'Acoustic whirlpool' device promises low-cost, in-field disease diagnosis

February 15, 2017 // By Julien Happich
An international team of researchers has leveraged the special mechanical properties of square glass microfluidics under acoustic vibrations to concentrate nanoparticles within a fluid to be analyzed.

In a paper published in the ACS Nano journal, "Enriching Nanoparticles via Acoustofluidics", they describe an acoustofluidic nanoparticle-enrichment device able to generate single vortex acoustic streaming inside a glass capillary through the use of low-power acoustic waves.

Operating at down to 5V, the low-power set up consists of a piezoelectric substrate (LiNbO3) with chirped interdigital transducers (IDTs) fabricated on top and a square glass capillary bonded on the substrate through a thin UV epoxy layer. By applying a radio frequency signal to the transducers (in the megahertz range), a SAW (surface acoustic wave) is generated and travels perpendicular to the glass capillary, actuating a torsional vibration mode and generating a type of acoustic streaming with a single vortex.

A 3D schematic of the acoustofluidic-based nanoparticle-enrichment device and (below) a side view showing how the SAW propagates on the surface and induces a torsional vibration in the glass capillary.

This seemingly simple setup was first proven and understood with mechanical simulation tools. Based on these results, the researchers were able to optimize and develop a working prototype, combining single vortex acoustic streaming with an acoustic radiation force to enrich submicrometer- and nanometer-sized particles within the small capillary volume.