Microparticle separation with an acoustic-gravity field controlled by phase-shift operation.

The elution of particles from a coupled acoustic-gravity channel has been controlled by a phase-shift operation. Two ultrasound transducers pasted onto the top and bottom walls of a separation channel were driven at the same frequency, but with different phases. Changing the phases of the ultrasounds has allowed the formation of a node near the channel wall, and particles are retained in the channel. Two types of particles are separated under an appropriate condition.