Abstract

Collective states of inanimate particles self-assemble through physical interactions and thermal motion. Despite some phenomenological resemblance, including signatures of criticality, the autonomous dynamics that binds motile agents into flocks, herds, or swarms allows for much richer behavior. Low-dimensional models have hinted at the crucial role played in this respect by perceived information, decision-making, and feedback, implying that the corresponding interactions are inevitably retarded. Here we present experiments on spherical Brownian microswimmers with delayed self-propulsion toward a spatially fixed target. We observe a spontaneous symmetry breaking to a transiently chiral dynamical state and concomitant critical behavior that do not rely on many-particle cooperativity. By comparison with the stochastic delay differential equation of motion of a single swimmer, we pinpoint the delay-induced effective synchronization of the swimmers with their own past as the key mechanism. Increasing numbers of swimmers self-organize into layers with pro- and retrograde orbital motion, synchronized and stabilized by steric, phoretic, and hydrodynamic interactions. Our results demonstrate how even most simple retarded interactions can foster emergent complex adaptive behavior in small active-particle ensembles.

Time-delayed interactions involving perception, decision, and reaction, are omnipresent in the living world. Here, the delayed self-propulsion of a microswimmer toward a target gives rise to chiral orbital motion via a symmetry-breaking bifurcation. Additional swimmers synchronize and stabilize it.

Details

Title
Spontaneous vortex formation by microswimmers with retarded attractions
Author
Wang, Xiangzun 1 ; Chen, Pin-Chuan 2 ; Kroy, Klaus 2   VIAFID ORCID Logo  ; Holubec, Viktor 3   VIAFID ORCID Logo  ; Cichos, Frank 1   VIAFID ORCID Logo 

 Leipzig University, Peter Debye Institute for Soft Matter Physics, Leipzig, Germany (GRID:grid.9647.c) (ISNI:0000 0004 7669 9786) 
 Leipzig University, Institute for Theoretical Physics, Leipzig, Germany (GRID:grid.9647.c) (ISNI:0000 0004 7669 9786) 
 Charles University, Department of Macromolecular Physics, Faculty of Mathematics and Physics, Prague, Czech Republic (GRID:grid.4491.8) (ISNI:0000 0004 1937 116X) 
Pages
56
Publication year
2023
Publication date
2023
Publisher
Nature Publishing Group
e-ISSN
20411723
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2760730437
Copyright
© The Author(s) 2023. This work is published under http://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.