Fluctuations and Rheology in Active Bacterial Suspensions

Abstract

We probe non-equilibrium properties of an active bacterial bath through measurements of correlations of passive tracer particles and the response function of a driven, optically trapped tracer. These measurements demonstrate violation of the fluctuation-dissipation theorem and enable us to extract the power spectrum of the active stress fluctuations. In some cases, we observe $1/\sqrt{\omega }$ scaling in the noise spectrum which we show can be derived from a theoretical model incorporating coupled stress, orientation, and concentration fluctuations of the bacteria.

4 pages, 4 figures, accepted to Phys. Rev. Lett

References in corpus (3)

• Minimal model for active nematics: quasi-long-range order and giant fluctuations
• Active nematics are intrinsically phase-separated
• Hydrodynamics of isotropic and liquid crystalline active polymer solutions

Cited by in corpus (2)

• Frequency-dependent fluctuation-dissipation relations in granular gases
• Dynamics of a stiff biopolymer in an actively contractile background: buckling, stiffening and negative dissipation