Motivated by the applications of ultrasonic particle manipulation in a biotechnological context, a study on acoustophoresis of hollow and core-shell particles is presented with analytical derivations, numerical simulations and confirming experiments. For a long-wavelength calculation of the acoustic radiation forces, the Gor'kov potential of hollow, air-filled particles and particles with solid or fluid core and shell is derived. The validity as well as the applicable range of the long-wavelength calculation is evaluated with numerical simulations in Comsol Multiphysics Ò. The results are experimentally verified in the acoustic field of an intrinsically two-dimensional fluid resonance mode, which allows for a more complex analysis than the common one-dimensional ultrasonic standing waves or their superposition to two-dimensional fields. Experiments were conducted with hollow glass particles (13.9 lm diameter) in a microfluidic chamber of 1.2 mm 9 1.2 mm 9 0.2 mm on a silicon-based device with piezoelectric excitation around 870 kHz. The described resonance mode is of additional interest for particle trapping and medium exchange on certain particle types, and it reveals a novel approach for particle characterization or separation. Keywords Acoustophoresis Á Acoustofluidics Á Ultrasonic particle manipulation Á Core-shell particles Á Gor'kov potential Electronic supplementary material The online version of this article (
Tumor extracts varying in carcinoembryonic antigen (CEA) content (0.4--2,280 ng/mg protein) did not affect the reactivity of cancer patients' leukocytes in the leukocyte migration inhibition test (LMIT). In addition, variations in the plasma CEA levels of tumor-bearing leukocyte donors did not influence the frequency of significant LMIT reactivity.
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