3J-5 Concentration of Particles in Suspension in a Continuous Stream Using Ultrasound Radiation Force

Exposure of suspended microparticles to an ultrasonic standing-wave field subjects them to acoustic radiation forces that cause the particles to migrate into pressure nodal or anti-nodal planes of the sound field. The objective of our work is to design a continuous-flow microparticle filter to separate particle suspensions into a cleared phase (reduced particle concentration) and an enriched phase (increased particle concentration). Based on the principle of the h-shaped ultrasonic separator, we propose a device in which the radiation-force pattern is slowly moved into the cavity, by superimposing two standing waves with a linear phase modulation between them. One then obtains a slowly-progressive standing wave, which theoretically improves the ability of the system to concentrate a particle suspension. We favorably compare theoretical ultrasound pressure, computed with an analytical 1D transfer-matrix approach, and measurements realized by acousto-optic interactions inside the separation chamber