Methodology for fractionating suspended particles using ultrasonic standing wave and divided flow fields

A methodology to fractionate suspended particles according to size and/or acoustic properties is reported. This fractionation is accomplished by simultaneously subjecting the particles to a resonant acoustic field and a laminar flow field propagating in an orthogonal direction. The acoustic field induces a redistribution of the particles within the cross-section of a narrow separator channel while the laminar flow transports the particles along the separator channel towards the exit. By altering the strength of the flow relative to the strength of the acoustic field, the desired fractionation can be controlled. Proof-of-principle experiments conducted with binary mixtures of polystyrene particles are reported. The performance of the experimental device was analyzed using a model based on calculations of the trajectory of particles through the chamber. The acoustic method has potential to rapidly and selectively factionate suspended solids with very low specific power consumption.