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Sheng M, Li J, Jiang X, Wang C, Li J, Zhang L, Fu S. Biomimetic Solid-Liquid Transition Structural Dye-Doped Liquid Crystal/Phase-Change-Material Microcapsules Designed for Wearable Bistable Electrochromic Fabric. ACS APPLIED MATERIALS & INTERFACES 2021; 13:33282-33290. [PMID: 34227793 DOI: 10.1021/acsami.1c08135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A novel polymer microcapsule-filled dye-doped liquid crystal (DDLC) and phase-change material (PCM) system inspired by biological materials was first proposed, which was further encapsulated into a calcium alginate substrate by wet spinning for making an electrochromic fiber with both bistable electric-optical capability and knitting characteristics. Results show that the optical appearance of the optimized microcapsules and fiber can be reversibly changed between colored and colorless states according to the electric field by switching the DDLCs between isotropic (I) and anisotropic (A) states. Moreover, both I and A states can remain stable for more than 1 week after removing the electric field, due to the synergy of the greatly increased spatial hindrance of the PCM with core loading of 22.58% and the confinement effect from the polymer microcapsule shell material. Aside from the long-term optical stability, the high content of the densely packed DDLCs also endows the electrochromic fiber with a satisfactory driving voltage of 9.7 V, which is below the human safe voltage, showing great potential in a wide range of applications, such as flexible displays, energy-saving smart windows, and wearable advanced textiles.
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Affiliation(s)
- Mingfei Sheng
- Key Laboratory of Science & Technology of Eco-Textile, Jiangnan University, Ministry of Education, Wuxi, Jiangsu 214122, China
| | - Jingjing Li
- The First Scientific Research Institute of Wuxi, Wuxi, Jiangsu 214122, China
| | - Xiaojun Jiang
- The First Scientific Research Institute of Wuxi, Wuxi, Jiangsu 214122, China
| | - Chengcheng Wang
- Key Laboratory of Science & Technology of Eco-Textile, Jiangnan University, Ministry of Education, Wuxi, Jiangsu 214122, China
| | - Jiashuang Li
- Key Laboratory of Science & Technology of Eco-Textile, Jiangnan University, Ministry of Education, Wuxi, Jiangsu 214122, China
| | - Liping Zhang
- Key Laboratory of Science & Technology of Eco-Textile, Jiangnan University, Ministry of Education, Wuxi, Jiangsu 214122, China
| | - Shaohai Fu
- Key Laboratory of Science & Technology of Eco-Textile, Jiangnan University, Ministry of Education, Wuxi, Jiangsu 214122, China
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Programming emergent symmetries with saddle-splay elasticity. Nat Commun 2019; 10:5104. [PMID: 31704934 PMCID: PMC6841980 DOI: 10.1038/s41467-019-13012-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 10/13/2019] [Indexed: 11/08/2022] Open
Abstract
The director field adopted by a confined liquid crystal is controlled by a balance between the externally imposed interactions and the liquid's internal orientational elasticity. While the latter is usually considered to resist all deformations, liquid crystals actually have an intrinsic propensity to adopt saddle-splay arrangements, characterised by the elastic constant [Formula: see text]. In most realisations, dominant surface anchoring treatments suppress such deformations, rendering [Formula: see text] immeasurable. Here we identify regimes where more subtle, patterned surfaces enable saddle-splay effects to be both observed and exploited. Utilising theory and continuum calculations, we determine experimental regimes where generic, achiral liquid crystals exhibit spontaneously broken surface symmetries. These provide a new route to measuring [Formula: see text]. We further demonstrate a multistable device in which weak, but directional, fields switch between saddle-splay-motivated, spontaneously-polar surface states. Generalising beyond simple confinement, our highly scalable approach offers exciting opportunities for low-field, fast-switching optoelectronic devices which go beyond current technologies.
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Solodkov NV, Shim JU, Jones JC. Self-assembly of fractal liquid crystal colloids. Nat Commun 2019; 10:198. [PMID: 30643151 PMCID: PMC6331632 DOI: 10.1038/s41467-018-08210-w] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 12/20/2018] [Indexed: 11/26/2022] Open
Abstract
Nematic liquid crystals are anisotropic fluids that self-assemble into vector fields, which are governed by geometrical and topological laws. Consequently, particulate or droplet inclusions self-assemble in nematic domains through a balance of topological defects. Here, we use double emulsions of water droplets inside radial nematic liquid crystal droplets to form various structures, ranging from linear chains to three-dimensional fractal structures. The system is modeled as a formation of satellite droplets, distributed around a larger, central core droplet and we extend the problem to explain the formation of fractal structures. We show that a distribution of droplet sizes plays a key role in determining the symmetry properties of the resulting geometric structures. The results are relevant to a variety of inclusions, ranging from colloids suspensions to multi-emulsion systems. Such systems have potential applications for novel switchable photonic structures as well as providing wider insights into the packing of self-assembled structures.
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Affiliation(s)
- Nikita V Solodkov
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - Jung-Uk Shim
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - J Cliff Jones
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK.
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Jones SA, Bailey J, Walker DRE, Bryan-Brown GP, Jones JC. Method for Tuneable Homeotropic Anchoring at Microstructures in Liquid Crystal Devices. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10865-10873. [PMID: 30132669 DOI: 10.1021/acs.langmuir.8b01951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A simple method for vapour-phase deposition of a silane surfactant is presented, which produces tuneable homeotropic anchoring in liquid crystals. Both the zenithal anchoring energy and surface slip are measured by fitting to the latching threshold versus pulse width characteristic of a zenithal bistable nematic liquid crystal device based on a deep, submicron grating. The method is shown to give microscopic anchoring strength between 5 × 10-5 and 2 × 10-4 J/m2, with a surface slip of about 100 nm. The silanated surfaces are characterized using atomic force microscopy and X-ray photoelectron spectroscopy, which show a direct relationship between the surface coverage of silane groups and the resulting anchoring energy.
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Affiliation(s)
- Sophie A Jones
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , U.K
| | - James Bailey
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , U.K
- Dynamic Vision Systems , Leeds Innovation Centre , 103 Clarendon Road , Leeds LS2 9DF , U.K
| | - David R E Walker
- DisplayData Limited , Malvern Hills Science Park , Malvern , Worcstershire WR13 5SZ , U.K
| | - Guy P Bryan-Brown
- DisplayData Limited , Malvern Hills Science Park , Malvern , Worcstershire WR13 5SZ , U.K
| | - J Cliff Jones
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , U.K
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Armas-Pérez JC, Li X, Martínez-González JA, Smith C, Hernández-Ortiz JP, Nealey PF, de Pablo JJ. Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:12516-12524. [PMID: 28946745 DOI: 10.1021/acs.langmuir.7b02522] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Liquid crystals are known to be particularly sensitive to orientational cues provided at surfaces or interfaces. In this work, we explore theoretically, computationally, and experimentally the behavior of liquid crystals on isolated nanoscale patterns with controlled anchoring characteristics at small length scales. The orientation of the liquid crystal is controlled through the use of chemically patterned polymer brushes that are tethered to a surface. This system can be engineered with remarkable precision, and the central question addressed here is whether a characteristic length scale exists at which information encoded on a surface is no longer registered by a liquid crystal. To do so, we adopt a tensorial description of the free energy of the hybrid liquid-crystal-surface system, and we investigate its morphology in a systematic manner. For long and narrow surface stripes, it is found that the liquid crystal follows the instructions provided by the pattern down to 100 nm widths. This is accomplished through the creation of line defects that travel along the sides of the stripes. We show that a "sharp" morphological transition occurs from a uniform undistorted alignment to a dual uniform/splay-bend morphology. The theoretical and numerical predictions advanced here are confirmed by experimental observations. Our combined analysis suggests that nanoscale patterns can be used to manipulate the orientation of liquid crystals at a fraction of the energetic cost that is involved in traditional liquid crystal-based devices. The insights presented in this work have the potential to provide a new fabrication platform to assemble low power bistable devices, which could be reconfigured upon application of small external fields.
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Affiliation(s)
- Julio C Armas-Pérez
- Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States
- División de Ciencias e Ingenierı́as, Campus León, Universidad de Guanajuato , Loma del Bosque 103, León, Guanajuato 37150, México
| | - Xiao Li
- Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States
| | - José A Martínez-González
- Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States
| | - Coleman Smith
- Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States
| | - J P Hernández-Ortiz
- Departamento de Materiales, Universidad Nacional de Colombia , Sede Medellín, Medellín, Colombia
| | - Paul F Nealey
- Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Juan J de Pablo
- Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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Kusumaatmaja H. Surveying the free energy landscapes of continuum models: Application to soft matter systems. J Chem Phys 2015; 142:124112. [PMID: 25833570 DOI: 10.1063/1.4916389] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A variety of methods are developed for characterising the free energy landscapes of continuum, Landau-type free energy models. Using morphologies of lipid vesicles and a multistable liquid crystal device as examples, I show that the methods allow systematic study of not only the most relevant minimum energy configurations, but also the transition pathways between any two minima, as well as their corresponding energy barriers and transition state configurations. A global view of the free energy landscapes can then be visualized using either a disconnectivity graph or a network representation. Different forms of free energy functionals and boundary conditions can be readily implemented, thus allowing these tools to be utilised for a broad range of problems.
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Affiliation(s)
- Halim Kusumaatmaja
- Department of Physics, University of Durham, South Road, Durham DH1 3LE, United Kingdom
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Kusumaatmaja H, Majumdar A. Free energy pathways of a multistable liquid crystal device. SOFT MATTER 2015; 11:4809-4817. [PMID: 25982775 DOI: 10.1039/c5sm00578g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The planar bistable device [Tsakonas et al., Appl. Phys. Lett., 2007, 90, 111913] is known to have two distinct classes of stable equilibria: the diagonal and rotated solutions. We model this device within the two-dimensional Landau-de Gennes theory, with a surface potential and without any external fields. We systematically compute a special class of transition pathways, referred to as minimum energy pathways, between the stable equilibria that provide new information about how the equilibria are connected in the Landau-de Gennes free energy landscape. These transition pathways exhibit an intermediate transition state, which is a saddle point of the Landau-de Gennes free energy. We numerically compute the structural details of the transition states, the optimal transition pathways and the free energy barriers between the equilibria, as a function of the surface anchoring strength. For strong anchoring, the transition pathways are mediated by defects whereas we get defect-free transition pathways for moderate and weak anchoring. In the weak anchoring limit, we recover a cusp catastrophe situation for which the rotated state acts as a transition state connecting two different diagonal states.
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Zografopoulos DC, Kriezis EE. Switchable beam steering with zenithal bistable liquid-crystal blazed gratings. OPTICS LETTERS 2014; 39:5842-5845. [PMID: 25361099 DOI: 10.1364/ol.39.005842] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Switchable beam steerers based on zenithal bistable liquid crystal (LC) gratings are designed and theoretically investigated. The nematic orientation profiles and the optical transmittance properties of the gratings are rigorously calculated, respectively, via a tensorial formulation of the Landau-de Gennes theory and the full-wave finite-element-method. By proper design of the grating geometry, beam steering with high diffraction efficiency is demonstrated between the two stable LC states. The tolerance of the device performance with respect to material parameters is assessed, evidencing spectral operation windows of more than 50 nm in the visible for a beam steering efficiency higher than 90%.
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Zografopoulos DC, Beccherelli R, Kriezis EE. Beam-splitter switches based on zenithal bistable liquid-crystal gratings. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:042503. [PMID: 25375511 DOI: 10.1103/physreve.90.042503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Indexed: 05/22/2023]
Abstract
The tunable optical diffractive properties of zenithal bistable nematic liquid-crystal gratings are theoretically investigated. The liquid-crystal orientation is rigorously solved via a tensorial formulation of the Landau-de Gennes theory and the optical transmission properties of the gratings are investigated via full-wave finite-element frequency-domain simulations. It is demonstrated that by proper design the two stable states of the grating can provide nondiffracting and diffracting operation, the latter with equal power splitting among different diffraction orders. An electro-optic switching mechanism, based on dual-frequency nematic materials, and its temporal dynamics are further discussed. Such gratings provide a solution towards tunable beam-steering and beam-splitting components with extremely low power consumption.
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Affiliation(s)
- Dimitrios C Zografopoulos
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Via del Fosso del Cavaliere 100, 00133 Rome, Italy
| | - Romeo Beccherelli
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Via del Fosso del Cavaliere 100, 00133 Rome, Italy
| | - Emmanouil E Kriezis
- Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece
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Cattaneo L, Zhang J, Zuiddam M, Savoini M, Rasing T. Gaining control through frustration: two-fold approach for Liquid Crystal three-dimensional command layers. NANO LETTERS 2014; 14:3903-3907. [PMID: 24936774 DOI: 10.1021/nl501155h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The alignment of Liquid Crystal (LC) molecules, essential for their applications in optical devices such as displays, is usually controlled by functionalizing their confining surfaces by either patterning or by specific surfactants that induce either parallel or perpendicular molecular arrangement. Inducing a bistable alignment, such as in the new zenithal bistable displays, offers new opportunities in terms of new functionalities and lower energy consumption but a full understanding of such bistable alignment appears still complicated. Here we present a simple phenomenological model that includes surface topography and chemistry. The predicted orientational transitions and bistable states are in excellent agreement with experiments, thus making this a proper tool to design multistable 3D command layers.
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Affiliation(s)
- Laura Cattaneo
- Institute for Molecules and Materials, Radboud University Nijmegen , Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
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Anquetil-Deck C, Cleaver DJ, Atherton TJ. Competing alignments of nematic liquid crystals on square-patterned substrates. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:041707. [PMID: 23214603 DOI: 10.1103/physreve.86.041707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Indexed: 06/01/2023]
Abstract
A theoretical analysis is presented of a nematic liquid crystal confined between substrates patterned with squares that promote vertical and planar alignment. Two approaches are used to elucidate the behavior across a wide range of length scales: Monte Carlo simulation of hard particles and Frank-Oseen continuum theory. Both approaches predict bistable degenerate azimuthal alignment in the bulk along the edges of the squares; the continuum calculation additionally reveals the possibility of an anchoring transition to diagonal alignment if the polar anchoring energy associated with the pattern is sufficiently weak. Unlike the striped systems previously analyzed, the Monte Carlo simulations suggest that there is no "bridging" transition for sufficiently thin cells. The extent to which these geometrically patterned systems resemble topographically patterned substrates, such as square wells, is also discussed.
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Affiliation(s)
- C Anquetil-Deck
- Materials and Engineering Research Institute, Sheffield Hallam University, City Campus, Howard Street, Sheffield, S1 1WB, United Kingdom
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Luo C, Majumdar A, Erban R. Multistability in planar liquid crystal wells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:061702. [PMID: 23005109 DOI: 10.1103/physreve.85.061702] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Indexed: 06/01/2023]
Abstract
A planar bistable liquid crystal device, reported in Tsakonas et al. [Appl. Phys. Lett. 90, 111913 (2007)], is modeled within the Landau-de Gennes theory for nematic liquid crystals. This planar device consists of an array of square micrometer-sized wells. We obtain six different classes of equilibrium profiles and these profiles are classified as diagonal or rotated solutions. In the strong anchoring case, we propose a Dirichlet boundary condition that mimics the experimentally imposed tangent boundary conditions. In the weak anchoring case, we present a suitable surface energy and study the multiplicity of solutions as a function of the anchoring strength. We find that diagonal solutions exist for all values of the anchoring strength W ≥ 0, while rotated solutions only exist for W ≥ W_{c}>0, where W_{c} is a critical anchoring strength that has been computed numerically. We propose a dynamic model for the switching mechanisms based on only dielectric effects. For sufficiently strong external electric fields, we numerically demonstrate diagonal-to-rotated and rotated-to-diagonal switching by allowing for variable anchoring strength across the domain boundary.
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Affiliation(s)
- Chong Luo
- Mathematical Institute, University of Oxford, 24-29 St. Giles', Oxford OX1 3LB, United Kingdom.
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