In the study, an electric spark of 4 cm was guided around an obstacle using ultrasonic fields.
For the first time, scientists have found that electric sparks can be guided using ultrasonic waves. A recent study by researchers from Spain, Finland, and Canada uncovered the way in which ultrasonic waves transport electricity through air.
Researchers revealed that this guidance occurs because the sparks heat up the air, which expands and lowers its density.
The hot air is then guided by ultrasonic waves into regions where the sound intensity is higher, and the next sparks follow these regions of lighter air because of its lower breakdown voltage, according to researchers.
Hard to control in open space
However, they are hard to control in open space as they split into chaotic branches that tend to go towards the closest metallic objects, according to researchers.
Dr. Asier Marzo from the Public University of Navarre, the lead researcher, explained that while they observed this phenomenon over a year ago, it took months to achieve control and even longer to understand the underlying mechanism.
The level of control of the electric sparks allows to guide the spark around obstacles, or to make it hit specific spots, even into non-conductive materials, according to researchers.
Precise control of sparks
Researchers also maintained that sparks could only be guided with laser-induced discharges, colloquially called Electrolysers, which required the use of dangerous lasers, as well as precise timing between the laser and the electric discharge.
The developed method uses ultrasound rather than lasers, and it is safe for the eyes and skin. The equipment is compact, affordable, and can be operated continuously, added the researchers.
Laser pulses can guide discharges but require high power
“Precise control of sparks allows their utilization in a wide variety of applications, such as atmospheric sciences, biological procedures and selective powering of circuits,” said Prof. Ari Salmi from the University of Helsinki.
Published in Science Advances journal, the study revealed that electric plasma forms sparks in midair that transfer electrical current. This current can power high-voltage electronics, kill bacteria, produce tactile sensations, or be used for welding. However, the formation of the spark is chaotic and hard to control. Laser pulses can guide discharges but require high power and are disruptive and cumbersome to control, highlighted the researchers.
Electric spark of 4 cm was guided around an obstacle using ultrasonic fields
“Here, we show that ultrasonic fields can guide plasma sparks, even around obstacles. The ultrasonic beams can be directed dynamically and within milliseconds, enabling precise, nondangerous, and fast control of high-voltage sparks,” said researchers in the study.
“This phenomenon can be used for applications in high-voltage switching and plasma treatments.”
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In the study, an electric spark of 4 cm was guided around an obstacle using ultrasonic fields.
Researchers concluded that the electric spark heats up the air; this heated air expands, thus decreasing in density. The heated lower-density air is shaped by the ultrasonic field that pushes it to the high-amplitude regions, and the region of lower-density air is a preferred discharge path.
This is in line with laser-guided discharge, but the heated lower-density region of air is created by the spark itself and shaped by the ultrasonic field, according to researchers.
“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 publication from the Public University of Navarre.
