Acoustic Levitation

For the fi rst time, researchers have succeeded in levitating and moving arbitrarily shaped objects using acoustic (sound) waves. The researchers, from the Swiss Federal Institute of Technology (ETH) in Zurich, have already used their newfound magical powers of levitation to collide a granule of coffee and water to create instant coffee in midair — and more excitingly, a droplet of water and a piece of sodium. The same approach could potentially work on humans, though, without further refi nements to the technology, we would probably explode or suffer catastrophic internal bleeding. Acoustic levitation is desirable because, unlike magnetic levitation, it can be used on any object — not just materials and liquids that are magnetic. Likewise, buoyancy can be used to “levitate” some liquids, but again there are strict limitations on what liquids can be used (they must be immiscible, as with water and oil). The only limitation with acoustic levitation is that the object’s diameter must correspond to half the wavelength of the acoustic waves. As you can see, the team have no issues levitating a toothpick — something that would be impossible with both magnetic and buoyancy levitation. Researchers are able to move their acoustically levitated objects up and down, as well as side to side. if you have enough power, you could levitate just about anything with acoustic waves — including a human. The power required would be immense, though, and at this point it isn’t clear if a human would even survive the acoustic forces. Furthermore, the power requirements would probably be well beyond the capabilities of today’s lithium-ion battery packs. (Levitating a water drop requires around 160 dB).