A Quantitative Study of the Secondary Acoustic Radiation Force on Biological Cells during Acoustophoresis.

We investigate cell-particle secondary acoustic radiation forces in a plain ultrasonic standing wave field inside a microfluidic channel. The effect of secondary acoustic radiation forces on biological cells is measured in a location between a pressure node and a pressure anti-node and the result is compared with theory by considering both compressibility and density dependent effects. The secondary acoustic force between motile red blood cells (RBCs) and MCF-7 cells and fixed 20 µm silica beads is investigated in a half-wavelength wide microchannel actuated at 2 MHz ultrasonic frequency.

Acoustic dipole and monopole effects in solid particle interaction dynamics during acoustophoresis.

A method is presented for measurements of secondary acoustic radiation forces acting on solid particles in a plain ultrasonic standing wave. The method allows for measurements of acoustic interaction forces between particles located in arbitrary positions such as in between a pressure node and a pressure antinode. By utilizing a model that considers both density- and compressibility-dependent effects, the observed particle-particle interaction dynamics can be well understood.