Selective Multidimensional Particle Fractionation Applying Acoustic Fields

The recent progress in the acoustic fractionation of particulate suspensions within microfluidic devices emphasizes the utility of the acoustic fractionation process also for gas-suspended particles as a significant advancement in the field of mechanical process engineering. In the literature, analytical and numerical studies have found the gas-based acoustic particle fractionation process to be suitable for particles in a size range below 10 µm. The viability remains experimentally unassessed. In this article, we present particle fractionation experiments conducted on gas-born particles suspended in high-intensity acoustic fields. A particle-size-dependent accumulation of particles in the acoustic sound velocity lobes and nodes could be observed, indicative of an acoustic fractionation process. Additionally, evidence of acoustic streaming and acoustic focusing has been found, both of which have the potential to impede the fractionation process. The experimental results align with the conclusions of numeric simulations. The in-process particle behavior is discussed in the context of the relevant literature and reinforces the notion of selective entrainment.