Swiss Breakthrough in Acoustic Levitation
Scientists at ETH Zurich Laboratory of Thermodynamics in Emerging Technologies have been able to use sound waves to levitate and manipulate small objects, in a breakthrough that may allow unleashing several applications, notably in the pharmaceutical industry. Dimos Poulikakos’ team performed midair matter experiments, such as combining small water droplets and inserting DNA in a cell by using high frequency, high intensity sound waves.
In the past, small objects have been levitated using sound waves, but never before it has been possible to move and direct them in midair.
Specifically, the principle behind the study is that sound waves exert pressure when they hit a surface, and if the intensity is high enough, the effect can be used to counteract
the consequences of gravity. Since the sound intensity to be used has to be extremely high (~160 dB, which would damage the eardrum), scientists used ultrasounds (24,000 Hz). The device resembles a chessboard and each square emits a sound; above there is a clear plastic plate, to reflect the sound waves. If the sound waves are strong enough, object can over and be moves around. The difficult part was to fine tune sound waves: If too intense, a water droplet would explode while if too weak, gravity wins and the droplet falls down. The solution came by slowly lowering the sound intensity of the giving square and bolstering the receiving one .
As a technique for contactless processing of materials, the study was published in Proceedings of the National Academy of Science and has had wide media coverage all around the world, with the scientific community regarding it as a very innovative approach. Japan Times, Washington Post, The Guardian