Microfluidics and Nanofluidics, Volume 16, Issue 3, pp 513-524. (2014).
Ivo Leibacher, Wolfgang Dietze, Philipp Hahn, Jingtao Wang, Steven Schmitt, Jürg Dual.
Department of Mechanical and Process Engineering, Institute of Mechanical Systems (IMES), Swiss Federal Institute of Technology (ETH Zurich), Tannenstrasse 3, 8092, Zurich, Switzerland and
Department of Biosystems Science and Engineering, Bioprocess Laboratory (BPL), Swiss Federal Institute of Technology (ETH Zurich), Mattenstrasse 26, 4058, Basel, Switzerland
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®. 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 um diameter) in a microfluidic chamber of 1.2 mm × 1.2 mm × 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.