Piezoelectric ultrasonic resonant micromotor with a volume of less than 1 mm3 for use in medical microbots

To improve on current methods of minimally invasive surgery, research is being carried out on systems that will permit procedures to be conducted on the micro-scale using remotely operated micro-robots. One of the major stumbling blocks to meeting this need has been the absence of a practical micromotor with a volume of less than 1 mm
³
with which to drive these devices. To rectify this, we present a piezoelectric ultrasonic resonant micromotor with a volume of approximately 0.75 mm
³
. The motor uses a novel helically cut stator that matches axial and torsional resonant frequencies, excited by a lead zirconate titanate element 0.03 mm
³
in volume. An earlier motor using the same stator design, but a larger overall volume, achieved a start-up torque of 47 nNm and no load angular velocity of 830 rad/s. This performance is on the order necessary to propel a swimming microbot in small human veins.