Persistence length regulates emergent dynamics in active roller ensembles

Soft Matter ◽  
2021 ◽  
Author(s):  
Bo Zhang ◽  
Hamid Karani ◽  
Petia M Vlahovska ◽  
Alexey Snezhko
Keyword(s):  
Collective Behavior ◽  
Persistence Length ◽  
Self Organization ◽  
Spontaneous Formation ◽  
Colloidal Fluids ◽  
Emergent Dynamics

Active colloidal fluids, biological and synthetic, often demonstrate complex self-organization and the emergence of collective behavior. Spontaneous formation of multiple vortices has been recently observed in a variety of active...

scholarly journals Emergence of self-organized multivortex states in flocks of active rollers

2020 ◽  
Vol 117 (18) ◽  
pp. 9706-9711 ◽  
Author(s):  
Koohee Han ◽  
Gašper Kokot ◽  
Oleh Tovkach ◽  
Andreas Glatz ◽  
Igor S. Aranson ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Collective Behavior ◽  
Rotational Motion ◽  
Collective Motion ◽  
Self Organization ◽  
Design Strategies ◽  
Vortex Phase ◽  
Active Elements ◽  
Self Organized ◽  
Dynamic Materials

Active matter, both synthetic and biological, demonstrates complex spatiotemporal self-organization and the emergence of collective behavior. A coherent rotational motion, the vortex phase, is of great interest because of its ability to orchestrate well-organized motion of self-propelled particles over large distances. However, its generation without geometrical confinement has been a challenge. Here, we show by experiments and computational modeling that concentrated magnetic rollers self-organize into multivortex states in an unconfined environment. We find that the neighboring vortices more likely occur with the opposite sense of rotation. Our studies provide insights into the mechanism for the emergence of coherent collective motion on the macroscale from the coupling between microscale rotation and translation of individual active elements. These results may stimulate design strategies for self-assembled dynamic materials and microrobotics.

scholarly journals Oceanic Rings and Jets as Statistical Equilibrium States

2011 ◽  
Vol 41 (10) ◽  
pp. 1860-1873 ◽  
Author(s):  
Antoine Venaille ◽  
Freddy Bouchet
Keyword(s):  
Coherent Structures ◽  
Large Scale ◽  
Wind Forcing ◽  
Statistical Equilibrium ◽  
Self Organization ◽  
Equilibrium Studies ◽  
Spontaneous Formation ◽  
Basin Scale ◽  
Quasigeostrophic Model ◽  
Unstable States

Abstract Equilibrium statistical mechanics of two-dimensional flows provides an explanation and a prediction for the self-organization of large-scale coherent structures. This theory is applied in this paper to the description of oceanic rings and jets, in the framework of a 1.5-layer quasigeostrophic model. The theory predicts the spontaneous formation of regions where the potential vorticity is homogenized, with strong and localized jets at their interface. Mesoscale rings are shown to be close to a statistical equilibrium: the theory accounts for their shape, drift, and ubiquity in the ocean, independently of the underlying generation mechanism. At basin scale, inertial states presenting midbasin eastward jets (and then different from the classical Fofonoff solution) are described as marginally unstable states. In that case, considering a purely inertial limit is a first step toward more comprehensive out-of-equilibrium studies that would take into account other essential aspects, such as wind forcing.

scholarly journals Larval Zebrafish Exhibit Collective Circulation in Confined Spaces

2021 ◽  
Vol 9 ◽  
Author(s):  
Haider Zaki ◽  
Enkeleida Lushi ◽  
Kristen E. Severi
Keyword(s):  
Social Interactions ◽  
Developmental Stage ◽  
Collective Behavior ◽  
Physical Environment ◽  
Model System ◽  
Biological Model ◽  
Self Organization ◽  
Confined Spaces ◽  
Larval Zebrafish ◽  
Advance Knowledge

Collective behavior may be elicited or can spontaneously emerge by a combination of interactions with the physical environment and conspecifics moving within that environment. To investigate the relative contributions of these factors in a small millimeter-scale swimming organism, we observed larval zebrafish, interacting at varying densities under circular confinement. If left undisturbed, larval zebrafish swim intermittently in a burst and coast manner and are socially independent at this developmental stage, before shoaling behavioral onset. Our aim was to explore the behavior these larvae as they swim together inside circular confinements. We report here our analysis of a new observation for this well-studied species: in circular confinement and at sufficiently high densities, the larvae collectively circle rapidly alongside the boundary. This is a new physical example of self-organization of mesoscale living active matter driven by boundaries and environment geometry. We believe this is a step forward toward using a prominent biological model system in a new interdisciplinary context to advance knowledge of the physics of social interactions.

scholarly journals Forces that control self-organization of chemically-propelled Janus tori

2022 ◽  
Author(s):  
Igor Aronson ◽  
Jiyuan Wang ◽  
Mu-Jie Huang ◽  
Remmi Baker-Sediako ◽  
Raymond Kapral
Keyword(s):  
Collective Behavior ◽  
Electrostatic Interactions ◽  
Bound States ◽  
Self Organization ◽  
Dipolar Interactions ◽  
Significant Progress ◽  
Multiple Factors ◽  
Predictive Understanding ◽  
The Individual

Abstract Control of the individual and collective behavior of self-propelled synthetic micro-objects has immediate application for nanotechnology, robotics, and precision medicine. Despite significant progress in the synthesis and characterization of self-propelled Janus (two-faced) particles, predictive understanding of their behavior remains challenging, especially if the particles have anisotropic forms. Here, by using molecular simulation, we describe the interactions of chemically-propelled microtori near a wall. The results show that a torus hovers at a certain distance from the wall due to a combination of gravity and hydrodynamic flows generated by the chemical activity. Moreover, electrostatic dipolar interactions between the torus and the wall result in a spontaneous tilt and horizontal translation, in a qualitative agreement with the experiment. Simulations of the dynamics of two tori near a wall provide evidence for the formation of stable self-propelled bound states. Our results illustrate that self-organization at the microscale occurs due to a combination of multiple factors, including hydrodynamic, chemical, and electrostatic interactions.

scholarly journals Collective Motion in Human Crowds

2018 ◽  
Vol 27 (4) ◽  
pp. 232-240 ◽  
Author(s):  
William H. Warren
Keyword(s):  
Collective Behavior ◽  
Collective Motion ◽  
Local Level ◽  
Self Organization ◽  
Coherent Motion ◽  
Global Level ◽  
Crowd Behavior ◽  
Local Interactions ◽  
Fish Schools ◽  
Emergency Situations

The balletic motion of bird flocks, fish schools, and human crowds is believed to emerge from local interactions between individuals in a process of self-organization. The key to explaining such collective behavior thus lies in understanding these local interactions. After decades of theoretical modeling, experiments using virtual crowds and analysis of real crowd data are enabling us to decipher the “rules of engagement” governing these interactions. On the basis of such results, my students and I built a dynamical model of how a pedestrian aligns his or her motion with that of a neighbor and how these binary interactions are combined within a neighborhood of interaction. Computer simulations of the model generate coherent motion at the global level and reproduce individual trajectories at the local level. This approach has yielded the first experiment-driven, bottom-up model of collective motion, providing a basis for understanding more complex patterns of crowd behavior in both everyday and emergency situations.

scholarly journals Self-organization in natural swarms of Photinus carolinus synchronous fireflies

2021 ◽  
Vol 7 (28) ◽  
pp. eabg9259
Author(s):  
Raphaël Sarfati ◽  
Julie C. Hayes ◽  
Orit Peleg
Keyword(s):  
Collective Behavior ◽  
Three Dimensional ◽  
Dynamic Network ◽  
Theoretical Models ◽  
Self Organization ◽  
Three Dimensional Reconstruction ◽  
Visual Occlusion ◽  
Photinus Carolinus ◽  
Dimensional Reconstruction ◽  
Synchronization Mechanisms

Fireflies flashing in unison is a mesmerizing manifestation of animal collective behavior and an archetype of biological synchrony. To elucidate synchronization mechanisms and inform theoretical models, we recorded the collective display of thousands of Photinus carolinus fireflies in natural swarms, and provide the first spatiotemporal description of the onset of synchronization. At low firefly density, flashes appear uncorrelated. At high density, the swarm produces synchronous flashes within periodic bursts. Using three-dimensional reconstruction, we demonstrate that flash bursts nucleate and propagate across the swarm in a relay-like process. Our results suggest that fireflies interact locally through a dynamic network of visual connections defined by visual occlusion from terrain and vegetation. This model illuminates the importance of the environment in shaping self-organization and collective behavior.

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