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As face masks continue to be a daily necessity for many people, they could potentially become hazardous waste for the environment. However, USF researchers are working on solutions to sterilize masks and alleviate this growing problem under the COVID-19 Rapid Response Research Grants Program.
Ying Zhong, a researcher at USF’s Green Research for Energy-Efficient Innovations lab, and Libin Ye, a researcher and professor of cellular molecular biology, created a team of five graduate students to experiment with a new form of sterilization technology to combat pathogenic viruses.
The team created a new form of sterilization technology that uses corona discharge – a phenomenon where an electric discharge causes ionization of nearby gas molecules which could then safely and effectively destroy pathogens on N95 masks. .
“Corona discharge is an electric discharge phenomenon with emitted blue-violet light, which illuminates the air near the discharge conductor,” said Zijian Weng, doctoral student. student in the engineering department.
“This happens when a high voltage is applied to the conductor, causing current to flow with a high potential from the conductor into the nearby air by ionizing and generating excited gas molecules, usually nitrogen molecules, which emit blue-violet light. “
Corona discharge is also a phenomenon that Zhong said he has already experienced in other areas of his research where it “induces permanent charges in polymer films.”
Zhong used this previous experience with corona discharge to explore its potential use for sterilizing the N95 mask. She reviewed different studies regarding corona discharge and its effects on disinfection and concluded that there was sufficient evidence supporting corona discharge as a way to disinfect and reuse N95 masks.
“I know that [corona discharge] can inject fillers, but can it also disinfect masks? Fortunately, I was able to identify a few articles to support this idea, â€Zhong said.
An N95 mask protects its users in two different ways, according to Ye. He said the material used in the masks contains small pores that are able to physically block 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 an electrostatic charge. N95 masks are made with a positive charge, Zhong said, and since many pathogens such as bacteria and viruses are negatively charged, this creates an effect where pathogens adhere to the masks rather than pass through.
“When a negatively charged droplet approaches a positively charged fiber, they will tend to attract each other,†Zhong said. “This is how loaded fibers [of the N95 mask] stop the charged droplet.
The problem with electrostatic charges in N95 masks, according to Zhong, is that after a while, this charge slowly degrades, decreasing the protective effect of the masks.
“When you use [the N95 mask] for hours, the electrostatics will be lost, â€Zhong said. “That’s why you can’t use regular means to disinfect [the mask] and keep the filtration efficiency.
Once a mask has lost much of its charge, a corona discharge device could be used to restore the mask’s level of protection to almost full capacity.
In a study published by Zhong and his team, it was found that corona discharge sterilization was able to keep N95 masks near maximum filtration efficiency even after being used and sterilized 15 times.
In addition to restoring the electrostatic forces in the N95 masks, the corona discharge technology has also been able to neutralize the pathogens already present on the mask.
It is still unclear how the corona discharge clears pathogens, but Ye said the team knows that the electrostatic forces and ions produced by the corona discharge device disrupt the vital components of these pathogens.
“We just know that these ions damage DNA and damage proteins. [of the pathogens], but we don’t know the process by which they damage DNA and proteins, â€Ye said.
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, according to Zhong.
The Corona landfill still has not reached the level of remediation of alternative chemical means, however, it is slowly approaching it, Zhong said. In an essay published by his team in published, the corona discharge was able to achieve a 99% to 99.9% sterilization rate of E. coli in 7.5 minutes.
Zhong said that not all viruses and bacteria respond to corona discharge sterilization at the same speed. The various responses, she said, are currently under investigation.
According to Ye.
Corona discharge only leaves a static charge on the surface it has been used on, Ye said, so there is no danger to the user. Besides efficiency, Ye also said the technology can be inexpensive, costing $ 50 to make a portable prototype powered by batteries.
Zhong started working on the N95 project in February 2019. Since then, the team has continued to develop this technology and publish research papers on its effectiveness.
Months after the project was created in January, Zhong’s team began filing for a patent and contacting biomedical manufacturers to introduce the technology to the public.
She said the technology could take around two years to release, depending on how the product development process unfolds.
“We have to work with the manufacturers… and we try to talk to the investors. We really hope that it can be marketed as soon as possible, â€Zhong said.
Zhong said she plans to continue her research on corona discharges and study how best to use them against various 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 house and disinfect as many masks as you want,†she said.
“We could also make it bigger and put it in clinics and hospitals to process multiple masks at the same time. We can even make the machine much bigger to process industry level masks. “
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