“Deep clean.” This sanitation lingo has appeared everywhere—restaurants, rental cars, office buildings—since businesses began reopening amid the coronavirus pandemic. Forget that nobody totally knows what it means, or that scientists are increasingly skeptical that the virus spreads by touching, say, a doorknob. The words are meant to reassure, to conjure disinfectant carts and vigorous scrubbing and safely glistening surfaces. But what if the world didn’t need to rely on all that elbow grease to ease our minds? What if all we needed was a little more…light?
To kill coronavirus and other pathogens, scientists have harnessed a form of ultraviolet light, UVC, that the ozone normally absorbs. This type of radiation harbors more energy and is thus more harmful to humans than UVA or UVB, the rays that leave sunburns. But hospitals and other institutions have long used UVC light to disinfect empty rooms and personal items, and early research suggests that the beams can indeed inactivate the new coronavirus in air and liquids, as well as on surfaces. The virus’s predecessor, SARS-CoV, is known to wither under UVC rays. “This is a pretty well-established method,” says Jonathan Posner, a professor of mechanical engineering and chemical engineering at the University of Washington.
Posner helps helm UW's Engineering Innovation in Health program, which learned earlier this year that first responders in the Seattle area were sending N95 respirators to Madigan Army Medical Center, south of Tacoma, to decontaminate them. The process could take a week, and it was expensive. The region needed a quicker, less centralized way to clean masks at a time when supplies could quickly disappear.
After some brainstorming, Posner and company settled on building a box with beams of UVC light. Over a 30-minute period, the microwave-like machine applies 1,000 millijoules per square centimeter of 254-nanometer light to disinfect as many as 15 N95 masks loaded onto a wired tray. The radiation can’t miss a spot, which a dome-shaped respirator complicated. “What we found was, if you put a mask in a chamber that had equal light from the bottom and the top, that the top surface would see three times as much dose as the inside surface just because of the shape and the curvature,” says Posner. “Obviously, shadowing and shape and curvature matter a lot when it comes to actual dose.”
Ultimately, the engineers were able to build around this problem. With the help of some Vashon manufacturers and the backing of the Medic One Foundation, UW Population Health Initiative, and Medtronic Foundation, the program has produced 54 boxes to date for fire departments and emergency medical teams across King County. They aim to distribute over 100 boxes ultimately.
EMTs and firefighters aren’t the only ones who can access this burgeoning technology. Bothell-based startup Vioguard has developed products in recent years that use UVC light to disinfect everyday items such as phones, keys, tablets, and pens. Its original “Cubby,” created long before Covid, was designed to clean a keyboard and a mouse; the latest iteration can accommodate more of the objects customers might find in the “clean” receptacle at store checkouts. It takes under a minute to disinfect them. “When you use chemicals, you're relying on a human to apply the chemicals correctly and leave them on long enough [for wetness] to dry,” says Mark Beeston, the company’s vice president of sales and marketing, “and with UVC, you place the object in the UVC, like the Cubby+, and it runs its cycle and it's disinfected the entire surface of the device you're trying to disinfect.”
At $899, the Cubby+ will bust most people's holiday gift budgets. But Beeston envisions a broader impact in the short term. “I think that the big advantage is for small businesses, putting it in the front lobby of your office space,” says Beeston.
Vioguard isn't alone in advancing this concept. Pricey UVC disinfectants are increasingly hitting the market. From an academic's perspective, however, Posner doesn’t think individual consumers should invest too much in using UVC light to clean surfaces. “If you leave a surface for a few days, it's not going to have any virus on it—five to seven days, probably less, and that's been well-proven,” the professor says. Another reason? Elbow grease works. “Any surface you can wipe down, you should just wipe down,” he says. “I just wipe down my devices with [isopropyl] alcohol, which will kill all the virus."
Large spaces might be another matter, Posner says, depending on the circumstances; quick room turnarounds at hospitals have always made sense for UVC. In other settings, though, we shouldn't count on this type of light to rid us of "deep cleaning" anytime soon.