Scientists Harness Ultrasound to Control Electric Plasma

An international team of researchers from the Public University of Navarre, the University of Helsinki, and the University of Waterloo has developed a method to control high-voltage electric plasma using ultrasonic fields. This innovative approach allows for the precise bending and directing of electrical arcs, which traditionally follow unpredictable paths in open air. By employing high-frequency sound waves, the scientists can create low-resistance channels that guide the plasma, enabling it to navigate around solid obstacles with remarkable accuracy.

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The researchers discovered that when a spark ignites, it heats the surrounding air to approximately 70 degrees Celsius, causing the air to expand and decrease in density. The ultrasonic waves reshape this atmosphere, trapping the hot air and forming an artificial tunnel for the electricity to travel through. This method contrasts with previous techniques that relied on high-powered lasers, which are expensive and pose safety risks. The ultrasonic approach is compact, affordable, and safe, allowing for continuous operation without the need for precise synchronization with the electrical discharge.

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The potential applications for this technology are extensive. Researchers envision using ultrasonically guided plasma for various purposes, including atmospheric sciences, biological procedures, and the selective powering of circuits. Notably, the technique allows plasma to strike non-conductive materials, which could revolutionize methods for wireless circuit switching, precision welding, and targeted biological applications. The ability to create tactile stimuli through controlled plasma could lead to innovative human-computer interfaces, such as a contactless Braille system.

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Currently, the technique is limited to alternating current (AC) sparks, as attempts to guide direct current (DC) sparks have been unsuccessful due to disruptions caused by ionic winds. However, the researchers remain optimistic about the future of this technology, particularly in enhancing human-computer interaction through the precise targeting of low-power plasma.

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Dr. Asier Marzo, the lead researcher, noted, “We observed this phenomenon more than one year ago, then it took us months to control it, and even longer to find an explanation.” Prof. Ari Salmi from the University of Helsinki emphasized the broad implications of this research, stating, “Precise control of sparks allows their utilization in a wide variety of applications, such as atmospheric sciences, biological procedures and selective powering of circuits.” Josu Irisarri, the first author of the publication, expressed excitement about the potential for creating controlled tactile stimuli, suggesting it could lead to the first contactless Braille system.

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• “We observed this phenomenon more than one year ago, then it took us months to control it, and even longer to find an explanation,” — Dr. Asier Marzo, Public University of Navarre

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• “Precise control of sparks allows their utilization in a wide variety of applications, such as atmospheric sciences, biological procedures and selective powering of circuits,” — Prof. Ari Salmi, University of Helsinki

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• “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,” — Josu Irisarri, Public University of Navarre

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This groundbreaking research, published in the journal *Science Advances*, marks a significant advancement in the field of plasma manipulation, opening new avenues for technological innovation.

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