In this video, some scientists at Clemson University manage not only to levitate a water droplet using sound, but manipulate its shape—and the results are really cool.
The droplet gets put between transducer and a reflector. The transducer creates sound at different frequencies and the reflector bounces that sound back. Between the two, they create a pressure gradient that keeps the droplet in the air.
“Exciting” the droplet at different resonance frequencies causes it to form an oscillating star shape.
When the pressure field strength is increased past a certain point, the droplet goes nuts, losing its symmetrical patterns and eventually disintegrating.
The research is from 2013, but the video has been making the rounds again now. Enjoy some fluid dynamics eye candy.
Below is a video for you if you want to see a more lengthy version of with scientific explanations inbetween: