Since face masks are still a daily necessity for many people, they could become potentially environmentally hazardous waste. However, USF researchers are working on solutions to sterilize the masks and alleviate this growing problem as part of the COVID-19 Rapid Response Research Grants program.
Ying Zhong, researcher at the USF Green Research for Energy-Efficient Innovations Lab, and Libin Ye, researcher and professor of cellular molecular biology, put together a team of five PhD students to experiment with a new form of sterilization technology to combat pathogenic viruses.
The team developed a novel form of sterilization technology that uses corona discharge – a phenomenon in which an electrical discharge causes nearby gas molecules to ionize, which could then safely and effectively destroy pathogens on the N95 face masks.
“Corona discharge is an electrical discharge phenomenon with bluish-purple light that illuminates the air near the discharge conductor,” said Zijian Weng, a Ph.D. Engineering student.
“It occurs when a high voltage is applied to the conductor, which causes the flow of current with a high potential from the conductor into the nearby air by ionizing and generating excited gas molecules, usually nitrogen molecules, which emit the bluish-violet light. “
Corona discharge is also a phenomenon that Zhong said she previously experimented with in other areas of her research where she “induced permanent charges in polymer films.”
Zhong used this earlier experience with corona discharge to investigate its potential use for N95 mask sterilization. She reviewed various studies on corona discharge and its effects on disinfection and concluded that there was enough evidence to support corona discharge as a means of disinfecting and reusing N95 masks.
“I know that [corona discharge] can it inject charges, but can it also disinfect masks? Fortunately, I was able to identify some articles that support this idea, ”said Zhong.
An N95 mask protects its users in two different ways, according to Ye. He said the material used in the masks contains tiny pores that are able to physically prevent bacteria and other pathogens from entering the body. The materials are layered to make it difficult for pathogens to pass through.
The second way is to use static electricity. N95 masks are made with a positive charge, Zhong said.
“When a negatively charged droplet comes near a positively charged fiber, they tend to attract each other,” says Zhong. “This is how the charged fibers become [of the N95 mask] stop the charged droplet. “
According to Zhong, the problem with electrostatic charges in the N95 masks is that this charge slowly dissipates after a while and the protective effect of the masks wears off.
“If you use [the N95 mask] the electrostatics are lost for hours, ”said Zhong. “That’s why you can’t use regular disinfection methods [the mask] and maintain the filtration efficiency. “
After a mask loses much of its charge, a corona discharge device could be used to restore the mask’s protection level to almost its full capacity.
In a study published by Zhong and her team, it was found that corona discharge sterilization was able to keep N95 masks near maximum filtration efficiency even after 15 uses and sterilization.
In addition to restoring electrostatic forces in N95 masks, the corona discharge technology was also able to neutralize pathogens that were already on the mask.
How the corona discharge eliminates pathogens is still unknown, but Ye said the team are aware of the electrostatic forces and ions created by the corona discharge device to destroy vital components of these pathogens.
“We only know that these ions damage the DNA and damage the proteins [of the pathogens], but we don’t know the process by which they damage DNA and proteins, ”said Ye.
While The exact mechanism by which corona discharge sterilization occurs has not yet been discovered, corona discharge has been shown to be an effective disinfectant, Zhong said.
The corona discharge has still not reached the sanitary level of alternative chemical agents, but is slowly approaching it, Zhong said. In a process published by her team in pubmed, Corona discharge could achieve 99% -99.9% sterilization rate of E. coli in 7.5 minutes.
Zhong said that not all viruses and bacteria respond equally quickly to sterilization from corona discharges. The various answers, she said, are currently being investigated.
In addition to disinfecting and charging N95 masks, the corona discharge is also much safer than alternative chemical hygiene products like disinfectant sprays, which can damage human tissues, according to Ye.
The corona discharge only leaves a static charge on the surface it was used on, so ye so there is no harm to the user. Aside from being effective, Ye also said the technology can be inexpensive and cost $ 50 to make a battery-powered handheld prototype.
Zhong started working on the N95 project in February 2019. Since then, the team has continued to develop this technology and published research articles on its effectiveness.
Months after the project was launched in January, Zhong’s team began filing a patent and contacting biomedical manufacturers to introduce this technology to the public.
She said it could take about two years for the technology to be released, depending on how the product development process goes.
“We have to work with manufacturers … and we try to talk to investors. We really hope it can be commercialized as soon as possible, ”said Zhong.
Zhong said she plans to continue researching corona discharge and how it can best be used against different types of bacterial viral pathogens. The plan, she said, is to explore different ways and settings in which corona discharge technology can be used.
“We can design a small portable box that you can put in your home and sanitize as many masks as you want,” she said.
“We could also make it bigger and use it in clinics and hospitals to treat multiple masks at the same time. We can even make the machine much larger to handle masks at the industry level. “