Two-dimensional Acoustophoresis in Square Microchannel Enables Sub-micrometer Particle Focusing

Here, a square microchannel acoustophoresis device capable of two-dimensional focusing of sub-micrometer particles is presented. This opens the route to acoustic manipulation of smaller bioparticles such as bacteria. The device performance is compared to a conventional rectangular acoustophoresis channel that focuses particles in one dimension. Utilizing the change in the acoustic streaming velocity field when focusing particles in two dimensions in a square microchannel the device is shown to focus particles as small as 0.5 μm. A numerical analysis of the streaming velocity field generated by the two-dimensional focusing shows that the phase shift between the two standing waves plays an important role for the ability to focus sub-micrometer particles.