1
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Oikonomeas-Koppasis N, Ketzetzi S, Kraft DJ, Schall P. Power-law intermittency in the gradient-induced self-propulsion of colloidal swimmers. SOFT MATTER 2024; 20:6103-6108. [PMID: 38868959 PMCID: PMC11305149 DOI: 10.1039/d4sm00603h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2024] [Accepted: 05/31/2024] [Indexed: 06/14/2024]
Abstract
Active colloidal microswimmers serve as archetypical active fluid systems, and as models for biological swimmers. Here, by studying in detail their velocity traces, we find robust power-law intermittency with system-dependent exponential cut off. We model the intermittent motion by an interplay of the field gradient-dependent active force, which depends on a fluid gradient and is reduced when the swimmer moves, and the locally fluctuating hydrodynamic drag, that is set by the wetting properties of the substrate. The model closely describes the velocity distributions of two disparate swimmer systems: AC field activated and catalytic swimmers. The generality is highlighted by the collapse of all data in a single master curve, suggesting the applicability to further systems, both synthetic and biological.
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Affiliation(s)
- Nick Oikonomeas-Koppasis
- Institute of Physics, University of Amsterdam, Science Park 904, P.O. Box 94485, 1090 GL, Amsterdam, The Netherlands.
| | - Stefania Ketzetzi
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Daniela J Kraft
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Peter Schall
- Institute of Physics, University of Amsterdam, Science Park 904, P.O. Box 94485, 1090 GL, Amsterdam, The Netherlands.
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2
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Liu S, Wu Y, Zhao X. A ternary mixture model with dynamic boundary conditions. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2024; 21:2050-2083. [PMID: 38454674 DOI: 10.3934/mbe.2024091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2024]
Abstract
The influence of short-range interactions between a multi-phase, multi-component mixture and a solid wall in confined geometries is crucial in life sciences and engineering. In this work, we extend the Cahn-Hilliard model with dynamic boundary conditions from a binary to a ternary mixture, employing the Onsager principle, which accounts for the cross-coupling between forces and fluxes in both the bulk and surface. Moreover, we have developed a linear, second-order and unconditionally energy-stable numerical scheme for solving the governing equations by utilizing the invariant energy quadratization method. This efficient solver allows us to explore the impacts of wall-mixture interactions and dynamic boundary conditions on phenomena like spontaneous phase separation, coarsening processes and the wettability of droplets on surfaces. We observe that wall-mixture interactions influence not only surface phenomena, such as droplet contact angles, but also patterns deep within the bulk. Additionally, the relaxation rates control the droplet spreading on surfaces. Furthermore, the cross-coupling relaxation rates in the bulk significantly affect coarsening patterns. Our work establishes a comprehensive framework for studying multi-component mixtures in confined geometries.
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Affiliation(s)
- Shuang Liu
- Department of Mathematics, University of North Texas, 1155 Union Circle, Denton, Texas 76203-5017, USA
| | - Yue Wu
- Department of Mathematical Sciences, University of Nottingham Ningbo China, Taikang East Road 199, Ningbo 315100, China
| | - Xueping Zhao
- Department of Mathematical Sciences, University of Nottingham Ningbo China, Taikang East Road 199, Ningbo 315100, China
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3
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Daddi-Moussa-Ider A, Golestanian R, Vilfan A. Minimum entropy production by microswimmers with internal dissipation. Nat Commun 2023; 14:6060. [PMID: 37770449 PMCID: PMC10539332 DOI: 10.1038/s41467-023-41280-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 08/29/2023] [Indexed: 09/30/2023] Open
Abstract
The energy dissipation and entropy production by self-propelled microswimmers differ profoundly from passive particles pulled by external forces. The difference extends both to the shape of the flow around the swimmer, as well as to the internal dissipation of the propulsion mechanism. Here we derive a general theorem that provides an exact lower bound on the total, external and internal, dissipation by a microswimmer. The problems that can be solved include an active surface-propelled droplet, swimmers with an extended propulsive layer and swimmers with an effective internal dissipation. We apply the theorem to determine the swimmer shapes that minimize the total dissipation while keeping the volume constant. Our results show that the entropy production by active microswimmers is subject to different fundamental limits than the entropy production by externally driven particles.
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Affiliation(s)
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS), 37077, Göttingen, Germany
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Andrej Vilfan
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS), 37077, Göttingen, Germany.
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia.
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4
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Ouazan-Reboul V, Golestanian R, Agudo-Canalejo J. Network Effects Lead to Self-Organization in Metabolic Cycles of Self-Repelling Catalysts. PHYSICAL REVIEW LETTERS 2023; 131:128301. [PMID: 37802958 DOI: 10.1103/physrevlett.131.128301] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 07/27/2023] [Indexed: 10/08/2023]
Abstract
Mixtures of particles that interact through phoretic effects are known to aggregate if they belong to species that exhibit attractive self-interactions. We study self-organization in a model metabolic cycle composed of three species of catalytically active particles that are chemotactic toward the chemicals that define their connectivity network. We find that the self-organization can be controlled by the network properties, as exemplified by a case where a collapse instability is achieved by design for self-repelling species. Our findings highlight a possibility for controlling the intricate functions of metabolic networks by taking advantage of the physics of phoretic active matter.
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Affiliation(s)
- Vincent Ouazan-Reboul
- Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Göttingen, Germany
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Göttingen, Germany
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Jaime Agudo-Canalejo
- Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Göttingen, Germany
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5
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Faltas MS, Sherief HH, Ismail MM. Thermophoresis migration of an aerosol spherical particle embedded in a Brinkman medium at small non-zero Péclet numbers. PHYSICS OF FLUIDS 2023; 35. [DOI: 10.1063/5.0160402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
The method of matched asymptotic expansions is used to investigate the problem of thermophoresis migration of an aerosol spherical particle immersed in a porous medium saturated by a viscous fluid at a small non-zero Péclet number Pe. A uniform temperature gradient is imposed on the system parallel to the diameter of the particle in the opposite direction of z axis. It is assumed that the Knudsen number is in the range of the slip fluid flow through the pores of the porous medium and is compatible with the assumption of the continuum model. The porous medium is modeled by the Brinkman equation and is assumed to be homogenous and isotropic, and the solid matrix is in thermal equilibrium with the fluid through the voids of the medium. In the analysis of motion, the thermal stress slip is considered in addition to the temperature jump, the thermal creep, and the frictional slip. The thermophoretic velocity of the particle is obtained in the closed form up to order Pe3 as a function of the thermal properties of the system and the permeability of the porous medium. The present asymptotic analytical solutions can be viewed as an effective method for checking the numerical schemes for future work on arbitrary values of the Péclet number. The limiting case of the thermophoretic velocity for the Stokes clear fluid is recovered.
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Affiliation(s)
- M. S. Faltas
- Department of Mathematics, Faculty of Science, Alexandria University , Baghdad St., Moharam Bek, 21568 Alexandria, Egypt
| | - H. H. Sherief
- Department of Mathematics, Faculty of Science, Alexandria University , Baghdad St., Moharam Bek, 21568 Alexandria, Egypt
| | - M. Mahmoud Ismail
- Department of Mathematics, Faculty of Science, Alexandria University , Baghdad St., Moharam Bek, 21568 Alexandria, Egypt
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6
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Domínguez A, Popescu MN. A fresh view on phoresis and self-phoresis. Curr Opin Colloid Interface Sci 2022. [DOI: 10.1016/j.cocis.2022.101610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Bartolucci G, Adame-Arana O, Zhao X, Weber CA. Controlling composition of coexisting phases via molecular transitions. Biophys J 2021; 120:4682-4697. [PMID: 34600899 DOI: 10.1016/j.bpj.2021.09.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 08/10/2021] [Accepted: 09/27/2021] [Indexed: 12/24/2022] Open
Abstract
Phase separation and transitions among different molecular states are ubiquitous in living cells. Such transitions can be governed by local equilibrium thermodynamics or by active processes controlled by biological fuel. It remains largely unexplored how the behavior of phase-separating systems with molecular transitions differs between thermodynamic equilibrium and cases in which the detailed balance of the molecular transition rates is broken because of the presence of fuel. Here, we present a model of a phase-separating ternary mixture in which two components can convert into each other. At thermodynamic equilibrium, we find that molecular transitions can give rise to a lower dissolution temperature and thus reentrant phase behavior. Moreover, we find a discontinuous thermodynamic phase transition in the composition of the droplet phase if both converting molecules attract themselves with similar interaction strength. Breaking the detailed balance of the molecular transition leads to quasi-discontinuous changes in droplet composition by varying the fuel amount for a larger range of intermolecular interactions. Our findings showcase that phase separation with molecular transitions provides a versatile mechanism to control properties of intracellular and synthetic condensates via discontinuous switches in droplet composition.
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Affiliation(s)
- Giacomo Bartolucci
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany
| | - Omar Adame-Arana
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Xueping Zhao
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany
| | - Christoph A Weber
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany.
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8
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Auschra S, Bregulla A, Kroy K, Cichos F. Thermotaxis of Janus particles. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:90. [PMID: 34218345 PMCID: PMC8254728 DOI: 10.1140/epje/s10189-021-00090-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 06/07/2021] [Indexed: 05/26/2023]
Abstract
The interactions of autonomous microswimmers play an important role for the formation of collective states of motile active matter. We study them in detail for the common microswimmer-design of two-faced Janus spheres with hemispheres made from different materials. Their chemical and physical surface properties may be tailored to fine-tune their mutual attractive, repulsive or aligning behavior. To investigate these effects systematically, we monitor the dynamics of a single gold-capped Janus particle in the external temperature field created by an optically heated metal nanoparticle. We quantify the orientation-dependent repulsion and alignment of the Janus particle and explain it in terms of a simple theoretical model for the induced thermoosmotic surface fluxes. The model reveals that the particle's angular velocity is solely determined by the temperature profile on the equator between the Janus particle's hemispheres and their phoretic mobility contrast. The distortion of the external temperature field by their heterogeneous heat conductivity is moreover shown to break the apparent symmetry of the problem.
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Affiliation(s)
- Sven Auschra
- Institute for Theoretical Physics, Leipzig University, 04103 Leipzig, Germany
| | - Andreas Bregulla
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103 Leipzig, Germany
| | - Klaus Kroy
- Institute for Theoretical Physics, Leipzig University, 04103 Leipzig, Germany
| | - Frank Cichos
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103 Leipzig, Germany
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9
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Wittmann M, Popescu MN, Domínguez A, Simmchen J. Active spheres induce Marangoni flows that drive collective dynamics. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:15. [PMID: 33683489 PMCID: PMC7940161 DOI: 10.1140/epje/s10189-020-00006-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 12/21/2020] [Indexed: 05/26/2023]
Abstract
For monolayers of chemically active particles at a fluid interface, collective dynamics is predicted to arise owing to activity-induced Marangoni flow even if the particles are not self-propelled. Here, we test this prediction by employing a monolayer of spherically symmetric active [Formula: see text] particles located at an oil-water interface with or without addition of a nonionic surfactant. Due to the spherical symmetry, an individual particle does not self-propel. However, the gradients produced by the photochemical fuel degradation give rise to long-ranged Marangoni flows. For the case in which surfactant is added to the system, we indeed observe the emergence of collective motion, with dynamics dependent on the particle coverage of the monolayer. The experimental observations are discussed within the framework of a simple theoretical mean-field model.
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Affiliation(s)
- Martin Wittmann
- Technical University Dresden, Zellescher Weg 19, 01069 Dresden, Germany
| | - Mihail N. Popescu
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany
| | - Alvaro Domínguez
- Física Teórica, Universidad de Sevilla, Apdo. 1065, 41080 Sevilla, Spain
- Instituto Carlos I de Física Teórica y Computacional, 18071 Granada, Spain
| | - Juliane Simmchen
- Technical University Dresden, Zellescher Weg 19, 01069 Dresden, Germany
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10
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Nasouri B, Vilfan A, Golestanian R. Minimum Dissipation Theorem for Microswimmers. PHYSICAL REVIEW LETTERS 2021; 126:034503. [PMID: 33543965 DOI: 10.1103/physrevlett.126.034503] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/23/2020] [Indexed: 06/12/2023]
Abstract
We derive a theorem for the lower bound on the energy dissipation rate by a rigid surface-driven active microswimmer of arbitrary shape in a fluid at a low Reynolds number. We show that, for any swimmer, the minimum dissipation at a given velocity can be expressed in terms of the resistance tensors of two passive bodies of the same shape with a no-slip and perfect-slip boundary. To achieve the absolute minimum dissipation, the optimal swimmer needs a surface velocity profile that corresponds to the flow around the perfect-slip body, and a propulsive force density that corresponds to the no-slip body. Using this theorem, we propose an alternative definition of the energetic efficiency of microswimmers that, unlike the commonly used Lighthill efficiency, can never exceed unity. We validate the theory by calculating the efficiency limits of spheroidal swimmers.
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Affiliation(s)
- Babak Nasouri
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany
| | - Andrej Vilfan
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany
- Jožef Stefan Institute, 1000 Ljubljana, Slovenia
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
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11
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Blanch-Mercader C, Guillamat P, Roux A, Kruse K. Integer topological defects of cell monolayers: Mechanics and flows. Phys Rev E 2021; 103:012405. [PMID: 33601623 DOI: 10.1103/physreve.103.012405] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 12/10/2020] [Indexed: 12/13/2022]
Abstract
Monolayers of anisotropic cells exhibit long-ranged orientational order and topological defects. During the development of organisms, orientational order often influences morphogenetic events. However, the linkage between the mechanics of cell monolayers and topological defects remains largely unexplored. This holds specifically at the timescales relevant for tissue morphogenesis. Here, we build on the physics of liquid crystals to determine material parameters of cell monolayers. In particular, we use a hydrodynamical description of an active polar fluid to study the steady-state mechanical patterns at integer topological defects. Our description includes three distinct sources of activity: traction forces accounting for cell-substrate interactions as well as anisotropic and isotropic active nematic stresses accounting for cell-cell interactions. We apply our approach to C2C12 cell monolayers in small circular confinements, which form isolated aster or spiral topological defects. By analyzing the velocity and orientational order fields in spirals as well as the forces and cell number density fields in asters, we determine mechanical parameters of C2C12 cell monolayers. Our work shows how topological defects can be used to fully characterize the mechanical properties of biological active matter.
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Affiliation(s)
- Carles Blanch-Mercader
- Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland
- Department of Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland
| | - Pau Guillamat
- Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland
| | - Aurélien Roux
- Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland
| | - Karsten Kruse
- Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland
- Department of Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland
- NCCR Chemical Biology, University of Geneva, 1211 Geneva, Switzerland
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12
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Popescu MN. Chemically Active Particles: From One to Few on the Way to Many. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6861-6870. [PMID: 32233489 PMCID: PMC7331135 DOI: 10.1021/acs.langmuir.9b03973] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 04/01/2020] [Indexed: 06/01/2023]
Abstract
Chemically active particles suspended in a liquid solution can achieve self-motility by locally changing the chemical composition of the solution via catalytic reactions at their surfaces. They operate intrinsically out of equilibrium, continuously extracting free energy from the environment to power the dissipative self-motility. The effective interactions involving active particles are, in general, nonreciprocal and anisotropic, even if the particles have simple shapes (e.g., Janus spheres). Accordingly, for chemically active particles a very rich behavior of collective motion and self-assembly may be expected to emerge, including phenomena such as microphase separation in the form of kinetically stable, finite-sized aggregates. Here, I succinctly review a number of recent experimental studies that demonstrate the self-assembly of structures, involving chemically active Janus particles, which exhibit various patterns of motion. These examples illustrate concepts such as "motors made out of motors" (as suggestively named by Fischer [Fischer, P. Nat. Phys. 2018, 14, 1072]). The dynamics of assembly and structure formation observed in these systems can provide benchmark, in-depth testing of the current understanding of motion and effective interactions produced by chemical activity. Finally, one notes that these significant achievements are likely just the beginning of the field. Recently reported particles endowed with time-dependent chemical activity or switchable reaction mechanisms open the way for exciting developments, such as periodic reshaping of self-assembled structures based on man-made internal clocks.
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13
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Wu X, Xue X, Wang J, Liu H. Phototropic Aggregation and Light-Guided Long-Distance Collective Transport of Colloidal Particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6819-6827. [PMID: 32476425 DOI: 10.1021/acs.langmuir.0c01244] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Phoretic swarming and collective transport of colloidal particles in response to environmental stimuli have attracted tremendous interest in a variety of fields. In this work, we investigate the light-actuated motion, aggregation, and light-guided long-distance mass transport of silica microspheres in simple spiropyran solutions under the illumination of UV spot sources. The phototactic motion is confirmed by the dependence of swarming on the illumination intensity and spiropyran concentrations, ON-OFF switching tests, pattern-masked UV sources, etc. The aggregates formed via swarming of silica spheres can chase after a moving UV source, however, relying on a critical speed of the UV source. Only when the UV source speed is below the critical value, the aggregates follow the UV spot at a constant relative speed to the light spot. Analysis on the shape of silica microsphere currents indicates that continuous illumination of the UV spot source and resultant chemical gradients are important for the formation of steady microsphere currents. Light-guided aggregation and long-distance mass transport are interesting for targeted delivery and remote-controlled enrichment of environmental hazards.
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Affiliation(s)
- Xiaoran Wu
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Jinzhai Road 96, Hefei, Anhui 230026, China
| | - Xiang Xue
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Jinzhai Road 96, Hefei, Anhui 230026, China
| | - Jinghang Wang
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Jinzhai Road 96, Hefei, Anhui 230026, China
| | - Hewen Liu
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Jinzhai Road 96, Hefei, Anhui 230026, China
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14
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Eloul S, Poon WCK, Farago O, Frenkel D. Reactive Momentum Transfer Contributes to the Self-Propulsion of Janus Particles. PHYSICAL REVIEW LETTERS 2020; 124:188001. [PMID: 32441974 DOI: 10.1103/physrevlett.124.188001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
We report simulations of a spherical Janus particle undergoing exothermic surface reactions around one pole only. Our model excludes self-phoretic transport by design. Nevertheless, net motion occurs from direct momentum transfer between solvent and colloid, with speed scaling as the square root of the energy released during the reaction. We find that such propulsion is dominated by the system's short-time response, when neither the time dependence of the flow around the colloid nor the solvent compressibility can be ignored. Our simulations agree reasonably well with previous experiments.
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Affiliation(s)
- Shaltiel Eloul
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Wilson C K Poon
- SUPA and School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - Oded Farago
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
- Biomedical Engineering Department, Ben Gurion University, Be'er Sheva 84105, Israel
| | - Daan Frenkel
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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15
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Nasouri B, Golestanian R. Exact Phoretic Interaction of Two Chemically Active Particles. PHYSICAL REVIEW LETTERS 2020; 124:168003. [PMID: 32383912 DOI: 10.1103/physrevlett.124.168003] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
We study the nonequilibrium interaction of two isotropic chemically active particles taking into account the exact near-field chemical interactions as well as hydrodynamic interactions. We identify regions in the parameter space wherein the dynamical system describing the two particles can have a fixed point-a phenomenon that cannot be captured under the far-field approximation. We find that, due to near-field effects, the particles may reach a stable equilibrium at a nonzero gap size or make a complex that can dissociate in the presence of sufficiently strong noise. We explicitly show that the near-field effects originate from a self-generated neighbor-reflected chemical gradient, similar to interactions of a self-propelling phoretic particle and a flat substrate.
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Affiliation(s)
- Babak Nasouri
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Goettingen, Germany
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Goettingen, Germany
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
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16
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Clarke N, Gibbions N, Long DR. Diffusio-osmosis and wetting on solid surfaces: a unified description based on a virtual work principle. SOFT MATTER 2020; 16:3485-3497. [PMID: 32211702 DOI: 10.1039/c9sm02118c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In order to account for diffusio-osmosis, Derjaguin proposed long ago that there is an excess pressure confined within a layer of typically a few nanometers in the vicinity of a solid surface immersed in a liquid and resulting from the interaction between the liquid and the surface. In the presence of a composition gradient in the liquid a confined pressure gradient parallel to the surface is therefore responsible for the diffusio-osmotic flow. This picture appears in contradiction with the contact theorem of colloidal science according to which such excess pressure does not exist. We propose a theoretical description for calculating hydrodynamic flows in inhomogeneous liquids in the vicinity of solid interfaces which is consistent with the contact theorem. This approach is based on a Gibbs free energy and a virtual work principle for calculating the driving forces in the liquid due to inhomogeneous composition along a capillary and to the interaction with the solid interfaces. Our approach allows us to show that the physics at play is the same in wetting or in diffusio-osmosis experiments, as one can go continuously from the latter to the former by making composition gradients sharper. We obtain an explicit expression for the diffusio-osmotic mobility which depends on the Gibbs free energy density in the vicinity of the interface and its dependance on the solute concentration in the liquid beyond the interfacial region, and which is inversely proportional to the liquid viscosity.
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Affiliation(s)
- Nigel Clarke
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
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17
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Peter T, Malgaretti P, Rivas N, Scagliarini A, Harting J, Dietrich S. Numerical simulations of self-diffusiophoretic colloids at fluid interfaces. SOFT MATTER 2020; 16:3536-3547. [PMID: 32215402 DOI: 10.1039/c9sm02247c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The dynamics of active colloids is very sensitive to the presence of boundaries and interfaces which therefore can be used to control their motion. Here we analyze the dynamics of active colloids adsorbed at a fluid-fluid interface. By using a mesoscopic numerical approach which relies on an approximated numerical solution of the Navier-Stokes equation, we show that when adsorbed at a fluid interface, an active colloid experiences a net torque even in the absence of a viscosity contrast between the two adjacent fluids. In particular, we study the dependence of this torque on the contact angle of the colloid with the fluid-fluid interface and on its surface properties. We rationalize our results via an approximate approach which accounts for the appearance of a local friction coefficient. By providing insight into the dynamics of active colloids adsorbed at fluid interfaces, our results are relevant for two-dimensional self assembly and emulsion stabilization by means of active colloids.
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Affiliation(s)
- T Peter
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany.
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19
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Campbell AI, Ebbens SJ, Illien P, Golestanian R. Experimental observation of flow fields around active Janus spheres. Nat Commun 2019; 10:3952. [PMID: 31477703 PMCID: PMC6718378 DOI: 10.1038/s41467-019-11842-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 07/30/2019] [Indexed: 12/13/2022] Open
Abstract
The phoretic mechanisms at stake in the propulsion of asymmetric colloids have been the subject of debates during the past years. In particular, the importance of electrokinetic effects on the motility of Pt-PS Janus sphere was recently discussed. Here, we probe the hydrodynamic flow field around a catalytically active colloid using particle tracking velocimetry both in the freely swimming state and when kept stationary with an external force. Our measurements provide information about the fluid velocity in the vicinity of the surface of the colloid, and confirm a mechanism for propulsion that was proposed recently. In addition to offering a unified understanding of the nonequilibrium interfacial transport processes at stake, our results open the way to a thorough description of the hydrodynamic interactions between such active particles and understanding their collective dynamics.
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Affiliation(s)
- Andrew I Campbell
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK
| | - Stephen J Ebbens
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK.
| | - Pierre Illien
- Sorbonne Université, CNRS, Laboratoire PHENIX, 4 place Jussieu, 75005, Paris, France
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077, Göttingen, Germany. .,Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, OX1 3PU, UK.
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20
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Michelin S, Lauga E. Universal optimal geometry of minimal phoretic pumps. Sci Rep 2019; 9:10788. [PMID: 31346194 PMCID: PMC6658517 DOI: 10.1038/s41598-019-46953-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 07/05/2019] [Indexed: 11/16/2022] Open
Abstract
Unlike pressure-driven flows, surface-mediated phoretic flows provide efficient means to drive fluid motion on very small scales. Colloidal particles covered with chemically-active patches with nonzero phoretic mobility (e.g. Janus particles) swim using self-generated gradients, and similar physics can be exploited to create phoretic pumps. Here we analyse in detail the design principles of phoretic pumps and show that for a minimal phoretic pump, consisting of 3 distinct chemical patches, the optimal arrangement of the patches maximizing the flow rate is universal and independent of chemistry.
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Affiliation(s)
- Sébastien Michelin
- LadHyX - Département de Mécanique, Ecole Polytechnique - CNRS, Institut Polytechnique de Paris, 91128, Palaiseau, France.
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom.
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21
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Weber CA, Zwicker D, Jülicher F, Lee CF. Physics of active emulsions. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:064601. [PMID: 30731446 DOI: 10.1088/1361-6633/ab052b] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phase separating systems that are maintained away from thermodynamic equilibrium via molecular processes represent a class of active systems, which we call active emulsions. These systems are driven by external energy input, for example provided by an external fuel reservoir. The external energy input gives rise to novel phenomena that are not present in passive systems. For instance, concentration gradients can spatially organise emulsions and cause novel droplet size distributions. Another example are active droplets that are subject to chemical reactions such that their nucleation and size can be controlled, and they can divide spontaneously. In this review, we discuss the physics of phase separation and emulsions and show how the concepts that govern such phenomena can be extended to capture the physics of active emulsions. This physics is relevant to the spatial organisation of the biochemistry in living cells, for the development of novel applications in chemical engineering and models for the origin of life.
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Affiliation(s)
- Christoph A Weber
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany. Center for Systems Biology Dresden, CSBD, Dresden, Germany. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States of America
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22
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Abstract
We investigate the self-propulsive motion of a drop containing an active polar field. The drop demonstrates spontaneous symmetry breaking from a uniform orientational order into a splay or bend instability depending on the types of active stress, namely, contractile or extensile, respectively. We develop an analytical theory of the mechanism of this instability, which has been observed only in numerical simulations. We show that both contractile and extensile active stresses result in the instability and self-propulsive motion. We also discuss asymmetry between contractile and extensile stresses and show that extensile active stress generates chaotic motion even under a simple model of the polarity field coupled with motion and deformation of the drop.
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Affiliation(s)
- Natsuhiko Yoshinaga
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and MathAM-OIL, AIST, Sendai 980-8577, Japan
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23
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Alert R, Blanch-Mercader C, Casademunt J. Active Fingering Instability in Tissue Spreading. PHYSICAL REVIEW LETTERS 2019; 122:088104. [PMID: 30932560 DOI: 10.1103/physrevlett.122.088104] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Indexed: 05/13/2023]
Abstract
During the spreading of epithelial tissues, the advancing tissue front often develops fingerlike protrusions. Their resemblance to traditional viscous fingering patterns in driven fluids suggests that epithelial fingers could arise from an interfacial instability. However, the existence and physical mechanism of such a putative instability remain unclear. Here, based on an active polar fluid model for epithelial spreading, we analytically predict a generic instability of the tissue front. On the one hand, active cellular traction forces impose a velocity gradient that leads to an accelerated front, which is, thus, unstable to long-wavelength perturbations. On the other hand, contractile intercellular stresses typically dominate over surface tension in stabilizing short-wavelength perturbations. Finally, the finite range of hydrodynamic interactions in the tissue selects a wavelength for the fingering pattern, which is, thus, given by the smallest between the tissue size and the hydrodynamic screening length. Overall, we show that spreading epithelia experience an active fingering instability based on a simple kinematic mechanism. Moreover, our results underscore the crucial role of long-range hydrodynamic interactions in the dynamics of tissue morphology.
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Affiliation(s)
- Ricard Alert
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Avinguda Diagonal 647, 08028 Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Carles Blanch-Mercader
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, 26 rue d'Ulm, 75005 Paris, France
- Department of Biochemistry, Faculty of Sciences, University of Geneva, 30, Quai Ernest-Ansermet, 1205 Genève, Switzerland
| | - Jaume Casademunt
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Avinguda Diagonal 647, 08028 Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Spain
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24
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Miloh T. Light-induced thermoosmosis about conducting ellipsoidal nanoparticles. Proc Math Phys Eng Sci 2019. [DOI: 10.1098/rspa.2018.0040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We consider the central problem of a non-spherical (ellipsoidal) polarizable (metallic) nanoparticle freely suspended in a conducting liquid phase which is irradiated (heated) by a laser under the Rayleigh (electrostatic) approximation. It is shown that, unlike the case of perfectly symmetric (spherical) particles, the surface temperature of general orthotropic particles exposed to continuous laser irradiation is
not uniform!
Thus, the induced surface slip (Soret type) velocity may lead to a self-induced thermoosmotic flow (sTOF) about the particle, in a similar manner to the electroosmotic flow driven by the Helmholtz—Smoluchowski slippage. Using the recent advancement in the theory of Lamé functions and ellipsoidal harmonics, we analytically present new solutions for two key physical problems. (i) Heat conduction and temperature distribution inside and outside a conducting laser-irradiated homogeneous tri-axial ellipsoid which is subjected to uniform Joule heating. (ii) Creeping (Stokes) sTOF around a fixed impermeable metallic ellipsoidal nanoparticle driven by a Soret-type surface slip velocity (i.e. proportional to the surface-temperature gradient).
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Affiliation(s)
- Touvia Miloh
- School of Mechanical Engineering, University of Tel-Aviv, Tel-Aviv 69978, Israel
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25
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Abstract
Despite mounting evidence that the same gradients, which active colloids use for swimming, induce important cross-interactions (phoretic interactions), they are still ignored in most many-body descriptions, perhaps to avoid complexity and a zoo of unknown parameters. Here we derive a simple model, which reduces phoretic far-field interactions to a pair-interaction whose strength is mainly controlled by one genuine parameter (swimming speed). The model suggests that phoretic interactions are generically important for autophoretic colloids (unless effective screening of the phoretic fields is strong) and should dominate over hydrodynamic interactions for the typical case of half-coating and moderately nonuniform surface mobilities. Unlike standard minimal models, but in accordance with canonical experiments, our model generically predicts dynamic clustering in active colloids at a low density. This suggests that dynamic clustering can emerge from the interplay of screened phoretic attractions and active diffusion.
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Affiliation(s)
- Benno Liebchen
- 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
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26
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Seki T, Okuzono T, Toyotama A, Yamanaka J. Mechanism of diffusiophoresis with chemical reaction on a colloidal particle. Phys Rev E 2019; 99:012608. [PMID: 30780366 DOI: 10.1103/physreve.99.012608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Indexed: 11/07/2022]
Abstract
A mechanism for diffusiophoresis of a charged colloidal particle undergoing surface chemical reaction is proposed. A theoretical model is constructed to describe the dynamics of the particle and the surrounding solution of a weak electrolyte. Theoretical analysis and numerical simulations of the model reveal that phoretic motion of the particle emerges in response to a concentration gradient of electrolyte. The concentration gradient breaks the spherical symmetry of the surface charge distribution, which gives rise to a net force on the particle and leads to directional motion of the particle.
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Affiliation(s)
- Tomotaka Seki
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Tohru Okuzono
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Akiko Toyotama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
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27
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Kanso E, Michelin S. Phoretic and hydrodynamic interactions of weakly confined autophoretic particles. J Chem Phys 2019; 150:044902. [DOI: 10.1063/1.5065656] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Affiliation(s)
- Eva Kanso
- Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California 90089-1191, USA
| | - Sébastien Michelin
- LadHyX—Département de Mécanique, Ecole Polytechnique—CNRS, 91128 Palaiseau, France
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28
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Morozov M, Michelin S. Nonlinear dynamics of a chemically-active drop: From steady to chaotic self-propulsion. J Chem Phys 2019; 150:044110. [DOI: 10.1063/1.5080539] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Matvey Morozov
- LadHyX—Département de Mécanique, École Polytechnique—CNRS, 91128 Palaiseau Cedex, France
| | - Sébastien Michelin
- LadHyX—Département de Mécanique, École Polytechnique—CNRS, 91128 Palaiseau Cedex, France
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29
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Popescu MN, Uspal WE, Domínguez A, Dietrich S. Effective Interactions between Chemically Active Colloids and Interfaces. Acc Chem Res 2018; 51:2991-2997. [PMID: 30403132 DOI: 10.1021/acs.accounts.8b00237] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chemically active colloids can achieve force- and torque-free motility ("self-propulsion") via the promotion, on their surface, of catalytic chemical reactions involving the surrounding solution. Such systems are valuable both from a theoretical perspective, serving as paradigms for nonequilibrium processes, as well as from an application viewpoint, according to which active colloids are envisioned to play the role of carriers ("engines") in novel lab-on-a-chip devices. The motion of such colloids is intrinsically connected with a "chemical field", i.e., the distribution near the colloid of the number densities of the various chemical species present in the solution, and with the hydrodynamic flow of the solution around the particle. In most of the envisioned applications, and in virtually all reported experimental studies, the active colloids operate under spatial confinement (e.g., within a microfluidic channel, a drop, a free-standing liquid film, etc.). In such cases, the chemical field and the hydrodynamic flow associated with an active colloid are influenced by any nearby confining surfaces, and these disturbances couple back to the particle. Thus, an effective interaction with the spatial confinement arises. Consequently, the particle is endowed with means to perceive and to respond to its environment. Understanding these effective interactions, finding the key parameters which control them, and designing particles with desired, preconfigured responses to given environments, require interdisciplinary approaches which synergistically integrate methods and knowledge from physics, chemistry, engineering, and materials science. Here we review how, via simple models of chemical activity and self-phoretic motion, progress has recently been made in understanding the basic physical principles behind the complex behaviors exhibited by active particles near interfaces. First, we consider the occurrence of "interface-bounded" steady states of chemically active colloids near simple, nonresponsive interfaces. Examples include particles "sliding" along, or "hovering" above, a hard planar wall while inducing hydrodynamic flow of the solution. These states lay the foundations for concepts like the guidance of particles by the topography of the wall. We continue to discuss responsive interfaces: a suitable chemical patterning of a planar wall allows one to bring the particles into states of motion which are spatially localized (e.g., within chemical stripes or along chemical steps). These occur due to the wall responding to the activity-induced chemical gradients by generating osmotic flows, which encode the surface-chemistry of the wall. Finally, we discuss how, via activity-induced Marangoni stresses, long-ranged effective interactions emerge from the strong hydrodynamic response of fluid interfaces. These examples highlight how in this context a desired behavior can be potentially selected by tuning suitable parameters (e.g., the phoretic mobility of the particle, or the strength of the Marangoni stress at an interface). This can be accomplished via a judicious design of the surface chemistry of the particle and of the boundary, or by the choice of the chemical reaction in solution.
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Affiliation(s)
- Mihail N. Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - William E. Uspal
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - Alvaro Domínguez
- Física Teórica, Universidad de Sevilla, Apdo. 1065, 41080 Sevilla, Spain
| | - Siegfried Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
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30
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Popescu MN, Uspal WE, Eskandari Z, Tasinkevych M, Dietrich S. Effective squirmer models for self-phoretic chemically active spherical colloids. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:145. [PMID: 30569319 DOI: 10.1140/epje/i2018-11753-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 11/09/2018] [Indexed: 05/10/2023]
Abstract
Various aspects of self-motility of chemically active colloids in Newtonian fluids can be captured by simple models for their chemical activity plus a phoretic-slip hydrodynamic boundary condition on their surface. For particles of simple shapes (e.g., spheres) --as employed in many experimental studies-- which move at very low Reynolds numbers in an unbounded fluid, such models of chemically active particles effectively map onto the well studied so-called hydrodynamic squirmers (S. Michelin and E. Lauga, J. Fluid Mech. 747, 572 (2014)). Accordingly, intuitively appealing analogies of "pusher/puller/neutral" squirmers arise naturally. Within the framework of self-diffusiophoresis we illustrate the above-mentioned mapping and the corresponding flows in an unbounded fluid for a number of choices of the activity function (i.e., the spatial distribution and the type of chemical reactions across the surface of the particle). We use the central collision of two active particles as a simple, paradigmatic case for demonstrating that in the presence of other particles or boundaries the behavior of chemically active colloids may be qualitatively different, even in the far field, from the one exhibited by the corresponding "effective squirmer", obtained from the mapping in an unbounded fluid. This emphasizes that understanding the collective behavior and the dynamics under geometrical confinement of chemically active particles necessarily requires to explicitly account for the dependence of the hydrodynamic interactions on the distribution of chemical species resulting from the activity of the particles.
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Affiliation(s)
- M N Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany.
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany.
| | - W E Uspal
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany
| | - Z Eskandari
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany
| | - M Tasinkevych
- Centro de Física Teórica e Computacional, Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, P-1749-016, Lisboa, Portugal
| | - S Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany
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31
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Robertson B, Huang MJ, Chen JX, Kapral R. Synthetic Nanomotors: Working Together through Chemistry. Acc Chem Res 2018; 51:2355-2364. [PMID: 30207448 DOI: 10.1021/acs.accounts.8b00239] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Active matter, some of whose constituent elements are active agents that can move autonomously, behaves very differently from matter without such agents. The active agents can self-assemble into structures with a variety of forms and dynamical properties. Swarming, where groups of living agents move cooperatively, is commonly observed in the biological realm, but it is also seen in the physical realm in systems containing small synthetic motors. The existence of diverse forms of self-assembled structures has stimulated the search for new applications that involve active matter. We consider active systems where the agents are synthetic chemically powered motors with various shapes and sizes that operate by phoretic mechanisms, especially self-diffusiophoresis. These motors are able to move autonomously in solution by consuming fuel from their environment. Chemical reactions take place on catalytic portions of the motor surface and give rise to concentration gradients that lead to directed motion. They can operate in this way only if the chemical composition of the system is maintained in a nonequilibrium state since no net fluxes are possible in a system at equilibrium. In contrast to many other active systems, chemistry plays an essential part in determining the properties of the collective dynamics and self-assembly of these chemically powered motor systems. The inhomogeneous concentration fields that result from asymmetric motor reactions are felt by other motors in the system and strongly influence how they move. This chemical coupling effect often dominates other interactions due to fluid flow fields and direct interactions among motors and determines the form that the collective dynamics takes. Since we consider small motors with micrometer and nanometer sizes, thermal fluctuations are strong and cannot be neglected. The media in which the motors operate may not be simple and may contain crowding agents or molecular filaments that influence how the motors assemble and move. The collective motion is also influenced by the chemical gradients that arise from reactions in the surrounding medium. By adopting a microscopic perspective, where the motors, fluid environment, and crowding elements are treated at the coarse-grained molecular level, all of the many-body interactions that give rise to the collective behavior naturally emerge from the molecular dynamics. Through simulations and theory, this Account describes how active matter made from chemically powered nanomotors moving in simple and more complicated media can form different dynamical structures that are strongly influenced by interactions arising from cooperative chemical reactions on the motor surfaces.
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Affiliation(s)
- Bryan Robertson
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Mu-Jie Huang
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Jiang-Xing Chen
- Department of Physics, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Raymond Kapral
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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32
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Domínguez A, Popescu MN. Phase coexistence in a monolayer of active particles induced by Marangoni flows. SOFT MATTER 2018; 14:8017-8029. [PMID: 30246847 DOI: 10.1039/c8sm00688a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Thermally or chemically active colloids generate thermodynamic gradients in the solution in which they are immersed and thereby induce hydrodynamic flows that affect their dynamical evolution. Here we study a mean-field model for the many-body dynamics of a monolayer of spherically symmetric active particles located at a fluid-fluid interface. Due to the spherical symmetry, the particles do not self-propel. Instead, the dynamics is driven by the long-ranged Marangoni flows, due to the response of the interface to the activity of the particles, which compete with the direct interaction between particles. We demonstrate analytically that, in spite of the intrinsic out-of-equilibrium character of the system, the monolayer evolves to a "pseudoequilibrium" state, in which the Marangoni flows force the coexistence of the thermodynamic phases associated to the direct interaction. In particular, we study the most interesting case of a r-3 soft repulsion that models electrostatic or magnetic interparticle forces. For a sufficiently large average density, two-dimensional phase transitions (freezing from liquid to hexatic, and melting from solid to hexatic) should be observable in a radially stratified, "onion-like" structure within the monolayer. Furthermore, the analysis allows us to conclude that, while the activity may be too weak to allow direct detection of such induced Marangoni flows, it is relevant as a collective effect in the emergence of the experimentally observable spatial structure of phase coexistences noted above. Finally, the relevance of these results for potential experimental realizations is critically discussed.
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Affiliation(s)
- Alvaro Domínguez
- Física Teórica, Universidad de Sevilla, Apdo. 1065, E-41080 Sevilla, Spain.
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33
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Friedrich BM. Load response of shape-changing microswimmers scales with their swimming efficiency. Phys Rev E 2018; 97:042416. [PMID: 29758744 DOI: 10.1103/physreve.97.042416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Indexed: 12/15/2022]
Abstract
External forces acting on a microswimmer can feed back on its self-propulsion mechanism. We discuss this load response for a generic microswimmer that swims by cyclic shape changes. We show that the change in cycle frequency is proportional to the Lighthill efficiency of self-propulsion. As a specific example, we consider Najafi's three-sphere swimmer. The force-velocity relation of a microswimmer implies a correction for a formal superposition principle for active and passive motion.
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34
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Varma A, Montenegro-Johnson TD, Michelin S. Clustering-induced self-propulsion of isotropic autophoretic particles. SOFT MATTER 2018; 14:7155-7173. [PMID: 30058650 PMCID: PMC6136269 DOI: 10.1039/c8sm00690c] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 06/07/2018] [Indexed: 05/25/2023]
Abstract
Self-diffusiophoretic particles exploit local concentration gradients of a solute species in order to self-propel at the micron scale. While an isolated chemically- and geometrically-isotropic particle cannot swim, we show that it can achieve self-propulsion through interactions with other individually-non-motile particles by forming geometrically-anisotropic clusters via phoretic and hydrodynamic interactions. This result identifies a new route to symmetry-breaking for the concentration field and to self-propulsion, that is not based on an anisotropic design, but on the collective dynamics of identical and homogeneous active particles. Using full numerical simulations as well as theoretical modelling of the clustering process, the statistics of the propulsion properties are obtained for arbitrary initial arrangement of the particles. The robustness of these results to thermal noise, and more generally the effect of Brownian motion of the particles, is also discussed.
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Affiliation(s)
- Akhil Varma
- LadHyX – Département de Mécanique
, Ecole Polytechnique – CNRS
,
91128 Palaiseau
, France
.
;
| | | | - Sébastien Michelin
- LadHyX – Département de Mécanique
, Ecole Polytechnique – CNRS
,
91128 Palaiseau
, France
.
;
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35
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Malgaretti P, Popescu MN, Dietrich S. Self-diffusiophoresis induced by fluid interfaces. SOFT MATTER 2018; 14:1375-1388. [PMID: 29383367 DOI: 10.1039/c7sm02347b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The influence of a fluid-fluid interface on self-phoresis of chemically active, axially symmetric, spherical colloids is analyzed. Distinct from the studies of self-phoresis for colloids trapped at fluid interfaces or in the vicinity of hard walls, here we focus on the issue of self-phoresis close to a fluid-fluid interface. In order to provide physically intuitive results highlighting the role played by the interface, the analysis is carried out for the case that the symmetry axis of the colloid is normal to the interface; moreover, thermal fluctuations are not taken into account. Similarly to what has been observed near hard walls, we find that such colloids can be set into motion even if their whole surface is homogeneously active. This is due to the anisotropy along the direction normal to the interface owing to the partitioning by diffusion, among the coexisting fluid phases, of the product of the chemical reaction taking place at the colloid surface. Different from results corresponding to hard walls, in the case of a fluid interface the direction of motion, i.e., towards the interface or away from it, can be controlled by tuning the physical properties of one of the two fluid phases. This effect is analyzed qualitatively and quantitatively, both by resorting to a far-field approximation and via an exact, analytical calculation which provides the means for a critical assessment of the approximate analysis.
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Affiliation(s)
- P Malgaretti
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
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36
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Blanch-Mercader C, Casademunt J. Hydrodynamic instabilities, waves and turbulence in spreading epithelia. SOFT MATTER 2017; 13:6913-6928. [PMID: 28825077 DOI: 10.1039/c7sm01128h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We present a hydrodynamic model of spreading epithelial monolayers described as polar viscous fluids, with active contractility and traction on a substrate. The combination of both active forces generates an instability that leads to nonlinear traveling waves, which propagate in the direction of polarity with characteristic time scales that depend on contact forces. Our viscous fluid model provides a comprehensive understanding of a variety of observations on the slow dynamics of epithelial monolayers, remarkably those that seemed to be characteristic of elastic media. The model also makes simple predictions to test the non-elastic nature of the mechanical waves, and provides new insights into collective cell dynamics, explaining plithotaxis as a result of strong flow-polarity coupling, and quantifying the non-locality of force transmission. In addition, we study the nonlinear regime of waves deriving an exact map of the model into the complex Ginzburg-Landau equation, which provides a complete classification of possible nonlinear scenarios. In particular, we predict the transition to different forms of weak turbulence, which in turn could explain the chaotic dynamics often observed in epithelia.
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Affiliation(s)
- C Blanch-Mercader
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain. and Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, 26 rue d' Ulm, 75005 Paris, France
| | - J Casademunt
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain. and Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, Barcelona, Spain
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37
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Desai N, Ardekani AM. Modeling of active swimmer suspensions and their interactions with the environment. SOFT MATTER 2017; 13:6033-6050. [PMID: 28884775 DOI: 10.1039/c7sm00766c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this article, we review mathematical models used to study the behaviour of suspensions of micro-swimmers and the accompanying biophysical phenomena, with specific focus on stimulus response. The methods discussed encompass a range of interactions exhibited by the micro-swimmers; including passive hydrodynamic (gyrotaxis) and gravitational (gravitaxis) effects, and active responses to chemical cues (chemotaxis) and light intensities (phototaxis). We introduce the simplest models first, and then build towards more sophisticated recent developments, in the process, identifying the limitations of the former and the new results obtained by the latter. We comment on the accuracy/validity of the models adopted, based on the agreement between theoretical results and experimental observations. We conclude by identifying some of the open problems and associated challenges faced by researchers in the realm of active suspensions.
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Affiliation(s)
- Nikhil Desai
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA.
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38
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Shen T, Vernerey F. Phoretic motion of soft vesicles and droplets: an XFEM/particle-based numerical solution. COMPUTATIONAL MECHANICS 2017; 60:143-161. [PMID: 29200544 PMCID: PMC5708599 DOI: 10.1007/s00466-017-1399-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 03/05/2017] [Indexed: 06/07/2023]
Abstract
When immersed in solution, surface-active particles interact with solute molecules and migrate along gradients of solute concentration. Depending on the conditions, this phenomenon could arise from either diffusiophoresis or the Marangoni effect, both of which involve strong interactions between the fluid and the particle surface. We introduce here a numerical approach that can accurately capture these interactions, and thus provide an efficient tool to understand and characterize the phoresis of soft particles. The model is based on a combination of the extended finite element-that enable the consideration of various discontinuities across the particle surface-and the particle-based moving interface method-that is used to measure and update the interface deformation in time. In addition to validating the approach with analytical solutions, the model is used to study the motion of deformable vesicles in solutions with spatial variations in both solute concentration and temperature.
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Affiliation(s)
- Tong Shen
- Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, Boulder, CO 80309-0427, USA
| | - Franck Vernerey
- Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, Boulder, CO 80309-0427, USA
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39
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Popescu MN, Uspal WE, Dietrich S. Chemically active colloids near osmotic-responsive walls with surface-chemistry gradients. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:134001. [PMID: 28140364 DOI: 10.1088/1361-648x/aa5bf1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Chemically active colloids move by creating gradients in the composition of the surrounding solution and by exploiting the differences in their interactions with the various molecular species in solution. If such particles move near boundaries, e.g. the walls of the container confining the suspension, gradients in the composition of the solution are also created along the wall. This give rise to chemi-osmosis (via the interactions of the wall with the molecular species forming the solution), which drives flows coupling back to the colloid and thus influences its motility. Employing an approximate 'point-particle' analysis, we show analytically that-owing to this kind of induced active response (chemi-osmosis) of the wall-such chemically active colloids can align with, and follow, gradients in the surface chemistry of the wall. In this sense, these artificial 'swimmers' exhibit a primitive form of thigmotaxis with the meaning of sensing the proximity of a (not necessarily discontinuous) physical change in the environment. We show that the alignment with the surface-chemistry gradient is generic for chemically active colloids as long as they exhibit motility in an unbounded fluid, i.e. this phenomenon does not depend on the exact details of the propulsion mechanism. The results are discussed in the context of simple models of chemical activity, corresponding to Janus particles with 'source' chemical reactions on one half of the surface and either 'inert' or 'sink' reactions over the other half.
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Affiliation(s)
- M N Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany. IV Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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40
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Popescu MN, Uspal WE, Tasinkevych M, Dietrich S. Perils of ad hoc approximations for the activity function of chemically powered colloids. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2017; 40:42. [PMID: 28389824 DOI: 10.1140/epje/i2017-11529-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 03/13/2017] [Indexed: 06/07/2023]
Abstract
Colloids can achieve motility by promoting at their surfaces chemical reactions in the surrounding solution. A well-studied case is that of self-phoresis, in which motility arises due to the spatial inhomogeneities in the chemical composition of the solution and the distinct interactions of the solvent molecules and of the reaction products with the colloid. For simple models of such chemically active colloids, the steady-state motion in an unbounded solution can be derived analytically in closed form. In contrast, for such chemically active particles moving in the vicinity of walls, the derivation of closed-form and physically intuitive solutions of the equations governing their dynamics turns out to be a severe challenge even for simple models. Therefore, recent studies of these phenomena have employed numerical methods as well as approximate analytical approaches based on multipolar expansions. We discuss and clarify certain conceptual aspects concerning the latter type of approach, which arise due to ad hoc truncations of the underlying so-called activity function, which describes the distribution of chemical reactions across the surface of the particle.
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Affiliation(s)
- M N Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany.
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany.
| | - W E Uspal
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany
| | - M Tasinkevych
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany
| | - S Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569, Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569, Stuttgart, Germany
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41
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Chen T, Xu C. Control-oriented modeling of colloid transport by solute gradients in dead-end channels. ASIA-PAC J CHEM ENG 2017. [DOI: 10.1002/apj.2068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Tehuan Chen
- Faculty of Mechanical Engineering and Mechanics; Ningbo University; Ningbo Zhejiang 315211 China
- State Key Laboratory of Industrial Control Technology; Zhejiang University; Hangzhou Zhejiang 310027 China
| | - Chao Xu
- State Key Laboratory of Industrial Control Technology; Zhejiang University; Hangzhou Zhejiang 310027 China
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42
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Fan WTL, Pak OS, Sandoval M. Ellipsoidal Brownian self-driven particles in a magnetic field. Phys Rev E 2017; 95:032605. [PMID: 28415285 DOI: 10.1103/physreve.95.032605] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Indexed: 06/07/2023]
Abstract
We study the two-dimensional Brownian dynamics of an ellipsoidal paramagnetic microswimmer moving at a low Reynolds number and subject to a magnetic field. Its corresponding mean-square displacement, showing the effect of a particles's shape, activity, and magnetic field on the microswimmer's diffusion, is analytically obtained. Comparison between analytical and computational results shows good agreement. In addition, the effect of self-propulsion on the transition time from anisotropic to isotropic diffusion of the ellipse is investigated.
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Affiliation(s)
- Wai-Tong Louis Fan
- Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - On Shun Pak
- Department of Mechanical Engineering, Santa Clara University, Santa Clara, California 95053, USA
| | - Mario Sandoval
- Department of Physics, Universidad Autonoma Metropolitana-Iztapalapa, Distrito Federal 09340, Mexico
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43
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Oriola D, Alert R, Casademunt J. Fluidization and Active Thinning by Molecular Kinetics in Active Gels. PHYSICAL REVIEW LETTERS 2017; 118:088002. [PMID: 28282157 DOI: 10.1103/physrevlett.118.088002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Indexed: 05/13/2023]
Abstract
We derive the constitutive equations of an active polar gel from a model for the dynamics of elastic molecules that link polar elements. Molecular binding kinetics induces the fluidization of the material, giving rise to Maxwell viscoelasticity and, provided that detailed balance is broken, to the generation of active stresses. We give explicit expressions for the transport coefficients of active gels in terms of molecular properties, including nonlinear contributions on the departure from equilibrium. In particular, when activity favors linker unbinding, we predict a decrease of viscosity with activity-active thinning-of kinetic origin, which could explain some experimental results on the cell cortex. By bridging the molecular and hydrodynamic scales, our results could help understand the interplay between molecular perturbations and the mechanics of cells and tissues.
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Affiliation(s)
- David Oriola
- Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Avinguda Diagonal 647 and Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
| | - Ricard Alert
- Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Avinguda Diagonal 647 and Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
| | - Jaume Casademunt
- Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Avinguda Diagonal 647 and Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
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44
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Blanch-Mercader C, Vincent R, Bazellières E, Serra-Picamal X, Trepat X, Casademunt J. Effective viscosity and dynamics of spreading epithelia: a solvable model. SOFT MATTER 2017; 13:1235-1243. [PMID: 28098306 DOI: 10.1039/c6sm02188c] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Collective cell migration in spreading epithelia in controlled environments has become a landmark in our current understanding of fundamental biophysical processes in development, regeneration, wound healing or cancer. Epithelial monolayers are treated as thin layers of a viscous fluid that exert active traction forces on the substrate. The model is exactly solvable and shows a broad range of applicabilities for the quantitative analysis and interpretation of force microscopy data of monolayers from a variety of experiments and cell lines. In addition, the proposed model provides physical insights into how the biological regulation of the tissue is encoded in a reduced set of time-dependent physical parameters. In particular the temporal evolution of the effective viscosity entails a mechanosensitive regulation of adhesion. Besides, the observation of an effective elastic tensile modulus can be interpreted as an emergent phenomenon in an active fluid.
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Affiliation(s)
- C Blanch-Mercader
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain. and Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, 26 rue d' Ulm, 75005 Paris, France
| | - R Vincent
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | - E Bazellières
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | - X Serra-Picamal
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain and Unitat de Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain
| | - X Trepat
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain and Unitat de Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain and Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain and Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, 28029 Madrid, Spain
| | - J Casademunt
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain. and Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, Barcelona, Spain
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45
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Sondak D, Hawley C, Heng S, Vinsonhaler R, Lauga E, Thiffeault JL. Can phoretic particles swim in two dimensions? Phys Rev E 2016; 94:062606. [PMID: 28085389 DOI: 10.1103/physreve.94.062606] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Indexed: 06/06/2023]
Abstract
Artificial phoretic particles swim using self-generated gradients in chemical species (self-diffusiophoresis) or charges and currents (self-electrophoresis). These particles can be used to study the physics of collective motion in active matter and might have promising applications in bioengineering. In the case of self-diffusiophoresis, the classical physical model relies on a steady solution of the diffusion equation, from which chemical gradients, phoretic flows, and ultimately the swimming velocity may be derived. Motivated by disk-shaped particles in thin films and under confinement, we examine the extension to two dimensions. Because the two-dimensional diffusion equation lacks a steady state with the correct boundary conditions, Laplace transforms must be used to study the long-time behavior of the problem and determine the swimming velocity. For fixed chemical fluxes on the particle surface, we find that the swimming velocity ultimately always decays logarithmically in time. In the case of finite Péclet numbers, we solve the full advection-diffusion equation numerically and show that this decay can be avoided by the particle moving to regions of unconsumed reactant. Finite advection thus regularizes the two-dimensional phoretic problem.
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Affiliation(s)
- David Sondak
- Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Cory Hawley
- Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Siyu Heng
- Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Rebecca Vinsonhaler
- Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Jean-Luc Thiffeault
- Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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46
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Reigh SY, Huang MJ, Schofield J, Kapral R. Microscopic and continuum descriptions of Janus motor fluid flow fields. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:20160140. [PMID: 27698037 PMCID: PMC5052725 DOI: 10.1098/rsta.2016.0140] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/01/2016] [Indexed: 05/27/2023]
Abstract
Active media, whose constituents are able to move autonomously, display novel features that differ from those of equilibrium systems. In addition to naturally occurring active systems such as populations of swimming bacteria, active systems of synthetic self-propelled nanomotors have been developed. These synthetic systems are interesting because of their potential applications in a variety of fields. Janus particles, synthetic motors of spherical geometry with one hemisphere that catalyses the conversion of fuel to product and one non-catalytic hemisphere, can propel themselves in solution by self-diffusiophoresis. In this mechanism, the concentration gradient generated by the asymmetric catalytic activity leads to a force on the motor that induces fluid flows in the surrounding medium. These fluid flows are studied in detail through microscopic simulations of Janus motor motion and continuum theory. It is shown that continuum theory is able to capture many, but not all, features of the dynamics of the Janus motor and the velocity fields of the fluid.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.
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Affiliation(s)
- Shang Yik Reigh
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
| | - Mu-Jie Huang
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6
| | - Jeremy Schofield
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6
| | - Raymond Kapral
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6
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47
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Domínguez A, Malgaretti P, Popescu MN, Dietrich S. Collective dynamics of chemically active particles trapped at a fluid interface. SOFT MATTER 2016; 12:8398-8406. [PMID: 27714377 DOI: 10.1039/c6sm01468b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Chemically active colloids generate changes in the chemical composition of their surrounding solution and thereby induce flows in the ambient fluid which affect their dynamical evolution. Here we study the many-body dynamics of a monolayer of spherically symmetric active particles trapped at a fluid-fluid interface. To this end we consider a model for the large-scale spatial distribution of particles which incorporates the direct pair interaction (including also the capillary interaction which is caused specifically by the interfacial trapping) as well as the effect of hydrodynamic interactions (including the Marangoni flow induced by the response of the interface to the chemical activity). The values of the relevant physical parameters for typical experimental realizations of such systems are estimated and various scenarios, which are predicted by our approach for the dynamics of the monolayer, are discussed. In particular, we show that the chemically-induced Marangoni flow can prevent the clustering instability driven by the capillary attraction.
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Affiliation(s)
- Alvaro Domínguez
- Física Teórica, Universidad de Sevilla, Apdo. 1065, 41080 Sevilla, Spain.
| | - P Malgaretti
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - M N Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - S Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
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48
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Gregory DA, Zhang Y, Smith PJ, Zhao X, Ebbens SJ. Reactive Inkjet Printing of Biocompatible Enzyme Powered Silk Micro-Rockets. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:4048-4055. [PMID: 27345008 DOI: 10.1002/smll.201600921] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 04/25/2016] [Indexed: 06/06/2023]
Abstract
Inkjet-printed enzyme-powered silk-based micro-rockets are able to undergo autonomous motion in a vast variety of fluidic environments including complex media such as human serum. By means of digital inkjet printing it is possible to alter the catalyst distribution simply and generate varying trajectory behavior of these micro-rockets. Made of silk scaffolds containing enzymes these micro-rockets are highly biocompatible and non-biofouling.
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Affiliation(s)
- David A Gregory
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, Mappin Street, S1 3JD, UK
| | - Yu Zhang
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, Mappin Street, S1 3JD, UK
| | - Patrick J Smith
- Department of Mechanical Engineering, University of Sheffield, Sheffield, 64 Garden Street, S1 4BJ, UK
| | - Xiubo Zhao
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, Mappin Street, S1 3JD, UK
- School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, 213164, China
| | - Stephen J Ebbens
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, Mappin Street, S1 3JD, UK
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49
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Apaza L, Sandoval M. Ballistic behavior and trapping of self-driven particles in a Poiseuille flow. Phys Rev E 2016; 93:062602. [PMID: 27415315 DOI: 10.1103/physreve.93.062602] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Indexed: 11/07/2022]
Abstract
We study the two- and three-dimensional dynamics of a Brownian self-driven particle at low Reynolds number in a Poiseuille flow. A deterministic analysis is also performed and we find that under certain conditions the swimmer becomes trapped, thus performing closed orbits as observed in related experiments. Further analysis enables us to provide an analytic expression to achieve this trapping phenomenon. We then turn to Brownian dynamics simulations, where we show the effect of a Poiseuille flow, self-propulsion, and confinement on the diffusion of the swimmer in both two and three dimensions. It is found that for long times the mean-square displacement (MSD) along the flow direction is always quadratic in time, whereas for shorter times (before the particle reaches the walls) its MSD has also a quartic time behavior. It is also found that self-propelled particles will spread less in a Poiseuille flow than passive ones under the same circumstances.
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Affiliation(s)
- Leonardo Apaza
- Faculty of Pure and Natural Sciences, Universidad Mayor de San Andres, La Paz, Bolivia
| | - Mario Sandoval
- Department of Physics, Universidad Autonoma Metropolitana-Iztapalapa, Distrito Federal 09340, Mexico
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50
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Malgaretti P, Popescu MN, Dietrich S. Active colloids at fluid interfaces. SOFT MATTER 2016; 12:4007-4023. [PMID: 27025167 DOI: 10.1039/c6sm00367b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
If an active Janus particle is trapped at the interface between a liquid and a fluid, its self-propelled motion along the interface is affected by a net torque on the particle due to the viscosity contrast between the two adjacent fluid phases. For a simple model of an active, spherical Janus colloid we analyze the conditions under which translation occurs along the interface and we provide estimates of the corresponding persistence length. We show that under certain conditions the persistence length of such a particle is significantly larger than the corresponding one in the bulk liquid, which is in line with the trends observed in recent experimental studies.
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Affiliation(s)
- P Malgaretti
- Max-Planck-Institut fur Intelligente Systeme, Theory of Inhomogeneous Condensed Matter, Heisenbergstrasse 3, Stuttgart, Germany.
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