This study reports on the breaking up of droplets which can be manipulated with acoustic fields. The oscillation of vortex in a breaking droplet is observed. The droplet size is dependent on the flow-rate combination of the two fluids as well as the frequency and power of the acoustic actuation. Acoustic microstreaming flow is observed in the dispersed phase at the cross-junction of the device. The microstreaming flow causes a stratified vortex flow structure within the dispersed phase. Two stratified vortex centers at the side poles of the droplet are found. 顯微粒子成像測速系統(tǒng)(Micro PIV)