Researchers Use Sound to Levitate a Chemical Reaction

Posted on July 16, 2013

BBC News reports that researchers at the Swiss Federal Institute of Technology (ETH) used acoustic waves to make objects, such as particles and liquid droplets, fly in mid-air. The toothpick above flies and floats on acoustic waves.

The researchers say in a release the the knowledge that acoustic waves can exert a force (the acoustic radiation pressure effect) on an object to keep it in suspension was discovered over 100 years ago. Until now, no one has been successfully able to control the motion of objects riding on acoustic waves in mid-air.

Daniele Foresti, a postdoctoral researcher at the Laboratory of Thermodynamics in Emerging Technologies, made it work by switching on multiple emitter-reflector modules in parallel. He varied the acoustic waves from module to module in order to transfer particles or droplets of liquid from one module to the next.

Foresti used this method to move a granule of instant coffee on to a droplet of water and merge the two. He also mixed two droplets of liquid with different pH values, one alkaline and the other acidic. A droplet of water and a particle of sodium metal come together in mid-air in this video clip. Take a look:

The research was published here in PNAS.

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