Millimeter-Scale Traveling Wave Rotary Ultrasonic Motors

Bidirectional rotary motion of a millimeter-scale traveling wave ultrasonic motor is demonstrated using solution-deposited thin-film lead zirconate titanate and wafer-scale microelectromechanical system fabrication techniques. Rotation speeds of a motor 3 mm in diameter have been characterized up to 2000 r/min as a function of voltage, phase, and frequency, with power consumption less than 4 mW. Frequency characterization shows no nonlinear behavior, while phase characterization shows that motion can be generated with a single source drive. Furthermore, imprint in the piezoelectric response was exploited to achieve higher speeds, starting voltages lower than 4 V, and demonstration of a 2-mm diameter motor up to 1730 r/min. Design and fabrication of the motors are also presented.