Active Suspensions have Nonmonotonic Flow Curves and Multiple Mechanical Equilibria

Aurore Loisy, Jens Eggers, Tanniemola B Liverpool*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

22 Citations (Scopus)
375 Downloads (Pure)


We point out unconventional mechanical properties of confined active fluids, such as bacterial suspensions, under shear. Using a minimal model of an active liquid crystal with no free parameters, we predict the existence of a window of bacteria concentration for which a suspension of E. Coli effectively behaves, at steady-state, as a negative viscosity fluid and reach a quantitative agreement with experimental measurements. Our theoretical analysis further shows that a negative apparent viscosity is due to a nonmonotonic local velocity profile, and it is associated with a nonmonotonic stress versus strain rate flow curve. This implies that fixed stress and fixed strain rate ensembles are not equivalent for active fluids.
Original languageEnglish
Article number018001
Number of pages5
JournalPhysical Review Letters
Issue number1
Early online date3 Jul 2018
Publication statusPublished - 6 Jul 2018

Structured keywords

  • BrisSynBio
  • Bristol BioDesign Institute


  • Escherichia coli/chemistry
  • Liquid Crystals/chemistry
  • Models, Biological
  • Models, Chemical
  • Models, Theoretical
  • Suspensions
  • Synthetic biology

Fingerprint Dive into the research topics of 'Active Suspensions have Nonmonotonic Flow Curves and Multiple Mechanical Equilibria'. Together they form a unique fingerprint.

Cite this