Transport Powered by Bacterial Turbulence

Abstract

We demonstrate that collective turbulent-like motion in a bacterial bath can power and steer directed transport of mesoscopic carriers through the suspension. In our experiments and simulations, a microwedge-like "bulldozer" draws energy from a bacterial bath of varied density. We obtain that a maximal transport speed is achieved in the turbulent state of the bacterial suspension. This apparent rectification of random motion of bacteria is caused by polar ordered bacteria inside the cusp region of the carrier, which is shielded from the outside turbulent fluctuations. Introduction. Suspensions of bacteria or synthetic microswimmers show fascinating collective behavior emerging from their self-propulsion [1-4] which results in many novel active states such as swarming [5][6][7][8] and "active turbulence" [9][10][11][12][13][14]. In contrast to hydrodynamic turbulence, the apparent turbulent (or swirling) state occurs at exceedingly low Reynolds numbers but at relatively large bacterial concentrations.

Unusual swelling of a polymer in a bacterial bath

“…Active matter itself has been intensely explored over the last years, both for living systems as bacteria [4], spermatozoa [5] and mammals [6,7] or is system of artificial microswimmers [8][9][10][11][12][13] with various propulsion mechanisms [14][15][16][17] and a plethora of nonequilibrium pattern formation phenomena were discovered [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. At fixed system boundaries active system show distinct clustering and trapping behaviour [34][35][36][37][38][39][40][41][42][43][44][45] and can be expoited to * kaiser@thphy.uni-duesseldorf.de steer the motion of microrotors and microcarriers [46][47][48] of fixed shape.…”

Generic Long-Range Interactions Between Passive Bodies in an Active Fluid

“…They have attracted much attention [2,3] due to a host of interesting physical phenomena [4][5][6][7][8][9], their relevance to many biological systems [10][11][12][13], and their potential use for self-assembly applications [14]. They have also been suggested as tools for novel engineering applications -for example, active fluids have been used to power microscopic gears [15][16][17][18][19][20][21]. This results from the fact that, when an asymmetric body is immersed in a fluid with broken time-reversal symmetry, it experiences a net force [22][23][24] which is coupled to the generation of ratchet-like currents [25,26].…”

Colloidal suspensions of C-particles: Entanglement, percolation and microrheology

“…In close analogy, the Gaussian Brownian torque ζ i has zero mean and second moment (19) in the body frame. Eqs.…”

“…More pronounced non-convexity is realized for colloidal bowls which may penetrate and get stacked [15]. While these are still rotational symmetric shapes, more complex non-convex particles with no rotational symmetry have been considered including bent rods such as banana-shaped [16,17] and boomerangshaped [18][19][20] particles up to closed rings or tori [21,22]. Ring-like particles can get completely entangled with important consequence for their dynamics and rheological properties.…”