Issue 12, 2012

Out-of-equilibrium forces between colloids

Abstract

Two colloidal probe particles are held with optical traps orthogonal to a uniformly flowing suspension of colloidal bath particles. Using confocal microscopy, the local bath suspension microstructure is characterized as a function of the probe separation and flow velocity. At sufficiently close separations, bath particles are excluded from passing between the probes, resulting in an asymmetric, non-equilibrium microstructure in which the major features are a depleted region between the probes and dense boundary layers along the surfaces that face away from the neighboring probe. As a consequence, the drag force acting on the probes is lower than that acting on a single probe and a net force pushes the probes together along their line of centers. The strength of the latter mutual force increases with increasing flow velocity. These experiments demonstrate that depletion-like forces can be induced between two particles by a non-equilibrium microstructure in a strongly driven suspension.

Graphical abstract: Out-of-equilibrium forces between colloids

Article information

Article type
Paper
Submitted
19 Sep 2011
Accepted
13 Jan 2012
First published
14 Feb 2012

Soft Matter, 2012,8, 3335-3341

Out-of-equilibrium forces between colloids

I. Sriram and E. M. Furst, Soft Matter, 2012, 8, 3335 DOI: 10.1039/C2SM06784F

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