Coronavirus particles

Handheld ultraviolet Covid-19-killing devices are on the horizon

Image credit: Science Photo Library

A handheld device that emits ultraviolet light to disinfect areas possibly contaminated by coronavirus is now feasible, according to researchers from two Japanese universities and the University of Minnesota.

UV radiation in the 200 to 300 nanometer range has been shown to destroy the Covid-19 virus and make it incapable of reproducing and infecting.

While widespread adoption of this approach is currently in demand, it requires UV radiation sources that emit sufficiently high doses of UV light.

Devices with these high doses do currently exist, but the UV radiation source is typically an expensive gas discharge lamp containing mercury, which requires high power, has a relatively short lifespan and is bulky.

High-performance UV light-emitting diodes would be a much more portable, long-lasting and energy-efficient solution, but while these LEDs exist applying a current to them for light emission is complicated by the fact that the electrode material also has to be transparent to UV light.

“You have to ensure a sufficient UV light dose to kill all the viruses,” said Penn State associate professor Roman Engel-Herbert. “This means you need a high-performance UV LED emitting a high intensity of UV light, which is currently limited by the transparent electrode material being used.”

While finding transparent electrode materials operating in the visible spectrum for displays, smartphones and LED lighting is a long-standing problem, the challenge is even more difficult for ultraviolet light.

“There is currently no good solution for a UV-transparent electrode,” said Joseph Roth, doctoral candidate in Materials Science and Engineering at Penn State.

“Right now, the current material solution commonly employed for visible light application is used despite it being too absorbing in the UV range. There is simply no good material choice for a UV-transparent conductor material that has been identified.”

Finding a new material with the right composition is key to advancing UV LED performance. The researchers believe that a solution might be found in a recently discovered new class of transparent conductors.

They underwent testing of a material called strontium niobite, which has been theoretically shown to work as a UV transparent conductor. While these films held the promise of the theoretical predictions, the researchers needed a deposition method to integrate them in a scalable way.

“We immediately tried to grow these films using the standard film-growth technique widely adopted in industry, called sputtering,” Roth said. “We were successful.”

This is a critical step towards technology maturation which makes it possible to integrate this new material into UV LEDs at low cost and high quantity.

“While our first motivation in developing UV transparent conductors was to build an economic solution for water disinfection, we now realise that this breakthrough discovery potentially offers a solution to deactivate Covid-19 in aerosols that might be distributed in HVAC systems of buildings,” Roth explained.

Other areas of application for virus disinfection are densely and frequently populated areas, such as theatres, sports arenas and public transportation vehicles such as buses, subways and airplanes.

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