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UW face mask
November 2, 2020

Pivoting for new problems: Engine researchers drive mask insights

Written By: Staff


When the COVID-19 pandemic hit the United States in spring 2020, Mechanical Engineering Professors Scott Sanders and David Rothamer were among the UW-Madison faculty, staff and students who stepped up and devoted their expertise and ingenuity to help in the fight against the novel coronavirus.

Sanders and Rothamer, who are experts in measuring gases and particles in internal combustion engine processes, pivoted to study mask materials, construction, fit and filtration. And they were well positioned to help, since the tools they already use in their combustion systems research can measure particles in the same size ranges as those expelled by breathing and talking as well as coughing and sneezing.

They conducted extensive testing to measure the effectiveness of different types of face masks at filtering aerosol particles.

In those tests, they used a mannequin wearing masks of varying styles and materials to demonstrate how tiny particles from a human breath and larger droplets from a cough escape from, or remain inside, each mask. They outlined the results in a video showing each mask’s effectiveness at containing both.

 Badger Seal
The Badger Seal is an inexpensive fitter that ensures a tighter mask seal around the wearer’s nose, mouth and face.

A key finding of their research is that the effective filtering efficiency increases if there are no gaps at the top, sides and bottom of the mask that could allow virus particles to escape. That prompted them to work with Lennon Rodgers, who specializes in engineering design and directs the Grainger Engineering Design Innovation Laboratory, the engineering makerspace at UW-Madison, to develop a simple and inexpensive fitter that ensures a tighter mask seal around the wearer’s nose, mouth and face.

Known as the Badger Seal, the mask fitter is a soft, adjustable “frame” with elastic worn either as ear loops or behind the head. With readily available materials, such as elastic cord and foam-covered wire or pipe cleaners, the fitter is easy to make at home in minutes. Production facilities beyond the UW makerspace are also beginning to make the Badger Seal.

When worn over non-medical-grade disposable masks, the Badger Seal significantly improves the masks’ filtration performance, according to research conducted by Sanders and Rothamer.

“Adding the Badger Seal to a three-ply disposable mask helps contain aerosols and droplets,” says Sanders. “For wearers, a sign of a tight fit is when the mask material moves in and out with each breath.”

In addition, Rothamer’s expertise in filtration allowed him to play a crucial role in a multidisciplinary UW-Madison effort to rapidly design a high-quality, non-medical-grade face mask from scratch.

Rothamer reworked the instruments in his combustion engine laboratory to measure the filtering properties of prototype masks designed by his collaborators, which included the university’s experts in textiles and infectious disease. In all, Rothamer tested 130 different combinations of materials for masks, and insights gleaned from these tests helped the team design a mask that provides the highest filtration, breathability and comfort possible for the end user.

The team consisted of dozens of people from across UW-Madison, including Majid Sarmadi, a School of Human Ecology professor with industry experience testing textile products, and Maria Kurutz, a SoHE design studies faculty associate, who patterned and sewed scores of prototypes. Peter Lukszys, a Wisconsin School of Business expert in supply chain management, drew up the group’s path from raw material to finished masks.

Rothamer’s lab tested pairs of prototype masks until the group arrived at a design comprising three layers of spun-bond polypropylene material that can be hand-washed at least five times without significant effects on filtration. The mask’s filtration efficiency exceeds any other publicly available cloth mask the team has tested, while its cost (about $3 each) is comparable to many single-use masks.

Lukszys helped the team find the right match for scaling up the sewing operation: Laacke & Joys, a 176-year-old manufacturer based in Brookfield, Wisconsin. As the fall semester began, as many as 24,000 of the new masks produced by Laacke & Joys were available for students and staff returning to campus.

“I’m really very pleased with what the team developed in such a short time in terms of filtration and pressure drop (breathability),” Rothamer says. “It just goes to show—if you get the right group of people together with the right complementing expertise, you can move these things surprisingly fast to achieve a high-quality product.”