Fixing Face Mask Form and Function

As the COVID-19 crisis continues to rage on with no vaccine on the imminent horizon, wearing face masks to curb the spread of bioaerosols carrying the SARS-CoV-2 virus remains one of the pandemic’s most crucial mitigation tools.

The gold standard for healthcare workers has been 3M’s N95 respirator, which has a very close facial fit and very efficient filtration of airborne particles. These aren’t recommended for the general public to prevent respiratory diseases because they are critical supplies to be reserved for healthcare workers and other medical first responders.

Masks for the general public are varied in both style and effectiveness. There are enormous ranges of disposable and reusable masks in a variety of materials. The problem is many of these have flaws that either render them too uncomfortable to wear or inadequately filter the air. An upgrade to mask design on both these fronts is integral to boost infection control.

Georgia Tech researchers approached mask design from an ergonomic perspective. Based on decades of filtration and textile material experience, they are creating a new mask to be comfortable enough for all-day wear that remains in place without frequent adjustment.

The modular mask combines a stretchable knitted Spandex/Lyocell blend with a barrier filtration material. The prototypes made so far for testing employ hook and eye fasteners—similar to the gold-standard N95 respirators—and have a pocket to place an optional filter for further protection. The prototypes haven’t shrunk or lost their shape after 20 washings.

The masks also tackle the fundamental flaw in existing reusable cloth masks of leaking air around the edges, bypassing their filtration mechanism. The leakage problem is depicted by eyeglasses fogging up as exhaled breath leaks around the nose. Georgia Tech’s two-part mask fastens behind the head like many N95 respirators. The front barrier component containing the filtration material is contoured for a tight fit while allowing space around the nose and mouth to prevent breathing restrictions and allow unrestricted speech. It’s made from the same moisture-wicking material used in athletic clothing, and the washable fabric filter is composed of a Spandex/polyester blend. The stretchable portion has holes for ears to help position the mask with conventional hook and eyelet hardware.

“We want people to be able to get the mask in the right place every time,” said Sundaresan Jayaraman, the Kolon Professor in Georgia Tech’s School of Materials Science and Engineering. “If you don’t position it correctly and easily, you are going to have to keep fiddling with it. We see that all the time on television with people adjusting their masks and letting them drop below their noses.”

The researchers published their face mask recommendations in The Journal of The Textile Institute and will make the mask specifications and patterns available for consumers and manufacturers. Necessary materials can be bought from retail fabric stores, and instructions describe how to measure for customizing the masks.

“Good filtration efficiency is not enough by itself,” said Jayaraman. “The combination of fit, filtration efficiency, and staying in the right place make for a good mask.”

In typical fashion, MIT engineers are currently developing a space-age solution to combat the virus. However, its concept is simple—go beyond filtering and inactivate viruses using heat.

The masks utilize a heated copper mesh. During respiration air flows continuously across the mesh and viral particles in the area are halted and switched off by the mesh and the high temperatures. The researchers created a reverse-flow reactor to accomplish this. As the wearer breathes in and out, airflow continually reverses, ensuring any viruses in the mask to traverse the mesh many times to raise deactivation likelihood. The copper mesh is wrapped in neoprene, an insulation material that stops the outside of the mask from becoming too hot to wear.

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

To develop the mask the researchers calculated the coronavirus degradation rate at different temperatures and trapping conditions. They discovered that a temperature of approximately 90 degrees Celsius could provoke between a thousandfold and millionfold viral particle reduction depending on the final mask size. The 90 degree C temperature can be achieved via running a small electrical current (powered by a small battery) across the 0.1-millimeter thick copper mesh or thermoelectric heater. Current prototypes use a 9-volt battery, which generates enough power to heat the mask for a few hours and cool the air before it’s inhaled.

“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,” Strano said. “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 costly than cloth or surgical masks, but they could be useful where risk of exposure is elevated and cost is less of a concern, according to the researchers. They have filed for a patent on the mask design, and intend to begin testing prototypes at MIT with collaborators.