A pair of researchers didn’t need a Harry Potter spell to levitate multiple objects at once. They just needed the power of sound waves.
In a paper published in the Proceedings of the National Academy of Sciences on Monday, researchers Asier Marzo Pérez of the Public University of Navarra and Bruce Drinkwater from the University of Bristol describe how they were able to use sound to levitate multiple objects independently of one another — a never-before-accomplished feat the researchers say could lead to next-generation medical procedures.
The duo started by building two arrays, each featuring 256 tiny speakers just one centimeter in diameter. Next, they placed those arrays on opposite walls with the speakers facing inward. Finally, they placed a sound-reflective surface on the ground between the arrays.
Using a computer, the researchers could cause the speakers to emit sound waves in the 40-kilohertz range. By manipulating the sound waves using a specially developed algorithm, the researchers found that they could exert a force on tiny objects placed on the reflected surface, causing them to levitate.
In their experiments, they managed to manipulate Styrofoam balls with diameters up to three millimeters, causing the balls to appear to dance in midair.
According to the researchers, we could one day use a version of their acoustic tweezers to conduct surgery-free medical procedures within the human body.
“The flexibility of ultrasonic waves allows us to operate at micrometric scales to move cells inside 3D printed structures or living tissue,” Marzo said in a news release.