Ultrasonic-Guided Plasma Sparks Deliver Power Over Wireless Wires — Even Steering Around Obstacles

Researchers from the Public University of Navarre, the University of Helsinki, and the University of Waterloo have come up with a technology that we are assured is very much not a joke: wireless wires, or in the parlance of their paper "electric plasma guided with ultrasonic fields."

"Electric plasma forms sparks in mid-air that transfer electrical current. This current can power high-voltage electronics, kill bacteria, produce tactile sensations, or be used for welding," the researchers explain. "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. Here, we show that ultrasonic fields can guide plasma sparks, even around obstacles."

Put simply, the team's work allows for a plasma spark to be directed — rather than branching out, it forms a focused "beam" towards a target point under the control of an array of ultrasonic emitters. By guiding the spark this way, it's possible to deliver its energy to a target device — acting exactly like the wires in a traditional circuit, but without the wires.

The team tested two ways to steer the spark. The first was simple enough: rotating the array of ultrasonic emitters one way or the other, which in turn steered the spark. The second controlled the emitters themselves: by activating only half the array, the focal point of the ultrasonic beam can be changed in order to steer the spark. "The ultrasonic beams can be directed dynamically and within milliseconds," the researchers explain, "enabling precise, non-dangerous, and fast control of high-voltage sparks. This phenomenon can be used for applications in high-voltage switching and plasma treatments."

Impressively, the team was also able to use two ultrasonic fields with different focus points to change the focused energy beam from a straight line into a curved shape — steering, in one experiment, the spark away from a conductor directly in its path. Another experiment saw the spark switching between target conductors in an LED matrix, with a third firing a spark at the individual fingers of an experimenter's hand to deliver wireless haptic feedback. With an active field, a spark took 15ms to be guided and 30ms to reach its maximum length; if the ultrasonic field is activated after the spark, it took 35ms to move to the desired target.

The team's work has been published in the journal Science Advances under open-access terms.