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arXiv · 1803.00533

Active suspensions have non-monotonic flow curves and multiple mechanical equilibria

Aurore Loisy·Jens Eggers·Tanniemola B. Liverpool
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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 \textit{E.~Coli} effectively behaves, at steady-state, as a negative viscosity fluid and reach quantitative agreement with experimental measurements. Our theoretical analysis further shows that a negative apparent viscosity is due to a non-monotonic local velocity profile, and is associated with a non-monotonic stress vs. strain rate flow curve. This implies that fixed stress and fixed strain rate ensembles are not equivalent for active fluids.

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Aurore Loisy, Jens Eggers, Tanniemola B. Liverpool. 2018-03-01. Active suspensions have non-monotonic flow curves and multiple mechanical equilibria. https://doi.org/10.1103/physrevlett.121.018001

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