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Publication - Professor Tanniemola Liverpool

    Active Suspensions have Nonmonotonic Flow Curves and Multiple Mechanical Equilibria

    Citation

    Loisy, A, Eggers, J & Liverpool, TB, 2018, ‘Active Suspensions have Nonmonotonic Flow Curves and Multiple Mechanical Equilibria’. Physical Review Letters, vol 121.

    Abstract

    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.

    Full details in the University publications repository