FIG. 3.

Acoustic streaming generated by focused ultrasound. (a) A cartoon of the magnitude of axial force imposed by the focused ultrasound and the resulting acoustic streaming velocity field. (b) Particle image velocimetry was used to measure velocity as a function of time at the focal point of the acoustic transducer. At typical operating conditions, the acceleration, denoted by the slope “a,” is nearly constant during the pulse envelope, after which energy is dissipated to the surrounding fluid.