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Bonn L, Ardaševa A, Mueller R, Shendruk TN, Doostmohammadi A. Fluctuation-induced dynamics of nematic topological defects. Phys Rev E 2022; 106:044706. [PMID: 36397561 DOI: 10.1103/physreve.106.044706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023]
Abstract
Topological defects are increasingly being identified in various biological systems, where their characteristic flow fields and stress patterns are associated with continuous active stress generation by biological entities. Here, using numerical simulations of continuum fluctuating nematohydrodynamics, we show that even in the absence of any specific form of active stresses associated with self-propulsion, mesoscopic fluctuations in either orientational alignment or hydrodynamics can independently result in flow patterns around topological defects that resemble the ones observed in active systems. Our simulations further show the possibility of extensile- and contractile-like motion of fluctuation-induced positive half-integer topological defects. Remarkably, isotropic stress fields also reproduce the experimentally measured stress patterns around topological defects in epithelia. Our findings further reveal that extensile- or contractile-like flow and stress patterns around fluctuation-induced defects are governed by passive elastic stresses and flow-aligning behavior of the nematics.
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Affiliation(s)
- Lasse Bonn
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen 2100, Denmark
| | - Aleksandra Ardaševa
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen 2100, Denmark
| | - Romain Mueller
- The Rudolf Peierls Centre for Theoretical Physics, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Tyler N Shendruk
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - Amin Doostmohammadi
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen 2100, Denmark
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2
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Stefopoulos G, Lendenmann T, Schutzius TM, Giampietro C, Roy T, Chala N, Giavazzi F, Cerbino R, Poulikakos D, Ferrari A. Bistability of Dielectrically Anisotropic Nematic Crystals and the Adaptation of Endothelial Collectives to Stress Fields. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2102148. [PMID: 35344288 PMCID: PMC9165505 DOI: 10.1002/advs.202102148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Endothelial monolayers physiologically adapt to flow and flow-induced wall shear stress, attaining ordered configurations in which elongation, orientation, and polarization are coherently organized over many cells. Here, with the flow direction unchanged, a peculiar bi-stable (along the flow direction or perpendicular to it) cell alignment is observed, emerging as a function of the flow intensity alone, while cell polarization is purely instructed by flow directionality. Driven by the experimental findings, the parallelism between endothelia is delineated under a flow field and the transition of dual-frequency nematic liquid crystals under an external oscillatory electric field. The resulting physical model reproduces the two stable configurations and the energy landscape of the corresponding system transitions. In addition, it reveals the existence of a disordered, metastable state emerging upon system perturbation. This intermediate state, experimentally demonstrated in endothelial monolayers, is shown to expose the cellular system to a weakening of cell-to-cell junctions to the detriment of the monolayer integrity. The flow-adaptation of monolayers composed of healthy and senescent endothelia is successfully predicted by the model with adjustable nematic parameters. These results may help to understand the maladaptive response of in vivo endothelial tissues to disturbed hemodynamics and the progressive functional decay of senescent endothelia.
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Affiliation(s)
- Georgios Stefopoulos
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
| | - Tobias Lendenmann
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
| | - Thomas M. Schutzius
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
| | - Costanza Giampietro
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
- Experimental Continuum MechanicsEMPA, Swiss Federal Laboratories for Materials Science and TechnologyÜberlandstrasse 129Dübendorf8600Switzerland
- Institute for Mechanical Systems, Department of Mechanical and Process EngineeringETH ZurichLeonhardstrasse 21Zurich8092Switzerland
| | - Tamal Roy
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
| | - Nafsika Chala
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
| | - Fabio Giavazzi
- Dipartimento di Biotecnologie Mediche e Medicina TraslazionaleUniversità degli Studi di MilanoVia F.lli Cervi 93Segrate20090Italy
| | - Roberto Cerbino
- Faculty of PhysicsUniversity of ViennaBoltzmanngasse 5ViennaAustria
| | - Dimos Poulikakos
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
| | - Aldo Ferrari
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process EngineeringETH ZurichSonneggstrasse 3Zurich8092Switzerland
- Experimental Continuum MechanicsEMPA, Swiss Federal Laboratories for Materials Science and TechnologyÜberlandstrasse 129Dübendorf8600Switzerland
- Institute for Mechanical Systems, Department of Mechanical and Process EngineeringETH ZurichLeonhardstrasse 21Zurich8092Switzerland
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Villada-Gil S, Palacio-Betancur V, Armas-Pérez JC, de Pablo JJ, Hernández-Ortiz JP. Fluctuations and phase transitions of uniaxial and biaxial liquid crystals using a theoretically informed Monte Carlo and a Landau free energy density. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:175101. [PMID: 30703761 DOI: 10.1088/1361-648x/ab0394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this work, we explore fluctuations during phase transitions of uniaxial and biaxial liquid crystals using a phenomenological free energy functional. We rely on a continuum-level description of the liquid crystal ordering with a tensorial parameter and a temperature dependent Landau polynomial expansion of the tensor's invariants. The free energy functional, over a three-dimensional periodic domain, is integrated with a Gaussian quadrature and minimized with a theoretically informed Monte Carlo method. We reconstruct analytical phase diagrams, following Landau and Doi's notations, to verify that the free energy relaxation reaches the global minimum. Importantly, our relaxation method is able to follow the thermodynamic behavior provided by other non-phenomenological approaches; we predict the first order character of the isotropic-nematic transition, and we identify the uniaxial-biaxial transition as second order. Finally, we use a finite-size scaling method, using the nematic susceptibility, to calculate the transition temperatures for 4-Cyano-4'-pentylbiphenyl (5CB) and N-(4-methoxybenzylidene)-4-butylaniline (MBBA). Our results show good agreement with experimental values, thereby validating our minimization method. Our approach is an alternative towards the relaxation of temperature dependent continuum-level free energy functionals, in any geometry, and can incorporate complicated elastic and surface energy densities.
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Affiliation(s)
- Stiven Villada-Gil
- Departamento de Materiales y Nanotecnología, Universidad Nacional de Colombia, Sede Medellín, Calle 75 # 79A-51, Bloque M17, Medellín, 050034, Colombia. Facultad de Ciencias Básicas, Sociales y Humanas, Politécnico Colombiano Jaime Isaza Cadavid, Medellín, Colombia
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4
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Controlling motile disclinations in a thick nematogenic material with an electric field. Sci Rep 2018; 8:2517. [PMID: 29410502 PMCID: PMC5802863 DOI: 10.1038/s41598-018-19891-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 01/10/2018] [Indexed: 11/20/2022] Open
Abstract
Manipulating topological disclination networks that arise in a symmetry-breaking phase transformation in widely varied systems including anisotropic materials can potentially lead to the design of novel materials like conductive microwires, self-assembled resonators, and active anisotropic matter. However, progress in this direction is hindered by a lack of control of the kinetics and microstructure due to inherent complexity arising from competing energy and topology. We have studied thermal and electrokinetic effects on disclinations in a three-dimensional nonabsorbing nematic material with a positive and negative sign of the dielectric anisotropy. The electric flux lines are highly nonuniform in uniaxial media after an electric field below the Fréedericksz threshold is switched on, and the kinetics of the disclination lines is slowed down. In biaxial media, depending on the sign of the dielectric anisotropy, apart from the slowing down of the disclination kinetics, a nonuniform electric field filters out disclinations of different topology by inducing a kinetic asymmetry. These results enhance the current understanding of forced disclination networks and establish the presented method, which we call fluctuating electronematics, as a potentially useful tool for designing materials with novel properties in silico.
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Bhattacharjee AK. Stochastic kinetics reveal imperative role of anisotropic interfacial tension to determine morphology and evolution of nucleated droplets in nematogenic films. Sci Rep 2017; 7:40059. [PMID: 28054600 PMCID: PMC5213422 DOI: 10.1038/srep40059] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/30/2016] [Indexed: 11/19/2022] Open
Abstract
For isotropic fluids, classical nucleation theory predicts the nucleation rate, barrier height and critical droplet size by ac- counting for the competition between bulk energy and interfacial tension. The nucleation process in liquid crystals is less understood. We numerically investigate nucleation in monolayered nematogenic films using a mesoscopic framework, in par- ticular, we study the morphology and kinetic pathway in spontaneous formation and growth of droplets of the stable phase in the metastable background. The parameter κ that quantifies the anisotropic elastic energy plays a central role in determining the geometric structure of the droplets. Noncircular nematic droplets with homogeneous director orientation are nucleated in a background of supercooled isotropic phase for small κ. For large κ, noncircular droplets with integer topological charge, accompanied by a biaxial ring at the outer surface, are nucleated. The isotropic droplet shape in a superheated nematic background is found to depend on κ in a similar way. Identical growth laws are found in the two cases, although an unusual two-stage mechanism is observed in the nucleation of isotropic droplets. Temporal distributions of successive events indi- cate the relevance of long-ranged elasticity-mediated interactions within the isotropic domains. Implications for a theoretical description of nucleation in anisotropic fluids are discussed.
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Affiliation(s)
- Amit Kumar Bhattacharjee
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560064, India
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6
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Xie S, Pelcovits RA, Hagan MF. Probing a self-assembled fd virus membrane with a microtubule. Phys Rev E 2016; 93:062608. [PMID: 27415321 DOI: 10.1103/physreve.93.062608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Indexed: 06/06/2023]
Abstract
The self-assembly of highly anisotropic colloidal particles leads to a rich variety of morphologies whose properties are just beginning to be understood. This article uses computer simulations to probe a particle-scale perturbation of a commonly studied colloidal assembly, a monolayer membrane composed of rodlike fd viruses in the presence of a polymer depletant. Motivated by experiments currently in progress, we simulate the interaction between a microtubule and a monolayer membrane as the microtubule "pokes" and penetrates the membrane face-on. Both the viruses and the microtubule are modeled as hard spherocylinders of the same diameter, while the depletant is modeled using ghost spheres. We find that the force exerted on the microtubule by the membrane is zero either when the microtubule is completely outside the membrane or when it has fully penetrated the membrane. The microtubule is initially repelled by the membrane as it begins to penetrate but experiences an attractive force as it penetrates further. We assess the roles played by translational and rotational fluctuations of the viruses and the osmotic pressure of the polymer depletant. We find that rotational fluctuations play a more important role than the translational ones. The dependence on the osmotic pressure of the depletant of the width and height of the repulsive barrier and the depth of the attractive potential well is consistent with the assumed depletion-induced attractive interaction between the microtubule and viruses. We discuss the relevance of these studies to the experimental investigations.
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Affiliation(s)
- Sheng Xie
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
| | - Robert A Pelcovits
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
| | - Michael F Hagan
- Department of Physics, Brandeis University, Waltham, Massachusetts 02454, USA
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7
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Everts JC, Punter MTJJM, Samin S, van der Schoot P, van Roij R. A Landau-de Gennes theory for hard colloidal rods: Defects and tactoids. J Chem Phys 2016; 144:194901. [DOI: 10.1063/1.4948785] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J. C. Everts
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | | | - S. Samin
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - P. van der Schoot
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
- Theory of Polymers and Soft Matter Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - R. van Roij
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
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8
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Armas-Pérez JC, Hernández-Ortiz JP, de Pablo JJ. Liquid crystal free energy relaxation by a theoretically informed Monte Carlo method using a finite element quadrature approach. J Chem Phys 2015; 143:243157. [DOI: 10.1063/1.4937628] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Julio C. Armas-Pérez
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Juan P. Hernández-Ortiz
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Departamento de Materiales y Minerales, Universidad Nacional de Colombia, Sede Medellín, Medellín, Colombia
| | - Juan J. de Pablo
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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9
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Armas-Pérez JC, Londono-Hurtado A, Guzmán O, Hernández-Ortiz JP, de Pablo JJ. Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields. J Chem Phys 2015; 143:044107. [DOI: 10.1063/1.4926790] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Julio C. Armas-Pérez
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | | | - Orlando Guzmán
- Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, DF 09340, México
| | - Juan P. Hernández-Ortiz
- Departamento de Materiales y Minerales, Universidad Nacional de Colombia, Sede Medellín, Medellín, Colombia
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Juan J. de Pablo
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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10
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Londoño-Hurtado A, Armas-Pérez JC, Hernández-Ortiz JP, de Pablo JJ. Homeotropic nano-particle assembly on degenerate planar nematic interfaces: films and droplets. SOFT MATTER 2015; 11:5067-5076. [PMID: 26027806 DOI: 10.1039/c5sm00940e] [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
A continuum theory is used to study the effects of homeotropic nano-particles on degenerate planar liquid crystal interfaces. Particle self-assembly mechanisms are obtained from careful examination of particle configurations on a planar film and on a spherical droplet. The free energy functional that describes the system is minimized according to Ginzburg-Landau and stochastic relaxations. The interplay between elastic and surface distortions and the desire to minimize defect volumes (boojums and half-Saturn rings) is shown to be responsible for the formation of intriguing ordered structures. As a general trend, the particles prefer to localize at defects to minimize the overall free energy. However, multiple metastable configurations corresponding to local minima can be easily observed due to the high energy barriers that separate distinct particle arrangements. We also show that by controlling anchoring strength and temperature one can direct liquid-crystal mediated nanoparticle self-assembly along well defined pathways.
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11
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Chaudhri A, Bell JB, Garcia AL, Donev A. Modeling multiphase flow using fluctuating hydrodynamics. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:033014. [PMID: 25314536 DOI: 10.1103/physreve.90.033014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Indexed: 06/04/2023]
Abstract
Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches.
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Affiliation(s)
- Anuj Chaudhri
- Computational Research Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - John B Bell
- Computational Research Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Alejandro L Garcia
- Department of Physics and Astronomy, San Jose State University, San Jose, California 95192, USA
| | - Aleksandar Donev
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, USA
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12
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Singh A, Ahmad S, Puri S, Singh S. Ordering kinetics in liquid crystals with long-ranged interactions. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2014; 37:2. [PMID: 24458552 DOI: 10.1140/epje/i2014-14002-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 10/04/2013] [Accepted: 01/03/2014] [Indexed: 06/03/2023]
Abstract
We present the results from comprehensive Monte Carlo (MC) simulations of ordering kinetics in d = 2 liquid crystals (LCs). Our LC system is described by the two-component Lebwohl-Lasher model with long-ranged interactions, V(r) ∼ r(-n). We find that systems with n ≥ 2 show the same dynamical behavior as the nearest-neighbor case (n = ∞). This contradicts available theoretical predictions.
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Affiliation(s)
- Amrita Singh
- Department of Physics, Banaras Hindu University, 221005, Varanasi, India
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13
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Singh A, Singh S. Phase ordering kinetics in uniaxial nematic liquid crystals with second- and fourth-rank interactions. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:122. [PMID: 24158262 DOI: 10.1140/epje/i2013-13122-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 07/10/2013] [Accepted: 10/08/2013] [Indexed: 06/02/2023]
Abstract
We present comprehensive results of the Monte Carlo (MC) simulations of the phase ordering dynamics in d = 2 nematic liquid crystals. We study a system of size N (2)(N = 512) with molecules confined to a 512×512 square lattice and report the results for two LC Hamiltonians: generalized Lebwohl-Lasher (GLL) model and r(-6) dependent anisotropic dispersion interaction potential. In these Hamiltonians a fourth-rank Legendre polynomial P4 interaction term is added to the usual second-rank P2 term. We find that in both the cases the presence of the P4 interaction term significantly influences the nematic domains morphology. Our numerical data show a diffusive growth law with a logarithmic correction: L(t) ∼ (t/ln t)(1/2).
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Affiliation(s)
- Amrita Singh
- Department of Physics, Banaras Hindu University, 221005, Varanasi, India
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14
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Yang Y, Barry E, Dogic Z, Hagan MF. Self-assembly of 2D membranes from mixtures of hard rods and depleting polymers(). SOFT MATTER 2012; 8:707-714. [PMID: 23139699 PMCID: PMC3489486 DOI: 10.1039/c1sm06201h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We combine simulations and experiments to elucidate the molecular forces leading to the assembly of two dimensional membrane-like structures composed of a one rod-length thick monolayer of aligned rods from an immiscible suspension of hard rods and depleting polymers. Computer simulations predict that monolayer membranes are thermodynamically stable above a critical rod aspect ratio and below a critical depletion interaction length scale. Outside of these conditions alternative structures such as stacked smectic columns or nematic droplets are thermodynamically stable. These predictions are confirmed by subsequent experiments using a model system of virus rod-like molecules and non-adsorbing polymer. Our work demonstrates that collective molecular protrusion fluctuations alone are sufficient to stabilize membranes composed of homogenous rods with simple excluded volume interactions.
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Affiliation(s)
| | - Edward Barry
- Department of Physics, Brandeis University, Waltham, MA, 02454, USA
| | - Zvonimir Dogic
- Department of Physics, Brandeis University, Waltham, MA, 02454, USA
| | - Michael F. Hagan
- Department of Physics, Brandeis University, Waltham, MA, 02454, USA
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15
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Yang Y, Hagan MF. Theoretical calculation of the phase behavior of colloidal membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:051402. [PMID: 22181412 DOI: 10.1103/physreve.84.051402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Indexed: 05/31/2023]
Abstract
We formulate a density functional theory that describes the phase behavior of hard rods and depleting polymers, as realized in recent experiments on suspensions of fd virus and nonadsorbing polymer. The theory predicts the relative stability of nematic droplets, stacked smectic columns, and a recently discovered phase of isolated monolayers of rods, or colloidal membranes. We find that a minimum rod aspect ratio is required for stability of colloidal membranes and that collective protrusion undulations are the dominant effect that stabilizes this phase. The theoretical predictions are shown to be qualitatively consistent with experimental and computational results.
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Affiliation(s)
- Yasheng Yang
- Department of Physics, Brandeis University, Waltham, Massachusetts 02454, USA
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16
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de Oliveira BF, Avelino PP, Moraes F, Oliveira JCRE. Nematic liquid crystal dynamics under applied electric fields. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:041707. [PMID: 21230295 DOI: 10.1103/physreve.82.041707] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 08/13/2010] [Indexed: 05/30/2023]
Abstract
In this paper we investigate the coarsening dynamics of liquid crystal textures in a two-dimensional nematic under applied electric fields, using numerical simulations performed using a publicly available liquid crystal algorithm developed by the authors. We consider both positive and negative dielectric anisotropies and two different possibilities for the orientation of the electric field (parallel and perpendicular to the two-dimensional lattice). We determine the effect of an applied electric field pulse on the evolution of the characteristic length scale and other properties of the liquid crystal texture network. In particular, we show that different types of defects are produced after the electric field is switched on, depending on the orientation of the electric field and the sign of the dielectric anisotropy.
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Affiliation(s)
- B F de Oliveira
- Centro de Física do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal
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17
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Bhattacharjee AK, Menon GI, Adhikari R. Fluctuating dynamics of nematic liquid crystals using the stochastic method of lines. J Chem Phys 2010; 133:044112. [DOI: 10.1063/1.3455206] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Kamil SM, Bhattacharjee AK, Adhikari R, Menon GI. Biaxiality at the isotropic-nematic interface with planar anchoring. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:041705. [PMID: 19905323 DOI: 10.1103/physreve.80.041705] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Indexed: 05/28/2023]
Abstract
We revisit the classic problem of the structure of the isotropic-nematic interface within Ginzburg-Landau-de Gennes theory, refining previous analytic treatments of biaxiality at the interface. We compare our analysis with numerical results obtained through a highly accurate spectral collocation scheme for the solution of the Landau-Ginzburg-de Gennes equations. In comparison to earlier work, we obtain improved agreement with numerics for both the uniaxial and biaxial profiles, accurate asymptotic results for the decay of biaxial order on both nematic and isotropic sides of the interface, and accurate fits to data from density-functional approaches to this problem.
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Affiliation(s)
- S M Kamil
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600 113, India
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