A new technique uses sound waves to levitate objects and move them in mid-air. Credit: Dimos Poulikakos/ETH Zürich

Researchers from ETH Zürich in Switzerland has managed to levitate objects using sound waves. They can also move objects around midair. The research has been published in the Proceedings of the National Academy of Sciences.

It is however nothing new to levitate objects midair using sound waves. But this new method goes further in allowing people to manipulate the suspended objects without physically influencing them in any other way than by using sound-waves.

The sound is actually waves, mechanical waves of different air pressures transmitted through some medium (like air or water). And by generated pressure differences at just the right amount – it is possible to perfectly counteract the force of gravity to make objects levitate.

Previous research has managed to levitate not only small drops of liquid but also mice. Back then the researchers used transducers to produce sound waves and reflectors to reflect the waves back – creating so-called standing waves.

But then the research halted since the researchers were not able to levitate liquids without splitting them apart and they were also unable to move objects around. Ever since it has remained more of a trick than a tool of possible use.

But this new research project uses more precise transducers. They are very powerful but small and closely packed together. This makes it possible to even affect the long thin object in midair. It is also possible to control liquids without splitting it into droplets.

The sound waves in the experiment operate at 24 kilohertz, which is just above the normal hearing range for humans.

The practical usage of the new technique could be to use it to mix fluids without contaminating them, for chemistry, medicine, biotechnology, genetics and stem cell research.

Surfing on acoustic waves