In March, Stanford University bioengineer Manu Prakash flew from France to his home in California and spent two weeks in personal quarantine. After being holed up in the room where he stores his snorkeling and scuba equipment, Prakash emerged with an idea for addressing two of the pandemic’s most pressing challenges.

First, he saw that the global supply chain for disposable N95 masks had broken down, and many hospitals lacked adequate personal protective equipment (PPE). Second, “the masks that are out there, that we put in the hands of our frontline workers, are not that good,” said Paraksh. “They’re often ill-fitting and uncomfortable, and if they don’t fit, they don’t protect.”

To address both of these issues, Prakash aspired to repurpose full-face snorkel masks, outfit them with 3D-printed filter-holders, and use them as a way to meet the growing demand for PPE.

The idea spawned international collaboration, which led to design and testing in Prakash’s lab and elsewhere and resulted in tens of thousands of snorkel masks being shipped and used around the world. The device functions as a combination of mask and face shield.

Mechanical engineer Laurel Kroo, who works in Prakash’s lab, described the design, testing, and distribution of ‘pneumask’ at the annual meeting of the American Physical Society’s Division of Fluid Dynamics.

The researchers in the collaborative project have published protocols for how to decontaminate the device, making it suitable for reuse. Clinical tests suggest that it can be worn comfortably for the entire duration of an eight-hour shift, the team said.

“From a fluid-dynamics perspective, a mask is a hydrodynamic device,” Prakash explained. “A lot is happening when you breathe in and breathe out. You have to have the right kind of filters. You have to think about rebreathing, and comfort.”

Prakash’s lab has turned its focus on many Covid-19 related projects. They helped launch the 1000×1000 project, which repurposes candy floss machines to produce protective, N95-grade mask material.

The machines usually melt and spins out liquid sugar in fine threads; to make filter material, the repurposed machines spin out nanofibres that can trap minuscule particles. And together with partners at other universities and companies, the group helped develop the ‘Pufferfish,’ an open-source, low-cost ICU ventilator. 

Meanwhile, Sunghwan Jung at Cornell University, who studies animals through the lens of fluid dynamics, has been working with researchers including Saikat Basu at South Dakota State University, in Brookings, and Leonardo Chamorro from the University of Illinois Urbana-Champaign on masks that take their shape from the nasal cavities of animals.

“Animals like dogs, opossums, and pigs are renowned for their super-sensitive sniffers,” Jung explained. “They have a very complicated nasal structure, and we tried to mimic that structure in our filters.”

Jung added that the human nose is “fairly straightforward and vacuous,” but dogs and pigs are different. They have twisty, tortuous nasal cavities, and that’s partly why they have such strong senses of smell. “Fluid mechanics tells us that if you have such a tortuous air pathway, you have more chances to capture more particles,” said Jung.

The researchers designed a mask filter that can be 3D-printed to have a similarly tortuous structure seen in these animals. The team said lab tests showed that it can block micron-sized particles and has a low-pressure drop, meaning people wouldn’t have to breathe hard while wearing it.

Jung said that these masks have not been approved or used in hospitals.