By way of acoustics, researchers have successfully levitated one of the largest objects yet: a two-inch solid polystyrene ball.
This hunk of foam is trapped in the gentle embrace of three 25 kHz ultrasonic transducers, transmitting sound above the frequency of human hearing. Traditionally, acoustic levitation uses two opposing sound waves to suspend an object smaller than the wavelengths themselves. This is the first time acoustic levitation has worked on an object 3.6 times larger than the acoustic wavelength.
But it’s not just a cool parlor trick. Breaking through this scale problem could lead to moving larger objects at different angles and manipulating them mid-air, useful for handling hot materials or liquid samples in space.