A piezoelectric elastic fin micromotor based on a PbZr(0.53 )Ti(0.47)O(3) thin film driving a micromachined silicon membrane was fabricated and studied. The stator was characterized by interferometry, and a laser set-up was used to measure the angular velocity and acceleration of the motor. The torque, the output power, and the efficiency of the device were extracted from these measurements. Values up to 1020 rpm and 0.94 microNm were observed for the velocity and the torque, respectively, which would be sufficient for a wristwatch application. The present version exhibited an efficiency of 0.17%, which could theoretically be increased to 4.8%

Ultrasonic motors for low electrical power applications are considered for portable devices such as an electronic wristwatch. For the study of a standing wave type motor, a modular approach was proposed, where stators and rotors are added in an assembly step. The mode conversion principle called the 'elastic fin motor' and its extension to an 'elastic force motor' suitable for a flat profile motor are discussed. Fabrication methods and the mechanical response of silicon diaphragms covered by PZT (PbZr x Ti 1−x O 3 ) and ZnO (zinc oxide) piezoelectric thin films are compared. A closed loop position control using an integrated piezoelectric stress detection is proposed and demonstrated. The target torque of 1 µN m at a mechanical power of a few µW has been achieved. A long-term test during 2 months of continuous operation proved an acceptable reliability for the specified applications.