Micro rotary-linear ultrasonic motor for endovascular diagnosis and surgery

We present a micro ultrasonic motor having rotary and linear motions (rotary-linear motor) suitable for endovascular diagnosis and surgery. The rotary-linear motor is miniaturized to the size needed to function in a blood vessel. The stator prototype is a cube of side 3.5 mm, and the main body is fabricated as a single metallic cube with a through-hole. Four piezoelectric elements are bonded to the sides of the stator. When AC voltage at each resonant frequency is applied to the piezoelectric elements, the circumference of the stator generates elliptical motions at each natural frequency. We can obtain the output from a shaft inserted through the hole. We developed the first prototype of the stator using the finite element method (FEM), and experimentally determined the output of the rotary-linear motor. In the rotary sense, approximately 260 rpm and 0.1 mNm were attained at a resonant frequency of 270 kHz, and in the linear sense about 50 mm/s and 0.01 mN was attained at 306 kHz by driving the system at applied voltages of 42 Vrms.