Fractionation of fine particle suspensions by coordinated planar ultrasonic and laminar flow fields in a rectangular acoustic chamber.

Abstract

Acoustics fields are being used to manipulate fine particles (0.1–20 μm) in liquid suspensions held within a thin rectangular channel. Ultrasonic fields are applied across the channel, resulting in particle migration in this direction. Particles with different physical characteristics (size, density, compressibility, shape) respond with different speeds to the sound field [Z. I. Mandralis and D. L. Feke, Fluid/Part. Sep. J. 3, 115–121 (1990)], resulting in partial separation across the channel. These partial separations are amplified into useful separations by applying cyclic, coordinated, bidirectional laminar flows. The response of the particles to the standing wave field will be described. A mathematical model that simulates the fractionation scheme has been developed. Results from the simulation demonstrate the effectiveness of the technique. Experimental results from a batch fractionation of 325 mesh polystyrene particles are presented. Scaleup and continuous operation schemes will be discussed.