A University of Helsinki-led research team has unveiled a massless ultrasound tube that moves matter through the air without touching it by using ultrasonic sound waves undetectable to the human ear.
The research team behind the magical-sounding invention said its massless ultrasound tube is ideal for transporting sticky substances that clog ordinary pipes, toxic substances, or delicate medical material sensitive to contamination.
Massless Ultrasound Tube Inspired by Dirty Pipes
When announcing the massless ultrasound tube, Ari Salmi, Professor of Electronics at the University of Helsinki, said he initially came up with the idea four years ago during an evening walk. According to Salmi, his team had been working on a device designed to clean the inner surfaces of traditional pipes using ultrasound waves.
“At a lunch with a colleague, we discussed that it would be handy if a pipe had no surface for dirt to stick to,” the researcher recalled.
Over time, and thanks to more evening walks with his dogs, Salmi realized the solution was to form the tube’s walls with ultrasound. After deciding to tackle the engineering challenges, Salmi enlisted colleagues from the Public University of Navarre and the University of Michigan to see if they could build a working massless ultrasound tube prototype.
“I Would Say This is the Closest Thing to Magic”
To create a massless tube of pure ultrasound, the Helsinki team positioned 256 small speakers in a predetermined, tube-like formation. When the team tuned the speakers to emit ultrasonic waves at 40 kilohertz, the invisible waves created an ultrasound tube that suspended and transported matter through the air.
“Of all the experimental setups I have seen, I would say this is the closest thing to magic,” Salmi said.
The team fine-tuned the speakers to manipulate liquid flowing through the massless ultrasound tube, thereby increasing their control. This included enough precision to dispense a single drop of liquid from the tube’s end.
“By changing how the speakers are controlled, we can reshape and turn the tube as needed,” explained project leader Dmitry Nikolaev.
Because the tube has no physical structure, it can transport corrosive or sticky substances that clog or degrade traditional pipes. It can also use its lack of physical form to transport delicate, “contamination-sensitive” substances in a touch-free manner.
Nikolaev said the ultrasound tube can also be adjusted to transport liquids and solids simply by changing the speaker positions and output. This includes changing the flow direction through the massless tube.
“Transporting a solid substance, for example, requires a different field configuration than transporting a liquid or a gas,” the researcher explained.
Beyond transporting physical matter, the massless ultrasound tube can guide an electrical charge through the air without wires, opening an entirely different set of possibilities.
Energy-Efficient, Scalable Prototype is Finished
When discussing the next steps, the Helsinki team noted that they have already completed construction of its prototype massless ultrasound tube. While it is only eight centimeters in diameter, Nikolaev said several such devices could be connected in a row to build a tube of any needed length.
The current version of the massless ultrasound tube draws about 50 watts of power. For comparison, 50 watts is roughly the same as a traditional incandescent light bulb, making it surprisingly energy efficient given its seemingly magical abilities.
Although humans cannot hear the sound waves produced by the ultrasound tube, the research team noted that dogs may be quite sensitive to it. For comparison, Nikolaev said that the sound at the core of the device “is comparable to a continuous roar of gunfire right next to your ear.”
“Even right here next to it, the sound could be compared to a jet engine if you were standing right beside it,” he explained. “But it is too high-pitched for the human ear.”
The study, “Contactless continuous guidance of matter in its main states using curved elongated Bessel-like acoustic fields,” was published in the Proceedings of the National Academy of Sciences.
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.