A new video from the Argonne National Laboratory demonstrates the levitation of liquid using sound waves.
Acoustic levitation is a fascinating application of sound technology. In 1987, NASA was using it to perform anti-gravity experiments, and in 2006, Chinese scientists used it to levitate small animals. There have been theories that the technology was used to levitate the stones to create Stonehenge and build pyramids (although, we take these theories with a large grain of salt), and a 1939 article in a German magazine describes Tibetan monks levitating stones using sound.
In the video below, a scientist at the Argonne National Laboratory is using acoustic levitation on individual droplets of liquid containing different pharmaceuticals, in order to evaporate the solution without it touching anything, to reduce it to an amorphous state, rather than crystalline. According to the Laboratory, amorphous pharmaceuticals are absorbed by the body more efficiently, but contact evaporation is more likely to produce the crystalline version. (Read more here.)
The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range — roughly 22 kilohertz. When the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave.
At certain points along a standing wave, known as nodes, there is no net transfer of energy at all. Because the acoustic pressure from the sound waves is sufficient to cancel the effect of gravity, light objects are able to levitate when placed at the nodes.
Head to How Stuff Works for a more in-depth explanation of how acoustic levitation works — and watch it for yourself in the video below.