We report the emergence of large zigzag bands in a population of reversibly actuated magnetic rotors that behave as active shakers, namely squirmers that shake the fluid around them without moving. The shakers collectively organize into dynamic structures displaying self-similar growth, and generate topological defects in form of cusps that connect vortices of rolling particles with alternating chirality. By combining experimental analysis with particle-based simulation, we show that the special flow field created by the shakers is the only ingredient needed to reproduce the observed spatiotemporal pattern. We unveil a self-organization scenario in a collection of driven particles in an viscoelastic medium emerging from the reduced particle degrees of freedom, as here the frozen orientational motion of the shakers.
@article{arxiv.2402.00493,
title = {Large scale zigzag pattern emerging from circulating active shakers},
author = {Gaspard Junot and Marco De Corato and Pietro Tierno},
journal= {arXiv preprint arXiv:2402.00493},
year = {2024}
}