Two-dimensional acoustic micromanipulation using a line-focused transducer

Control of position of particles using acoustic radiation pressure in water was studied in order to develop a non-contact micromanipulation technique. The radiation pressure traps particles suspended in water and forms agglomeration every half wavelength in an ultrasonic standing wave field. This paper describes a method to transport the particles two-dimensionally using a line-focused transducer with multiple electrodes. The transducer was fixed upward in water and a ceramic plate reflector was set at the focal line. When an alumina suspension was poured with a pipette into the sound field, the particles were trapped and agglomerated near the reflector. Changing the frequency alters the wavelength and hence the interval of agglomeration. Therefore 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 by using the line-focused transducer.