Active turbulence in a gas of self-assembled spinners

Strongly interacting colloids driven out-of-equilibrium by an external periodic forcing often develop nontrivial collective dynamics and self-assembled patterns. Ferromagnetic micro-particles, suspended at a liquid interface and energized by a uniaxial in-plane alternating magnetic field spontaneously form arrays of self-assembled spinners rotating in either direction. We show that the spinners, emerging as a result of spontaneous symmetry breaking of clock/counterclockwise rotation of self-assembled particle chains, generate vigorous vortical flows at the interface. An ensemble of spinners exhibits chaotic dynamics due to self-generated advection flows. The same-chirality spinners (clockwise or counterclockwise) tend to aggregate and form dynamic clusters. Self-induced interface currents promote active diffusion that could be tuned by the parameters of the external excitation field. Furthermore, erratic motion of spinners at the interface generates chaotic fluid flow reminiscent of two-dimensional turbulence. The work provides insight into fundamental aspects of collective transport in active spinner materials.