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Issue 22, 2012
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A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces

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Abstract

We present a numerical study of the transient acoustophoretic motion of microparticles suspended in a liquid-filled microchannel and driven by the acoustic forces arising from an imposed standing ultrasound wave: the acoustic radiation force from the scattering of sound waves on the particles and the Stokes drag force from the induced acoustic streaming flow. These forces are calculated numerically in two steps. First, the thermoacoustic equations are solved to first order in the imposed ultrasound field taking into account the micrometer-thin but crucial thermoviscous boundary layer near the rigid walls. Second, the products of the resulting first-order fields are used as source terms in the time-averaged second-order equations, from which the net acoustic forces acting on the particles are determined. The resulting acoustophoretic particle velocities are quantified for experimentally relevant parameters using a numerical particle-tracking scheme. The model shows the transition in the acoustophoretic particle motion from being dominated by streaming-induced drag to being dominated by radiation forces as a function of particle size, channel geometry, and material properties.

Graphical abstract: A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces

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Publication details

The article was received on 28 May 2012, accepted on 18 Jul 2012 and first published on 23 Jul 2012


Article type: Paper
DOI: 10.1039/C2LC40612H
Citation: Lab Chip, 2012,12, 4617-4627
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    A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces

    P. B. Muller, R. Barnkob, M. J. H. Jensen and H. Bruus, Lab Chip, 2012, 12, 4617
    DOI: 10.1039/C2LC40612H

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