How bioengineers tackled the leaky mask problem

  • October 19, 2021

Less obvious is the leakage from the mask’s sides and bottom, which a sneeze or cough can increase many times over.  While three-ply disposable masks provide some protection for the wearer and those around them, they could be much safer for all.

That’s the conclusion of a team of researchers from the Brigham and Women’s Hospital, Harvard University, Massachusetts Institute of Technology (MIT) and Massachusetts General Hospital.  They set out to develop a more practical everyday mask that could be mass-produced and sold at a comparable price.  They recently posted a non-peer reviewed preprint of their research on medRxiv.

A pair of old friends, Bioengineer Jeffrey Karp and Physician-Scientist Anthony Samir, took up the challenge.  Karp heads an eponymous medical engineering lab at Brigham, while Samir runs a bench-to-bedside bioengineering lab and research center at Mass General.  The two Boston institutions formed the Mass General Brigham Center for COVID Innovation in March 2020.  They tasked Karp and Samir with leading an N95 mask working group to solve the N95 shortage plaguing healthcare workers.

Although scientists had not yet proven it at the time, both men quickly realized that transmission of the SARS-CoV2 coronavirus was highly likely to be aerosol-based and that everyone would need to wear masks to control the virus’ spread.  Their challenge was to provide that effective protection, at community scale, not only from minute viral particles but also from larger particles that people spread when they cough or sneeze.  So they convened a group of U.S. and U.K. filtration experts to discuss materials that could provide N95-level filtration.

They concluded that the types of polypropylene used in the everyday three-ply surgical mask are highly effective in filtering aerosols, and the materials are also plentiful and inexpensive.  However, regular surgical masks have a significant flaw — they just do not fit properly, allowing in about 40% unfiltered outside air under the mask during inhalation.  Similarly, about 40% of the wearer’s unfiltered exhalation can escape through gaps at the edges of the mask.  So, the team decided to focus on redesigning these masks using the same materials to drastically reduce that leakage.

That meant extending the nose wire all around the mask and making the ear loops adjustable.  Those changes make their new Ultra Fit mask conformable to anyone’s face, Samir recently told Medical Design & Outsourcing.  “In doing that, we were able to drastically improve the performance of the mask, so leakage goes down on average by a factor of more than four in novice users,” Samir added.  “So, from 40% leakage, we go down to less than 10% leakage in most people, and in experienced users we’re going down to less than 5% leakage in a lot of people.  And that’s a really, really big improvement for a mask that leaks 40%.”

The researchers — who also included Daryl Chulho Hyun, a former biodesign fellow at Oxford University, postdoctoral research fellow Martin Jensen, and others — made one more significant change.  They added a flap near the interior edges to capture aerosolized droplets before they can leak outside the mask.  A flange made of composite spunbond (melt-blown polypropylene) pushes the flap against the face when the wearer coughs or sneezes.  They performed numerous tests using thermography and laser-scatter droplet imaging to measure the flap’s performance.  The tests showed a major reduction in leakage of unfiltered exhaled air around the mask.

Hyun prototyped numerous mask iterations and tested them repeatedly to arrive at a high-performing, low-cost mask.  Karp and Samir then recruited Hank Miller, CEO of Boston-based Harry Miller Co., a 100-year-old textile manufacturer, to develop a prototype and manufacturing plan.  They also brought in Steven Gordon, an MIT PhD Mechanical Engineer and serial entrepreneur, to help them work out how to mass-produce the new mask and run a company to manufacture and distribute it.

Gordon had started a company called Intelligent Automation Systems in 1987 in Cambridge, Mass., to develop automated manufacturing systems that would help keep manufacturing in the U.S.  After Brooks Automation (NSDQ: BRKS) bought Intelligent Automation in 2002, Gordon co-founded Intelligent Bio-Systems, which developed DNA-sequencing instruments, reagents and software systems.  Qiagen (NYSE: QGEN) bought Intelligent Bio-Systems in 2012.

“I’ve been able to contribute to the design of the mask, which was rudimentary when I first got involved, to a place where it could be manufactured at high volume,” said Gordon, now CEO of Katharos Labs.  “When they developed the mask, they had this long wire that was bent in all kinds of crazy shapes …. It kind of worked, but it would be a nightmare to manufacture it.”  Gordon suggested using individual wires to span each side of the mask, corner to corner, and cinching it shut with the ear loops.  Then, the wearer can press the wires against the face for a custom, close fit and finish sealing mask by adjusting the variable-length ear loops, he explained.  “Our sense is that this could be used in schools, for events like concerts or weddings, in airports, on airplanes, public transportation and in the workplace,” added Karp.  “I think that one of the really nice things about this mask is that because each person is fitting it to their face and it’s really personalized, once you have it in place, it doesn’t only have greater protection — you can actually feel it.”

Gordon, Hyun, Karp, Miller and Samir formed a company, Katharos Labs (“katharos” means “purity” in Greek), in October 2020 to make and market the Ultra Fit mask.  Katharos’ leaders opted to start manufacturing in China because of its robust surgical mask production infrastructure.  However, their plan is to use Gordon’s expertise to modify and modernize existing mask-making equipment in the U.S. to automate domestic fabrication for mass production at a low cost.

The researchers have also prepared a paper about how they developed and tested the Ultra Fit mask, including details about their efforts to validate the fit and field experiments by students wearing the masks in a classroom and mathematical modeling of infection spread on a subway.  In both settings, the Ultra Fit mask approached the efficacy of N95 respirators to prevent the community spread of COVID-19, they reported.  They had not submitted the paper to any journals for publication at press time.

The researchers also ran experiments cleansing the mask by hand and in a washing machine to determine if it can retain its filtration properties.  It has the potential to withstand multiple hand washes; however, the experiments to determine how many will continue, according to Karp.  They are also continuing to test the mask to determine compliance with new NIOSH and ASTM standards, he added.

Katharos Labs’ leaders are confident they will find a market for their mask, even with mask mandates being lifted and many Americans acting like the pandemic is over.  More than half of the U.S. population had received at least one vaccine dose by late June, according to the CDC.  Many other countries, however, are much farther behind.  Karp believes the threat of variants and seasonal outbreaks from COVID and other viruses like the flu is imminent.  “We have to educate the general community that having a high-quality, well-fitting, high-performance mask is critical.  A lot of people put a mask on because they’re required to,” he said.  “But a mask that leaks a lot is not a mask that is working well.”

REFERENCE:  Medical Design & Outsourcing; 07 JUL 2021; Nancy Crotti

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