Bacterial activity hinders particle sedimentation

Jaspreet Singh, Alison E. Patteson, Bryan O. Torres Maldonado, Prashant K. Purohit, Paulo E. Arratia

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Sedimentation in active fluids has come into focus due to the ubiquity of swimming micro-organisms in natural and industrial processes. Here, we investigate sedimentation dynamics of passive particles in a fluid as a function of bacteriaE. coliconcentration. Results show that the presence of swimming bacteria significantly reduces the speed of the sedimentation front even in the dilute regime, in which the sedimentation speed is expected to be independent of particle concentration. Furthermore, bacteria increase the dispersion of the passive particles, which determines the width of the sedimentation front. For short times, particle sedimentation speed has a linear dependence on bacterial concentration. Mean square displacement data shows, however, that bacterial activity decays over long experimental (sedimentation) times. An advection-diffusion equation coupled to bacteria population dynamics seems to capture concentration profiles relatively well. A single parameter, the ratio of single particle speed to the bacteria flow speed can be used to predict front sedimentation speed.

Original languageEnglish (US)
Pages (from-to)4151-4160
Number of pages10
JournalSoft Matter
Issue number15
StatePublished - Apr 21 2021

ASJC Scopus subject areas

  • General Chemistry
  • Condensed Matter Physics


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