Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session S20: Active Matter in Complex Environments III
8:00 AM–11:00 AM,
Thursday, March 17, 2022
Room: McCormick Place W-185BC
Sponsoring
Units:
DSOFT DBIO GSNP DFD
Chair: Dan Beller, UC Merced
Abstract: S20.00015 : Flow Fluctuations in Confined Bacterial Suspension*
10:48 AM–11:00 AM
Presenter:
Cristian Villalobos Concha
(Universidad de Chile)
Authors:
Cristian Villalobos Concha
(Universidad de Chile)
Maria Luisa Cordero
(Universidad de Chile)
Rodrigo B Soto
(Univ de Chile)
In this work, we study experimentally and numerically the flow fluctuations generated by a confined suspension of E.coli bacteria. The suspension is encapsulated in a double emulsion, where an oil droplet gets trapped inside a bacteria-in-oil emulsion. By measuring the mean square displacement (MSD) and the velocity autocorrelation function of the oil droplet, we found that it performs a persistent random walk at short times with a characteristic persistence time τ ≈ 0.3 s. Due to the confinement, the MSD reaches a plateau at long times and the velocity correlation function shows a negative peak.
We propose a Langevin-type equation with reflective boundary conditions, where a colored noise term models the flow generated by the bacterial suspension and is characterized by two parameters: its amplitude and correlation time. The numerical solution of this model is in good agreement with the experiments and allows us to obtain the characteristic properties of the noise associated with the bacterial bath.
*Funding from ANID through Millennium Nucleus Physics of Active Matter and Beca de Doctorado Nacional 21201766 is gratefully acknowledge.
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