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Acoustic Levitation: Surfing Objects on Sound Waves

Scientists have been looking for effective ways to levitate objects for decades. Several methods exist nowadays, such as magnetism and light, electrostatic fields or sound waves, but they all have their own drawbacks.

Acoustic levitation has generally been the preferred method, as unlike its counterparts, it can float larger objects than light can and does not require the material to have special magnetic properties. The only problem with using sound waves is, however, how to control the levitating objects.

X-Men’s mutant Banshee emits a ‘sonic scream’ which allows him to hover and fly.

X-Men’s mutant Banshee emits a ‘sonic scream’ which allows him to hover and fly.

Swiss researchers from the Federal Institute of Technology in Zurich (ETH) have come up with a solution and have managed, for the first time, to obtain controlled movement of a floating object using sound waves.

ETH postdoctoral researcher Daniele Foresti, who led the experiment, used an array of sound wave generating modules to control the movement of various objects. By modifying the acoustic waves from one module to another, Foresti managed to obtain planar movement of levitated objects, practically surfing them on the sound waves.

Foresti and his colleagues used the technique successfully to levitate and move water drops, hydrocarbons, solvents and even a toothpick. In another impressive test, the researchers levitated a drop of water and a granule of instant coffee which they then combined in mid air.

According to the Swiss scientist, the system used frequencies of 24 kHz, beyond the upper limit of human hearing (20 kHz). Ultrasounds of these frequencies were used in order to protect scientists’ hearing, given that in order to levitate even small objects such as drops of water, the sound waves must be pretty loud, of around 160-165 decibels – which is about as loud as the sound of a rocket launch.

The wavelength used in the experiment allows the levitation of objects 4 to 5 mm in diameter, regardless of their length. The louder the acoustic waves, the denser the materials that can be levitated, including glass, aluminum, steel or ceramic, Foresti added.

controlled levitation

A toothpick was levitated and moved with sound waves during the Swiss researchers’ experiment.

This breakthrough could lead to many different applications of acoustic levitation technology. The controlled movement of a floating object may come in handy, most of all in various chemical and biological experiments where particles could be analyzed without worrying of chemical changes or contamination from containers. The technology could thus have major implications for the development of biopharmaceuticals and electronics.

[source : techbeat]