the saddle-splay Gauss constant K_{4}, as was recently recognized by Yoshioka et al. [Soft Matter 12, 2400 (2016)1744-683X10.1039/C5SM02838H], the anchoring energy does also play an important role that cannot be neglected.
Collapse
Affiliation(s)
- Guilhem Poy
- Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France
| | - Felix Bunel
- Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France
| | - Patrick Oswald
- Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France
| |
Collapse
|