| The application of ultrasonic, planar, standing wave fields for the fractionation of fine particle suspensions (0.1-100 {dollar}mu{dollar}m) is studied. Theoretical predictions show that particles with differences in size, density, or compressibility respond at different rates to the imposed acoustic wave fields.; Three fractionation processes are described that achieve continuous, fast, and sharp fractionation of micron sized particles based on the transient response of the particles to the sound field. The devices utilize different combinations of orthogonal acoustic standing wave and laminar flow fields. Experiments are performed on suspensions of polystyrene particles (325 mesh) in water in order to demonstrate the effectiveness of the techniques. The results are in good agreement with simple theoretical models that are developed for each method.; The acoustic fractionation methods proposed in this work provide viable alternatives to classical fractionation methods. Their advantages are increased resolution, high production rates, and low energy requirement. Unique separations of neutrally buoyant particles and particles exhibiting compressibility differences can also be achieved. |
