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This UV-light ‘bug zapper’ can decontaminate 600 N95 masks an hour

The best option is for doctors to not reuse masks, but during the shortages of the last few months, a team of engineers from Lehigh University helped a nearby hospital come up with a stopgap solution to make reusing masks safer.

This UV-light ‘bug zapper’ can decontaminate 600 N95 masks an hour
[Photo: courtesy St. Luke’s University Hospital]

In a room at St. Luke’s University Hospital in Bethlehem, Pennsylvania, sits an octagonal machine, 80 inches in diameter and about 5 feet tall, that glows with the bright blue of UV lights. It’s been nicknamed the “bug zapper,” both because it resembles an oversized one, and because, essentially, it zaps away the bug behind COVID-19. Using powerful UV-C lights, the device can decontaminate about 200 N95 masks with just 15 minutes of ultraviolet light exposure. That works out to about 600 masks per hour.

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A team of engineers from Lehigh University and experts from St. Luke’s University Health Network collaborated to build the device—which is technically named the “High-Throughput Symmetrical and Non-Shadowing Ultraviolet Sterilization System”—together over two-and-a-half weeks, They designed it over Zoom meetings and coordinated socially distant drop-offs of materials and assembled sections, which were put together at the hospital by St. Luke’s biomedical engineer Jay Johnson.

[Photo: courtesy St. Luke’s University Hospital]
The collaboration was kicked off when Christopher Roscher, an anesthesiologist at St. Luke’s, emailed Nelson Tansu, a Lehigh professor and director of the school’s Center for Photonics and Nanoelectronics. Roscher realized early on that the hospital, like many health facilities, was probably going to have to reuse masks as they dealt with the COVID-19 pandemic and PPE shortage. He knew that research has shown UV-C lights to remove pathogens and decontaminate materials, and asked Nelson if Lehigh could help create a way to reuse masks as safely as possible.

[Photo: courtesy St. Luke’s University Hospital]

“No health system wants to reuse single-use items,” Roscher says. “We’re operating under crisis conditions, crisis standards, and all health systems have needed to do things they never thought they would do in this setting.” He actually hopes the “bug zapper” isn’t something the hospital needs going forward, but so far it’s proven to be useful tool. Since using the device in April, he estimates the hospital—which is between New York City and Philadelphia and saw many COVID-19 patients—decontaminated more than 27,000 masks. “By doing this, it allowed us to extend our supplies,” he says, “so that there wasn’t a day that came that we had to tell people that we didn’t have any N95s.”

The design of the system is complex because decontaminating masks isn’t as simple as just shining a UV-C light on them. “One of the really important things when focusing on these masks is that they have all sorts of nooks and crannies and crevices that create shadows,” Roscher says. “If the design doesn’t consider all those things, you can leave parts or significant portions of the mask unexposed or underexposed.”

The device’s octagonal shape and internal reflectors—made of polished diamond-plate aluminum—bounce the light around the device to allow for that uniform exposure, making sure the UV-C light hits all the surfaces and folds of the masks that just an overhead light may miss. Each of the eight sides of the frame can rotate, allowing staff to flip the masks in batches so both sides get decontaminated, rather than having to step inside and flip them all by hand. “We were working on a cylinder shape [at first] because we’re so focused on how to get this thing done and the urgency of the hospital,” says Tansu. “We did not really look into the practical aspect, how do you flip the mask then, if there’s 200 masks per cycle?” It was his 8-year-old son that suggested the octagonal shape, when Tansu was working late one night on the project.

By flipping the frames rather than each mask, it also protects the machine’s operators from the UV-C light, which at the intensity needed to decontaminate medical equipment, is harmful to humans. UV-C light decontaminates medical equipment by breaking apart the genetic material of viruses and bacteria, and thus it can also degrade the mask itself, wearing out the material or specifically the seal if overused. Roscher and Tansu aren’t sure how many times masks can be decontaminated in the “bug zapper” before they lose their integrity, but Roscher says they check each mask for holes or to make sure the seal is intact, to ensure the mask is still effective.

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[Photo: courtesy St. Luke’s University Hospital]

Roscher and Tansu still haven’t ever met in person, but they’ve talked a lot over Zoom and texts, and both say how grateful they are that their teams could come together digitally to create this device. Other hospitals have expressed interest in building their own “bug zappers,” and the teams are happy to share the design and their ideas, stressing that this device is for crisis-use only and not for at-home use.

Ultraviolet light has long been used to curb the spread of viruses and bacteria in hospitals, and the pandemic has spurred additional UV-C usage in everything from subway cars to airports. While St. Luke’s device ensured that hospital staff never had to go without an N95 mask, and was designed in line with the CDC and experts such as N95Decon, more research still needs to be done, Roscher says. As the pandemic, hopefully, begins to wane and health workers can come up for air, he hopes we’ll learn more about this method—including exactly how many times a mask can be decontaminated and still be safe to use—so that hospitals are more prepared for a possible second wave.

“In March, the question was, ‘Do I use no mask at all, or do I decontaminate the mask and reuse it, because we run out of supplies completely?’ Everyone would look at that mask problem and say, ‘Oh, you reuse the mask,'” he says. “Going forward [we need to] answer the question of how many times we can reuse it effectively, and what other alternative strategies are there? Hopefully now’s the time to have that conversation.”

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