CONTROL OF A STANDING-WAVE FIELD USING A LINE-FOCUSED TRANSDUCER FOR 2-DIMENSIONAL MANIPULATION OF PARTICLES

Control of the positions of particles using acoustic radiation pressur e in water was studied to develop a noncontact micromanipulation techn ique. In this paper a method to transport the particles two-dimensiona lly using an ultrasonic standing wave field between a line-focused tra nsducer with multiple electrodes and a reflector placed at the focal l ine is described. When alumina suspension of mean diameter 16 mu m was poured into the standing wave field of 2.1 MHz, the particles were tr apped and agglomerated at sound pressure nodes existing at half wavele ngth on the sound beam axis near the reflector. Changing the frequency alters the wave-length and hence the interval of agglomeration. There fore the trapped particles were transported along the sound beam axis. When the next electrodes were driven, the standing wave field shifted laterally and the trapped particles moved to the corresponding nodal points. Thus two-dimensional transportation was realized using the lin e-focused transducer. A sound field generated by the line-focused tran sducer was discussed based on numerical calculations to design an opti mum shape of a transducer for manipulation.