Tanya Weaver Mon 10 Feb 2025
Collected at: https://eandt.theiet.org/2025/02/10/ultrasound-waves-precisely-guide-electric-sparks-through-thin-air-new-study
A new study has demonstrated how ultrasonic waves can be used to transport electricity through the air and around obstacles.
The formation of electric sparks is chaotic, with branches splitting out in random directions.
The path of the electrical current is guided by subtle differences in air density and charge, and attraction to conductive materials, such as metal. For these reasons, electricity is difficult to precisely control. Take a lightning bolt, for example.
However, a new study has demonstrated a way to guide electric sparks through the air.
Researchers at the University of Helsinki, the Public University of Navarre in Spain and the University of Waterloo in Canada have shown how ultrasonic beams can direct high-voltage sparks.
The researchers claim that the method allows sparks to be directed so precisely that they can bend around obstacles, and hit specific spots on a material even if that material isn’t conductive.
Asier Marzo, lead researcher from the Public University of Navarre, said: ”We observed this phenomenon more than one year ago, then it took us months to control it, and even longer to find an explanation.”
Ultrasonic waves do not directly push the electricity – rather they shape its path.
This occurs because, as an electric spark ignites, it heats up the air around it. This hot air now has a lower density. Ultrasonic waves guide this hotter, lower-density air into regions where the sound intensity is higher. This means that it can guide the electric sparks with surprising precision.
While previous studies have shown that sparks can be guided with laser-induced discharges, this method can be dangerous and requires precise timing between the laser and the electric discharge.
The researchers tested their ultrasound technique using two 360-degree rings of ultrasound emitters surrounding the point where a spark is generated through a Tesla coil.
When the ultrasound is switched on, the plasma spark transforms from a tree-like shape of random branches into a single line. This line can then be aimed in different directions by either physically tilting the ring of emitters, or adjusting the strength of different emitters within the ring.
The researchers were able to steer the plasma to hit specific electrodes and avoid others.
Professor Ari Salmi from the University of Helsinki said: “Precise control of sparks allows their utilisation in a wide variety of applications, such as atmospheric sciences, biological procedures and selective powering of circuits.”
Crucially, unlike the use of lasers, this technique does not pose any danger to the eyes or skin. The researchers claim it is also compact, affordable and can be operated continuously.
“I am excited about the possibility of using very faint sparks for creating controlled tactile stimuli in the hand, perhaps creating the first contactless Braille system,” said Josu Irisarri, first author of the study from the Public University of Navarre.
The study – Electric plasma guided with ultrasonic fields – has been published in the journal Science Advances.
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