Three degree-of-freedom piezoelectric ultrasonic micro-motor with a major diameter of 350 µm

A three degree-of-freedom (DOF) micro-motor comprising a hollow cylindrical transducer with slots novelly inserted, mounted to a lead zirconium titanate (PZT) piezoelectric element, was developed. Reversible rotation about three orthogonal axes was obtained at frequencies above 190 kHz. The peak torque about the transverse ( x and y ) and longitudinal ( z ) axes was 1.33, 1.23 and 2.38 nNm, respectively, at 21.2 V RMS . An electrical control scheme was employed to demonstrate the ability to operate these micro-motors at the low speeds necessary for many applications, including minimally invasive surgery (MIS). This micro-motor represents a significant step towards the development of true microscopic multi-DOF actuators, which can be integrated with MIS equipment, for example, in order to provide surgeons with better operability, dexterity and control deep within a patient's body.