151
|
Blow ML, Thampi SP, Yeomans JM. Biphasic, lyotropic, active nematics. PHYSICAL REVIEW LETTERS 2014; 113:248303. [PMID: 25541809 DOI: 10.1103/physrevlett.113.248303] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Indexed: 05/23/2023]
Abstract
We perform dynamical simulations of a two-dimensional active nematic fluid in coexistence with an isotropic fluid. Drops of active nematic become elongated, and an effective anchoring develops at the nematic-isotropic interface. The activity also causes an undulatory instability of the interface. This results in defects of positive topological charge being ejected into the nematic, leaving the interface with a diffuse negative charge. Quenching the active lyotropic fluid results in a steady state in which phase-separating domains are elongated and then torn apart by active stirring.
Collapse
Affiliation(s)
- Matthew L Blow
- Centro de Física Teórica e Computacional, Avenida Professor Gama Pinto 2, P-1649-003 Lisboa, Portugal and Departamento de Física da Faculdade de Ciências, Universidade de Lisboa, P-1749-016 Lisboa, Portugal
| | - Sumesh P Thampi
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, United Kingdom
| | - Julia M Yeomans
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, United Kingdom
| |
Collapse
|
152
|
Thampi SP, Golestanian R, Yeomans JM. Active nematic materials with substrate friction. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:062307. [PMID: 25615093 DOI: 10.1103/physreve.90.062307] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Indexed: 06/04/2023]
Abstract
Active turbulence in dense active systems is characterized by high vorticity on a length scale that is large compared to that of individual entities. We describe the properties of active turbulence as momentum propagation is screened by frictional damping. As friction is increased, the spacing between the walls in the nematic director field decreases as a consequence of the more rapid velocity decays. This leads to, first, a regime with more walls and an increased number of topological defects, and then to a jammed state in which the walls deliminate bands of opposing flow, analogous to the shear bands observed in passive complex fluids.
Collapse
Affiliation(s)
- Sumesh P Thampi
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford, OX1 3NP, United Kingdom
| | - Ramin Golestanian
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford, OX1 3NP, United Kingdom
| | - Julia M Yeomans
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford, OX1 3NP, United Kingdom
| |
Collapse
|
153
|
Giomi L, Bowick MJ, Mishra P, Sknepnek R, Cristina Marchetti M. Defect dynamics in active nematics. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130365. [PMID: 25332389 PMCID: PMC4223672 DOI: 10.1098/rsta.2013.0365] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Topological defects are distinctive signatures of liquid crystals. They profoundly affect the viscoelastic behaviour of the fluid by constraining the orientational structure in a way that inevitably requires global changes not achievable with any set of local deformations. In active nematic liquid crystals, topological defects not only dictate the global structure of the director, but also act as local sources of motion, behaving as self-propelled particles. In this article, we present a detailed analytical and numerical study of the mechanics of topological defects in active nematic liquid crystals.
Collapse
Affiliation(s)
- Luca Giomi
- SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy Instituut-Lorentz, Universiteit Leiden, PO Box 9506, 2300 RA Leiden, The Netherlands
| | - Mark J Bowick
- Physics Department and Syracuse Biomaterials Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Prashant Mishra
- Physics Department, Syracuse University, Syracuse, NY 13244, USA
| | - Rastko Sknepnek
- School of Engineering, Physics, and Mathematics, University of Dundee, Dundee DD1 4HN, UK
| | - M Cristina Marchetti
- Physics Department and Syracuse Biomaterials Institute, Syracuse University, Syracuse, NY 13244, USA
| |
Collapse
|
154
|
Henkin G, DeCamp SJ, Chen DTN, Sanchez T, Dogic Z. Tunable dynamics of microtubule-based active isotropic gels. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20140142. [PMID: 25332391 PMCID: PMC4223677 DOI: 10.1098/rsta.2014.0142] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We investigate the dynamics of an active gel of bundled microtubules (MTs) that is driven by clusters of kinesin molecular motors. Upon the addition of ATP, the coordinated action of thousands of molecular motors drives the gel to a highly dynamical turbulent-like state that persists for hours and is only limited by the stability of constituent proteins and the availability of the chemical fuel. We characterize how enhanced transport and emergent macroscopic flows of active gels depend on relevant molecular parameters, including ATP, kinesin motor and depletant concentrations, MT volume fraction, as well as the stoichiometry of the constituent motor clusters. Our results show that the dynamical and structural properties of MT-based active gels are highly tunable. They also indicate existence of an optimal concentration of molecular motors that maximize far-from-equilibrium activity of active isotropic MT gels.
Collapse
Affiliation(s)
- Gil Henkin
- Department of Physics, Brandeis University, Waltham, MA 02454, USA
| | - Stephen J DeCamp
- Department of Physics, Brandeis University, Waltham, MA 02454, USA
| | - Daniel T N Chen
- Department of Physics, Brandeis University, Waltham, MA 02454, USA
| | - Tim Sanchez
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02438, USA
| | - Zvonimir Dogic
- Department of Physics, Brandeis University, Waltham, MA 02454, USA
| |
Collapse
|
155
|
Mishra S, Puri S, Ramaswamy S. Aspects of the density field in an active nematic. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:rsta.2013.0364. [PMID: 25332390 PMCID: PMC4223671 DOI: 10.1098/rsta.2013.0364] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Active nematics are conceptually the simplest orientationally ordered phase of self-driven particles, but have proved to be a perennial source of surprises. We show here through numerical solution of coarse-grained equations for the order parameter and density that the growth of the active nematic phase from the isotropic phase is necessarily accompanied by a clumping of the density. The growth kinetics of the density domains is shown to be faster than the [Formula: see text] law expected for variables governed by a conservation law. Other results presented include the suppression of density fluctuations in the stationary ordered nematic by the imposition of an orienting field. We close by posing some open questions.
Collapse
Affiliation(s)
- Shradha Mishra
- Department of Theoretical Sciences, S N Bose National Centre for Basic Sciences, Kolkata 700 098, India
| | - Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
| | - Sriram Ramaswamy
- TIFR Centre for Interdisciplinary Sciences, Hyderabad 500 075, India
| |
Collapse
|
156
|
Thampi SP, Golestanian R, Yeomans JM. Vorticity, defects and correlations in active turbulence. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130366. [PMID: 25332382 PMCID: PMC4223673 DOI: 10.1098/rsta.2013.0366] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We describe a numerical investigation of a continuum model of an active nematic, concentrating on the regime of active turbulence. Results are presented for the effect of three parameters, activity, elastic constant and rotational diffusion constant, on the order parameter and flow fields. Defects and distortions in the director field act as sources of vorticity, and thus vorticity is strongly correlated to the director field. In particular, the characteristic length of decay of vorticity and order parameter correlations is controlled by the defect density. By contrast, the decay of velocity correlations is determined by a balance between activity and dissipation. We highlight the role of microscopic flow generation mechanisms in determining the flow patterns and characteristic scales of active turbulence and contrast the behaviour of extensile and contractile active nematics.
Collapse
Affiliation(s)
- Sumesh P Thampi
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, UK
| | - Ramin Golestanian
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, UK
| | - Julia M Yeomans
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, UK
| |
Collapse
|
157
|
Affiliation(s)
- Julia M Yeomans
- Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, UK
| |
Collapse
|
158
|
Neef M, Kruse K. Generation of stationary and moving vortices in active polar fluids in the planar Taylor-Couette geometry. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:052703. [PMID: 25493812 DOI: 10.1103/physreve.90.052703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Indexed: 06/04/2023]
Abstract
We study the dynamics of an active polar fluid in the interstitial space between two fixed coaxial cylinders. For sufficiently large expansive or contractive active stresses, the fluid presents roll instabilities of axially symmetric states leading to the spontaneous formation of vortices in the flow field. These vortices are either stationary or travel around the inner cylinder. Increasing the activity further, our numerical solutions indicate the existence of active turbulence that coexists with regular vortex solutions.
Collapse
Affiliation(s)
- M Neef
- Theoretische Physik, Universität des Saarlandes, Postfach 151150, 66041 Saarbrücken, Germany
| | - K Kruse
- Theoretische Physik, Universität des Saarlandes, Postfach 151150, 66041 Saarbrücken, Germany
| |
Collapse
|
159
|
Putzig E, Baskaran A. Phase separation and emergent structures in an active nematic fluid. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:042304. [PMID: 25375491 PMCID: PMC4459651 DOI: 10.1103/physreve.90.042304] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Indexed: 05/29/2023]
Abstract
We consider a phenomenological continuum theory for an active nematic fluid and show that there exists a universal, model-independent instability which renders the homogeneous nematic state unstable to order fluctuations. Using numerical and analytic tools we show that, in the vicinity of a critical point, this instability leads to a phase-separated state in which the ordered regions form bands in which the direction of nematic order is perpendicular to the direction of the density gradient. We argue that the underlying mechanism that leads to this phase separation is a universal feature of active fluids of different symmetries.
Collapse
Affiliation(s)
- Elias Putzig
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Aparna Baskaran
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| |
Collapse
|
160
|
Keber FC, Loiseau E, Sanchez T, DeCamp SJ, Giomi L, Bowick MJ, Marchetti MC, Dogic Z, Bausch AR. Topology and dynamics of active nematic vesicles. Science 2014; 345:1135-9. [PMID: 25190790 DOI: 10.1126/science.1254784] [Citation(s) in RCA: 309] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Engineering synthetic materials that mimic the remarkable complexity of living organisms is a fundamental challenge in science and technology. We studied the spatiotemporal patterns that emerge when an active nematic film of microtubules and molecular motors is encapsulated within a shape-changing lipid vesicle. Unlike in equilibrium systems, where defects are largely static structures, in active nematics defects move spontaneously and can be described as self-propelled particles. The combination of activity, topological constraints, and vesicle deformability produces a myriad of dynamical states. We highlight two dynamical modes: a tunable periodic state that oscillates between two defect configurations, and shape-changing vesicles with streaming filopodia-like protrusions. These results demonstrate how biomimetic materials can be obtained when topological constraints are used to control the non-equilibrium dynamics of active matter.
Collapse
Affiliation(s)
- Felix C Keber
- Department of Physics, Technische Universität München, 85748 Garching, Germany. Institute for Advanced Study, Technische Universität München, 85748 Garching, Germany
| | - Etienne Loiseau
- Department of Physics, Technische Universität München, 85748 Garching, Germany
| | - Tim Sanchez
- Department of Physics, Brandeis University, Waltham, MA 02474, USA
| | - Stephen J DeCamp
- Department of Physics, Brandeis University, Waltham, MA 02474, USA
| | - Luca Giomi
- SISSA International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy. Instituut-Lorentz for Theoretical Physics, Leiden University, 2333 CA Leiden, Netherlands
| | - Mark J Bowick
- Physics Department and Syracuse Biomaterials Institute, Syracuse University, Syracuse, NY 13244, USA
| | - M Cristina Marchetti
- Physics Department and Syracuse Biomaterials Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Zvonimir Dogic
- Institute for Advanced Study, Technische Universität München, 85748 Garching, Germany. Department of Physics, Brandeis University, Waltham, MA 02474, USA
| | - Andreas R Bausch
- Department of Physics, Technische Universität München, 85748 Garching, Germany.
| |
Collapse
|
161
|
Ngo S, Peshkov A, Aranson IS, Bertin E, Ginelli F, Chaté H. Large-scale chaos and fluctuations in active nematics. PHYSICAL REVIEW LETTERS 2014; 113:038302. [PMID: 25083667 DOI: 10.1103/physrevlett.113.038302] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Indexed: 06/03/2023]
Abstract
We show that dry active nematics, e.g., collections of shaken elongated granular particles, exhibit large-scale spatiotemporal chaos made of interacting dense, ordered, bandlike structures in a parameter region including the linear onset of nematic order. These results are obtained from the study of both the well-known (deterministic) hydrodynamic equations describing these systems and of the self-propelled particle model they were derived from. We prove, in particular, that the chaos stems from the generic instability of the band solution of the hydrodynamic equations. Revisiting the status of the strong fluctuations and long-range correlations in the particle model, we show that the giant number fluctuations observed in the chaotic phase are a trivial consequence of density segregation. However anomalous, curvature-driven number fluctuations are present in the homogeneous quasiordered nematic phase and characterized by a nontrivial scaling exponent.
Collapse
Affiliation(s)
- Sandrine Ngo
- Service de Physique de l'Etat Condensé, CNRS URA 2464, CEA-Saclay, 91191 Gif-sur-Yvette, France and Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and SUPA, Physics Department, IPAM and Institute for Complex Systems and Mathematical Biology, King's College, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom
| | - Anton Peshkov
- Service de Physique de l'Etat Condensé, CNRS URA 2464, CEA-Saclay, 91191 Gif-sur-Yvette, France and Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, 75252 Paris, France
| | - Igor S Aranson
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
| | - Eric Bertin
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and Laboratoire Interdisciplinaire de Physique, Université Joseph Fourier Grenoble, CNRS UMR 5588, BP 87, 38402 Saint-Martin d'Hères, France and Université de Lyon, Laboratoire de Physique, ENS Lyon, CNRS, 46 allée d'Italie, 69007 Lyon, France
| | - Francesco Ginelli
- SUPA, Physics Department, IPAM and Institute for Complex Systems and Mathematical Biology, King's College, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom
| | - Hugues Chaté
- Service de Physique de l'Etat Condensé, CNRS URA 2464, CEA-Saclay, 91191 Gif-sur-Yvette, France and Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, 75252 Paris, France
| |
Collapse
|
162
|
Shi XQ, Ma YQ. Topological structure dynamics revealing collective evolution in active nematics. Nat Commun 2014; 4:3013. [PMID: 24346733 PMCID: PMC3905717 DOI: 10.1038/ncomms4013] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 11/26/2013] [Indexed: 11/29/2022] Open
Abstract
Topological defects frequently emerge in active matter like bacterial colonies, cytoskeleton extracts on substrates, self-propelled granular or colloidal layers and so on, but their dynamical properties and the relations to large-scale organization and fluctuations in these active systems are seldom touched. Here we reveal, through a simple model for active nematics using self-driven hard elliptic rods, that the excitation, annihilation and transportation of topological defects differ markedly from those in non-active media. These dynamical processes exhibit strong irreversibility in active nematics in the absence of detailed balance. Moreover, topological defects are the key factors in organizing large-scale dynamic structures and collective flows, resulting in multi-spatial temporal effects. These findings allow us to control the self-organization of active matter through topological structures. Topological defects are observed in a range of active systems, but their dynamical properties are largely unknown. Here, the authors use a simulation of self-propelled hard-rods to generate topological defects in active nematics, finding that their anomalous dynamics may lead to large-scale collective motions.
Collapse
Affiliation(s)
- Xia-qing Shi
- 1] Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China [2] National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Yu-qiang Ma
- 1] Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China [2] National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| |
Collapse
|
163
|
Weber CA, Bock C, Frey E. Defect-mediated phase transitions in active soft matter. PHYSICAL REVIEW LETTERS 2014; 112:168301. [PMID: 24815670 DOI: 10.1103/physrevlett.112.168301] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Indexed: 06/03/2023]
Abstract
How do topological defects affect the degree of order in active matter? To answer this question we investigate an agent-based model of self-propelled particles, which accounts for polar alignment and short-ranged repulsive interactions. For strong alignment forces we find collectively moving polycrystalline states with fluctuating networks of grain boundaries. In the regime where repulsive forces dominate, the fluctuations generated by the active system give rise to quasi-long-range transitional order, but-unlike the thermal system-without creating topological defects.
Collapse
Affiliation(s)
- Christoph A Weber
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, D-80333 Munich, Germany
| | - Christopher Bock
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, D-80333 Munich, Germany
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, D-80333 Munich, Germany
| |
Collapse
|
164
|
Giomi L, DeSimone A. Spontaneous division and motility in active nematic droplets. PHYSICAL REVIEW LETTERS 2014; 112:147802. [PMID: 24766017 DOI: 10.1103/physrevlett.112.147802] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Indexed: 06/03/2023]
Abstract
We investigate the mechanics of an active droplet endowed with internal nematic order and surrounded by an isotropic Newtonian fluid. Using numerical simulations we demonstrate that, due to the interplay between the active stresses and the defective geometry of the nematic director, this system exhibits two of the fundamental functions of living cells: spontaneous division and motility, by means of self-generated hydrodynamic flows. These behaviors can be selectively activated by controlling a single physical parameter, namely, an active variant of the capillary number.
Collapse
Affiliation(s)
- Luca Giomi
- SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy
| | - Antonio DeSimone
- SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy
| |
Collapse
|
165
|
Abstract
Collective motion of self-propelled organisms or synthetic particles, often termed "active fluid," has attracted enormous attention in the broad scientific community because of its fundamentally nonequilibrium nature. Energy input and interactions among the moving units and the medium lead to complex dynamics. Here, we introduce a class of active matter--living liquid crystals (LLCs)--that combines living swimming bacteria with a lyotropic liquid crystal. The physical properties of LLCs can be controlled by the amount of oxygen available to bacteria, by concentration of ingredients, or by temperature. Our studies reveal a wealth of intriguing dynamic phenomena, caused by the coupling between the activity-triggered flow and long-range orientational order of the medium. Among these are (i) nonlinear trajectories of bacterial motion guided by nonuniform director, (ii) local melting of the liquid crystal caused by the bacteria-produced shear flows, (iii) activity-triggered transition from a nonflowing uniform state into a flowing one-dimensional periodic pattern and its evolution into a turbulent array of topological defects, and (iv) birefringence-enabled visualization of microflow generated by the nanometers-thick bacterial flagella. Unlike their isotropic counterpart, the LLCs show collective dynamic effects at very low volume fraction of bacteria, on the order of 0.2%. Our work suggests an unorthodox design concept to control and manipulate the dynamic behavior of soft active matter and opens the door for potential biosensing and biomedical applications.
Collapse
|
166
|
Pismen LM. Dynamics of defects in an active nematic layer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:050502. [PMID: 24329200 DOI: 10.1103/physreve.88.050502] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Indexed: 06/03/2023]
Abstract
Defect dynamics in a thin active nematic layer is studied by asymptotic matching of solutions in the defect core and the far field. The analysis is facilitated by the correspondence between the two-dimensional nematic and complex scalar field models. Self-propulsion and topological interactions are identified as the primary drivers of the defect motion, surpassing the influence of both passive backflow and active flow induced by other defects.
Collapse
Affiliation(s)
- L M Pismen
- Department of Chemical Engineering and Minerva Center for Nonlinear Physics of Complex Systems, Technion-Israel Institute of Technology, Haifa 32000, Israel
| |
Collapse
|
167
|
Thampi SP, Golestanian R, Yeomans JM. Velocity correlations in an active nematic. PHYSICAL REVIEW LETTERS 2013; 111:118101. [PMID: 24074119 DOI: 10.1103/physrevlett.111.118101] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Indexed: 05/25/2023]
Abstract
The flow properties of a continuum model for an active nematic are studied and compared with recent experiments on suspensions of microtubule bundles and molecular motors. The velocity correlation length is found to be independent of the strength of the activity while the characteristic velocity scale increases monotonically as the activity is increased, both in agreement with the experimental observations. We interpret our results in terms of the creation and annihilation dynamics of a gas of topological defects.
Collapse
Affiliation(s)
- Sumesh P Thampi
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, United Kingdom
| | | | | |
Collapse
|