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We probe nonequilibrium 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/√w 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.
Chen, D. T., Lau, A. C., Hough, L. A., Islam, M. F., Goulian, M., Lubensky, T. C., & Yodh, A. G. (2007). Fluctuations and Rheology in Active Bacterial Suspensions. Retrieved from http://repository.upenn.edu/physics_papers/126
Date Posted: 31 March 2011
This document has been peer reviewed.