Particle concentration by acoustic standing waves

Concentration of particles in acoustic standing waves is well known. Other authors have built SAW devices with two opposing transducers, typically at frequencies between 12 and 40 MHz, to create standing waves in a microfluidic channel for concentration of microparticles and bacteria. We have investigated standing waves produced by boundary reflections from a single interdigitated transducer operating near 6 MHz. Observations of particle motions show both concentration in the acoustic field and acoustic streaming. We have modeled the generation of standingacoustic waves in three dimensions with and without a water channel. At the low frequencies used in this work, the waves generated are bulk plate waves rather than surface acoustic waves.