Virucidal face mask uses heat to kill coronavirus

Virucidal face mask uses heat to kill coronavirus

Technology News |
By Rich Pell

The reusable mask would include a heated copper mesh that’s powered by a battery and surrounded by insulating neoprene. As the wearer of the mask breathes in and out, air flows repeatedly across the mesh, and any viral particles in the air are slowed and inactivated by the mesh and high temperatures.

Such a mask, say the researchers, could be useful for health care professionals, as well as members of the public in situations where social distancing would be difficult to achieve, such as a crowded bus.

“This is a completely new mask concept in that it doesn’t primarily block the virus,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT. “It actually lets the virus go through the mask, but slows and inactivates it.”

“The masks that we wear now are designed to capture some of the virus,” says Strano. “They do offer protection, but there’s no one really thinking about inactivating the virus and sterilizing the air.”

In setting out to design a mask that would kill viruses using heat, the researchers decided to use copper mesh as the heating and capture element, and performed some mathematical modeling to determine the optimal temperature range they would need to achieve to kill coronaviruses flowing inward or outward from natural breathing.

“The vast majority of masks today function by filtration, filtering particles by size or electric charge,” says MIT graduate student Samuel Faucher. “This mask relies on a different mechanism and works predominantly by thermal inactivation.”

The researchers calculated how rapidly coronaviruses degrade at different temperatures and trapping conditions, and found that a temperature of about 90°C (194°F) could achieve between a thousandfold and millionfold reduction in viral particles, depending on the final mask size. Further, they showed that that temperature can be achieved by running an electrical current across a 0.1-millimeter-thick copper mesh or thermoelectric heater, powered by a small battery.

The current prototypes include a 9-volt battery, which would provide enough power to heat the mask for a few hours and would cool the air before it is inhaled, say the researchers.

“Of course, we need to be mindful of the safety and comfort of mask users,” says Faucher. “The air will be cooled after viral inactivation to make the mask comfortable and safe to use.”

The researchers say they were able to enhance the efficiency of virus deactivation by taking advantage of the breath to create a type of reactor known as a reverse-flow reactor. As the person wearing the mask breathes in and out, the air flow continually reverses, allowing any viruses in the mask to pass over the mesh many times and making it more likely that they will be deactivated. Purified air flows out of vents on both sides of the mask.

“This design,” says Strano, “means you can wear a small mask, something that will fit on your face, but the virus can spend much more time getting deactivated than it would without the reverse flow reactor design.”

The copper mesh in the mask is surrounded by neoprene, an insulating material that prevents the outside of the mask from becoming too hot to wear.

“Achieving the temperature for virus inactivation while thermally insulating the person’s face and ensuring acceptably cool air inhalation made for an interesting heat transfer challenge,” says Buongiorno, the TEPCO Professor of Nuclear Science and Engineering at MIT, “which we resolved with neoprene insulation and regenerative heating.”

One potential advantage of heated masks over conventional masks, say the researchers, is that because they kill the virus, they don’t need to be decontaminated or thrown away after use. Additionally, they may offer extra protection by eliminating the virus rather than only filtering it.

“What we show is that it’s possible to wear something on your face that’s not too cumbersome, that can actually allow you to breathe medically sterile air,” says Strano. “The prospect of being able to breathe in medically sterile air and breathe out medically sterile air, protecting the people around you and protecting yourself, is just the next step. It’s better technology.”

Heated masks would be more expensive than cloth masks or surgical masks, say the researchers, but they may be useful in situations where exposure risk is high and cost is less of a concern. The researchers say they have filed for a patent on their mask design and plan to begin testing prototypes at MIT with collaborators.

For more, see “A Virucidal Face Mask Based on the Reverse-flow Reactor Concept for Thermal Inactivation of SARS-CoV-2.”

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