Ellipsoidal particles driven by intensity gradients through viscous fluids

Summary, in English

We investigate the vdrift velocity vdrift 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 vdrift 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(ω). Near frequencies where the real part of ɛmf(ω) changes sign (ɛm is the relative dielectric function of the medium in which the partcle is immersed), vdrift 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.