A speck of polystyrene seemingly floating above a device. Credit: Physical Review Letters
A tiny polystyrene bead hangs in midair, nearly 40 centimeters above a square array of ultrasonic emitters. No wire holds it. There are no magnets; not that it would matter since the object is made of plastic. Nothing else surrounds it. The bean is levitating.
It defies gravity because an invisible beam of sound pushes it upward, steering it through space. It is not quite the tractor beam of Star Trek lore—the system mainly pushes upward rather than reeling objects toward itself—but color me impressed.
Researchers at the University of Tsukuba in Japan and the University of Bristol have demonstrated what they describe as the first stable three-dimensional acoustic levitation inside the high-pressure core of a single ultrasonic beam generated by a phased array. Their device worked as far as 397 millimeters from its source, roughly six times farther than a conventional single-sided acoustic trap tested with the same hardware. Acoustic traps have so far been the main tech used to levitate objects without using magnetism.
The Levitation Equation
Scientists have levitated small objects with sound before. It is hardly new. Sound carries momentum, and sufficiently intense waves can exert tiny forces on matter. But conventional acoustic levitators usually create standing waves between opposing emitters or surfaces. The object settles into a stable pocket between regions of high pressure.
That works well, but it means equipment has to surround the object. Even previous single-sided systems effectively created small acoustic traps whose grip weakened quickly with distance.
“When you have a conventional acoustic levitator, the soundwaves from opposing directions stabilize the object within the device,” Bruce Drinkwater, a professor of ultrasonics at Bristol, said in a statement.
“Past attempts to develop single-sided levitators have struggled because the force that keeps the object in place gets weaker as the object moves further from the source.”
The team overcame the limitation with a zero-order Bessel beam, a special kind of beam that keeps a narrow, intense central region over a relatively long distance instead of rapidly spreading outward.
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A 16-by-16 array of 40-kilohertz ultrasonic transducers—frequencies too high for humans to hear—generated the beam. Properly shaped, the sound exerted an upward force that opposed gravity while simultaneously nudging the particle toward the beam’s center.
The researchers managed to move particles sideways at about 5.7 centimeters per second and vertically at about 4.3 centimeters per second. They levitated two particles at once, as well as non-spherical objects including a dried tea leaf, a piece of silica aerogel, and a disk of potato starch.
The beam could even reform after encountering an obstruction. In one experiment, the researchers placed a 50-millimeter cube in its path and still levitated a particle above it—an effect related to the Bessel beam’s ability to reconstruct its central structure after part of it gets blocked. However, the object fluctuated vertically.
Experimental demonstration and numerical simulation of levitation beyond an obstacle. (a) Simulated sound pressure field using BEM, showing the reconstruction of the Bessel beam profile beyond the obstacle. (b) Photograph of a particle levitated above the obstacle. Credit: Physical Review Letters
Sound Applications
The research comes amid growing interest in using sound as a way to physically make things move.
Earlier in August 2026, for instance, EPFL researchers made tiny robots powered by sound. The shapes of some of their parts convert acoustic energy into jets of air, allowing one 150-microgram microflier to rise without an onboard motor or electronics.
Acoustic levitation researchers, meanwhile, have experimented with contactless chemistry, volumetric displays and even 3D printing. The appeal is straightforward: an acoustic field can behave like a robotic hand that never actually touches its payload.
“Because our technique enables long-range, non-contact manipulation in open environments, we anticipate this method could be used for automated experiments, three-dimensional displays, handling fragile materials and hazardous substances,” Tatsuki Fushimi of the University of Tsukuba said in a statement.
Researchers already knew how to make sound hold matter in the air. Now they can do it from much farther away—without having to build a complicated machine around the thing they want to move.
The study was published in the journal Physical Review Letters.
