Non-contact micromanipulation using an ultrasonic standing wave field

Transportation of particles using acoustic radiation pressure in water is studied to develop non-contact micromanipulation technique. The radiation pressure traps particles suspended in water to form agglomeration every half wavelength in a standing wave field. Using two sets of standing wave fields crossing to each other, the shape of agglomeration was varied. Applying focused acoustic radiation pressure of traveling wave, a limited part of trapped particles was transported for long distance. Using a concave transducer to generate a standing wave, trapped particles were transported stably along the sound beam axis by changing the ultrasonic frequency. The resolution of transportation to the order of submicron is possible to achieve. Furthermore, the column of trapped particles was separated and transported oppositely by using an appropriate value of frequency increment. Although intense ultrasound generates acoustic streaming, it was possible to avoid its influence using a burst wave.