Active phase separation by turning towards regions of higher density

Jie Zhang, Ricard Alert, Jing Yan, Ned S. Wingreen, Steve Granick

Research output: Contribution to journalArticlepeer-review

Abstract

Studies of active matter, from molecular assemblies to animal groups, have revealed two broad classes of behaviour: a tendency to align yields orientational order and collective motion, whereas particle repulsion leads to self-trapping and motility-induced phase separation. Here we report a third class of behaviour: orientational interactions that produce active phase separation. Combining theory and experiments on self-propelled Janus colloids, we show that stronger repulsion on the rear than on the front of these particles produces non-reciprocal torques that reorient particle motion towards high-density regions. Particles thus self-propel towards crowded areas, which leads to phase separation. Clusters remain fluid and exhibit fast particle turnover, in contrast to the jammed clusters that typically arise from self-trapping, and interfaces are sufficiently wide that they span entire clusters. Overall, our work identifies a torque-based mechanism for phase separation in active fluids, and our theory predicts that these orientational interactions yield coexisting phases that lack internal orientational order.

Original languageEnglish (US)
JournalNature Physics
DOIs
StateAccepted/In press - 2021

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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