Levitating objects with sound

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Step into Jun Rekimoto’s lab at the University of Tokyo and you might see a screw floating through the air. Don’t worry, it’s normal: Rekimoto’s team has built a new device that uses sound to levitate objects and — for the first time — maneuver them in all directions. For decades physicists have levitated milli­meter-sized objects by trapping them in pockets of low pressure between the crest of one sound wave and the trough of another.

But moving those suspended objects has been difficult. Rekimoto’s team set up four arrays of speakers pointed at the center of a half-meter-wide chamber. Once the researchers got an object hovering, they tweaked the intensity of waves in each array to move the object up and down, left and right, and back and forth.

They describe manipulating beads, feathers and alcohol droplets December 14 at arXiv.org. Eventually the technique could remotely mix compounds to create pharmaceuticals without impurities.

FLYING HIGH  When researchers tweak the intensity of sound waves in an array of speakers, objects can levitate and be moved in all directions. Credit: Yoichi Ochiai/Univ. of Tokyo