Ellipsoidal particles driven by intensity gradients through viscous fluids.
We investigate the drift velocity v(drift) of ellipsoidal polarizable particles (ellipsoids and coated ellipsoids), driven through a viscous fluid by an electric or electromagnetic field intensity gradient. At low Reynolds number and in the dipole approximation v(drift) is proportional to the square of the principal axis along the direction of motion multiplied by a form factor, which is weakly depending on the shape of the particle, and by a frequency and shape dependent factor f(omega). Near frequencies where the real part of epsilon (m)f(omega) changes sign ( epsilon (m) is the relative dielectric function of the medium in which the partcle is immersed), v(drift) is sensitive to the shape of the particle. We suggest that our results can be used for the experimental separation of neutral polarizable particles with respect to size or shape.
Ambjörnsson
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Department of Applied Physics, Chalmers University of Technology and Göteborg University, SE-412 96 Göteborg, Sweden.
Apell
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