Reconfigurable emergent patterns in active chiral fluids

Abstract

Active fluids comprised of autonomous spinning units injecting energy and angular momentum at the microscopic level represent a promising platform for active materials design. The complexity of the accessible dynamic states is expected to dramatically increase in the case of chiral active units. Here, we use shape anisotropy of colloidal particles to introduce chiral rollers with activity-controlled curvatures of their trajectories and spontaneous handedness of their motion. By controlling activity through variations of the energizing electric field, we reveal emergent dynamic phases, ranging from a gas of spinners to aster-like vortices and rotating flocks, with either polar or nematic alignment of the particles. We demonstrate control and reversibility of these dynamic states by activity. Our findings provide insights into the onset of spatial and temporal coherence in a broad class of active chiral systems, both living and synthetic, and hint at design pathways for active materials based on self-organization and reconfigurability.

Collective behaviour of swarmalators on a 1D ring

“…In Biology, sperm [11,12], vinegar eels [13,14], and other microswimmers [15][16][17] synchronize the wriggling of their tails which is speculated to hydrodynamically couple to their motion. In Chemistry, magnetic Janus particles [18][19][20], dieletric Quinke rollers [21][22][23], and other active entities [24] lock their rotations enabling a kind of sync-dependent self-assembly. In Engineering, land-based robots and aerial drones can be programmed to swarm based on their synchronizable internal clocks [25][26][27].…”

Surfactants and rotelles in active chiral fluids

“…Downsizing spinner chains is a challenge but might be achieved by appropriate new techniques. Rotating microparticles have been manufactured in various ways (16,24,26,45,46). Adding connectors between particles is possible in principle (47)(48)(49).…”

“…The dynamic behavior of active chiral fluids is highly complex. Most notably, active chiral fluids exhibit active turbulence (14), aster-like vortices and rotating flocks (15)(16)(17), odd viscosity in the bulk (8), and enhanced surface flow near surfaces and interfaces (18)(19)(20). Chiral fluids have been experimentally realized at different scales (7,12,(21)(22)(23)(24)(25)(26).…”

Emergent vortices and phase separation in systems of chiral active particles with dipolar interactions

“…29 Recent studies of circle swimmers with short-range anisotropic interactions have revealed even more intriguing features. For example, simulations have demonstrated that chiral active particles with an asymmetric 24,30,31 or elongated 32 shape display vortex structures. Chiral active particles with chemotactic alignment can form a global traveling wave.…”