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Issue 1, 2017
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Dynamics of a microorganism in a sheared viscoelastic liquid

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In this paper, we investigate the dynamics of a model spherical microorganism, called squirmer, suspended in a viscoelastic fluid undergoing unconfined shear flow. The effect of the interplay of shear flow, fluid viscoelasticity, and self-propulsion on the orientational dynamics is addressed. In the limit of weak viscoelasticity, quantified by the Deborah number, an analytical expression for the squirmer angular velocity is derived by means of the generalized reciprocity theorem. Direct finite element simulations are carried out to study the squirmer dynamics at larger Deborah numbers. Our results show that the orientational dynamics of active microorganisms in a sheared viscoelastic fluid greatly differs from that observed in Newtonian suspensions. Fluid viscoelasticity leads to a drift of the particle orientation vector towards the vorticity axis or the flow-gradient plane depending on the Deborah number, the relative weight between the self-propulsion velocity and the flow characteristic velocity, and the type of swimming. Generally, pullers and pushers show an opposite equilibrium orientation. The results reported in the present paper could be helpful in designing devices where separation of microorganisms, based on their self-propulsion mechanism, is obtained.

Graphical abstract: Dynamics of a microorganism in a sheared viscoelastic liquid

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Publication details

The article was received on 22 Mar 2016, accepted on 30 Jun 2016 and first published on 04 Jul 2016

Article type: Paper
DOI: 10.1039/C6SM00697C
Citation: Soft Matter, 2017,13, 196-211
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    Dynamics of a microorganism in a sheared viscoelastic liquid

    M. De Corato and G. D'Avino, Soft Matter, 2017, 13, 196
    DOI: 10.1039/C6SM00697C

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