Optimization of a bulk-driven surface micromachined ultrasonic micromotor

This paper reports on performance and optimization of an ultrasonically driven surface micromachined motor. The rotor thickness and diameter are 2.5 μm and 1000 μm respectively, and is actuated by a piezoelectric PZT (lead-zirconate-titanate) plate with segmented electrodes. The motor operates with sub-three volt peak-to-peak excitation in atmospheric pressure. Parametric excitation of a plate in conjunction with mode splitting is observed on the stator hub resulting in traveling modes with vibration amplitude of approximately 1μm. The rotation direction can be controlled by selectively exciting different electrodes on the PZT plate. The piezoelectric plate is adhesively mounted to silicon die after the surface micromachine fabrication making the method suitable for actuating micromachines from any surface micromachine process