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COMSOL Analysis of Acoustic Streaming and Microparticle Acoustophoresis

H. Bruus1 P.B. Muller1 R. Barnkob1 M.J.H. Jensen2
1Technical University of Denmark, Kongens Lyngby, Denmark
2COMSOL, Kongens Lyngby, Denmark

COMSOL simulation of the acoustophoretic motion of polystyrene microparticles (diameter 0.5, 2.0, and 5.0 um) resulting from time-avaraged second-order acoustic fields.

We have simulated the ultrasound-induced acoustophoretic motion of microparticles suspended in an aqueous solution. The full first-order thermoviscous acoustics equations have been implented on a rectangular microfluidic 2D domain excited with an ultrasound field tuned to resonance near 2 MHz. The micrometer-thin but crucial viscous boundary layers at the rigid walls have been fully resolved. The imposed first-order ultrasound field generates second-order fields that leads to streaming flows and radiation forces with a non-zero time-average, which act on the suspended microparticles. We have characterized the cross-over from streaming-dominated vortex motion of small particles (< 2 um) to radiation-dominated linear motion of larger particles (> 2 um).

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