Acoustic Tube Guides Matter Through Air Using Ultrasound
Researchers have developed a wall-less conduit that moves liquids, powders, and electric discharges without solid boundaries.
By Giovanni Sapere
2 min readHuman-Edited, AI-Assisted
A research team led by the University of Helsinki has demonstrated an invention that transports liquids, mist, powders, and electric discharge through open air without solid containers. Powered by ultrasonic waves emitted by 256 miniature transducers, the contactless channel creates an invisible boundary that guides matter horizontally in midair.
How acoustic levitation forms an invisible conduit
The invention holds flowing matter in place by generating acoustic waves at a frequency of 40 kilohertz, as reported by TechXplore. The sound is emitted by 256 small speakers arranged inside a cylinder located approximately 5 centimeters from the stream. Instead of using a solid pipe, the device shapes sound waves into curved, elongated Bessel-like acoustic fields that trap the matter and prevent it from dispersing.
“Of all the experimental setups I have seen, I would say this is the closest thing to magic.”
— Ari Salmi, professor of electronics at the University of Helsinki
“By changing how the speakers are controlled, we can reshape and turn the tube as needed.”
— Dmitry Nikolaev, postdoctoral researcher at the University of Helsinki
The origins and collaborative development
The concept originated four years earlier during an evening walk taken by inventor Ari Salmi, a professor of electronics at the University of Helsinki, according to TechXplore. While previously developing ultrasonic devices to clean pipe interiors, Salmi considered the benefits of a conduit completely devoid of physical surfaces where dirt could adhere. Bringing the concept to life required an iterative trial-and-error phase conducted in partnership with researchers from the Public University of Navarre and the University of Michigan.
Prototype specifications and potential applications
The current experimental prototype measures 8 centimeters in length, which is shorter than the outer diameter of the cylinder itself, as detailed by TechXplore. Operating the 8-centimeter section requires 50 watts of electrical power, an energy demand comparable to an incandescent light bulb. Postdoctoral researcher Dmitry Nikolaev noted that while the high acoustic intensity inside the core is imperceptible to humans, the sound frequency can be perceived by dogs.
Adaptable material transport and what to watch
Because physical contact is eliminated, this innovation offers practical utility for transporting corrosive, sticky, or contamination-sensitive materials that typically foul or erode standard plumbing, as reported by TechXplore. Operators can adjust the speaker array to alter the tube's trajectory on demand or dispense liquid in individual droplets. With potential for future patent protection, ongoing development is expected to focus on modular expansion, as connecting multiple 8-centimeter units in sequence could allow researchers to build longer acoustic pipelines of arbitrary length for advanced robotics and space applications.
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