Ultrasound Prototype Creates a Wall-Free Tube for Matter

A small stream of liquid can flow horizontally through open air within a wall-free tube defined by ultrasound, according to an experimental demonstration by researchers at the University of Helsinki. The completed prototype is eight centimetres long and uses 256 small speakers to emit ultrasonic waves at a frequency of about 40 kilohertz. The researchers also report that the direction of the tube can be changed by adjusting the speakers, that liquid can be dispensed with single-drop precision, and that the acoustic field can guide an electrical discharge along a selected route. These results establish a laboratory-scale method for contactless guidance rather than a completed system for transporting materials over long distances.

The prototype forms a curved, elongated Bessel-like acoustic field around the moving liquid. Its speakers surround the stream, but the water does not touch the apparatus or a conventional pipe. In the published work, the liquid remained in place while moving quietly through the sound-defined channel. The researchers report that the method can guide matter in its main states, with separate field configurations required for solids, liquids and gases. However, the release presents the water stream as the principal experimental demonstration; it does not quantify performance across a range of transported materials or establish how the method performs over extended periods.

Postdoctoral researcher Dmitry Nikolaev, who led the project team, said the tube can be reshaped and turned by changing how the speakers are controlled. Its route can therefore be redirected when a liquid needs to reach a different destination, and the system can dispense liquid with single-drop precision. The design also allows different arrangements to be used for different physical states: a solid substance requires a different field configuration from a liquid or a gas. These capabilities were presented as properties of the experimental approach, with the eight-centimetre module serving as the completed proof-of-principle device.

The concept originated with Ari Salmi, a professor of electronics at the University of Helsinki, during work on an ultrasound-based device for cleaning the inside surfaces of pipes. After discussing with a colleague how useful it would be if a pipe had no surface for dirt to stick to, Salmi developed the idea of using ultrasound to form the walls of a tube. Turning that idea into a working prototype required trial and error to determine how the speakers should operate so that a tube would form. The project was conducted by the University of Helsinki’s Electronics Research Laboratory with colleagues from the Public University of Navarre and the University of Michigan.

Researchers identified possible uses for the contactless tube in transporting corrosive or sticky substances that can cause problems in ordinary pipes. The absence of solid walls may also be useful for delicate, contamination-sensitive material because the transported substance does not contact the inside of a pipe or container. These are proposed applications rather than outcomes demonstrated in the reported experiment. The acoustic section draws about 50 watts of electrical power, roughly the same as an old-fashioned incandescent light bulb, and the researchers say similar modules could be connected in a row to create a longer tube. The prototype’s sound level is also substantial: although the ultrasound is too high-pitched for people to hear, Nikolaev compared its intensity to a continuous roar of gunfire beside the ear, or to standing near a jet engine, and noted that dogs may also be sensitive to it.

Subject of Research: Experimental contactless guidance of matter using ultrasound-generated acoustic fields

Article Title: Ultrasound creates a tube that guides matter through the air

Article References: Ultrasound creates a tube that guides matter through the air. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: ultrasound, acoustic fields, contactless transport, speaker arrays, liquid guidance, Bessel-like fields, University of Helsinki, electrical discharge, experimental prototype, creates, tube, guides