Alison E. Patteson: 0000-0002-4004-1734

Document Type



Spring 3-10-2021




National Science Foundation, University Research Foundation, NSF Graduate Research Fellowship

Funding ID

DMR-1709763, DMR-1505662


We thank A. Gopinath, J. Bush, D. Durian, S. Spagnolie, A. Baskaran, and R. Radhakrishnan for fruitful discussions. A. E. Patteson, B.Maldonado, and P. E. Arratia acknowledge support by the National Science Foundation grant DMR-1709763. J. Singh and P. K. Purohit acknowledge support through National Science Foundation grant DMR-1505662 and the University Research Foundation at the University of Pennsylvania. A. E. Patteson was supported by NSF Graduate Research Fellowship.

Official Citation

Singh, J., Patteson, A. E., Torres Maldonado, B. O., Purohit, P. K., & Arratia, P. E. (2021). Bacterial activity hinders particle sedimentation. Soft Matter, 17(15), 4151-4160. https://doi.org/10.1039/d0sm02115f




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 bacteria E. coli concentration. 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.

Creative Commons License

Creative Commons Attribution 3.0 License
This work is licensed under a Creative Commons Attribution 3.0 License.

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