WMU researchers develop framework for creating more efficient masks

KALAMAZOO, Mich.—A little more than a year ago, the average American may have worn a mask for a home improvement project or during flu season at the doctor's office. Since then, people have bought them in bulk to wear to school, work and play. But the efficacy of face coverings on the market is wide-ranging—an issue a team of researchers at Western Michigan University may be on track to change.

Drs. Steve Durbin, a professor in the Department of Electrical and Computer Engineering, and Robert Makin, an assistant professor in the department, developed a method for predicting particle removal efficiency of polypropylene-based filters used in personal protective equipment (PPE)—such as N95 masks—based on how fibers are arranged in the mask material. Their discovery could pave the way for a process to create more effective masks or make equally effective masks out of other materials.

"What we found was that, at least for the ability to remove the particles, the key is disorder at the fiber level—not just how you actually build the mask," says Durbin. "It suggests there are alternatives to testing the raw materials that you're going to make your mask from before you actually fabricate your mask. And you could predict how well it's going to work."

Makin, whose doctoral thesis examined disorder in materials used for electronics, made the discovery by chance. Instead of baking or picking up a new hobby to pass time at the beginning of the pandemic, he found his mind wandering to the science behind PPE and ways he might be able to contribute to the fight against COVID-19.

"We were locked inside our homes for a while and I saw a lot about these masks. I kept seeing high-magnification electron microscopy images of them, and they looked very similar to what we had already studied in semiconductor crystals," says Makin. "I was curious if what we had found with disorder in those systems applied to polymer-based materials; turned out that it did. So it's kind of cool."

Durbin describes disorder as deviations from an ideal structure in nature. He and Makin discovered that in the case of polypropylene-based filters, such as those used in N95 masks, those variations impact the properties of the fibers in a predictable way.

"It's actually very surprising that we found what really controls how well these masks work is a material-level property that you can tune with whatever knobs you have when you go to make that particular sample on a machine," Durbin says. "They directly impact how your final product is going to work."

Durbin and Makin are now working to patent the process for evaluating the filtration efficiency of the material and potentially commercialize their discovery through Western's Office of Research and Innovation.

"To see something that you discover in a lab actually be applied and used in everyday life would be really great," Makin says.

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