Pizza tossing physics to inspire micro-motor design

April 28th, 2009 - 12:23 pm ICT by IANS  

Sydney, April 28 (IANS) Scientists have unravelled the physics of the perfect pizza toss, which will help them design micro-motors thinner than a human hair.
Daniel Liu, a doctoral student supervised by associate professor James Friend and senior lecturer and Leslie Yeo at Australia’s Monash University, videotaped a professional pizza tosser at work.

The team then calculated how best to describe the way the dough travels through the air - including how much it rotates, how quickly it spins, its stability and the energy efficiency of the toss itself.

The result is a set of nonlinear differential equations that captures the art of pizza tossing.

“In brief, if you toss a pizza dough one toss at a time - that is, if you toss then catch - your hands should move in a helical fashion, like they are moving along a spiral, a curved line laid along a cylinder,” Friend said.

“If you are tossing the pizza continuously, not stopping to catch it and stop every time, then your hands should move in circles,” he added.

The model could help researchers design the next generation of standing wave ultrasonic motors (SWUMs), which operate on principles similar to those of pizza tossing.

The tiny motors have the potential to be used for minimally invasive neuro-microsurgery. In these electric motors, the fixed component, the stator, is made to vibrate ultrasonically, and this causes the moveable part, the disc-like rotor, to be “tossed” - both rotated and lifted, said a Monash release.

“The SWUM works exactly like a pizza chef tossing dough, with the hands representing the vibrating stator of the SWUM and the dough representing the rotor. The difference is only in the details: a chef tosses dough, about once a second, a few tens of centimetres into the air. A SWUM tosses the rotor a few million times a second into the air,” Friend said.

He said scientists around the world have been using trial and error to make variations of the SWUMs, and while they might have worked, there had not been a thorough understanding of the forces involved until now.

“Some of the maths are a bit tricky,” Friend said. “The most puzzling questions with SWUMs are answered in this study. We think that further investigation of the work will prove fruitful for the understanding and design of SWUMs.”

The scientists are the same principals who recently developed the world’s smallest useful motor, only a quarter mm wide, that could be used in the propulsion system of

miniature machines to swim through the bloodstream to inaccessible places, potentially

revolutionising future surgical procedures.

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