Plasma device designed for consumers can quickly disinfect surfaces

Credit: CC0 Public Domain
Credit: CC0 Public Domain

Now scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory and the New Jersey Institute of Technology (NJIT) have demonstrated the first flexible, hand-held, device based on low-temperature plasma, a gas that consists of atoms, molecules, and free-floating electrons and ions that consumers can quickly and easily use to disinfect surfaces without special training.

Recent experiments show that the prototype, which operates at room temperature under normal atmospheric pressure, can eliminate 99.99 percent of the bacteria on surfaces, including textiles and metals in just 90 seconds. The device has shown a still-higher 99.9999 percent effective when used with the antiseptic hydrogen peroxide. Scientists think it will be similarly effective against viruses.

PPPL physicist Sophia Gershman, first author of a paper in Scientific Reports that describes the device and the research behind it said, we're testing it right now with human viruses.

Positive results welcomed

The positive results were welcome at PPPL, which is widening its fusion research and plasma science portfolios.

Jon Menard, deputy director for research at PPPL said, we are very excited to see plasmas used for a broader range of applications that could potentially improve human health.

Gershman said, the flexible hand-held device called a dielectric barrier discharge (DBD), is built like a sandwich. It's a high-voltage slice of bread on cheese that is an insulator and a grounded piece of bread with holes in it.

The high-voltage slice of bread is an electrode made of copper tape. The other slice is a grounded electrode patterned with holes to let the plasma flow through. Between these slices lies the cheese of insulating tape.

Gershman said, basically, it's all flexible tape like Scotch tape or duct tape. The ground electrode faces the users and makes the device safe to use.

The room-temperature plasma interacts with air to produce what is called reactive oxygen and nitrogen species molecules and atoms of the two elements along with a mixture of electrons, currents, and electrical fields. The electrons and fields team up to enable the reactive species to penetrate and destroy bacteria cell walls and kill the cells.

Room-temperature plasmas, which compare with the fusion plasmas PPPL studies that are many times hotter than the core of the sun, are produced by sending short pulses of high-speed electrons through gases like air, creating the plasma and leaving no time for it to heat up. Such plasmas are also far cooler than the thousand-degree plasmas that the laboratory studies to synthesize nanoparticles and conduct other research.

A special feature of the device is its ability to improve the action of hydrogen peroxide, a common antiseptic cleanser.

The authors wrote, we demonstrate faster disinfection than plasma or hydrogen peroxide alone in stable low power operation. Hence, plasma activation of a low concentration hydrogen peroxide solution, using a hand-held flexible DBD device results in a dramatic improvement in disinfection.

Novel collaboration

Achieving these results was a novel collaboration that brought together the plasma physics expertise of PPPL and the biological know-how of a laboratory at NJIT.

Gal Haspel, a professor of biological sciences at NJIT and a co-author of the paper said, while we usually are a neurobiology lab that studies locomotion, we were eager to collaborate with PPPL on a project related to Covid-19.

Performing the plasma disinfection tests was co-author Maria Benem Harreguy, a graduate student in biological sciences at NJIT, with assistance from Gershman.

Gershman said, she did all the experiments and without her, we wouldn't have this study.

PPL physicist and co-author Yevgeny Raitses, who directs the Princeton Collaborative Temperature Plasma Research Facility (PCRF)—a joint venture of PPPL and Princeton University supported by the DOE Office of Science (FES) that provided resources for this work through a user project said, The idea for this research began as soon as we got into the COVID lockdown last March. We at PCRF were thinking of how to help in fighting against COVID through our low-temperature plasma research, and it's been exciting for us to continue this collaboration.

Raitses guided the PPPL side of the project, which included setting up the DBD based on a printed surface design and characterizing the plasma discharge in this device, and oversaw the ongoing collaboration with NJIT. Going forward.

He said, we are working to get access to a facility in which we will be able to apply the DBD and other relevant devices against the SARS CoV-2 virus that causes Covid-19. Also underway is research with immunologists and virologists at Princeton University and Rutgers University to expand the applicability of developed plasma devices to a broader range of viruses.

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