Piezoelectric ultrasonic resonant motor with stator diameter less than 250 µm: theProteusmotor

Minimally invasive and in vivo surgery is limited by the ability to provide controllable and powerful motion at scales appropriate for navigation within the human body. A motor for in vivo microbot propulsion is presented with a stator diameter of ϕ250 µm, demonstrating the potential to directly drive a flagellum for swimming at up to 1295 rpm with a torque of 13 nN m. The motor uses coupled axial-torsional vibration at 652–682 kHz in a helically cut structure excited by a thickness-polarized piezoelectric element. The output power is 4.25 µW, on the order of what is necessary to navigate small human arteries.