Invention sparked by COVID-19 pandemic safely disinfects surfaces continuously

An invention to apply plasma to frequently touched items for continuous disinfection could provide a safe, effective, non-chemical way to reduce pathogens on various surfaces such as keypads, escalator handrails, and other high-touch surfaces, Princeton Plasma Physics Laboratory (PPPL) inventors say.

The invention, which is in the patent pending phase of the process, would provide “cold” plasma, or room-temperature plasma, from different positional orientations, and would keep surfaces disinfected without the need to use hand sanitizer, sprays, ultraviolet light, or other liquid or chemical-based solutions.

“This is a continuous, in-situ answer to disinfecting surfaces that people touch frequently,” said Charles Gentile, one of the PPPL inventors. Kenneth Silber, a 38-year professional in PPPL Information Technology’s department, and Gentile developed the technology.

The technology could be used on such surfaces as subway poles and turnstiles, elevator button keypads, touch screens, vending machines, ATMs, slot machines, retail payment ATMs, grocery conveyor belts, elevator handrails, building intercoms, entry door handles and push bars, and shared microphones, to name a few examples. “These are places where this technology could work perfectly. The technology provides for a compact, efficient, and inexpensive method of plasma generation for the purpose of disinfecting surfaces,” the inventors said.

Silber said the idea came to him while he was considering returning to his workplace, and was trying to find a way to keep hand sanitizer applications automated at PPPL so that surfaces in bathrooms and entrance door handles/push bars would already be disinfected when someone needed them, perhaps a sensor that would spray before the person touched the surface. After talking with Gentile, now retired from PPPL, they came up with what they say is a better idea, using a novel deployment geometry to direct continuous cold plasma on targeted surfaces.

“Employing our approach you don’t have to keep wiping it down,” Silber said. “It’s continuously disinfecting. Imagine, every night, not having to wipe down subway car poles and handles that people hold on to.”

Plasma is a natural disinfectant – viruses and bacteria are killed when exposed. Plasma is ubiquitous and makes up 99 percent of the visible universe. On Earth, plasma is used in TV screens, semiconductor manufacturing, neon signs, lightning, and can be seen in the Aurora borealis, or Northern Lights. The plasma used at PPPL for fusion energy research is heated to many times the temperature of the center of the sun in order to fuse light elements to produce energy, like the sun and stars. But the plasma for this invention is “cold” plasma, or at least, room temperature, no more than 50 degrees C. “You wouldn’t even feel it” under this use, Gentile said.

The technology has several advantages, Gentile said. Alcohol-based liquid sanitizers can cause health problems, and this eliminates that problem. Also, it operates continuously and there is no labor cost, meaning no one has to spend time wiping down surfaces. Finally, ultraviolet treatment creates shadows that block some areas of being disinfected. This eliminates that as well.

“We know plasma will kill viruses. We know how to make inexpensive plasma, and we know how to make low-temperature plasma,” Gentile said. “The challenge is to engineer an in-situ deployment configuration that will work in multiple applications. That’s the technology we have developed.”

The device employs piezoelectric discharge technology to produce plasma. Piezoelectric devices are used in many applications from igniting some gas barbecue grills, to fast responding valves often found in vacuum-based technologies.

Since plasma is effective against pathogens, the use of the technology could reduce flu, the common cold, and any other infectious contagion you can pick up from touching contaminated surfaces, the inventors say. “This could reduce people getting sick in general,” Silber said. “There are 3 million escalators in the United States, with two handrails each. That’s 6 million handrails touched daily. Imagine if we could keep those constantly disinfected.”

“This technology has the potential to continuously sanitize commonly touched surfaces,” said Chris Wright of Princeton University’s Office of Technology Licensing. “The technology is available for licensing, and we are actively discussing how to move the invention from lab to market with multiple interested parties.”

The work, explained on the Princeton University technology transfer web site(link is external), was funded by the U.S. Department of Energy using Laboratory Directed Research and Development funds.

PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science(link is external).

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In situ generated cold plasma for the disinfection of various high-touch surfaces.(Animation by Kyle Palmer/PPPL Office of Communications)