Control of collective activity to crystallize an oscillator gas

Abstract

Motility-induced phase separation occurs in assemblies of self-propelled units when activity is coupled negatively to density. In contrast, the consequences of a positive coupling between density and activity on the collective behaviour of active matter remain unexplored. Here, we show that collective activity can emerge from such a positive coupling among non-motile building blocks. We perform experiments with self-sustained oscillators powered by contact-charge electrophoresis. Although the oscillators are non-motile by design, they spontaneously form an active gas when confined together. The super-elastic nature of collisions constitutes a positive density-activity coupling and underlies the active gas properties. Elucidating the origin of binary collisions allows us to precisely control the structure of the active gas and its eventual crystallization. Beyond considering the overlooked positive coupling between density and activity, our work suggests that rich collective properties can emerge not only from the symmetry of interactions between active building blocks, but also from their adaptable and responsive behaviour.

References in corpus (19)

• Motility-Induced Phase Separation
• Dynamical clustering and phase separation in suspensions of self-propelled colloidal particles
• Emergence of macroscopic directed motion in populations of motile colloids
• Dynamic clustering in active colloidal suspensions with chemical signaling
• Collective Motion of Vibrated Polar Disks
• Oscillators that sync and swarm
• Active Turbulence
• Pattern formation in self-propelled particles with density-dependent motility
• Topological structure and dynamics of three dimensional active nematics
• Selective and Collective Actuation in Active Solids
• A self-driven phase transition drives Myxococcus xanthus fruiting body formation
• Statistical mechanics of a chiral active fluid
• Metamachines of Pluripotent Colloids
• Biophysics underlying the swarm to biofilm transition
• Chiral active hexatics: Giant number fluctuations, waves and destruction of order
• Pulsating active matter
• Self-propelling colloidal finite state machines
• Long-ranged order and flow alignment in sheared $p-$atic liquid crystals
• Determination of the interactions in confined macroscopic Wigner islands: theory and experiments