A pipe with no walls: Helsinki researchers guide water through thin air on sound alone

Researchers at the University of Helsinki have built a pipe with no walls at all. A ring of 256 tiny speakers makes ultrasonic waves — sound too high for human ears — that hold a stream of liquid in mid-air and guide it along, the way banks guide a river. The prototype tube is 8 centimetres (about 3 inches) long, can be bent or redirected just by changing how the speakers are controlled, and can release liquid with single-drop precision. Because nothing touches the flow, it could one day move corrosive, sticky or easily contaminated liquids that damage ordinary pipes. The work, done with partners in Spain and the USA, was published in the Proceedings of the National Academy of Sciences. Lead researcher Ari Salmi called it 'the closest thing to magic' he had seen in a lab.

SDG 9 · Industry, innovation and infrastructure — Mechanism: tech innovation