Engineering news
Developed by a research team from the University of Tsukuba in Japan and the University of Bristol, the method uses an ultrasonic beam to levitate and move small objects in mid-air over distances of up to 40cm.
Acoustic levitation uses soundwaves to suspend objects in mid-air without physical contact – meaning it could be hugely beneficial for handling fragile materials, contamination-sensitive samples and hazardous substances.
In advanced manufacturing, the technique can support contactless handling and positioning of fragile parts such as microchips, wafers or thin glass. In biomedical engineering, it can move or mix droplets and sensitive samples without container contact, helping to reduce contamination and material waste.
Conventional acoustic levitation systems rely on soundwaves being generated within an enclosed space, but the new technique is reportedly the first time a single-sided design has been able to demonstrate stable acoustic levitation in three dimensions.
“When you have a conventional acoustic levitator, the soundwaves from opposing directions stabilise 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 further from the source,” explained ultrasonics specialist Professor Bruce Drinkwater from the University of Bristol.
“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 1.5mm-diameter polystyrene sphere at up to 40cm from the sound source, approximately six times further than previously achieved using single-sided acoustic traps.
The team was able to manipulate the levitated object in three dimensions using ultrasound from only one side. They were also able to levitate multiple objects, non-spherical objects and objects located beyond other physical objects.
Professor Tatsuki Fushimi from the University of Tsukuba said: “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.”
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.”
The work was published in Physical Review Letters.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.