SSLEEC – UV Lights & Viruses

UV lights — those emitting in the very short, ultraviolet, wavelengths — are promising to disinfect masks for reuse, as well as to decontaminate shared surfaces and spaces and neutralize the virus in recirculated air

Graphic of artist's representation of UV lights to kill viruses

The COVID-19 outbreak brought with it an almost immediate and unprecedented national shortage of personal protective gear needed by health-care workers and others seeking to prevent the spread of the virus. N95 masks intended for single use by front-line health workers were being cleaned and reused. Questions arose: Were they clean? Were they safe? Were they still effective?

Further, cases of COVID-19 spiked wherever large groups breathed recirculated air in closed spaces, such as on navy and cruise ships, and in hospitals, restaurants, churches, elder-care facilities, and prisons. While some of those facilities were closed temporarily by state and local stay-at-home orders, caseloads spiked in prisons and on navy ships, for example, which had to continue operating or, in the case of cruise ships, were not allowed to dock. As of June 1, according to the Santa Barbara County Public Health Department, 1,669 cases of COVID-19 had been identified in the entire county (population 91,350) — just under 2 percent — while Lompoc federal prison had 971 cases among an inmate population of about 1,500, an infection rate of ore than 60 percent.

Given that COVID-19 will likely be with us for some time, and some other new virus may catch us off guard in the future, solutions are clearly needed to disinfect masks for reuse, as well as to decontaminate shared surfaces and spaces and neutralize the virus in recirculated air. UV lights — those emitting in the very short, ultraviolet, wavelengths — are promising. Already, some jails and prisons are using robots topped by a cylindrical bank of UV lights to decontaminate cells and shared spaces, such as dining halls. UV light damages human skin and eyes, so the rooms are emptied before the robots go through, sanitizing everything in them. A UVC robot is used at the county jail in Grand Rapids, Michigan, and as of mid-May, the 1,400-bed jail had seen only two positive cases of COVID-19, even though Michigan has one of the highest positive case counts in the country.

For the past twenty years, the Solid State Lighting and Energy Electronics Center (SSLEEC) in the UC Santa Barbara College of Engineering has been a world leader in developing ever-more-powerful and energy-efficient solid-state LED lighting. For about fifteen years, smaller SSLEEC research efforts have been directed at developing LEDs emitting in the ultraviolet wavelengths of 200-280 nanometers (UVC), primarily with an eye to water purification in areas of the world lacking water-treatment infrastructure. UVC lights have been used for decades by municipal water plants, because they destroy the DNA of many microbes, rendering drinking water safe.

While we receive ultraviolet light in the form of UVA and UVB from the Sun, UVC, the ultraviolet light of choice for purifying air and water and for inactivating microbes, can be generated here only via man-made processes. According to UCSB materials professor and SSLEEC co-director and ECE Prof. Steve Denbaars, the center’s UV-C work has intensified over the past four years. Meanwhile, with government funding for UV LED extremely limited, many other universities in the United States have stopped working on them altogether.

Until recently, UVC decontamination systems — whether in municipal water-treatment plants or devices like the SteriPEN, which backpackers use to purify water — have been enabled not by semiconductor-based LEDs, but rather by mercury-vapor lamps. If the glass breaks in the SteriPEN, mercury is released, rendering the device useless. 

One big drawback to using mercury lamps for disinfection of enclosed spaces is that they require a lot of voltage to operate, which is difficult to achieve for a portable device should it need to run on battery backup during a power outage. But LEDs, which are small, non-toxic, run on little power, and are essentially shatter-proof “can go everywhere,” says Denbaars. “You could even imagine having a UV LED on your cellphone to decontaminate it if someone else touches it.” 

When, in March, UCSB Executive Vice Chancellor for Research Joseph Incandela ordered UCSB labs to ramp down campus laboratories in response to the outbreak, exceptions were made for what was deemed “essential research.” SSLEEC’s UV projects qualified and were allowed to continue. “Pre-COVID, we had one [PhD] student working on it; now we have five,” Denbaars notes. “Once we got declared essential research, we shifted people from the white-LED projects to the UV LED projects.”

With COVID, Denbaars says, “You have a tipping-point application, because you can’t decontaminate an entire room by spraying, and you can’t decontaminate your food by spraying it with Clorox,” he says. “You can’t even decontaminate your mask with Clorox, or with alcohol. But you can decontaminate it with UV light. The other way to decontaminate masks is to use vapor hydrogen peroxide, but to do that you have to buy a special reactor made for hydrogen peroxide, which is expensive, and that process allows you to use the mask only about three times.

COE News "The Pathway to UV Lights that Can Destroy Viruses" (full article)