In the nascent days of the COVID-19 pandemic, Jiaxing Huang watched as the novel virus overwhelmed the hospitals in his native China. A professor of materials science and engineering at Northwestern University, he contacted colleagues back home to brainstorm how to apply their expertise to mitigate future pandemics and sent the subsequently published suggestions to the National Science Foundation.
The NSF had a similar idea, eventually putting out a call for rapid response non-medical research grant proposals to address the spread of the SARS-CoV-2 virus. But not before awarding Huang. In mid-March, he became the first materials scientist to receive a $200,000 grant to develop a chemical add-on for traditional masks that can destroy COVID-19. Now Huang and his team have put their other research aside to concentrate on this new project.
“I was trying to motivate my peers and students that even though we don’t work on the front lines or in virus-related research, there are still ways we can help,” says Huang. “We want to be part of the long-term effort to contribute—not just for the current pandemic, but to be better prepared for future ones as well.”
Studies have shown that masks and respirators reduce coronavirus spread and infection rates, and several states are mandating them in public or when not practicing social distancing. Increased demand, coupled with shortages, have caused their average prices to as much as quadruple. Medical technology analysis firm Life Science Intelligence estimates that global sales of masks and respirators will exceed pre-pandemic estimates by 211% and 305%, respectively, depending on how the COVID-19 virus spreads.
With medical-grade masks and respirators in short supply for healthcare workers and civilians making do with makeshift fabric versions, the quest is on for more effective, antimicrobial, and reusable facial protection for everyone. It’s particularly urgent in the U.S., the global leader in COVID-19 cases, which have climbed to nearly 1.4 million and threaten to worsen as states relax shelter-in-place measures.
Harnessing copper in masks
Right now, the gold standard for protecting people from the virus is the disposable medical-grade N95 respirator, which traps particles through layers of filters and electrostatic charge. This enables N95 respirators to filter out 95% of non-oil particles as small as 0.3 microns in diameter. Although the coronavirus is smaller, between 0.05 and 0.2 microns in diameter, wearing masks with smaller pores is problematic because they make breathing more difficult. The N95 masks instead thwart the virus’s path with multiple layers, while static electricity draws SARS-CoV-2 to the fabric. However, they’re made for one-time use, since liquids and humidity (including aerosolized droplets, sneezing, and exhaling) dampen those charges and render the masks less effective the more they’re worn.
Even before the pandemic, researchers and manufacturers from around the world were trying to create reusable masks that both filtered and destroyed bacteria and viruses. A number of antimicrobial masks already on the market use copper-infused filters and nanofabrics, which are engineered with tiny particles to give them enhanced attributes like water, odor, and microbial resistance.
Copper has long-established antimicrobial properties that include killing the COVID-19 virus within four hours. Positively charged copper ions attract and trap bacteria and most viruses, which are negatively charged. The copper ions then penetrate the microbes and destroy their ability to replicate, significantly reducing the number of infectious particles that might get through the pores of the mask. (Silver and zinc ions, also used in some masks, deactivate microbes in similar fashion.)
But just having an antimicrobial layer or coating isn’t enough. People shopping for such masks need to consider a combination of factors—the pore size, number and type of layers, as well as the seal. For example, medical N95 respirators have metal bars that wearers can bend so the top edge conforms to their nose bridges and lower cheeks.
“One of the ways in which COVID-19 is spread is through nose and mouth secretions (droplet transmission) and probably by airborne transmission (like breathing out the virus),” says Carl Fichtenbaum, an infectious disease professor at the University of Cincinnati College of Medicine. “If somebody were to sneeze or cough, the mask should not fall off their face. So you have to know whether the copper or other chemically enhanced masks have the same ability as an N95 mask to form a tight seal and whether there are sufficient layers to prevent droplets or airborne particles from getting through.”
If somebody were to sneeze or cough, the mask should not fall off their face.”
Masks that use copper technology vary widely in terms of degrees of effectiveness, price, and longevity, with some intended for healthcare use and others purely as an upgrade from fabric masks. Costs for single masks generally run from $10 to $70, with antimicrobial properties lasting from 30 washes to the life of the product. Some companies have tested their products against other viruses, though none have against COVID-19, which requires highly specialized facilities that aren’t readily available. “Virus size, infectivity level, and chemical properties vary and influence how well masks work,” adds Fichtenbaum.
Some high-tech masks come at a high price, in the $50 to $70 range. Israeli fiber technology company Argaman has one featuring four copper-infused layers and copper oxide filters from Czech firm Respilon, which also sells its own masks. Israeli startup Sonovia uses zinc oxide coating and five-micron filtration that is supposed to last a year.
Companies that specialize in copper-infused antimicrobial apparel and mask specialty outlets offered more affordable versions. Copper Compression and the U.K.-based Copper Clothing offer four-layer masks blocking 99% of particulates, while Copper Mask uses six-ply copper and HEPA filters blocking 92%. Another company, Kuhn Copper Solutions—founded by microbiologist Phyllis Kuhn, an early advocate of copper use in hospitals—specializes in copper mesh masks and inserts that can be combined with traditional or cloth versions.
You can also find copper-infused cotton masks at some furniture and apparel outlets—like The Futon Shop, CustomInk, and Atoms shoes—that hopped on the copper bandwagon by leveraging existing production pipelines.
Nobly, some of these companies have done their part to address the mask shortage. Copper Compression donated 18,000 masks to New York and New Jersey-area hospitals, while Atoms is donating one mask for every mask sold to the New York City Housing Authority.
Engineering masks that disinfect themselves
The pandemic has also prompted universities from around the world to step up research into new mask technology, most notably through integrating antiviral chemicals or repurposing water filtration techniques.
Rather than reinvent the copper-infused mask, Northwestern’s Huang is looking at an inexpensive way to incorporate chemicals traditionally found in sanitation products, which are known to deactivate a broad range of viruses. He’s looking into sprays, as well as chemically treated fabrics, patches, and inserts for disposable or DIY masks—all of which would ramp up the effectiveness of existing masks. “What we need to worry about is how to fix these agents so they don’t [release] easily when people inhale and get into their lungs,” he says. “But then we need to have them go away during exhalation. That’s the science challenge.”
What we can do best is really to show people that this idea works.”
Huang’s grant gives him a year to publish his findings, which he hopes will inspire others to design products using them. “What we can do best is really to show people that this idea works,” he says. “That’s our contribution: speed up the technical solutions.”
Meanwhile, Israeli researchers have attempted a similar approach that’s already being tested at the Galilee Medical Center. Mechanical engineering professor Eyal Zussman of the Technion-Israel Institute of Technology led a team that developed a 3D-printed nanoscale fiber sticker coated with antiseptics that trap particles and neutralize viruses in droplets that land on the mask. The sticker attaches to a traditional mask to provide extra protection.
Other researchers are finding ways to apply water purification technology to air filtration. Chris Arnusch, a water research professor at Ben Gurion University (BGU), also in Israel, spent five years developing porous graphene membranes with antimicrobial and antiviral properties for use in water purification. Now, he’s trying to validate the technology for air, with an eye toward adapting it for masks or air filters. Pure graphene is an atom-thick layer of graphite, a component used in pencil lead, that’s incredibly strong and conducts electricity. Arnusch creates a foam-like form of graphene for his filters by training a laser on plastic surfaces. Armed with seed funding from BGU and the Israeli government, he’s now teaming up with a startup to commercialize this and other products.
“In the case of my water filters, the pores are larger than the bacteria and viruses,” says Arnusch. “But if you electrify the surface in water, it kills the bacteria and viruses as they pass through. I’m trying to see if it works in the air. Once proven, we just need to adapt it to a mask or air filter.”
Laser-induced graphene also interested Hong Kong Polytechnic University researchers, who are applying the material to disposable surgical masks to make them self-sterilizing and ultra water-repellent, so virus-laden droplets roll off. In an April paper, they noted that sunlight could theoretically sterilize a graphene-coated mask by heating it to 176°F.
Once proven, we just need to adapt it to a mask or air filter.”
University of Cincinnati researchers are also developing mask filters by adapting water filtration technology to air. The project involves integrating a carbon nanotube heater into a fabric that’s made of carbon nanotubes and polymer fibers. The nanotubes’ small diameters and collective high surface area could effectively separate microbes, while heating the carbon could kill them. Having successfully applied this carbon nanotube heater technique to the water purification industry, the team is trying to use it to filter air, with support from the National Institute for Occupational Safety and Health, a division of the Centers for Disease Control and Prevention.
In battling COVID-19, even the most effective masks need to work in conjunction with other protective measures, like social distancing and hand-washing. And it may be too early to know if high-tech masks work better than their simpler cousins.
“The bottom line, of course, is that you have to have this tested in a real-life environment to see whether what you say it does, it actually does,” says Fichtenbaum. “There’s been testing on a variety of masks, with different results from different viruses. Not every virus is the same.”