Acoustic levitation moves objects – Swiss lab study

“A liquid droplet is levitated in the space between sound-emitting platforms (bottom) and a sound-reflecting surface (top).” DIMOS POULIKAKOS Source: Nature.com

Josh Howgego reports for Nature that, “Sound waves levitate and move objects.”

The author sites a study published in the Proceedings of the National Academy of Sciences.  He writes:

Water droplets, coffee granules, fragments of polystyrene and even a toothpick are among the items that have been flying around in a Swiss laboratory lately — all of them kept in the air by sound waves. The device that achieves this acoustic levitation is the first to be capable of handling several objects simultaneously.

Howgego mentions previous studies that used electromagnetism to achieve levitation, in particular one that lifted frogs into the air.  But, Previous studies on sound wave levitation have only been successful in suspending objects in air.  But, this one makes them move.  Here’s how that works:

To also move and manipulate levitating objects, Dimos Poulikakos, a mechanical engineer at the Swiss Federal Institute of Technology (ETH) in Zurich, and his colleagues built sound-making platforms using piezoelectric crystals, which shrink or stretch depending on the voltage applied to them. Each platform is the size of a pinky nail.

The platforms emit sound waves which move upward until they reach surface lying above, where they bounce back. When the downward-moving reflected waves overlap with the upward-moving source waves, the two ‘cancel out’ in the middle, at so-called node points. Objects placed there remain stuck in place because of the pressure of sound waves coming from both directions.

Read the full report on Nature.com, click here.

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