Issue 23, 2020

Unjamming of active rotators


Active particle assemblies can exhibit a wide range of interesting dynamical phases depending on internal parameters such as density, adhesion strength or self-propulsion. Active self-rotations are rarely studied in this context, although they can be relevant for active matter systems, as we illustrate by analyzing the motion of Chlamydomonas reinhardtii algae under different experimental conditions. Inspired by this example, we simulate the dynamics of a system of interacting active disks endowed with active torques and self-propulsive forces. At low packing fractions, adhesion causes the formation of small rotating clusters, resembling those observed when algae are stressed. At higher densities, the model shows a jamming to unjamming transition promoted by active torques and hindered by adhesion. We also study the interplay between self-propulsion and self-rotation and derive a phase diagram. Our results yield a comprehensive picture of the dynamics of active rotators, providing useful guidance to interpret experimental results in cellular systems where rotations might play a role.

Graphical abstract: Unjamming of active rotators

Article information

Article type
13 Mar 2020
27 May 2020
First published
28 May 2020

Soft Matter, 2020,16, 5478-5486

Unjamming of active rotators

L. Ravazzano, S. Bonfanti, M. C. Lionetti, M. R. Fumagalli, R. Guerra, O. Chepizhko, C. A. M. La Porta and S. Zapperi, Soft Matter, 2020, 16, 5478 DOI: 10.1039/D0SM00440E

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