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Issue 44, 2018
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Active particles under confinement and effective force generation among surfaces

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Abstract

We consider the effect of geometric confinement on the steady-state properties of a one-dimensional active suspension subject to thermal noise. The random active force is modeled by an Ornstein–Uhlenbeck process and the system is studied both numerically, by integrating the Langevin governing equations, and analytically by solving the associated Fokker–Planck equation under suitable approximations. The comparison between the two approaches displays a fairly good agreement and in particular, we show that the Fokker–Planck approach can predict the structure of the system both in the wall region and in the bulk-like region where the surface forces are negligible. The simultaneous presence of thermal noise and active forces determines the formation of a layer, extending from the walls towards the bulk, where the system exhibits polar order. We relate the presence of such ordering to the mechanical pressure exerted on the container's walls and show how it depends on the separation of the boundaries and determines a Casimir-like attractive force mediated by the active suspension.

Graphical abstract: Active particles under confinement and effective force generation among surfaces

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Publication details

The article was received on 09 Sep 2018, accepted on 19 Oct 2018 and first published on 23 Oct 2018


Article type: Paper
DOI: 10.1039/C8SM01840E
Citation: Soft Matter, 2018,14, 9044-9054
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    Active particles under confinement and effective force generation among surfaces

    L. Caprini and U. Marini Bettolo Marconi, Soft Matter, 2018, 14, 9044
    DOI: 10.1039/C8SM01840E

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