Acoustic 'Tractor Beam' Levitates Objects Using Ultrasound

by Devin Coldewey /  / Updated 
A visual representation of the "acoustic hologram," invisible to our eyes but still tangible.
A visual representation of the "acoustic hologram," invisible to our eyes but still tangible.Asier Marzo / Bruce Drinkwater / Sriram Subramanian

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Researchers in Europe have developed a "tractor beam" made of sound waves, but don't expect any Star Trek-style starship towing just yet. Asier Marzo, a Ph.D. student at the Public University of Navarre, worked with professors from the Universities of Sussex and Bristol to produce what they call an "acoustic hologram" that can hold small objects, move them around and rotate them, and — earning the technique its "tractor beam" moniker — pull them in.

It works by sending out ultrasound vibrations that interfere and harmonize with each other, affecting the air molecules and forming an invisible — but tangible — shape.

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"It is the same as when you go to the doctor for an echography or when they destroy kidney stones with ultrasound," wrote Marzo in an email to NBC News. "We are going to try to apply the same principle but for manipulating the particles."

Handling objects without touching them is a potentially powerful tool in everything from medicine to particle physics, and there have been other tractor beams produced, even some using ultrasound. But those devices need to surround the object with sound-emitting surfaces — enclosing it in a cube or the like — while Marzo's produces a similar effect with just a single surface.

This innovation greatly adds to the practical applications of the device — a tractor beam is much more useful if it isn't stuck inside a box. At the moment it reliably hoists tiny beads up to 4mm (0.16 inches) wide, but a larger version of the device using the same principle should be able to float a beach ball 30 feet in the air, Marzo said.

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"With more powerful tractor beams capable of levitating bigger objects and from farther distances, I imagine applications in controlling adrift floating objects in zero-gravity environments (i.e. the International Space Station)," wrote Marzo. "We are also exploring how to manipulate thousands of particles individually. This would enable the development of 3D displays composed of millions of levitating particles that act as tangible pixels."

The acoustic hologram is described in Marzo et al.'s paper, published Tuesday in the journal Nature Communications.

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