1
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Wu-Zhang B, Fedosov DA, Gompper G. Collective behavior of squirmers in thin films. SOFT MATTER 2024; 20:5687-5702. [PMID: 38639062 DOI: 10.1039/d4sm00075g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Bacteria in biofilms form complex structures and can collectively migrate within mobile aggregates, which is referred to as swarming. This behavior is influenced by a combination of various factors, including morphological characteristics and propulsive forces of swimmers, their volume fraction within a confined environment, and hydrodynamic and steric interactions between them. In our study, we employ the squirmer model for microswimmers and the dissipative particle dynamics method for fluid modeling to investigate the collective motion of swimmers in thin films. The film thickness permits a free orientation of non-spherical squirmers, but constraints them to form a two-layered structure at maximum. Structural and dynamic properties of squirmer suspensions confined within the slit are analyzed for different volume fractions of swimmers, motility types (e.g., pusher, neutral squirmer, puller), and the presence of a rotlet dipolar flow field, which mimics the counter-rotating flow generated by flagellated bacteria. Different states are characterized, including a gas-like phase, swarming, and motility-induced phase separation, as a function of increasing volume fraction. Our study highlights the importance of an anisotropic swimmer shape, hydrodynamic interactions between squirmers, and their interaction with the walls for the emergence of different collective behaviors. Interestingly, the formation of collective structures may not be symmetric with respect to the two walls. Furthermore, the presence of a rotlet dipole significantly mitigates differences in the collective behavior between various swimmer types. These results contribute to a better understanding of the formation of bacterial biofilms and the emergence of collective states in confined active matter.
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Affiliation(s)
- Bohan Wu-Zhang
- Theoretical Physics of Living Matter, Institute of Biological Information Processing and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany.
| | - Dmitry A Fedosov
- Theoretical Physics of Living Matter, Institute of Biological Information Processing and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany.
| | - Gerhard Gompper
- Theoretical Physics of Living Matter, Institute of Biological Information Processing and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany.
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2
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Ye H, Ouyang Z, Lin J. On particle motion in a confined square domain filled with active fluids. SOFT MATTER 2024; 20:1786-1799. [PMID: 38305105 DOI: 10.1039/d3sm01321a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
The motion of passive particles in a confined square domain filled with active fluids has been numerically simulated using a direct-fictitious domain method. The ratio of particle diameter to the side length of the square domain (dp/L) is adopted to classify the degree of confinement (i.e., strong or weak confinement). The translational mean-squared displacement (MSDT) of weakly-confined particles scales well with the reported theoretical and experimental results in a short time and eventually reaches a plateau because of the confined environment. Additionally, the radial probability densities of the particle positions gradually increase with increasing distance from the center of the square domain at relatively high activity levels, displaying an apparent rise near the boundary and maximize near the corner. Conversely, the strongly confined particles migrate toward the center of the square domain or approach the corner with continuous rotation. In addition, the localized minima of the angular velocity of the particles show a periodic behavior, with the vortices periodically becoming more organized. Moreover, with increasing activity, two distinct linearly correlated regimes emerge in the relationship between the particle's rotational velocity and the activity. A comprehensive analysis of the collective dynamics reveals that the cutoff length is Rc ≈ 0.19(2.375dp), pointing to the distance at which the velocities of two particles are uncorrelated. Moreover, the spatial correlation function (Ip) shows a small peak at Rr ≈ 0.12(1.5dp), suggesting a relatively strong correlation between a given particle and another particle located at a distance Rr from it. Interestingly, both Rc and Rr are smaller than those observed in an unbounded flow, which indicates that boundary confinement significantly influences the ability of the particles to form coherent structures.
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Affiliation(s)
- Hao Ye
- Department of Mechanics, State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, 310027 Hangzhou, China.
| | - Zhenyu Ouyang
- Zhejiang Provincial Engineering Research Center for the Safety of Pressure Vessel and Pipeline, 315210 Ningbo, China.
| | - Jianzhong Lin
- Department of Mechanics, State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, 310027 Hangzhou, China.
- Zhejiang Provincial Engineering Research Center for the Safety of Pressure Vessel and Pipeline, 315210 Ningbo, China.
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3
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Fylling C, Tamayo J, Gopinath A, Theillard M. Multi-population dissolution in confined active fluids. SOFT MATTER 2024; 20:1392-1409. [PMID: 38305767 DOI: 10.1039/d3sm01196h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
Autonomous out-of-equilibrium agents or cells in suspension are ubiquitous in biology and engineering. Turning chemical energy into mechanical stress, they generate activity in their environment, which may trigger spontaneous large-scale dynamics. Often, these systems are composed of multiple populations that may reflect the coexistence of multiple species, differing phenotypes, or chemically varying agents in engineered settings. Here, we present a new method for modeling such multi-population active fluids subject to confinement. We use a continuum multi-scale mean-field approach to represent each phase by its first three orientational moments and couple their evolution with those of the suspending fluid. The resulting coupled system is solved using a parallel adaptive level-set-based solver for high computational efficiency and maximal flexibility in the confinement geometry. Motivated by recent experimental work, we employ our method to study the spatiotemporal dynamics of confined bacterial suspensions and swarms dominated by fluid hydrodynamic effects. Our in silico explorations reproduce observed emergent collective patterns, including features of active dissolution in two-population active-passive swarms, with results clearly suggesting that hydrodynamic effects dominate dissolution dynamics. Our work lays the foundation for a systematic characterization and study of collective phenomena in natural or synthetic multi-population systems such as bacteria colonies, bird flocks, fish schools, colloid swimmers, or programmable active matter.
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Affiliation(s)
- Cayce Fylling
- Department of Applied Mathematics, University of California Merced, Merced, CA95343, USA.
| | - Joshua Tamayo
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA.
| | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA.
| | - Maxime Theillard
- Department of Applied Mathematics, University of California Merced, Merced, CA95343, USA.
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4
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Luo W, Baskaran A, Pelcovits RA, Powers TR. Flow states of two dimensional active gels driven by external shear. SOFT MATTER 2024; 20:738-753. [PMID: 38168972 DOI: 10.1039/d3sm00919j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Using a minimal hydrodynamic model, we theoretically and computationally study the Couette flow of active gels in straight and annular two-dimensional channels subject to an externally imposed shear. The gels are isotropic in the absence of externally- or activity-driven shear, but have nematic order that increases with shear rate. Using the finite element method, we determine the possible flow states for a range of activities and shear rates. Linear stability analysis of an unconfined gel in a straight channel shows that an externally imposed shear flow can stabilize an extensile fluid that would be unstable to spontaneous flow in the absence of the shear flow, and destabilize a contractile fluid that would be stable against spontaneous flow in the absence of shear flow. These results are in rough agreement with the stability boundaries between the base shear flow state and the nonlinear flow states that we find numerically for a confined active gel. For extensile fluids, we find three kinds of nonlinear flow states in the range of parameters we study: unidirectional flows, oscillatory flows, and dancing flows. To highlight the activity-driven spontaneous component of the nonlinear flows, we characterize these states by the average volumetric flow rate and the wall stress. For contractile fluids, we only find the linear shear flow and a nonlinear unidirectional flow in the range of parameters that we studied. For large magnitudes of the activity, the unidirectional contractile flow develops a boundary layer. Our analysis of annular channels shows how curvature of the streamlines in the base flow affects the transitions among flow states.
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Affiliation(s)
- Wan Luo
- School of Engineering, Brown University, Providence, RI 02912, USA.
- Center for Fluid Mechanics, Brown University, Providence, RI 02912, USA
| | - Aparna Baskaran
- Martin Fisher School of Physics, Brandeis University, Waltham, MA 02453, USA
| | - Robert A Pelcovits
- Department of Physics, Brown University, Providence, RI 02912, USA
- Brown Theoretical Physics Center, Brown University, Providence, RI 02912, USA
| | - Thomas R Powers
- School of Engineering, Brown University, Providence, RI 02912, USA.
- Center for Fluid Mechanics, Brown University, Providence, RI 02912, USA
- Department of Physics, Brown University, Providence, RI 02912, USA
- Brown Theoretical Physics Center, Brown University, Providence, RI 02912, USA
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5
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Becton M, Hou J, Zhao Y, Wang X. Dynamic Clustering and Scaling Behavior of Active Particles under Confinement. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:144. [PMID: 38251109 PMCID: PMC10819351 DOI: 10.3390/nano14020144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 01/05/2024] [Accepted: 01/07/2024] [Indexed: 01/23/2024]
Abstract
A systematic investigation of the dynamic clustering behavior of active particles under confinement, including the effects of both particle density and active driving force, is presented based on a hybrid coarse-grained molecular dynamics simulation. First, a series of scaling laws are derived with power relationships for the dynamic clustering time as a function of both particle density and active driving force. Notably, the average number of clusters N¯ assembled from active particles in the simulation system exhibits a scaling relationship with clustering time t described by N¯∝t-m. Simultaneously, the scaling behavior of the average cluster size S¯ is characterized by S¯∝tm. Our findings reveal the presence of up to four distinct dynamic regions concerning clustering over time, with transitions contingent upon the particle density within the system. Furthermore, as the active driving force increases, the aggregation behavior also accelerates, while an increase in density of active particles induces alterations in the dynamic procession of the system.
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Affiliation(s)
- Matthew Becton
- School of ECAM, College of Engineering, University of Georgia, Athens, GA 30602, USA; (M.B.); (J.H.)
| | - Jixin Hou
- School of ECAM, College of Engineering, University of Georgia, Athens, GA 30602, USA; (M.B.); (J.H.)
| | - Yiping Zhao
- Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA;
| | - Xianqiao Wang
- School of ECAM, College of Engineering, University of Georgia, Athens, GA 30602, USA; (M.B.); (J.H.)
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6
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Saintillan D. Dispersion of run-and-tumble microswimmers through disordered media. Phys Rev E 2023; 108:064608. [PMID: 38243487 DOI: 10.1103/physreve.108.064608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 11/20/2023] [Indexed: 01/21/2024]
Abstract
Understanding the transport properties of microorganisms and self-propelled particles in porous media has important implications for human health as well as microbial ecology. In free space, most microswimmers perform diffusive random walks as a result of the interplay of self-propulsion and orientation decorrelation mechanisms such as run-and-tumble dynamics or rotational diffusion. In an unstructured porous medium, collisions with the microstructure result in a decrease in the effective spatial diffusivity of the particles from its free-space value. Here, we analyze this problem for a simple model system consisting of noninteracting point particles performing run-and-tumble dynamics through a two-dimensional disordered medium composed of a random distribution of circular obstacles, in the absence of Brownian diffusion or hydrodynamic interactions. The particles are assumed to collide with the obstacles as hard spheres and subsequently slide on the obstacle surface with no frictional resistance while maintaining their orientation, until they either escape or tumble. We show that the variations in the long-time diffusivity can be described by a universal dimensionless hindrance function f(ϕ,Pe) of the obstacle area fraction ϕ and Péclet number Pe, or ratio of the swimmer run length to the obstacle size. We analytically derive an asymptotic expression for the hindrance function valid for dilute media (Peϕ≪1), and its extension to denser media is obtained using stochastic simulations. As we explain, the model is also easily generalized to describe dispersion in three dimensions.
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Affiliation(s)
- David Saintillan
- Department of Mechanical and Aerospace Engineering, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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7
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Schimming CD, Reichhardt CJO, Reichhardt C. Friction-mediated phase transition in confined active nematics. Phys Rev E 2023; 108:L012602. [PMID: 37583137 DOI: 10.1103/physreve.108.l012602] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 06/28/2023] [Indexed: 08/17/2023]
Abstract
Using a minimal continuum model, we investigate the interplay between circular confinement and substrate friction in active nematics. Upon increasing the friction from low to high, we observe a dynamical phase transition from a circulating flow phase to an anisotropic flow phase in which the flow tends to align perpendicular to the nematic director at the boundary. We demonstrate that both the flow structure and dynamic correlations in the latter phase differ from those of an unconfined, active turbulent system and may be controlled by the prescribed nematic boundary conditions. Our results show that substrate friction and geometric confinement act as valuable control parameters in active nematics.
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Affiliation(s)
- Cody D Schimming
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C J O Reichhardt
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C Reichhardt
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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8
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Puggioni L, Boffetta G, Musacchio S. Giant vortex dynamics in confined bacterial turbulence. Phys Rev E 2022; 106:055103. [PMID: 36559438 DOI: 10.1103/physreve.106.055103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 10/13/2022] [Indexed: 06/17/2023]
Abstract
We report the numerical evidence of a new state of bacterial turbulence in confined domains. By means of extensive numerical simulations of the Toner-Tu-Swift-Hohenberg model for dense bacterial suspensions in circular geometry, we discover the formation a stable, ordered state in which the angular momentum symmetry is broken. This is achieved by self-organization of a turbulent-like flow into a single, giant vortex of the size of the domain. The giant vortex is surrounded by an annular region close to the boundary, characterized by small-scale, radial vorticity streaks. The average radial velocity profile of the vortex is found to be in agreement with a simple analytical prediction. We also provide an estimate of the temporal and spatial scales of a suitable experimental setup comparable with our numerical findings.
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Affiliation(s)
- L Puggioni
- Dipartimento di Fisica and INFN, Università degli Studi di Torino, via P. Giuria 1, 10125 Torino, Italy
| | - G Boffetta
- Dipartimento di Fisica and INFN, Università degli Studi di Torino, via P. Giuria 1, 10125 Torino, Italy
| | - S Musacchio
- Dipartimento di Fisica and INFN, Università degli Studi di Torino, via P. Giuria 1, 10125 Torino, Italy
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9
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Keogh RR, Chandragiri S, Loewe B, Ala-Nissila T, Thampi SP, Shendruk TN. Helical flow states in active nematics. Phys Rev E 2022; 106:L012602. [PMID: 35974522 DOI: 10.1103/physreve.106.l012602] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 06/09/2022] [Indexed: 06/15/2023]
Abstract
We show that confining extensile nematics in three-dimensional (3D) channels leads to the emergence of two self-organized flow states with nonzero helicity. The first is a pair of braided antiparallel streams-this double helix occurs when the activity is moderate, anchoring negligible, and reduced temperature high. The second consists of axially aligned counter-rotating vortices-this grinder train arises between spontaneous axial streaming and the vortex lattice. These two unanticipated helical flow states illustrate the potential of active fluids to break symmetries and form complex but organized spatiotemporal structures in 3D fluidic devices.
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Affiliation(s)
- Ryan R Keogh
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - Santhan Chandragiri
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
| | - Benjamin Loewe
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - Tapio Ala-Nissila
- MSP Group, QTF Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11000, FI-00076 Aalto, Espoo, Finland
- Interdisciplinary Centre for Mathematical Modelling, Department of Mathematical Sciences, Loughborough University, Loughborough LE11 3TU, United Kingdom
| | - Sumesh P Thampi
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
| | - Tyler N Shendruk
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
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10
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Wolf AE, Heinrich MA, Breinyn IB, Zajdel TJ, Cohen DJ. Short-term bioelectric stimulation of collective cell migration in tissues reprograms long-term supracellular dynamics. PNAS NEXUS 2022; 1:pgac002. [PMID: 35360553 PMCID: PMC8962779 DOI: 10.1093/pnasnexus/pgac002] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 09/03/2021] [Accepted: 01/07/2022] [Indexed: 01/28/2023]
Abstract
The ability to program collective cell migration can allow us to control critical multicellular processes in development, regenerative medicine, and invasive disease. However, while various technologies exist to make individual cells migrate, translating these tools to control myriad, collectively interacting cells within a single tissue poses many challenges. For instance, do cells within the same tissue interpret a global migration 'command' differently based on where they are in the tissue? Similarly, since no stimulus is permanent, what are the long-term effects of transient commands on collective cell dynamics? We investigate these questions by bioelectrically programming large epithelial tissues to globally migrate 'rightward' via electrotaxis. Tissues clearly developed distinct rear, middle, side, and front responses to a single global migration stimulus. Furthermore, at no point poststimulation did tissues return to their prestimulation behavior, instead equilibrating to a 3rd, new migratory state. These unique dynamics suggested that programmed migration resets tissue mechanical state, which was confirmed by transient chemical disruption of cell-cell junctions, analysis of strain wave propagation patterns, and quantification of cellular crowd dynamics. Overall, this work demonstrates how externally driving the collective migration of a tissue can reprogram baseline cell-cell interactions and collective dynamics, even well beyond the end of the global migratory cue, and emphasizes the importance of considering the supracellular context of tissues and other collectives when attempting to program crowd behaviors.
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Affiliation(s)
- Abraham E Wolf
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | | | | | - Tom J Zajdel
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Daniel J Cohen
- To whom correspondence should be addressed. Address: Attn. , 111 Hoyt Laboratory, Princeton, NJ 08544, USA. E-mail:
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11
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Reinken H, Heidenreich S, Bär M, Klapp SHL. Ising-like Critical Behavior of Vortex Lattices in an Active Fluid. PHYSICAL REVIEW LETTERS 2022; 128:048004. [PMID: 35148157 DOI: 10.1103/physrevlett.128.048004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 11/29/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Turbulent vortex structures emerging in bacterial active fluids can be organized into regular vortex lattices by weak geometrical constraints such as obstacles. Here we show, using a continuum-theoretical approach, that the formation and destruction of these patterns exhibit features of a continuous second-order equilibrium phase transition, including long-range correlations, divergent susceptibility, and critical slowing down. The emerging vorticity field can be mapped onto a two-dimensional (2D) Ising model with antiferromagnetic nearest-neighbor interactions by coarse graining. The resulting effective temperature is found to be proportional to the strength of the nonlinear advection in the continuum model.
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Affiliation(s)
- Henning Reinken
- Technische Universität Berlin, Institute of Theoretical Physics, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Sebastian Heidenreich
- Physikalisch-Technische Bundesanstalt Braunschweig und Berlin, Department of Mathematical Modelling and Data Analysis, Abbestraße 2-12, 10587 Berlin, Germany
| | - Markus Bär
- Physikalisch-Technische Bundesanstalt Braunschweig und Berlin, Department of Mathematical Modelling and Data Analysis, Abbestraße 2-12, 10587 Berlin, Germany
| | - Sabine H L Klapp
- Technische Universität Berlin, Institute of Theoretical Physics, Straße des 17. Juni 135, 10623 Berlin, Germany
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12
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Huang D, Du Y, Jiang H, Hou Z. Emergent spiral vortex of confined biased active particles. Phys Rev E 2021; 104:034606. [PMID: 34654190 DOI: 10.1103/physreve.104.034606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 06/15/2021] [Indexed: 11/07/2022]
Abstract
Confinement is known to have profound effects on the collective dynamics of many active systems. Here, we investigate a modeled active system in circular confinement consisting of biased active particles, where the direction of active force deviates a biased angle from the principle orientation of the anisotropic interaction. We find that such particles can spontaneously form a spiral vortex with two concentric and counter-rotating regions near the boundary. The emerged vortex can be measured by the vortex order parameter which shows nonmonotonic dependencies on both the biased angle and the strength of the anisotropic interaction. Our work can provide an understanding of such dynamic behaviors and enable different strategies for designing ordered collective behaviors.
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Affiliation(s)
- Deping Huang
- Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at Microscales, iChEM, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yunfei Du
- Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at Microscales, iChEM, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Huijun Jiang
- Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at Microscales, iChEM, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhonghuai Hou
- Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at Microscales, iChEM, University of Science and Technology of China, Hefei, Anhui 230026, China
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13
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Liu ZT, Shi Y, Zhao Y, Chaté H, Shi XQ, Zhang TH. Activity waves and freestanding vortices in populations of subcritical Quincke rollers. Proc Natl Acad Sci U S A 2021; 118:e2104724118. [PMID: 34588304 PMCID: PMC8501844 DOI: 10.1073/pnas.2104724118] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2021] [Indexed: 11/18/2022] Open
Abstract
Virtually all of the many active matter systems studied so far are made of units (biofilaments, cells, colloidal particles, robots, animals, etc.) that move even when they are alone or isolated. Their collective properties continue to fascinate, and we now understand better how they are unique to the bulk transduction of energy into work. Here we demonstrate that systems in which isolated but potentially active particles do not move can exhibit specific and remarkable collective properties. Combining experiments, theory, and numerical simulations, we show that such subcritical active matter can be realized with Quincke rollers, that is, dielectric colloidal particles immersed in a conducting fluid subjected to a vertical DC electric field. Working below the threshold field value marking the onset of motion for a single colloid, we find fast activity waves, reminiscent of excitable systems, and stable, arbitrarily large self-standing vortices made of thousands of particles moving at the same speed. Our theoretical model accounts for these phenomena and shows how they can arise in the absence of confining boundaries and individual chirality. We argue that our findings imply that a faithful description of the collective properties of Quincke rollers need to consider the fluid surrounding particles.
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Affiliation(s)
- Zeng Tao Liu
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Yan Shi
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Yongfeng Zhao
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hugues Chaté
- Service de Physique de l'Etat Condensé, Commissariat à l'Energie Atomique (CEA), CNRS, Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France;
- Computational Science Research Center, Beijing 100193, China
| | - Xia-Qing Shi
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China;
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Tian Hui Zhang
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China;
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
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14
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Abstract
When the motion of a motile cell is observed closely, it appears erratic, and yet the combination of nonequilibrium forces and surfaces can produce striking examples of organization in microbial systems. While most of our current understanding is based on bulk systems or idealized geometries, it remains elusive how and at which length scale self-organization emerges in complex geometries. Here, using experiments and analytical and numerical calculations, we study the motion of motile cells under controlled microfluidic conditions and demonstrate that probability flux loops organize active motion, even at the level of a single cell exploring an isolated compartment of nontrivial geometry. By accounting for the interplay of activity and interfacial forces, we find that the boundary's curvature determines the nonequilibrium probability fluxes of the motion. We theoretically predict a universal relation between fluxes and global geometric properties that is directly confirmed by experiments. Our findings open the possibility to decipher the most probable trajectories of motile cells and may enable the design of geometries guiding their time-averaged motion.
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15
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Nourhani A, Saintillan D. Spontaneous directional flow of active magnetic particles. Phys Rev E 2021; 103:L040601. [PMID: 34006000 DOI: 10.1103/physreve.103.l040601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 03/17/2021] [Indexed: 11/07/2022]
Abstract
We predict the emergence of large-scale polar order and spontaneous directional flows in a class of self-propelled autonomous particles that interact via passive repulsion between off-center sites. The coupling of active motion with the passive torque acting about the particle centers results in hybrid active-passive interactions responsible for a macroscopic phase transition from an isotropic state to a polar-aligned state in systems of particles with front interaction sites. We employ a continuum kinetic theory to explain that the emergence of long-ranged orientational order, which occurs in unbounded domains at finite densities, can be externally activated independently of the self-propulsion mechanism and drives a macroscopic particle flow in a direction selected by symmetry breaking.
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Affiliation(s)
- Amir Nourhani
- Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA.,Department of Biology, University of Akron, Akron, Ohio 44325, USA.,Department of Mathematics, University of Akron, Akron, Ohio 44325, USA.,Department of Chemical, Biomolecular, and Corrosion Engineering, University of Akron, Akron, Ohio 44325, USA.,Biomimicry Research and Innovation Center, University of Akron, Akron, Ohio 44325, USA
| | - David Saintillan
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093, USA
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16
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Chen W, Mani N, Karani H, Li H, Mani S, Tang JX. Confinement discerns swarmers from planktonic bacteria. eLife 2021; 10:e64176. [PMID: 33884952 PMCID: PMC8112864 DOI: 10.7554/elife.64176] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 04/21/2021] [Indexed: 12/14/2022] Open
Abstract
Powered by flagella, many bacterial species exhibit collective motion on a solid surface commonly known as swarming. As a natural example of active matter, swarming is also an essential biological phenotype associated with virulence, chemotaxis, and host pathogenesis. Physical changes like cell elongation and hyper-flagellation have been shown to accompany the swarming phenotype. Less studied, however, are the contrasts of collective motion between the swarming cells and their counterpart planktonic cells of comparable cell density. Here, we show that confining bacterial movement in circular microwells allows distinguishing bacterial swarming from collective swimming. On a soft agar plate, a novel bacterial strain Enterobacter sp. SM3 in swarming and planktonic states exhibited different motion patterns when confined to circular microwells of a specific range of sizes. When the confinement diameter was between 40 μm and 90 μm, swarming SM3 formed a single-swirl motion pattern in the microwells whereas planktonic SM3 formed multiple swirls. Similar differential behavior is observed across several other species of gram-negative bacteria. We also observed 'rafting behavior' of swarming bacteria upon dilution. We hypothesize that the rafting behavior might account for the motion pattern difference. We were able to predict these experimental features via numerical simulations where swarming cells are modeled with stronger cell-cell alignment interaction. Our experimental design using PDMS microchip disk arrays enabled us to observe bacterial swarming on murine intestinal surface, suggesting a new method for characterizing bacterial swarming under complex environments, such as in polymicrobial niches, and for in vivo swarming exploration.
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Affiliation(s)
- Weijie Chen
- Department of Physics, Brown UniversityProvidenceUnited States
- Department of Medicine, Albert Einstein College of MedicineBronxUnited States
| | - Neha Mani
- Department of Physics, Brown UniversityProvidenceUnited States
| | - Hamid Karani
- Department of Physics, Brown UniversityProvidenceUnited States
| | - Hao Li
- Department of Medicine, Albert Einstein College of MedicineBronxUnited States
| | - Sridhar Mani
- Department of Medicine, Albert Einstein College of MedicineBronxUnited States
| | - Jay X Tang
- Department of Physics, Brown UniversityProvidenceUnited States
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17
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-N Young Y, J Shelley M, B Stein D. The many behaviors of deformable active droplets. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2021; 18:2849-2881. [PMID: 33892575 DOI: 10.3934/mbe.2021145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Active fluids consume fuel at the microscopic scale, converting this energy into forces that can drive macroscopic motions over scales far larger than their microscopic constituents. In some cases, the mechanisms that give rise to this phenomenon have been well characterized, and can explain experimentally observed behaviors in both bulk fluids and those confined in simple stationary geometries. More recently, active fluids have been encapsulated in viscous drops or elastic shells so as to interact with an outer environment or a deformable boundary. Such systems are not as well understood. In this work, we examine the behavior of droplets of an active nematic fluid. We study their linear stability about the isotropic equilibrium over a wide range of parameters, identifying regions in which different modes of instability dominate. Simulations of their full dynamics are used to identify their nonlinear behavior within each region. When a single mode dominates, the droplets behave simply: as rotors, swimmers, or extensors. When parameters are tuned so that multiple modes have nearly the same growth rate, a pantheon of modes appears, including zigzaggers, washing machines, wanderers, and pulsators.
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Affiliation(s)
- Y -N Young
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, USA
| | - Michael J Shelley
- Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA
- Courant Institute, New York University, New York, New York 10012, USA
| | - David B Stein
- Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA
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18
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Varghese M, Baskaran A, Hagan MF, Baskaran A. Confinement-Induced Self-Pumping in 3D Active Fluids. PHYSICAL REVIEW LETTERS 2020; 125:268003. [PMID: 33449756 DOI: 10.1103/physrevlett.125.268003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 09/25/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
Two dimensional active fluids display a transition from turbulent to coherent flow upon decreasing the size of the confining geometry. A recent experiment suggests that the behavior in three dimensions is remarkably different; emergent flows transition from turbulence to coherence upon increasing the confinement height to match the width. Using a simple hydrodynamic model of a suspension of extensile rodlike units, we provide the theoretical explanation for this puzzling behavior. Furthermore, using extensive numerical simulations supported by theoretical arguments, we map out the conditions that lead to coherent flows and elucidate the critical role played by the aspect ratio of the confining channel. The mechanism that we identify applies to a large class of symmetries and propulsion mechanisms, leading to a unified set of design principles for self-pumping 3D active fluids.
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Affiliation(s)
- Minu Varghese
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Arvind Baskaran
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Michael F Hagan
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Aparna Baskaran
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
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19
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Chandrakar P, Varghese M, Aghvami SA, Baskaran A, Dogic Z, Duclos G. Confinement Controls the Bend Instability of Three-Dimensional Active Liquid Crystals. PHYSICAL REVIEW LETTERS 2020; 125:257801. [PMID: 33416339 DOI: 10.1103/physrevlett.125.257801] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 10/15/2020] [Accepted: 11/11/2020] [Indexed: 06/12/2023]
Abstract
Spontaneous growth of long-wavelength deformations is a defining feature of active liquid crystals. We investigate the effect of confinement on the instability of 3D active liquid crystals in the isotropic phase composed of extensile microtubule bundles and kinesin molecular motors. When shear aligned, such fluids exhibit finite-wavelength self-amplifying bend deformations. By systematically changing the channel size we elucidate how the instability wavelength and its growth rate depend on the channel dimensions. Experimental findings are qualitatively consistent with a minimal hydrodynamic model, where the fastest growing deformation is set by a balance of active driving and elastic relaxation. Our results demonstrate that confinement determines the structure and dynamics of active fluids on all experimentally accessible length scales.
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Affiliation(s)
- Pooja Chandrakar
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Minu Varghese
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - S Ali Aghvami
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Aparna Baskaran
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Zvonimir Dogic
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Guillaume Duclos
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
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20
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Malvar S, Cardoso LOB, Karolski B, Perpetuo EA, Carmo BS, Meneghini JR. A rheological approach to identify efficient biopolymer producing bacteria. Biotechnol Bioeng 2020; 118:622-632. [PMID: 33090455 DOI: 10.1002/bit.27595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 09/22/2020] [Accepted: 09/28/2020] [Indexed: 11/09/2022]
Abstract
This study investigates the relationship between collective motion and propulsion of bacterial consortia and their biopolymer production efficiency. Rheological tests were conducted for suspensions of two different methanotrophic bacterial consortia obtained after enrichment of sediment samples from mangrove sites in Brazil. We considered the linear viscoelasticity region and analyzed the values of storage and loss moduli as functions of days of cultivation, for different values of the volume fraction. The suspensions' rheological behaviors reflected the bacterial growth stage. We found that the formation of structures over time in some types of consortia can hinder the movement of bacteria in the search for nutrients. The change in complex viscosity of the two consortia followed a different and rich behavior that appears to be closely related to their capacity to capture methane. Our analysis showed a possible correlation between collective motion, viscosity reduction, and biopolymer production. The pieces of evidence from this study suggest that the efficiency of bacterial motion is directly related to biopolymer production, and this could facilitate the process of identifying the best consortium of biopolymer producing bacteria.
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Affiliation(s)
- Sara Malvar
- Department of Mechanical Engineering, Escola Politécnica, University of São Paulo, São Paulo, SP, Brazil
| | - Letícia O B Cardoso
- The Interunit Program in Biotechnology, University of São Paulo, São Paulo, SP, Brazil.,Environmental Research and Education Center - CEPEMA, Escola Politécnica, University of São Paulo, Cubatão, SP, Brazil
| | - Bruno Karolski
- Environmental Research and Education Center - CEPEMA, Escola Politécnica, University of São Paulo, Cubatão, SP, Brazil
| | - Elen A Perpetuo
- Environmental Research and Education Center - CEPEMA, Escola Politécnica, University of São Paulo, Cubatão, SP, Brazil.,Institute of Marine Sciences, Federal University of São Paulo, Santos, SP, Brazil
| | - Bruno S Carmo
- Department of Mechanical Engineering, Escola Politécnica, University of São Paulo, São Paulo, SP, Brazil
| | - Julio R Meneghini
- Department of Mechanical Engineering, Escola Politécnica, University of São Paulo, São Paulo, SP, Brazil
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21
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Hardoüin J, Laurent J, Lopez-Leon T, Ignés-Mullol J, Sagués F. Active microfluidic transport in two-dimensional handlebodies. SOFT MATTER 2020; 16:9230-9241. [PMID: 32926045 DOI: 10.1039/d0sm00610f] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Unlike traditional nematic liquid crystals, which adopt ordered equilibrium configurations compatible with the topological constraints imposed by the boundaries, active nematics are intrinsically disordered because of their self-sustained internal flows. Controlling the flow patterns of active nematics remains a limiting step towards their use as functional materials. Here we show that confining a tubulin-kinesin active nematic to a network of connected annular microfluidic channels enables controlled directional flows and autonomous transport. In single annular channels, for narrow widths, the typically chaotic streams transform into well-defined circulating flows, whose direction or handedness can be controlled by introducing asymmetric corrugations on the channel walls. The dynamics is altered when two or three annular channels are interconnected. These more complex topologies lead to scenarios of synchronization, anti-correlation, and frustration of the active flows, and to the stabilisation of high topological singularities in both the flow field and the orientational field of the material. Controlling textures and flows in these microfluidic platforms opens unexplored perspectives towards their application in biotechnology and materials science.
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Affiliation(s)
- Jérôme Hardoüin
- Departament de Ciència de Materials i Química Física, Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain. and Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | - Justine Laurent
- Laboratoire de Physique et Mécanique des Milieux hétérogènes (PMMH), CNRS, ESPCI Paris, PSL Research University, Paris, France and Laboratoire Gulliver, UMR CNRS 7083, ESPCI Paris, PSL Research University, Paris, France
| | - Teresa Lopez-Leon
- Laboratoire de Physique et Mécanique des Milieux hétérogènes (PMMH), CNRS, ESPCI Paris, PSL Research University, Paris, France and Laboratoire Gulliver, UMR CNRS 7083, ESPCI Paris, PSL Research University, Paris, France
| | - Jordi Ignés-Mullol
- Departament de Ciència de Materials i Química Física, Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain. and Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | - Francesc Sagués
- Departament de Ciència de Materials i Química Física, Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain. and Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
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22
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Sprenger AR, Shaik VA, Ardekani AM, Lisicki M, Mathijssen AJTM, Guzmán-Lastra F, Löwen H, Menzel AM, Daddi-Moussa-Ider A. Towards an analytical description of active microswimmers in clean and in surfactant-covered drops. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2020; 43:58. [PMID: 32920676 DOI: 10.1140/epje/i2020-11980-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/10/2020] [Indexed: 05/24/2023]
Abstract
Geometric confinements are frequently encountered in the biological world and strongly affect the stability, topology, and transport properties of active suspensions in viscous flow. Based on a far-field analytical model, the low-Reynolds-number locomotion of a self-propelled microswimmer moving inside a clean viscous drop or a drop covered with a homogeneously distributed surfactant, is theoretically examined. The interfacial viscous stresses induced by the surfactant are described by the well-established Boussinesq-Scriven constitutive rheological model. Moreover, the active agent is represented by a force dipole and the resulting fluid-mediated hydrodynamic couplings between the swimmer and the confining drop are investigated. We find that the presence of the surfactant significantly alters the dynamics of the encapsulated swimmer by enhancing its reorientation. Exact solutions for the velocity images for the Stokeslet and dipolar flow singularities inside the drop are introduced and expressed in terms of infinite series of harmonic components. Our results offer useful insights into guiding principles for the control of confined active matter systems and support the objective of utilizing synthetic microswimmers to drive drops for targeted drug delivery applications.
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Affiliation(s)
- Alexander R Sprenger
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225, Düsseldorf, Germany.
| | - Vaseem A Shaik
- School of Mechanical Engineering, Purdue University, 47907, West Lafayette, IN, USA
| | - Arezoo M Ardekani
- School of Mechanical Engineering, Purdue University, 47907, West Lafayette, IN, USA
| | - Maciej Lisicki
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland
| | - Arnold J T M Mathijssen
- Department of Bioengineering, Stanford University, 443 Via Ortega, 94305, Stanford, CA, USA
- Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, 19104, Philadelphia, PA, USA
| | - Francisca Guzmán-Lastra
- Centro de Investigación DAiTA Lab, Facultad de Estudios Interdisciplinarios, Universidad Mayor, Av. Manuel Montt 367, Providencia, Santiago de Chile, Chile
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225, Düsseldorf, Germany
| | - Andreas M Menzel
- Institut für Physik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany
| | - Abdallah Daddi-Moussa-Ider
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225, Düsseldorf, Germany
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23
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Berman SA, Mitchell KA. Trapping of swimmers in a vortex lattice. CHAOS (WOODBURY, N.Y.) 2020; 30:063121. [PMID: 32611071 DOI: 10.1063/5.0005542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
We examine the motion of rigid, ellipsoidal swimmers subjected to a steady vortex flow in two dimensions. Numerical simulations of swimmers in a spatially periodic array of vortices reveal a range of possible behaviors, including trapping inside a single vortex and motility-induced diffusion across many vortices. While the trapping probability vanishes at a sufficiently high swimming speed, we find that it exhibits surprisingly large oscillations as this critical swimming speed is approached. Strikingly, at even higher swimming speeds, we find swimmers that swim perpendicular to their elongation direction can again become trapped. To explain this complex behavior, we investigate the underlying swimmer phase-space geometry. We identify the fixed points and periodic orbits of the swimmer equations of motion that regulate swimmer trapping inside a single vortex cell. For low to intermediate swimming speeds, we find that a stable periodic orbit surrounded by invariant tori forms a transport barrier to swimmers and can trap them inside individual vortices. For swimming speeds approaching the maximum fluid speed, we find instead that perpendicular swimmers can be trapped by asymptotically stable fixed points. A bifurcation analysis of the stable periodic orbit and the fixed points explains the complex and non-monotonic breakdown and re-emergence of swimmer trapping as the swimmer speed and shape are varied.
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Affiliation(s)
- Simon A Berman
- Department of Physics, University of California, Merced, Merced, California 95344, USA
| | - Kevin A Mitchell
- Department of Physics, University of California, Merced, Merced, California 95344, USA
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24
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A combined rheometry and imaging study of viscosity reduction in bacterial suspensions. Proc Natl Acad Sci U S A 2020; 117:2326-2331. [PMID: 31964833 PMCID: PMC7007524 DOI: 10.1073/pnas.1912690117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Suspending self-propelled "pushers" in a liquid lowers its viscosity. We study how this phenomenon depends on system size in bacterial suspensions using bulk rheometry and particle-tracking rheoimaging. Above the critical bacterial volume fraction needed to decrease the viscosity to zero, [Formula: see text], large-scale collective motion emerges in the quiescent state, and the flow becomes nonlinear. We confirm a theoretical prediction that such instability should be suppressed by confinement. Our results also show that a recent application of active liquid-crystal theory to such systems is untenable.
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25
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Wang Z, Si T, Hao J, Guan Y, Qin F, Yang B, Cao W. Defect dynamics in clusters of self-propelled rods in circular confinement. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:150. [PMID: 31773335 DOI: 10.1140/epje/i2019-11911-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
Rod-shaped active micro/nano-particles, such as bacterial and bipolar metallic micro/nano-motors, demonstrate novel collective phenomena far from the equilibrium state compared to passive particles. We apply a simulation approach --dissipative particle dynamics (DPD)-- to explore the collectively ordered states of self-propelled rods (SPRs). The SPRs are confined in a finite circular zone and repel each other when two rods touch each other. It is found that for a long enough rods system, the global vortex patterns, dynamic pattern oscillation between hedgehog pattern and vortex pattern, and hedgehog patterns are observed successively with increasing active force Fa. For the vortex pattern, the total interaction energy between the rods U is linear with active force Fa, i.e., U ∼ Fa . While the relation U ∼ Fa2 is obtained for the hedgehog structure. It is observed that a new hedgehog pattern with one defect core is created by two ejections of polar cluster in opposite directions from the original hedgehog pattern, and then merges into one through the diffusion of the two aggregates, i.e., the creation and annihilation of topological charges.
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Affiliation(s)
- Zhengjia Wang
- Condensed Matter Science and Technology Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, 150080, Harbin, P.R. China
| | - Tieyan Si
- School of Physics, Harbin Institute of Technology, 150080, Harbin, P.R. China
| | - Junhua Hao
- Department of Physics, Tianjin University Renai College, 301636, Tianjin, P.R. China.
| | - Yu Guan
- Amur State University, 675004, Blagoveshchensk, Russia
| | - Feng Qin
- Condensed Matter Science and Technology Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, 150080, Harbin, P.R. China
| | - Bin Yang
- Condensed Matter Science and Technology Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, 150080, Harbin, P.R. China
| | - Wenwu Cao
- Condensed Matter Science and Technology Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, 150080, Harbin, P.R. China
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26
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Magnetotactic bacteria in a droplet self-assemble into a rotary motor. Nat Commun 2019; 10:5082. [PMID: 31705050 PMCID: PMC6841940 DOI: 10.1038/s41467-019-13031-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Accepted: 10/08/2019] [Indexed: 11/08/2022] Open
Abstract
From intracellular protein trafficking to large-scale motion of animal groups, the physical concepts driving the self-organization of living systems are still largely unraveled. Self-organization of active entities, leading to novel phases and emergent macroscopic properties, recently shed new light on these complex dynamical processes. Here we show that under the application of a constant magnetic field, motile magnetotactic bacteria confined in water-in-oil droplets self-assemble into a rotary motor exerting a torque on the external oil phase. A collective motion in the form of a large-scale vortex, reversable by inverting the field direction, builds up in the droplet with a vorticity perpendicular to the magnetic field. We study this collective organization at different concentrations, magnetic fields and droplet radii and reveal the formation of two torque-generating areas close to the droplet interface. We characterize quantitatively the mechanical energy extractable from this new biological and self-assembled motor.
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27
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Kempf F, Mueller R, Frey E, Yeomans JM, Doostmohammadi A. Active matter invasion. SOFT MATTER 2019; 15:7538-7546. [PMID: 31451816 DOI: 10.1039/c9sm01210a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Biologically active materials such as bacterial biofilms and eukaryotic cells thrive in confined micro-spaces. Here, we show through numerical simulations that confinement can serve as a mechanical guidance to achieve distinct modes of collective invasion when combined with growth dynamics and the intrinsic activity of biological materials. We assess the dynamics of the growing interface and classify these collective modes of invasion based on the activity of the constituent particles of the growing matter. While at small and moderate activities the active material grows as a coherent unit, we find that blobs of active material collectively detach from the cohort above a well-defined activity threshold. We further characterise the mechanical mechanisms underlying the crossovers between different modes of invasion and quantify their impact on the overall invasion speed.
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Affiliation(s)
- Felix Kempf
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München - Theresienstr. 37, D-80333 Munich, Germany
| | - Romain Mueller
- The Rudolf Peierls Centre for Theoretical Physics - Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München - Theresienstr. 37, D-80333 Munich, Germany
| | - Julia M Yeomans
- The Rudolf Peierls Centre for Theoretical Physics - Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
| | - Amin Doostmohammadi
- The Rudolf Peierls Centre for Theoretical Physics - Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
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28
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Bárdfalvy D, Nordanger H, Nardini C, Morozov A, Stenhammar J. Particle-resolved lattice Boltzmann simulations of 3-dimensional active turbulence. SOFT MATTER 2019; 15:7747-7756. [PMID: 31393504 DOI: 10.1039/c9sm00774a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Collective behaviour in suspensions of microswimmers is often dominated by the impact of long-ranged hydrodynamic interactions. These phenomena include active turbulence, where suspensions of pusher bacteria at sufficient densities exhibit large-scale, chaotic flows. To study this collective phenomenon, we use large-scale (up to N = 3 × 106) particle-resolved lattice Boltzmann simulations of model microswimmers described by extended stresslets. Such system sizes enable us to obtain quantitative information about both the transition to active turbulence and characteristic features of the turbulent state itself. In the dilute limit, we test analytical predictions for a number of static and dynamic properties against our simulation results. For higher swimmer densities, where swimmer-swimmer interactions become significant, we numerically show that the length- and timescales of the turbulent flows increase steeply near the predicted finite-system transition density.
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Affiliation(s)
- Dóra Bárdfalvy
- Division of Physical Chemistry, Lund University, Box 124, S-221 00 Lund, Sweden.
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29
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Soni H, Luo W, Pelcovits RA, Powers TR. Stability of the interface of an isotropic active fluid. SOFT MATTER 2019; 15:6318-6330. [PMID: 31322161 DOI: 10.1039/c9sm01216h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We study the linear stability of an isotropic active fluid in three different geometries: a film of active fluid on a rigid substrate, a cylindrical thread of fluid, and a spherical fluid droplet. The active fluid is modeled by the hydrodynamic theory of an active nematic liquid crystal in the isotropic phase. In each geometry, we calculate the growth rate of sinusoidal modes of deformation of the interface. There are two distinct branches of growth rates; at long wavelength, one corresponds to the deformation of the interface, and one corresponds to the evolution of the liquid crystalline degrees of freedom. The passive cases of the film and the spherical droplet are always stable. For these geometries, a sufficiently large activity leads to instability. Activity also leads to propagating damped or growing modes. The passive cylindrical thread is unstable for perturbations with wavelength longer than the circumference. A sufficiently large activity can make any wavelength unstable, and again leads to propagating damped or growing modes. Our calculations are carried out for the case of zero Frank elasticity. While Frank elasticity is a stabilizing mechanism as it penalizes distortions of the order parameter tensor, we show that it has a small effect on the instabilities considered here.
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Affiliation(s)
- Harsh Soni
- School of Engineering, Brown University, Providence, RI 02912, USA.
| | - Wan Luo
- School of Engineering, Brown University, Providence, RI 02912, USA.
| | | | - Thomas R Powers
- School of Engineering, Brown University, Providence, RI 02912, USA. and Department of Physics, Brown University, Providence, RI 02912, USA
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30
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Opathalage A, Norton MM, Juniper MPN, Langeslay B, Aghvami SA, Fraden S, Dogic Z. Self-organized dynamics and the transition to turbulence of confined active nematics. Proc Natl Acad Sci U S A 2019; 116:4788-4797. [PMID: 30804207 PMCID: PMC6421422 DOI: 10.1073/pnas.1816733116] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We study how confinement transforms the chaotic dynamics of bulk microtubule-based active nematics into regular spatiotemporal patterns. For weak confinements in disks, multiple continuously nucleating and annihilating topological defects self-organize into persistent circular flows of either handedness. Increasing confinement strength leads to the emergence of distinct dynamics, in which the slow periodic nucleation of topological defects at the boundary is superimposed onto a fast procession of a pair of defects. A defect pair migrates toward the confinement core over multiple rotation cycles, while the associated nematic director field evolves from a distinct double spiral toward a nearly circularly symmetric configuration. The collapse of the defect orbits is punctuated by another boundary-localized nucleation event, that sets up long-term doubly periodic dynamics. Comparing experimental data to a theoretical model of an active nematic reveals that theory captures the fast procession of a pair of [Formula: see text] defects, but not the slow spiral transformation nor the periodic nucleation of defect pairs. Theory also fails to predict the emergence of circular flows in the weak confinement regime. The developed confinement methods are generalized to more complex geometries, providing a robust microfluidic platform for rationally engineering 2D autonomous flows.
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Affiliation(s)
| | | | | | - Blake Langeslay
- Department of Physics, Brandeis University, Waltham, MA 02453
| | - S Ali Aghvami
- Department of Physics, Brandeis University, Waltham, MA 02453
| | - Seth Fraden
- Department of Physics, Brandeis University, Waltham, MA 02453;
| | - Zvonimir Dogic
- Department of Physics, Brandeis University, Waltham, MA 02453;
- Department of Physics, University of California, Santa Barbara, CA 93106
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Norton MM, Baskaran A, Opathalage A, Langeslay B, Fraden S, Baskaran A, Hagan MF. Insensitivity of active nematic liquid crystal dynamics to topological constraints. Phys Rev E 2018; 97:012702. [PMID: 29448352 DOI: 10.1103/physreve.97.012702] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Indexed: 11/07/2022]
Abstract
Confining a liquid crystal imposes topological constraints on the orientational order, allowing global control of equilibrium systems by manipulation of anchoring boundary conditions. In this article, we investigate whether a similar strategy allows control of active liquid crystals. We study a hydrodynamic model of an extensile active nematic confined in containers, with different anchoring conditions that impose different net topological charges on the nematic director. We show that the dynamics are controlled by a complex interplay between topological defects in the director and their induced vortical flows. We find three distinct states by varying confinement and the strength of the active stress: A topologically minimal state, a circulating defect state, and a turbulent state. In contrast to equilibrium systems, we find that anchoring conditions are screened by the active flow, preserving system behavior across different topological constraints. This observation identifies a fundamental difference between active and equilibrium materials.
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Affiliation(s)
- Michael M Norton
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Arvind Baskaran
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Achini Opathalage
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Blake Langeslay
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Seth Fraden
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Aparna Baskaran
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Michael F Hagan
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
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Loisy A, Eggers J, Liverpool TB. Active Suspensions have Nonmonotonic Flow Curves and Multiple Mechanical Equilibria. PHYSICAL REVIEW LETTERS 2018; 121:018001. [PMID: 30028150 DOI: 10.1103/physrevlett.121.018001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 02/16/2018] [Indexed: 06/08/2023]
Abstract
We point out unconventional mechanical properties of confined active fluids, such as bacterial suspensions, under shear. Using a minimal model of an active liquid crystal with no free parameters, we predict the existence of a window of bacteria concentration for which a suspension of E. Coli effectively behaves, at steady-state, as a negative viscosity fluid and reach a quantitative agreement with experimental measurements. Our theoretical analysis further shows that a negative apparent viscosity is due to a nonmonotonic local velocity profile, and it is associated with a nonmonotonic stress versus strain rate flow curve. This implies that fixed stress and fixed strain rate ensembles are not equivalent for active fluids.
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Affiliation(s)
- Aurore Loisy
- School of Mathematics, University of Bristol-Bristol BS8 1 TW, United Kingdom
| | - Jens Eggers
- School of Mathematics, University of Bristol-Bristol BS8 1 TW, United Kingdom
| | - Tanniemola B Liverpool
- School of Mathematics, University of Bristol-Bristol BS8 1 TW, United Kingdom
- BrisSynBio, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, United Kingdom
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Gao T, Li Z. Self-Driven Droplet Powered By Active Nematics. PHYSICAL REVIEW LETTERS 2017; 119:108002. [PMID: 28949156 DOI: 10.1103/physrevlett.119.108002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Indexed: 06/07/2023]
Abstract
Active matter defines a class of far-away-from-equilibrium systems comprising self-driven microparticles. Their anomalous physical properties could be applied in areas such as mixing or separation, micropumps, and self-healing materials. To realize such applications, a thorough understanding of the physical mechanisms as well as the development of methods to manipulate various active systems is required. Using a coarse-grained active liquid crystal model, we designed and investigated a single self-driven droplet which encapsulated a dense suspension comprising nonmotile but mobile active particles that generate extensile stresses. We showed that such droplets can be driven into motion and can have tunable mobilities owing to their internal collective motion, which is characterized by induced active flows and motile disclination defects. Furthermore, it was illustrated that the interplay among the internal directional flows, liquid crystalline structures, droplet size, and surface tension resulted in different types of locomotion and rotation.
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Affiliation(s)
- Tong Gao
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
| | - Zhaorui Li
- Department of Mechanical Engineering, Texas A&M University-Corpus Christi, Corpus Christi, Texas 78412, USA
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Shendruk TN, Doostmohammadi A, Thijssen K, Yeomans JM. Dancing disclinations in confined active nematics. SOFT MATTER 2017; 13:3853-3862. [PMID: 28345089 DOI: 10.1039/c6sm02310j] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The spontaneous emergence of collective flows is a generic property of active fluids and often leads to chaotic flow patterns characterised by swirls, jets, and topological disclinations in their orientation field. However, the ability to achieve structured flows and ordered disclinations is of particular importance in the design and control of active systems. By confining an active nematic fluid within a channel, we find a regular motion of disclinations, in conjunction with a well defined and dynamic vortex lattice. As pairs of moving disclinations travel through the channel, they continually exchange partners producing a dynamic ordered state, reminiscent of Ceilidh dancing. We anticipate that this biomimetic ability to self-assemble organised topological disclinations and dynamically structured flow fields in engineered geometries will pave the road towards establishing new active topological microfluidic devices.
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Affiliation(s)
- Tyler N Shendruk
- The Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford, OX1 3NP, UK.
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