Organizing bacterial vortex lattices by periodic obstacle arrays

Abstract

Recent experiments have shown that the complex spatio-temporal vortex structures emerging in active fluids are susceptible to weak geometrical constraints. This observation poses the fundamental question of how boundary effects stabilize a highly ordered pattern from seemingly turbulent motion. Here we show, by a combination of continuum theory and experiments on a bacterial suspension, how artificial obstacles guide the flow profile and reorganize topological defects, which enables the design of bacterial vortex lattices with tunable properties. To this end, the continuum model is extended by appropriate boundary conditions. Beyond the stabilization of square and hexagonal lattices, we also provide a striking example of a chiral, antiferromagnetic lattice exhibiting a net rotational flow, which is induced by arranging the obstacles in a Kagome-like array.

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

“…Vortices emerge, for instance, in various systems composed of biological motile constituents, including microtubules 76 and bacterial suspensions. [77][78][79] Further, biological circle swimmers, such as FtsZ filaments, 23,80 and spermatozoa of sea urchins, 81 are found to be able to self-organize into an array of vortices. Vortex patterns can also be observed in synthetic colloidal systems of magnetic rollers.…”

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

“…Vortices emerge, for instance, in various systems composed of biological motile constituents, including microtubules 79 and bacterial suspensions. [80][81][82] Further, biological circle swimmers, such as FtsZ filaments, 23,83 and spermatozoa of sea urchins, 84 are found to be able to selforganize into an array of vortices. Vortex patterns can also be observed in synthetic colloidal systems of magnetic rollers.…”

Emergence of Lanes and Turbulent-like Motion in Active Spinner Fluid

“…These systems consist of self-driven units that have relatively simple individual dynamics but collectively exhibit macroscopic coherent motions [2]. While flocks of birds and schools of fish are the commonly given examples of such emergent collective behavior, similar phenomena have been observed on much smaller scales with active microagents such as bacteria [3][4][5][6][7][8][9][10], chemically-activated motile colloids [11][12][13][14][15], microtubule-kinesin bundles (active nematics) [16], living liquid crystals (suspensions of motile bacteria in liquid crystals) [17,18], and field-driven colloids [19][20][21][22][23][24][25][26][27].…”