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McGovern AD, Huang MJ, Wang J, Kapral R, Aranson IS. Multifunctional Chiral Chemically-Powered Micropropellers for Cargo Transport and Manipulation. Small 2024; 20:e2304773. [PMID: 37936335 DOI: 10.1002/smll.202304773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 10/03/2023] [Indexed: 11/09/2023]
Abstract
Practical applications of synthetic self-propelled nano and microparticles for microrobotics, targeted drug delivery, and manipulation at the nanoscale are rapidly expanding. However, fabrication limitations often hinder progress, resulting in relatively simple shapes and limited functionality. Here, taking advantage of 3D nanoscale printing, chiral micropropellers powered by the hydrogen peroxide reduction reaction are fabricated. Due to their chirality, the propellers exhibit multifunctional behavior controlled by an applied magnetic field: spinning in place (loitering), directed migration in the prescribed direction, capture, and transport of polymer cargo particles. Design parameters of the propellers are optimized by computation modeling based on mesoscale molecular dynamics. It is predicted by computer simulations, and confirmed experimentally, that clockwise rotating propellers attract each other and counterclockwise repel. These results shed light on how chirality and shape optimization enhance the functionality of synthetic autonomous micromachines.
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Affiliation(s)
- Ashlee D McGovern
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Mu-Jie Huang
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6, Canada
| | - Jiyuan Wang
- School of Electrical and Control Engineering, Heilongjiang University of Science and Technology, Harbin, 150022, P. R. China
| | - Raymond Kapral
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6, Canada
| | - Igor S Aranson
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Mathematics, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
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2
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Zhang B, Glatz A, Aranson IS, Snezhko A. Spontaneous shock waves in pulse-stimulated flocks of Quincke rollers. Nat Commun 2023; 14:7050. [PMID: 37923744 PMCID: PMC10624688 DOI: 10.1038/s41467-023-42633-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 10/16/2023] [Indexed: 11/06/2023] Open
Abstract
Active matter demonstrates complex spatiotemporal self-organization not accessible at equilibrium and the emergence of collective behavior. Fluids comprised of microscopic Quincke rollers represent a popular realization of synthetic active matter. Temporal activity modulations, realized by modulated external electric fields, represent an effective tool to expand the variety of accessible dynamic states in active ensembles. Here, we report on the emergence of shockwave patterns composed of coherently moving particles energized by a pulsed electric field. The shockwaves emerge spontaneously and move faster than the average particle speed. Combining experiments, theory, and simulations, we demonstrate that the shockwaves originate from intermittent spontaneous vortex cores due to a vortex meandering instability. They occur when the rollers' translational and rotational decoherence times, regulated by the electric pulse durations, become comparable. The phenomenon does not rely on the presence of confinement, and multiple shock waves continuously arise and vanish in the system.
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Affiliation(s)
- Bo Zhang
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, and Department of Physics, Nanjing University, Nanjing, 210093, China.
| | - Andreas Glatz
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
- Department of Physics, Northern Illinois University, DeKalb, IL, 60115, USA
| | - Igor S Aranson
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, 16802, USA
- Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA
- Department of Mathematics, Pennsylvania State University, University Park, PA, 16802, USA
| | - Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
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3
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Liao W, Aranson IS. Viscoelasticity enhances collective motion of bacteria. PNAS Nexus 2023; 2:pgad291. [PMID: 37719751 PMCID: PMC10503537 DOI: 10.1093/pnasnexus/pgad291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 08/28/2023] [Indexed: 09/19/2023]
Abstract
Bacteria form human and animal microbiota. They are the leading causes of many infections and constitute an important class of active matter. Concentrated bacterial suspensions exhibit large-scale turbulent-like locomotion and swarming. While the collective behavior of bacteria in Newtonian fluids is relatively well understood, many fundamental questions remain open for complex fluids. Here, we report on the collective bacterial motion in a representative biological non-Newtonian viscoelastic environment exemplified by mucus. Experiments are performed with synthetic porcine gastric mucus, natural cow cervical mucus, and a Newtonian-like polymer solution. We have found that an increase in mucin concentration and, correspondingly, an increase in the suspension's elasticity monotonously increases the length scale of collective bacterial locomotion. On the contrary, this length remains practically unchanged in Newtonian polymer solution in a wide range of concentrations. The experimental observations are supported by computational modeling. Our results provide insight into how viscoelasticity affects the spatiotemporal organization of bacterial active matter. They also expand our understanding of bacterial colonization of mucosal surfaces and the onset of antibiotic resistance due to swarming.
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Affiliation(s)
- Wentian Liao
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Igor S Aranson
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
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4
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Rubio LD, Collins M, Sen A, Aranson IS. Ultrasound Manipulation and Extrusion of Active Nanorods. Small 2023; 19:e2300028. [PMID: 37246278 DOI: 10.1002/smll.202300028] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 04/20/2023] [Indexed: 05/30/2023]
Abstract
Synthetic self-propelled nano and microparticles have a growing appeal for targeted drug delivery, collective functionality, and manipulation at the nanoscale. However, it is challenging to control their positions and orientations under confinement, e.g., in microchannels, nozzles, and microcapillaries. This study reports on the synergistic effect of acoustic and flow-induced focusing in microfluidic nozzles. In a microchannel with a nozzle, the balance between the acoustophoretic forces and the fluid drag due to streaming flows generated by the acoustic field controls the microparticle's dynamics. This study manipulates the positions and orientations of dispersed particles and dense clusters inside the channel at a fixed frequency by tuning the acoustic intensity. The main findings are: first, this study successfully manipulates the positions and orientations of individual particles and dense clusters inside the channel at a fixed frequency by tuning the acoustic intensity. Second, when an external flow is applied, the acoustic field separates and selectively extrudes shape-anisotropic passive particles and self-propelled active nanorods. Finally, the observed phenomena are explained by multiphysics finite-element modeling. The results shed light on the control and extrusion of active particles in confined geometries and enable applications for acoustic cargo (e.g., drug) delivery, particle injection, and additive manufacturing via printed self-propelled active particles.
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Affiliation(s)
- Leonardo Dominguez Rubio
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 18602, USA
| | - Matthew Collins
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Ayusman Sen
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Igor S Aranson
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 18602, USA
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5
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Abstract
Bacteria are among the oldest and most abundant species on Earth. Bacteria successfully colonize diverse habitats and play a significant role in the oxygen, carbon, and nitrogen cycles. They also form human and animal microbiota and may become sources of pathogens and a cause of many infectious diseases. Suspensions of motile bacteria constitute one of the most studied examples of active matter: a broad class of non-equilibrium systems converting energy from the environment (e.g., chemical energy of the nutrient) into mechanical motion. Concentrated bacterial suspensions, often termed active fluids, exhibit complex collective behavior, such as large-scale turbulent-like motion (so-called bacterial turbulence) and swarming. The activity of bacteria also affects the effective viscosity and diffusivity of the suspension. This work reports on the progress in bacterial active matter from the physics viewpoint. It covers the key experimental results, provides a critical assessment of major theoretical approaches, and addresses the effects of visco-elasticity, liquid crystallinity, and external confinement on collective behavior in bacterial suspensions.
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Affiliation(s)
- Igor S Aranson
- Departments of Biomedical Engineering, Chemistry, and Mathematics, Pennsylvania State University, University Park, PA 16802, United States of America
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6
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Aranson IS, Pikovsky A. Confinement and Collective Escape of Active Particles. Phys Rev Lett 2022; 128:108001. [PMID: 35333075 DOI: 10.1103/physrevlett.128.108001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 12/28/2021] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Active matter broadly covers the dynamics of self-propelled particles. While the onset of collective behavior in homogenous active systems is relatively well understood, the effect of inhomogeneities such as obstacles and traps lacks overall clarity. Here, we study how interacting, self-propelled particles become trapped and released from a trap. We have found that captured particles aggregate into an orbiting condensate with a crystalline structure. As more particles are added, the trapped condensates escape as a whole. Our results shed light on the effects of confinement and quenched disorder in active matter.
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Affiliation(s)
- Igor S Aranson
- Departments of Biomedical Engineering, Chemistry, and Mathematics, Penn State University, University Park, Pennsylvania 16802, USA
| | - Arkady Pikovsky
- Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam-Golm, Germany
- Department of Control Theory, Nizhny Novgorod State University, Gagarin Avenue 23, 606950 Nizhny Novgorod, Russia
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Gompper G, Winkler RG, Speck T, Solon A, Nardini C, Peruani F, Löwen H, Golestanian R, Kaupp UB, Alvarez L, Kiørboe T, Lauga E, Poon WCK, DeSimone A, Muiños-Landin S, Fischer A, Söker NA, Cichos F, Kapral R, Gaspard P, Ripoll M, Sagues F, Doostmohammadi A, Yeomans JM, Aranson IS, Bechinger C, Stark H, Hemelrijk CK, Nedelec FJ, Sarkar T, Aryaksama T, Lacroix M, Duclos G, Yashunsky V, Silberzan P, Arroyo M, Kale S. The 2020 motile active matter roadmap. J Phys Condens Matter 2020; 32:193001. [PMID: 32058979 DOI: 10.1088/1361-648x/ab6348] [Citation(s) in RCA: 137] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Activity and autonomous motion are fundamental in living and engineering systems. This has stimulated the new field of 'active matter' in recent years, which focuses on the physical aspects of propulsion mechanisms, and on motility-induced emergent collective behavior of a larger number of identical agents. The scale of agents ranges from nanomotors and microswimmers, to cells, fish, birds, and people. Inspired by biological microswimmers, various designs of autonomous synthetic nano- and micromachines have been proposed. Such machines provide the basis for multifunctional, highly responsive, intelligent (artificial) active materials, which exhibit emergent behavior and the ability to perform tasks in response to external stimuli. A major challenge for understanding and designing active matter is their inherent nonequilibrium nature due to persistent energy consumption, which invalidates equilibrium concepts such as free energy, detailed balance, and time-reversal symmetry. Unraveling, predicting, and controlling the behavior of active matter is a truly interdisciplinary endeavor at the interface of biology, chemistry, ecology, engineering, mathematics, and physics. The vast complexity of phenomena and mechanisms involved in the self-organization and dynamics of motile active matter comprises a major challenge. Hence, to advance, and eventually reach a comprehensive understanding, this important research area requires a concerted, synergetic approach of the various disciplines. The 2020 motile active matter roadmap of Journal of Physics: Condensed Matter addresses the current state of the art of the field and provides guidance for both students as well as established scientists in their efforts to advance this fascinating area.
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Affiliation(s)
- Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
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8
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Patelli A, Djafer-Cherif I, Aranson IS, Bertin E, Chaté H. Understanding Dense Active Nematics from Microscopic Models. Phys Rev Lett 2019; 123:258001. [PMID: 31922774 DOI: 10.1103/physrevlett.123.258001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 09/13/2019] [Indexed: 06/10/2023]
Abstract
We study dry, dense active nematics at both particle and continuous levels. Specifically, extending the Boltzmann-Ginzburg-Landau approach, we derive well-behaved hydrodynamic equations from a Vicsek-style model with nematic alignment and pairwise repulsion. An extensive study of the phase diagram shows qualitative agreement between the two levels of description. We find in particular that the dynamics of topological defects strongly depends on parameters and can lead to "arch" solutions forming a globally polar, smecticlike arrangement of Néel walls. We show how these configurations are at the origin of the defect ordered states reported previously. This work offers a detailed understanding of the theoretical description of dense active nematics directly rooted in their microscopic dynamics.
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Affiliation(s)
- Aurelio Patelli
- Service de Physique de l'Etat Condensé, CEA, CNRS, Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France
| | - Ilyas Djafer-Cherif
- Service de Physique de l'Etat Condensé, CEA, CNRS, Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France
- School of Mathematics, University of Bristol, Bristol BS8 1TW, United Kingdom
| | - Igor S Aranson
- Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Eric Bertin
- Univ. Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France
| | - Hugues Chaté
- Service de Physique de l'Etat Condensé, CEA, CNRS, Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France
- Computational Science Research Center, Beijing 100094, China
- LPTMC, Sorbonne Université, CNRS, 75005 Paris, France
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9
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Baker RD, Montenegro-Johnson T, Sediako AD, Thomson MJ, Sen A, Lauga E, Aranson IS. Shape-programmed 3D printed swimming microtori for the transport of passive and active agents. Nat Commun 2019; 10:4932. [PMID: 31666512 PMCID: PMC6821728 DOI: 10.1038/s41467-019-12904-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 09/30/2019] [Indexed: 12/20/2022] Open
Abstract
Through billions of years of evolution, microorganisms mastered unique swimming behaviors to thrive in complex fluid environments. Limitations in nanofabrication have thus far hindered the ability to design and program synthetic swimmers with the same abilities. Here we encode multi-behavioral responses in microscopic self-propelled tori using nanoscale 3D printing. We show experimentally and theoretically that the tori continuously transition between two primary swimming modes in response to a magnetic field. The tori also manipulated and transported other artificial swimmers, bimetallic nanorods, as well as passive colloidal particles. In the first behavioral mode, the tori accumulated and transported nanorods; in the second mode, nanorods aligned along the toriʼs self-generated streamlines. Our results indicate that such shape-programmed microswimmers have a potential to manipulate biological active matter, e.g. bacteria or cells. While there are many demonstrations of self-propelled synthetic particles, there are fewer realisations of multimode swimming for the same particle. Here the authors demonstrate two swimming behaviours in magnetically manipulated microtori and show that these can manipulate other active particles.
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Affiliation(s)
- Remmi Danae Baker
- Department of Material Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
| | | | - Anton D Sediako
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, M5S 3G8, Canada
| | - Murray J Thomson
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, M5S 3G8, Canada
| | - Ayusman Sen
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA.
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, UK
| | - Igor S Aranson
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA. .,Department of Mathematics, The Pennsylvania State University, University Park, PA, 16802, USA. .,Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
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10
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Baker R, Kauffman JE, Laskar A, Shklyaev OE, Potomkin M, Dominguez-Rubio L, Shum H, Cruz-Rivera Y, Aranson IS, Balazs AC, Sen A. Fight the flow: the role of shear in artificial rheotaxis for individual and collective motion. Nanoscale 2019; 11:10944-10951. [PMID: 31139774 DOI: 10.1039/c8nr10257k] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
To navigate in complex fluid environments, swimming organisms like fish or bacteria often reorient their bodies antiparallel or against the flow, more commonly known as rheotaxis. This reorientation motion enables the organisms to migrate against the fluid flow, as observed in salmon swimming upstream to spawn. Rheotaxis can also be realized in artificial microswimmers - self-propelled particles that mimic swimming microorganisms. Here we study experimentally and by computer simulations the rheotaxis of self-propelled gold-platinum nanorods in microfluidic channels. We observed two distinct modes of artificial rheotaxis: a high shear domain near the bottom wall of the microfluidic channel and a low shear regime in the corners. Reduced fluid drag in the corners promotes the formation of many particle aggregates that rheotax collectively. Our study provides insight into the biomimetic functionality of artificial self-propelled nanorods for dynamic self-assembly and the delivery of payloads to targeted locations.
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Affiliation(s)
- Remmi Baker
- Department of Material Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA
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11
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Abstract
Active matter is a wide class of nonequilibrium systems consisting of interacting self-propelled agents transducing the energy stored in the environment into mechanical motion. Numerous examples range from microscopic cytoskeletal filaments and swimming organisms (bacteria and unicellular algae), synthetic catalytic nanomotors, colloidal self-propelled Janus particles, to macroscopic bird flocks, fish schools, and even human crowds. Active matter demonstrates a remarkable tendency toward self-organization and development of collective states with the long-range spatial order. Furthermore, active materials exhibit properties that are not present in traditional materials like plastics or ceramics: self-repair, shape change, and adaptation. A suspension of microscopic swimmers, such as motile bacteria or self-propelled colloids (active suspensions), is possibly the simplest and the most explored realization of active matter. Recent studies of active suspensions revealed a wealth of unexpected behaviors, from a dramatic reduction of the effective viscosity, enhanced mixing and self-diffusion, rectification of chaotic motion, to artificial rheotaxis (drift against the imposed flow) and cross-stream migration. To date, most of the studies of active matter are performed in isotropic suspending medium, like water with the addition of some "fuel", e.g., nutrient for bacteria or H2O2 for catalytic bimetallic AuPt nanorods. A highly structured anisotropic suspending medium represented by lyotropic liquid crystal (water-soluble) opens enormous opportunities to control and manipulate active matter. Liquid crystals exhibit properties intermediate between solid and liquids; they may flow like a liquid but respond to deformations as a solid due to a crystal-like orientation of molecules. Liquid crystals doped by a small amount of active component represent a new class of composite materials (living liquid crystals or LLCs) with unusual mechanical and optical properties. LLCs demonstrate a variety of highly organized dynamic collective states, spontaneous formation of dynamic textures of topological defects (singularities of local molecular orientation), controlled and reconfigurable transport of cargo particles, manipulation of individual trajectories of microswimmers, and many others. Besides insights into fundamental mechanisms governing active materials, living liquid crystals may have intriguing applications, such as the design of new classes of soft adaptive bioinspired materials capable to respond to physical and chemical stimuli, such as light, magnetic, and electric fields, mechanical shear, airborne pollutants, and bacterial toxins. This Account details the most recent developments in the field of LLCs and discusses how the anisotropy of liquid crystals can be harnessed to control and manipulate active materials.
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Affiliation(s)
- Igor S. Aranson
- Departments of Biomedical Engineering, Chemistry and Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, United States
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12
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Peruani F, Aranson IS. Cold Active Motion: How Time-Independent Disorder Affects the Motion of Self-Propelled Agents. Phys Rev Lett 2018; 120:238101. [PMID: 29932716 DOI: 10.1103/physrevlett.120.238101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 04/18/2018] [Indexed: 06/08/2023]
Abstract
Assemblages of self-propelled particles, often termed active matter, exhibit collective behavior due to competition between neighbor alignment and noise-induced decoherence. However, very little is known of how the quenched (i.e., time-independent) disorder impacts active motion. Here we report on the effects of quenched disorder on the dynamics of self-propelled point particles. We identified three major types of quenched disorder relevant in the context of active matter: random torque, force, and stress. We demonstrate that even in the absence of external fluctuations ("cold active matter"), quenched disorder results in nontrivial dynamic phases not present in their "hot" counterpart. In particular, by analyzing when the equations of motion exhibit a Hamiltonian structure and when attractors may be present, we identify in which scenarios particle trapping, i.e., the asymptotic convergence of particle trajectories to bounded areas in space ("traps"), can and cannot occur. Our study provides new fundamental insights into active systems realized by self-propelled particles on natural and synthetic disordered substrates.
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Affiliation(s)
- Fernando Peruani
- Université Côte d'Azur, Laboratoire J.A. Dieudonné, UMR 7351 CNRS, Parc Valrose, F-06108 Nice Cedex 02, France
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA and Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
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13
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Michalska M, Gambacorta F, Divan R, Aranson IS, Sokolov A, Noirot P, Laible PD. Tuning antimicrobial properties of biomimetic nanopatterned surfaces. Nanoscale 2018; 10:6639-6650. [PMID: 29582025 DOI: 10.1039/c8nr00439k] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Nature has amassed an impressive array of structures that afford protection from microbial colonization/infection when displayed on the exterior surfaces of organisms. Here, controlled variation of the features of mimetics derived from etched silicon allows for tuning of their antimicrobial efficacy. Materials with nanopillars up to 7 μm in length are extremely effective against a wide range of microbial species and exceed the performance of natural surfaces; in contrast, materials with shorter/blunter nanopillars (<2 μm) selectively killed specific species. Using a combination of microscopies, the mechanisms by which bacteria are killed are demonstrated, emphasizing the dependence upon pillar density and tip geometry. Additionally, real-time imaging reveals how cells are immobilized and killed rapidly. Generic or selective protection from microbial colonization could be conferred to surfaces [for, e.g., internal medicine, implants (joint, dental, and cosmetic), food preparation, and the agricultural industry] patterned with these materials as coatings.
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Affiliation(s)
- Martyna Michalska
- Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA.
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14
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Abstract
Colloidal particles subject to an external periodic forcing exhibit complex collective behavior and self-assembled patterns. A dispersion of magnetic microparticles confined at the air-liquid interface and energized by a uniform uniaxial alternating magnetic field exhibits dynamic arrays of self-assembled spinners rotating in either direction. Here, we report on experimental and simulation studies of active turbulence and transport in a gas of self-assembled spinners. We show that the spinners, emerging as a result of spontaneous symmetry breaking of clock/counterclockwise rotation of self-assembled particle chains, generate vigorous vortical flows at the interface. An ensemble of spinners exhibits chaotic dynamics due to self-generated advection flows. The same-chirality spinners (clockwise or counterclockwise) show a tendency to aggregate and form dynamic clusters. Emergent self-induced interface currents promote active diffusion that could be tuned by the parameters of the external excitation field. Furthermore, the erratic motion of spinners at the interface generates chaotic fluid flow reminiscent of 2D turbulence. Our work provides insight into fundamental aspects of collective transport in active spinner materials and yields rules for particle manipulation at the microscale.
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Affiliation(s)
- Gašper Kokot
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439
| | - Shibananda Das
- Institute of Complex Systems, Forschungszentrum Jülich, 52425 Jülich, Germany
- Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Roland G Winkler
- Institute of Complex Systems, Forschungszentrum Jülich, 52425 Jülich, Germany
- Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Gerhard Gompper
- Institute of Complex Systems, Forschungszentrum Jülich, 52425 Jülich, Germany;
- Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802
| | - Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439;
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15
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Kokot G, Kolmakov GV, Aranson IS, Snezhko A. Dynamic self-assembly and self-organized transport of magnetic micro-swimmers. Sci Rep 2017; 7:14726. [PMID: 29116208 PMCID: PMC5677019 DOI: 10.1038/s41598-017-15193-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 10/20/2017] [Indexed: 01/01/2023] Open
Abstract
We demonstrate experimentally and in computer simulations that magnetic microfloaters can self-organize into various functional structures while energized by an external alternating (ac) magnetic field. The structures exhibit self-propelled motion and an ability to carry a cargo along a pre-defined path. The morphology of the self-assembled swimmers is controlled by the frequency and amplitude of the magnetic field.
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Affiliation(s)
- Gašper Kokot
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL, 60439, USA
| | - German V Kolmakov
- Physics Department, New York City College of Technology, the City University of New York, Brooklyn, NY, 11201, USA.
| | - Igor S Aranson
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, 16802, USA
| | - Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL, 60439, USA
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16
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Abstract
Crawling cell motility is vital to many biological processes such as wound healing and the immune response. Using a minimal model we investigate the effects of patterned substrate adhesiveness and biophysical cell parameters on the direction of cell motion. We show that cells with low adhesion site formation rates may move perpendicular to adhesive stripes while those with high adhesion site formation rates results in motility only parallel to the substrate stripes. We explore the effects of varying the substrate pattern geometry and the strength of actin polymerization on the directionality of the crawling cell. These results reveal that high strength of actin polymerization results in motion perpendicular to substrate stripes only when the substrate is relatively nonadhesive; in particular, this suggests potential applications in motile cell sorting and guiding on engineered substrates.
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Affiliation(s)
- Matthew S Mizuhara
- Department of Mathematics and Statistics, The College of New Jersey, Ewing, New Jersey 08628, USA
| | - Leonid Berlyand
- Department of Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Igor S Aranson
- Departments of Biomedical Engineering, Chemistry and Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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17
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Potomkin M, Tournus M, Berlyand LV, Aranson IS. Flagella bending affects macroscopic properties of bacterial suspensions. J R Soc Interface 2017; 14:rsif.2016.1031. [PMID: 28566507 DOI: 10.1098/rsif.2016.1031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 05/03/2017] [Indexed: 12/28/2022] Open
Abstract
To survive in harsh conditions, motile bacteria swim in complex environments and respond to the surrounding flow. Here, we develop a mathematical model describing how flagella bending affects macroscopic properties of bacterial suspensions. First, we show how the flagella bending contributes to the decrease in the effective viscosity observed in dilute suspension. Our results do not impose tumbling (random reorientation) as was previously done to explain the viscosity reduction. Second, we demonstrate how a bacterium escapes from wall entrapment due to the self-induced buckling of flagella. Our results shed light on the role of flexible bacterial flagella in interactions of bacteria with shear flow and walls or obstacles.
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Affiliation(s)
- M Potomkin
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - M Tournus
- Aix Marseille Univ, CNRS, Centrale Marseille, I2M, Marseille, France
| | - L V Berlyand
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - I S Aranson
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA .,Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA.,Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
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18
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Amiri A, Harvey C, Buchmann A, Christley S, Shrout JD, Aranson IS, Alber M. Reversals and collisions optimize protein exchange in bacterial swarms. Phys Rev E 2017; 95:032408. [PMID: 28415180 PMCID: PMC5508969 DOI: 10.1103/physreve.95.032408] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Indexed: 11/07/2022]
Abstract
Swarming groups of bacteria coordinate their behavior by self-organizing as a population to move over surfaces in search of nutrients and optimal niches for colonization. Many open questions remain about the cues used by swarming bacteria to achieve this self-organization. While chemical cue signaling known as quorum sensing is well-described, swarming bacteria often act and coordinate on time scales that could not be achieved via these extracellular quorum sensing cues. Here, cell-cell contact-dependent protein exchange is explored as a mechanism of intercellular signaling for the bacterium Myxococcus xanthus. A detailed biologically calibrated computational model is used to study how M. xanthus optimizes the connection rate between cells and maximizes the spread of an extracellular protein within the population. The maximum rate of protein spreading is observed for cells that reverse direction optimally for swarming. Cells that reverse too slowly or too fast fail to spread extracellular protein efficiently. In particular, a specific range of cell reversal frequencies was observed to maximize the cell-cell connection rate and minimize the time of protein spreading. Furthermore, our findings suggest that predesigned motion reversal can be employed to enhance the collective behavior of biological synthetic active systems.
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Affiliation(s)
- Aboutaleb Amiri
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Cameron Harvey
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Amy Buchmann
- Department of Mathematics, Tulane University, New Orleans, Louisiana 70118, USA
| | | | - Joshua D Shrout
- Department of Civil and Environmental Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Igor S Aranson
- Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA and Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Mark Alber
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana 46556, USA and Department of Mathematics, University of California, Riverside, California 92521, USA
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19
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Abstract
Assemblages of microscopic colloidal particles exhibit fascinating collective motion when energized by electric or magnetic fields. The behaviors range from coherent vortical motion to phase separation and dynamic self-assembly. Although colloidal systems are relatively simple, understanding their collective response, especially under out-of-equilibrium conditions, remains elusive. We report on the emergence of flocking and global rotation in the system of rolling ferromagnetic microparticles energized by a vertical alternating magnetic field. By combing experiments and discrete particle simulations, we have identified primary physical mechanisms, leading to the emergence of large-scale collective motion: spontaneous symmetry breaking of the clockwise/counterclockwise particle rotation, collisional alignment of particle velocities, and random particle reorientations due to shape imperfections. We have also shown that hydrodynamic interactions between the particles do not have a qualitative effect on the collective dynamics. Our findings shed light on the onset of spatial and temporal coherence in a large class of active systems, both synthetic (colloids, swarms of robots, and biopolymers) and living (suspensions of bacteria, cell colonies, and bird flocks).
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Affiliation(s)
- Andreas Kaiser
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, IL 60439, USA
| | - Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, IL 60439, USA
| | - Igor S. Aranson
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, IL 60439, USA
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60202, USA
- Corresponding author.
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20
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Zhang R, Roberts T, Aranson IS, de Pablo JJ. Lattice Boltzmann simulation of asymmetric flow in nematic liquid crystals with finite anchoring. J Chem Phys 2016; 144:084905. [PMID: 26931724 DOI: 10.1063/1.4940342] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Liquid crystals (LCs) display many of the flow characteristics of liquids but exhibit long range orientational order. In the nematic phase, the coupling of structure and flow leads to complex hydrodynamic effects that remain to be fully elucidated. Here, we consider the hydrodynamics of a nematic LC in a hybrid cell, where opposite walls have conflicting anchoring boundary conditions, and we employ a 3D lattice Boltzmann method to simulate the time-dependent flow patterns that can arise. Due to the symmetry breaking of the director field within the hybrid cell, we observe that at low to moderate shear rates, the volumetric flow rate under Couette and Poiseuille flows is different for opposite flow directions. At high shear rates, the director field may undergo a topological transition which leads to symmetric flows. By applying an oscillatory pressure gradient to the channel, a net volumetric flow rate is found to depend on the magnitude and frequency of the oscillation, as well as the anchoring strength. Taken together, our findings suggest several intriguing new applications for LCs in microfluidic devices.
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Affiliation(s)
- Rui Zhang
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Tyler Roberts
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Juan J de Pablo
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
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21
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Abstract
Interactions of microswimmers with their fluid environment are exceptionally complex. Macroscopic shear flow alters swimming trajectories in a highly nontrivial way and results in dramatic reduction of viscosity and heterogeneous bacterial distributions. Here we report on experimental and theoretical studies of rapid expulsion of microswimmers, such as motile bacteria, by a vortical flow created by a rotating microparticle. We observe a formation of a macroscopic depletion area in a high-shear region, in the vicinity of a microparticle. The rapid migration of bacteria from the shear-rich area is caused by a vortical structure of the flow rather than intrinsic random fluctuations of bacteria orientations, in stark contrast to planar shear flow. Our mathematical model reveals that expulsion is a combined effect of motility and alignment by a vortical flow. Our findings offer a novel approach for manipulation of motile microorganisms and shed light on bacteria–flow interactions. The control of microswimmers such as bacteria is important for emerging applications of active bioinspired materials. Here, the authors demonstrate the use of vortical shear to expel suspended motile bacteria from the vicinity of a rotating microparticle.
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Affiliation(s)
- Andrey Sokolov
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.,Department of Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60202, USA
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22
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23
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Abstract
We report on the velocity statistics of an out-of-equilibrium magnetic suspension in a spinner phase confined at a liquid interface. The suspension is energized by a uniaxial alternating magnetic field applied parallel to the interface. In a certain range of the magnetic field parameters the system spontaneously undergoes a transition into a dynamic spinner phase (ensemble of hydrodynamically coupled magnetic micro-rotors) comprised of two subsystems: self-assembled spinning chains and a gas of rotating single particles. Both subsystems coexist in a dynamic equilibrium via continuous exchange of the particles. Spinners excite surface flows that significantly increase particle velocity correlations in the system. For both subsystems the velocity distributions are strongly non-Maxwellian with nearly exponential high-energy tails, P(v) ∼ exp(-|v/v0|). The kurtosis, the measure of the deviation from the Gaussian statistics, is influenced by the frequency of the external magnetic field. We show that in the single-particle gas the dissipation is mostly collisional, whereas the viscous damping dominates over collisional dissipation for the self-assembled spinners. The dissipation increases with the frequency of the applied magnetic field. Our results provide insights into non-trivial dissipation mechanisms determining self-assembly processes in out-of-equilibrium magnetic suspensions.
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Affiliation(s)
- Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA.
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24
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Tournus M, Kirshtein A, Berlyand LV, Aranson IS. Flexibility of bacterial flagella in external shear results in complex swimming trajectories. J R Soc Interface 2015; 12:20140904. [PMID: 25376876 DOI: 10.1098/rsif.2014.0904] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many bacteria use rotating helical flagella in swimming motility. In the search for food or migration towards a new habitat, bacteria occasionally unbundle their flagellar filaments and tumble, leading to an abrupt change in direction. Flexible flagella can also be easily deformed by external shear flow, leading to complex bacterial trajectories. Here, we examine the effects of flagella flexibility on the navigation of bacteria in two fundamental shear flows: planar shear and Poiseuille flow realized in long channels. On the basis of slender body elastodynamics and numerical analysis, we discovered a variety of non-trivial effects stemming from the interplay of self-propulsion, elasticity and shear-induced flagellar bending. We show that in planar shear flow the bacteria execute periodic motion, whereas in Poiseuille flow, they migrate towards the centre of the channel or converge towards a limit cycle. We also find that even a small amount of random reorientation can induce a strong response of bacteria, leading to overall non-periodic trajectories. Our findings exemplify the sensitive role of flagellar flexibility and shed new light on the navigation of bacteria in complex shear flows.
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Affiliation(s)
- M Tournus
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - A Kirshtein
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - L V Berlyand
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - I S Aranson
- Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60202, USA
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25
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Nagai KH, Sumino Y, Montagne R, Aranson IS, Chaté H. Collective motion of self-propelled particles with memory. Phys Rev Lett 2015; 114:168001. [PMID: 25955073 DOI: 10.1103/physrevlett.114.168001] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Indexed: 05/11/2023]
Abstract
We show that memory, in the form of underdamped angular dynamics, is a crucial ingredient for the collective properties of self-propelled particles. Using Vicsek-style models with an Ornstein-Uhlenbeck process acting on angular velocity, we uncover a rich variety of collective phases not observed in usual overdamped systems, including vortex lattices and active foams. In a model with strictly nematic interactions the smectic arrangement of Vicsek waves giving rise to global polar order is observed. We also provide a calculation of the effective interaction between vortices in the case where a telegraphic noise process is at play, explaining thus the emergence and structure of the vortex lattices observed here and in motility assay experiments.
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Affiliation(s)
- Ken H Nagai
- School of Materials Science, Japan Advanced Institute of Science and Technology, Ishikawa 923-1292, Japan
| | - Yutaka Sumino
- Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan
| | - Raul Montagne
- Departamento de Fisica, UFRPE, 52171-900 Recife, Pernambuco, Brazil
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Hugues Chaté
- Service de Physique de l'Etat Condensé, CNRS UMR 3680, CEA-Saclay, 91191 Gif-sur-Yvette, France
- LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, 75252 Paris, France
- Beijing Computational Science Research Center, 3 Heqing Road, Beijing 100080, China
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26
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27
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Abstract
Collective migration of eukaryotic cells plays a fundamental role in tissue growth, wound healing and immune response. The motion, arising spontaneously or in response to chemical and mechanical stimuli, is also important for understanding life-threatening pathologies, such as cancer and metastasis formation. We present a phase-field model to describe the movement of many self-organized, interacting cells. The model takes into account the main mechanisms of cell motility - acto-myosin dynamics, as well as substrate-mediated and cell-cell adhesion. It predicts that collective cell migration emerges spontaneously as a result of inelastic collisions between neighboring cells: collisions lead to a mutual alignment of the cell velocities and to the formation of coherently-moving multi-cellular clusters. Small cell-to-cell adhesion, in turn, reduces the propensity for large-scale collective migration, while higher adhesion leads to the formation of moving bands. Our study provides valuable insight into biological processes associated with collective cell motility.
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Affiliation(s)
- Jakob Löber
- Institut für Theoretische Physik, Hardenbergstrasse 36, EW 7-1, Technische Universität Berlin, 10623 Berlin, Germany
| | - Falko Ziebert
- 1] Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany [2] Institut Charles Sadron, CNRS-UPR22, 23 rue du Loess, 67034 Strasbourg Cedex 2, France
| | - Igor S Aranson
- 1] Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA [2] Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60202, USA
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28
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Sokolov A, Zhou S, Lavrentovich OD, Aranson IS. Individual behavior and pairwise interactions between microswimmers in anisotropic liquid. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 91:013009. [PMID: 25679710 DOI: 10.1103/physreve.91.013009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Indexed: 06/04/2023]
Abstract
A motile bacterium swims by generating flow in its surrounding liquid. Anisotropy of the suspending liquid significantly modifies the swimming dynamics and corresponding flow signatures of an individual bacterium and impacts collective behavior. We study the interactions between swimming bacteria in an anisotropic environment exemplified by lyotropic chromonic liquid crystal. Our analysis reveals a significant localization of the bacteria-induced flow along a line coaxial with the bacterial body, which is due to strong viscosity anisotropy of the liquid crystal. Despite the fact that the average viscosity of the liquid crystal is two to three orders of magnitude higher than the viscosity of pure water, the speed of bacteria in the liquid crystal is of the same order of magnitude as in water. We show that bacteria can transport a cargo (a fluorescent particle) along a predetermined trajectory defined by the direction of molecular orientation of the liquid crystal. We demonstrate that while the hydrodynamic interaction between flagella of two close-by bacteria is negligible, the observed convergence of the swimming speeds as well as flagella waves' phase velocities may occur due to viscoelastic interaction between the bacterial bodies.
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Affiliation(s)
- Andrey Sokolov
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Shuang Zhou
- Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - Oleg D Lavrentovich
- Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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29
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Scherpelz P, Padavić K, Rançon A, Glatz A, Aranson IS, Levin K. Phase imprinting in equilibrating Fermi gases: the transience of vortex rings and other defects. Phys Rev Lett 2014; 113:125301. [PMID: 25279634 DOI: 10.1103/physrevlett.113.125301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Indexed: 06/03/2023]
Abstract
We present numerical simulations of phase imprinting experiments in ultracold trapped Fermi gases, which were obtained independently and are in good agreement with recent experimental results. Our focus is on the sequence and evolution of defects using the fermionic time-dependent Ginzburg-Landau equation, which contains dissipation necessary for equilibration. In contrast to other simulations, we introduce small, experimentally unavoidable symmetry breaking, particularly that associated with thermal fluctuations and with the phase-imprinting tilt angle, and we illustrate their dramatic effects. As appears consistent with experiment, the former causes vortex rings in confined geometries to move to the trap surface and rapidly decay into more stable vortex lines. The latter aligns the precessing and relatively long-lived vortex filaments, rendering them difficult to distinguish from solitons.
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Affiliation(s)
- Peter Scherpelz
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Karmela Padavić
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Adam Rançon
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Andreas Glatz
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA and Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
| | - K Levin
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
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30
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Tricard S, Shepherd RF, Stan CA, Snyder PW, Cademartiri R, Zhu D, Aranson IS, Shakhnovich EI, Whitesides GM. Mechanical Model of Globular Transition in Polymers. Chempluschem 2014. [DOI: 10.1002/cplu.201402203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Simon Tricard
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - Robert F. Shepherd
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - Claudiu A. Stan
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - Phillip W. Snyder
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - Rebecca Cademartiri
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - Danny Zhu
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - Igor S. Aranson
- Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (USA)
| | - Eugene I. Shakhnovich
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
| | - George M. Whitesides
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 (USA)
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31
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Ngo S, Peshkov A, Aranson IS, Bertin E, Ginelli F, Chaté H. Large-scale chaos and fluctuations in active nematics. Phys Rev Lett 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] [What about the content of this article? (0)] [Affiliation(s)] [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.
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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
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32
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Abstract
We demonstrate that collective turbulentlike motion in a bacterial bath can power and steer the directed transport of mesoscopic carriers through the suspension. In our experiments and simulations, a microwedgelike "bulldozer" draws energy from a bacterial bath of varied density. We obtain that an optimal transport speed is achieved in the turbulent state of the bacterial suspension. This apparent rectification of random motion of bacteria is caused by polar ordered bacteria inside the cusp region of the carrier, which is shielded from the outside turbulent fluctuations.
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Affiliation(s)
- Andreas Kaiser
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - Anton Peshkov
- Laboratoire de Physique et Mécanique des Milieux Hétérogénes, Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris, 75231 Paris Cedex 05, France and Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Andrey Sokolov
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Borge ten Hagen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - Igor S Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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33
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Abstract
Self-propelled motion, emerging spontaneously or in response to external cues, is a hallmark of living organisms. Systems of self-propelled synthetic particles are also relevant for multiple applications, from targeted drug delivery to the design of self-healing materials. Self-propulsion relies on the force transfer to the surrounding. While self-propelled swimming in the bulk of liquids is fairly well characterized, many open questions remain in our understanding of self-propelled motion along substrates, such as in the case of crawling cells or related biomimetic objects. How is the force transfer organized and how does it interplay with the deformability of the moving object and the substrate? How do the spatially dependent traction distribution and adhesion dynamics give rise to complex cell behavior? How can we engineer a specific cell response on synthetic compliant substrates? Here we generalize our recently developed model for a crawling cell by incorporating locally resolved traction forces and substrate deformations. The model captures the generic structure of the traction force distribution and faithfully reproduces experimental observations, like the response of a cell on a gradient in substrate elasticity (durotaxis). It also exhibits complex modes of cell movement such as "bipedal" motion. Our work may guide experiments on cell traction force microscopy and substrate-based cell sorting and can be helpful for the design of biomimetic "crawlers" and active and reconfigurable self-healing materials.
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Affiliation(s)
- Jakob Löber
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
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35
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Piet DL, Straube AV, Snezhko A, Aranson IS. Model of dynamic self-assembly in ferromagnetic suspensions at liquid interfaces. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 88:033024. [PMID: 24125361 DOI: 10.1103/physreve.88.033024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Indexed: 06/02/2023]
Abstract
Ferromagnetic microparticles suspended at the interface between immiscible liquids and energized by an external alternating magnetic field show a rich variety of self-assembled structures, from linear snakes to radial asters. In order to obtain insight into the fundamental physical mechanisms and the overall balance of forces governing self-assembly, we develop a modeling approach based on analytical solutions of the time-averaged Navier-Stokes equations. These analytical expressions for the self-consistent hydrodynamic flows are then employed to modify effective interactions between the particles, which in turn are formulated in terms of the time-averaged quantities. Our method allows effective computational verification of the mechanisms of self-assembly and leads to a testable prediction, e.g., on the transitions between various patterns versus viscosity of the solvent.
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Affiliation(s)
- D L Piet
- Department of Engineering Science and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA and Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
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Ziebert F, Aranson IS. Effects of adhesion dynamics and substrate compliance on the shape and motility of crawling cells. PLoS One 2013; 8:e64511. [PMID: 23741334 PMCID: PMC3669322 DOI: 10.1371/journal.pone.0064511] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 04/12/2013] [Indexed: 11/18/2022] Open
Abstract
Computational modeling of eukaryotic cells moving on substrates is an extraordinarily complex task: many physical processes, such as actin polymerization, action of motors, formation of adhesive contacts concomitant with both substrate deformation and recruitment of actin etc., as well as regulatory pathways are intertwined. Moreover, highly nontrivial cell responses emerge when the substrate becomes deformable and/or heterogeneous. Here we extended a computational model for motile cell fragments, based on an earlier developed phase field approach, to account for explicit dynamics of adhesion site formation, as well as for substrate compliance via an effective elastic spring. Our model displays steady motion vs. stick-slip transitions with concomitant shape oscillations as a function of the actin protrusion rate, the substrate stiffness, and the rates of adhesion. Implementing a step in the substrate's elastic modulus, as well as periodic patterned surfaces exemplified by alternating stripes of high and low adhesiveness, we were able to reproduce the correct motility modes and shape phenomenology found experimentally. We also predict the following nontrivial behavior: the direction of motion of cells can switch from parallel to perpendicular to the stripes as a function of both the adhesion strength and the width ratio of adhesive to non-adhesive stripes.
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Affiliation(s)
- Falko Ziebert
- Physikalisches Institut, Albert-Ludwigs-Universität, Freiburg, Germany
- Institut Charles Sadron, Strasbourg, France
| | - Igor S. Aranson
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States of America
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois, United States of America
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Piet DL, Straube AV, Snezhko A, Aranson IS. Viscosity control of the dynamic self-assembly in ferromagnetic suspensions. Phys Rev Lett 2013; 110:198001. [PMID: 23705741 DOI: 10.1103/physrevlett.110.198001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Indexed: 06/02/2023]
Abstract
Recent studies of dynamic self-assembly in ferromagnetic colloids suspended in liquid-air or liquid-liquid interfaces revealed a rich variety of dynamic structures ranging from linear snakes to axisymmetric asters, which exhibit novel morphology of the magnetic ordering accompanied by large-scale hydrodynamic flows. Based on controlled experiments and first principles theory, we argue that the transition from snakes to asters is governed by the viscosity of the suspending liquid where less viscous liquids favor snakes and more viscous, asters. By obtaining analytic solutions of the time-averaged Navier-Stokes equations, we gain insight into the role of mean hydrodynamic flows and an overall balance of forces governing the self-assembly. Our results illustrate that the viscosity can be used to control the outcome of the dynamic self-assembly in magnetic colloidal suspensions.
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Affiliation(s)
- D L Piet
- Department of Engineering Science and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
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Abstract
In this paper we develop a continuum theory of clustering in ensembles of self-propelled inelastically colliding rods with applications to collective dynamics of common gliding bacteria Myxococcus Xanthus. A multiphase hydrodynamic model that couples densities of oriented and isotropic phases is described. This model is used for the analysis of an instability that leads to spontaneous formation of directionally moving dense clusters within initially dilute isotropic "gas" of myxobacteria. Numerical simulations of this model confirm the existence of stationary dense moving clusters and also elucidate the properties of their collisions. The results are shown to be in a qualitative agreement with experiments.
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Affiliation(s)
- Cameron W. Harvey
- Center for the Study of Biocomplexity and Department of Physics, University of Notre Dame Notre Dame, Indiana 46556, USA
| | - Mark Alber
- Department of Applied and Computational Mathematics and Statistics, Department of Physics, and Center for the Study of Biocomplexity, University of Notre Dame, Notre Dame, IN 46656, USA; Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Lev S. Tsimring
- BioCircuits Institute and San Diego Center for Systems Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | - Igor S. Aranson
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439; Department of Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Rd, Evanston, IL
60208, USA
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Peshkov A, Aranson IS, Bertin E, Chaté H, Ginelli F. Nonlinear field equations for aligning self-propelled rods. Phys Rev Lett 2012; 109:268701. [PMID: 23368625 DOI: 10.1103/physrevlett.109.268701] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Indexed: 06/01/2023]
Abstract
We derive a set of minimal and well-behaved nonlinear field equations describing the collective properties of self-propelled rods from a simple microscopic starting point, the Vicsek model with nematic alignment. Analysis of their linear and nonlinear dynamics shows good agreement with the original microscopic model. In particular, we derive an explicit expression for density-segregated, banded solutions, allowing us to develop a more complete analytic picture of the problem at the nonlinear level.
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Affiliation(s)
- Anton Peshkov
- Service de Physique de l'Etat Condensé, CEA-Saclay, URA 2464 CNRS, 91191 Gif-sur-Yvette, France
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Abstract
A suspension of microswimmers, the simplest realization of active matter, exhibits novel material properties: the emergence of collective motion, reduction in viscosity, increase in diffusivity, and extraction of useful energy. Bacterial dynamics in dilute suspensions suggest that hydrodynamic interactions and collisions between the swimmers lead to collective motion at higher concentrations. On the example of aerobic bacteria Bacillus subtilis, we report on spatial and temporal correlation functions measurements of collective state for various swimming speeds and concentrations. The experiments produced a puzzling result: while the energy injection rate is proportional to the swimming speed and concentration, the correlation length remains practically constant upon small speeds where random tumbling of bacteria dominates. It highlights two fundamental mechanisms: hydrodynamic interactions and collisions; for both of these mechanisms, the change of the swimming speed or concentration alters an overall time scale.
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Affiliation(s)
- Andrey Sokolov
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
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M. Haines B, S. Aranson I, Berlyand L, A. Karpeev D. Effective viscosity of bacterial suspensions: a three-dimensional PDE model with stochastic torque. ACTA ACUST UNITED AC 2012. [DOI: 10.3934/cpaa.2012.11.19] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
Computational modelling of cell motility on substrates is a formidable challenge; regulatory pathways are intertwined and forces that influence cell motion are not fully quantified. Additional challenges arise from the need to describe a moving deformable cell boundary. Here, we present a simple mathematical model coupling cell shape dynamics, treated by the phase-field approach, to a vector field describing the mean orientation (polarization) of the actin filament network. The model successfully reproduces the primary phenomenology of cell motility: discontinuous onset of motion, diversity of cell shapes and shape oscillations. The results are in qualitative agreement with recent experiments on motility of keratocyte cells and cell fragments. The asymmetry of the shapes is captured to a large extent in this simple model, which may prove useful for the interpretation of experiments.
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Affiliation(s)
- Falko Ziebert
- Physikalisches Institut, Albert-Ludwigs-Universität, Freiburg, Germany.
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44
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Abstract
We investigate the long-standing puzzle of phase separation in a granular monolayer vibrated from below. Although this system is three dimensional, an interesting dynamics occurs mostly in the horizontal plane, perpendicular to the direction of vibration. Experiments [Olafsen and Urbach, Phys. Rev. Lett. 81, 4369 (1998)] demonstrated that for a high amplitude of vibration the system is in the gaslike phase, but when the amplitude becomes smaller than a certain threshold, a phase separation occurs: A solidlike dense condensate of particles forms in the center of the system, surrounded by particles in the gaslike phase. We explain theoretically the experimentally observed coexistence of dilute and dense phases, employing Navier-Stokes granular hydrodynamics. We show that the phase separation is associated with a negative compressibility of granular gas.
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Affiliation(s)
- Evgeniy Khain
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
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Snezhko A, Aranson IS. Magnetic manipulation of self-assembled colloidal asters. Nat Mater 2011; 10:698-703. [PMID: 21822260 DOI: 10.1038/nmat3083] [Citation(s) in RCA: 229] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 06/28/2011] [Indexed: 05/13/2023]
Abstract
Self-assembled materials must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots.
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Ryan SD, Haines BM, Berlyand L, Ziebert F, Aranson IS. Viscosity of bacterial suspensions: hydrodynamic interactions and self-induced noise. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 83:050904. [PMID: 21728480 DOI: 10.1103/physreve.83.050904] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Indexed: 05/31/2023]
Abstract
The viscosity of a suspension of swimming bacteria is investigated analytically and numerically. We propose a simple model that allows for efficient computation for a large number of bacteria. Our calculations show that long-range hydrodynamic interactions, intrinsic to self-locomoting objects in a viscous fluid, result in a dramatic reduction of the effective viscosity. In agreement with experiments on suspensions of Bacillus subtilis, we show that the viscosity reduction is related to the onset of large-scale collective motion due to interactions between the swimmers. The simulations reveal that the viscosity reduction occurs only for relatively low concentrations of swimmers: Further increases of the concentration yield an increase of the viscosity. We derive an explicit asymptotic formula for the effective viscosity in terms of known physical parameters and show that hydrodynamic interactions are manifested as self-induced noise in the absence of any explicit stochasticity in the system.
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Affiliation(s)
- Shawn D Ryan
- Department of Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Snezhko A, Barlan K, Aranson IS, Gelfand VI. Statistics of active transport in Xenopus melanophores cells. Biophys J 2011; 99:3216-23. [PMID: 21081069 DOI: 10.1016/j.bpj.2010.09.065] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 09/09/2010] [Accepted: 09/28/2010] [Indexed: 11/15/2022] Open
Abstract
The transport of cell cargo, such as organelles and protein complexes in the cytoplasm, is determined by cooperative action of molecular motors stepping along polar cytoskeletal elements. Analysis of transport of individual organelles generated useful information about the properties of the motor proteins and underlying cytoskeletal elements. In this work, for the first time (to our knowledge), we study collective movement of multiple organelles using Xenopus melanophores, pigment cells that translocate several thousand of pigment granules (melanosomes), spherical organelles of a diameter of ∼1 μm. These cells disperse melanosomes in the cytoplasm in response to high cytoplasmic cAMP, while at low cAMP melanosomes cluster at the cell center. Obtained results suggest spatial and temporal organization, characterized by strong correlations between movement of neighboring organelles, with correlation length of ∼4 μm and pair lifetime ∼5 s. Furthermore, velocity statistics revealed strongly non-Gaussian velocity distribution with high velocity tails demonstrating exponential behavior suggestive of strong velocity correlations. Depolymerization of vimentin intermediate filaments using a dominant-negative vimentin mutant or actin with cytochalasin B reduced correlation of behavior of individual particles. Based on our analysis, we concluded that steric repulsion is dominant, but both intermediate filaments and actin microfilaments are involved in dynamic cross-linking organelles in the cytoplasm.
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Affiliation(s)
- Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA.
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Belkin M, Glatz A, Snezhko A, Aranson IS. Model for dynamic self-assembled magnetic surface structures. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:015301. [PMID: 20866678 DOI: 10.1103/physreve.82.015301] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Indexed: 05/29/2023]
Abstract
We propose a first-principles model for the dynamic self-assembly of magnetic structures at a water-air interface reported in earlier experiments. The model is based on the Navier-Stokes equation for liquids in shallow water approximation coupled to Newton equations for interacting magnetic particles suspended at a water-air interface. The model reproduces most of the observed phenomenology, including spontaneous formation of magnetic snakelike structures, generation of large-scale vortex flows, complex ferromagnetic-antiferromagnetic ordering of the snake, and self-propulsion of bead-snake hybrids.
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Affiliation(s)
- M Belkin
- Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208, USA
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49
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Abstract
Measurements of the shear viscosity in suspensions of swimming Bacillus subtilis in free-standing liquid films have revealed that the viscosity can decrease by up to a factor of 7 compared to the viscosity of the same liquid without bacteria or with nonmotile bacteria. The reduction in viscosity is observed in two complementary experiments: one studying the decay of a large vortex induced by a moving probe and another measuring the viscous torque on a rotating magnetic particle immersed in the film. The viscosity depends on the concentration and swimming speed of the bacteria.
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Affiliation(s)
- Andrey Sokolov
- Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, Illinois 60616, USA
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50
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Melhus MF, Aranson IS, Volfson D, Tsimring LS. Effect of noise on solid-to-liquid transition in small granular systems under shear. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:041305. [PMID: 19905306 DOI: 10.1103/physreve.80.041305] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Indexed: 05/28/2023]
Abstract
The effect of noise on the solid-to-liquid transition of a dense granular assembly under planar shear is studied numerically using soft-particle molecular dynamics simulations in two dimensions. We focus on small systems in a thin planar Couette cell, examining the bistable region while increasing shear, with varying amounts of random noise, and determine statistics of the shear required for fluidization. In the absence of noise, the threshold value of the shear stress depends on the preparation of the system and has a broad distribution. However, adding force fluctuations both lowers the mean threshold value of the shear stress and decreases its variability. This behavior is interpreted as thermoactivated escape through a fluctuating barrier.
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Affiliation(s)
- Martin F Melhus
- Department of Physics, Northwestern University, Evanston, Illinois 60208-3112, USA
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