An ultrasonic stage for controlled spin of micro particles

In this work, we proposed and developed an ultrasonic stage which can make different kinds of micro particles spin at its center. The stage consists of a circular copper plate and two piezoelectric half-rings bonded onto the bottom surface of the copper plate. The two piezoelectric half-rings have the same size and property, but opposite polarization in the thickness direction. They form a ring concentric with the copper plate. The spin direction of micro particles can be reversed by changing the operating frequency of stage. The spin speed can be controlled by operating frequency and voltage of the stage, and it reaches 955 rpm for a single glass ball with 0.51 mm diameter. The spin of micro particles is caused by travelling waves around the center of the stage, and the travelling waves are generated by anti-symmetric flexible vibration of the stage, excited by the two piezoelectric half-rings.