Spontaneous self-propulsion and nonequilibrium shape fluctuations of a droplet enclosing active particles

Gašper Kokot, Hammad A. Faizi, Gerardo E. Pradillo, Alexey Snezhko, Petia M. Vlahovska*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Active particles, such as swimming bacteria or self-propelled colloids, spontaneously assemble into large-scale dynamic structures. Geometric boundaries often enforce different spatio-temporal patterns compared to unconfined environment and thus provide a platform to control the behavior of active matter. Here, we report collective dynamics of active particles enclosed by soft, deformable boundary, that is responsive to the particles’ activity. We reveal that a quasi two-dimensional fluid droplet enclosing motile colloids powered by the Quincke effect (Quincke rollers) exhibits strong shape fluctuations with a power spectrum consistent with active fluctuations driven by particle-interface collisions. A broken detailed balance confirms the nonequilibrium nature of the shape dynamics. We further find that rollers self-organize into a single drop-spanning vortex, which can undergo a spontaneous symmetry breaking and vortex splitting. The droplet acquires motility while the vortex doublet exists. Our findings provide insights into the complex collective behavior of active colloidal suspensions in soft confinement.

Original languageEnglish (US)
Article number91
JournalCommunications Physics
Issue number1
StatePublished - Dec 2022

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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