A cylindrical ultrasonic micromotor based on PZT thin film

We introduced a hydrothermal method to deposit the PZT thin film on a titanium tube to make a stator transducer for an ultrasonic motor. The titanium tube was 2.4 mm diameter, 10 mm long and 0.25 mm thick. On the side wall, the thin film was formed about 8 μm in thickness. Four driving electrodes were painted on the PZT film. The electrodes were strip shaped and they divided 4 parts in circumference of the side wall. Two pairs of the strip electrodes facing each other were connected to individual RF power supplies to excite degenerated fundamental bending vibration modes. The two generators have 90 degree phase difference to excite mode rotation. The transducer was driven at a resonance of about 106 kHz. For the driving voltage from 20 to 33 V_p-p, we obtained rotation of 0 to 300 rpm