Scientific Frontline: Extended "At a Glance" Summary: Zero-Order Bessel Beam Acoustic Levitation
The Core Concept: This technique is a novel, single-sided acoustic levitation method utilizing a zero-order Bessel beam to suspend and manipulate small objects in mid-air over distances up to 40 centimeters.
Key Distinction/Mechanism: Conventional acoustic levitators require opposing soundwaves within an enclosed space to stabilize objects, and previous single-sided attempts failed at a distance because the acoustic force pushed objects away. This new method overcomes that limitation by employing a zero-order Bessel beam, which maintains a narrow, high-intensity central core over long distances, extending the levitation range sixfold.
Major Frameworks/Components:
- Zero-Order Bessel Beam: A specialized ultrasonic waveform that resists diffraction, staying narrow and maintaining high intensity over extended distances.
- Single-Sided Acoustic Trapping: The capability to capture and manipulate objects in three dimensions using ultrasound emitted from a single direction.
- High-Pressure Core Stabilization: The mechanism of holding particles, such as 1.5-millimeter polystyrene spheres, securely within the high-pressure zones of the beam.
Branch of Science: Acoustics, Applied Physics, and Ultrasonics.
Future Application: Anticipated use cases include automated laboratory experiments, three-dimensional physical displays, and the contactless handling of fragile, contamination-sensitive, or hazardous substances in open environments.
Why It Matters: By enabling long-range, non-contact manipulation from a single side, this advancement removes the spatial and physical constraints of traditional enclosed levitators. It makes it possible to levitate multiple, non-spherical, or partially obscured objects in wide-open spaces.
Scientists have developed a new acoustic levitation technique using an ultrasonic beam capable of levitating and moving small objects in midair over distances of up to 40 cm, six times farther than previously achieved using conventional methods.
The study, carried out by a research team from the University of Tsukuba in Japan and the University of Bristol, was published in the journal Physical Review Letters.
Acoustic levitation is a technique that uses sound waves to suspend objects in midair without physical contact—meaning it has the potential to be hugely beneficial for handling fragile materials, contamination-sensitive samples, and hazardous substances.
Conventional acoustic levitation systems rely on sound waves being generated within an enclosed space, but the new technique marks the first time a single-sided design has demonstrated stable acoustic levitation in three dimensions.
Yusuke Koroyasu, lead author and PhD student at the University of Tsukuba, said, "This research prospered through the close collaboration between researchers at Bristol and Tsukuba. My time in Bristol provided invaluable opportunities to discuss ideas and develop the work together, and I am grateful for the support and guidance I received from colleagues at both institutions."
Bruce Drinkwater, professor of ultrasonics at the University of Bristol, explained, “When you have a conventional acoustic levitator, the sound waves from opposing directions stabilize the object within the device. Past attempts to develop single-sided levitators have struggled because the force that keeps the object in place gets weaker as the object moves farther from the source.
“Eventually the force starts pushing the object away instead of holding it steady, making long-distance levitation impossible. To overcome this, we used a special type of ultrasonic beam called a zero-order Bessel beam, which, unlike a normal sound beam, stays narrow and maintains a high-intensity central core over a much longer distance.”
By exploiting the Bessel beam’s unique properties, the researchers successfully achieved stable levitation of a 1.5 mm diameter polystyrene sphere at distances of up to 40 cm from the sound source, approximately six times farther than previously achieved using single-sided acoustic traps.
The team manipulated the levitated object in three dimensions using ultrasound from only one side and successfully levitated multiple objects, nonspherical objects, and objects located beyond other physical objects.
Tatsuki Fushimi, professor at the University of Tsukuba, said, “Because our technique enables long-range, noncontact manipulation in open environments, we anticipate this method could be used for automated experiments, three-dimensional displays, and handling fragile materials and hazardous substances.”
Published in journal: Physical Review Letters
Title: Midair Single-Sided Acoustic Levitation in High-Pressure Regions of Zero-Order Bessel Beams
Authors: Yusuke Koroyasu, Christopher Stone, Yoichi Ochiai, Takayuki Hoshi, Bruce W. Drinkwater, and Tatsuki Fushimi
Source/Credit: University of Bristol
Edited by: Scientific Frontline
Reference Number: phy082626_01
