Memory-less response and violation of the fluctuation-dissipation theorem in colloids suspended in an active bath

We investigate experimentally and numerically the stochastic dynamics and the time-dependent response of colloids subject to a small external perturbation in a dense bath of motile E. coli bacteria. The external field is a magnetic field acting on a superparamagnetic microbead suspended in an active...

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Bibliographic Details
Published in:Scientific reports 2017-12, Vol.7 (1), p.17588-7, Article 17588
Main Authors: Maggi, Claudio, Paoluzzi, Matteo, Angelani, Luca, Di Leonardo, Roberto
Format: Article
Language:English
Subjects:
Bacteria
Biomechanical Phenomena
Colloids
Copper
E coli
Equilibrium
Escherichia coli
Friction
Magnetic fields
Models, Theoretical
Noise
Reynolds number
Rheology
Stochastic Processes
Stochasticity
Suspensions
Time Factors
Viscosity
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Summary:We investigate experimentally and numerically the stochastic dynamics and the time-dependent response of colloids subject to a small external perturbation in a dense bath of motile E. coli bacteria. The external field is a magnetic field acting on a superparamagnetic microbead suspended in an active medium. The measured linear response reveals an instantaneous friction kernel despite the complexity of the bacterial bath. By comparing the mean squared displacement and the response function we detect a clear violation of the fluctuation dissipation theorem.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-017-17900-2