Collective motion of polar active particles on a sphere

Due to its inherent out-of-equilibrium nature, active matter in confinement may exhibit collective behavior absent in unconfined systems. Extensive studies have indicated that hydrodynamic or steric interactions between active particles and boundary play an important role in the emergence of collective behavior. However, besides introducing external couplings at the single-particle level, the confinement also induces an inhomogeneous density distribution due to particle-position correlations, whose effect on collective behavior remains unclear. Here, we investigate this effect in a minimal chiral active matter composed of self-spinning rotors through simulation, experiment, and theory. We find that the density inhomogeneity leads to a position-dependent frictional stress that results from interrotor friction and couples the spin to the translation of the particles, which can then drive a striking spatially oscillating collective motion of the chiral active matter along the confinement boundary. Moreover, depending on the oscillation properties, the collective behavior has three different modes as the packing fraction varies. The structural origins of the transitions between the different modes are well identified by the percolation of solid-like regions or the occurrence of defect-induced particle rearrangement. Our results thus show that the confinement-induced inhomogeneity, dynamic structure, and compressibility have significant influences on collective behavior of active matter and should be properly taken into account.

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Dry Aligning Dilute Active Matter

Annual Review of Condensed Matter Physics ◽

10.1146/annurev-conmatphys-031119-050752 ◽

2020 ◽

Vol 11 (1) ◽

pp. 189-212 ◽

Cited By ~ 23

Author(s):

Hugues Chaté

Keyword(s):

Long Range ◽

Collective Motion ◽

Local Level ◽

Orientational Order ◽

Two Dimensions ◽

Active Matter ◽

Long Range Correlations ◽

Active Particles ◽

Growing Domain

Active matter physics is about systems in which energy is dissipated at some local level to produce work. This is a generic situation, particularly in the living world but not only. What is at stake is the understanding of the fascinating, sometimes counterintuitive, emerging phenomena observed, from collective motion in animal groups to in vitro dynamical self-organization of motor proteins and biofilaments. Dry aligning dilute active matter (DADAM) is a corner of the multidimensional, fast-growing domain of active matter that has both historical and theoretical importance for the entire field. This restrictive setting only involves self-propulsion/activity, alignment, and noise, yet unexpected collective properties can emerge from it. This review provides a personal but synthetic and coherent overview of DADAM, focusing on the collective-level phenomenology of simple active particle models representing basic classes of systems and on the solutions of the continuous hydrodynamic theories that can be derived from them. The obvious fact that orientational order is advected by the aligning active particles at play is shown to be at the root of the most striking properties of DADAM systems: ( a) direct transitions to orientational order are not observed; ( b) instead generic phase separation occurs with a coexistence phase involving inhomogeneous nonlinear structures; ( c) orientational order, which can be long range even in two dimensions, is accompanied by long-range correlations and anomalous fluctuations; ( d) defects are not point-like, topologically bound objects.

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Collective Motion of Active Particles

Russian Physics Journal ◽

10.1023/b:rupj.0000042776.25572.7f ◽

2004 ◽

Vol 47 (4) ◽

pp. 453-460

Author(s):

A. I. Olemskoi ◽

O. V. Yushchenko

Keyword(s):

Collective Motion ◽

Active Particles

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Active spheres induce Marangoni flows that drive collective dynamics

The European Physical Journal E ◽

10.1140/epje/s10189-020-00006-5 ◽

2021 ◽

Vol 44 (2) ◽

Author(s):

Martin Wittmann ◽

Mihail N. Popescu ◽

Alvaro Domínguez ◽

Juliane Simmchen

Keyword(s):

Field Model ◽

Collective Motion ◽

Mean Field ◽

Spherically Symmetric ◽

Fluid Interface ◽

Mean Field Model ◽

Collective Dynamics ◽

Active Particles ◽

Oil Water ◽

Marangoni Flows

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 $$\hbox {TiO}_2$$ TiO 2 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. Graphic abstract

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Phase separation and emergence of collective motion in a one-dimensional system of active particles

The Journal of Chemical Physics ◽

10.1063/1.5085840 ◽

2019 ◽

Vol 150 (14) ◽

pp. 144905 ◽

Cited By ~ 4

Author(s):

Lucas Barberis ◽

Fernando Peruani

Keyword(s):

Phase Separation ◽

Collective Motion ◽

Dimensional System ◽

One Dimensional ◽

Active Particles

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A particle-field approach bridges phase separation and collective motion in active matter

Nature Communications ◽

10.1038/s41467-020-18978-5 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Robert Großmann ◽

Igor S. Aranson ◽

Fernando Peruani

Keyword(s):

Phase Separation ◽

Granular Media ◽

Collective Motion ◽

Dynamical Property ◽

Active Matter ◽

Nematic Order ◽

Nonequilibrium Phenomena ◽

Active Particles ◽

Orientational Ordering ◽

Spatio Temporal

Abstract Whereas self-propelled hard discs undergo motility-induced phase separation, self-propelled rods exhibit a variety of nonequilibrium phenomena, including clustering, collective motion, and spatio-temporal chaos. In this work, we present a theoretical framework representing active particles by continuum fields. This concept combines the simplicity of alignment-based models, enabling analytical studies, and realistic models that incorporate the shape of self-propelled objects explicitly. By varying particle shape from circular to ellipsoidal, we show how nonequilibrium stresses acting among self-propelled rods destabilize motility-induced phase separation and facilitate orientational ordering, thereby connecting the realms of scalar and vectorial active matter. Though the interaction potential is strictly apolar, both, polar and nematic order may emerge and even coexist. Accordingly, the symmetry of ordered states is a dynamical property in active matter. The presented framework may represent various systems including bacterial colonies, cytoskeletal extracts, or shaken granular media.

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Bursts of activity in collective cell migration

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1600503113 ◽

2016 ◽

Vol 113 (41) ◽

pp. 11408-11413 ◽

Cited By ~ 28

Author(s):

Oleksandr Chepizhko ◽

Costanza Giampietro ◽

Eleonora Mastrapasqua ◽

Mehdi Nourazar ◽

Miriam Ascagni ◽

...

Keyword(s):

Cell Migration ◽

Scaling Laws ◽

Domain Walls ◽

Collective Motion ◽

Cell Types ◽

Living Cells ◽

Collective Cell Migration ◽

Relaxation Dynamics ◽

Active Particles ◽

Different Cell Types

Dense monolayers of living cells display intriguing relaxation dynamics, reminiscent of soft and glassy materials close to the jamming transition, and migrate collectively when space is available, as in wound healing or in cancer invasion. Here we show that collective cell migration occurs in bursts that are similar to those recorded in the propagation of cracks, fluid fronts in porous media, and ferromagnetic domain walls. In analogy with these systems, the distribution of activity bursts displays scaling laws that are universal in different cell types and for cells moving on different substrates. The main features of the invasion dynamics are quantitatively captured by a model of interacting active particles moving in a disordered landscape. Our results illustrate that collective motion of living cells is analogous to the corresponding dynamics in driven, but inanimate, systems.

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