Scientists hoping to design a tiny, spinning motor capable of assisting in brain surgery are cribbing secrets from an unlikely source: Pizza-dough throwers.
Standing-wave ultrasonic motors are related to the motors used in the auto-image stabilization feature on cameras. They work simply enough: The
steady part of the motor–the stator–vibrates a rotor, causing it to lift and spin. But getting the timing of the vibrations just right is tricky–to date, it’s been done by trial and error. Thus, even though scientists have designed nanoscale ultra-sonic motors, they haven’t worked because no one has understood the timing physics precisely enough.
That’s where the pizza dough comes in. Daniel Liu, a PhD student at Monash University in Australia, realized that in tossing a rotor and making it spin, ultrasonic motors behave much like expert pizza-dough throwers. So he filmed the pizza makers at work, to document how the dough wobbled and spun in response to the thrower’s hands–which themselves swirled in a complex series of circles and helices. He then described the motion in a series of equations. These in turn solve fundamental questions in ultrasonic-motor design–for example, how the rotor bends and spins based on the stator frequency.
Liu and his supervisors, James Friend and Leslie Yeo, believe that the new equations will make it possible to create motors as thin as a human hair. Tiny motors with surgical applications are their specialty: They previously created the worlds smallest motor, which whips a tail around to propel itself, much like a tiny flagellate.