Facemasks As the Latest Wearable Sensors

Colour-changing strips integrated into nonwoven facemasks that work on the same principle as pregnancy testing kits may soon be used to detect Covid-19 in a user’s breath or saliva.

A University of California San Diego project, which received $1.3 million from the US National Institutes of Health (NIH), is aimed at providing simple, affordable and reliable surveillance for Covid-19 infections that can be done daily and easily implemented in resource-poor settings. It is part of the NIHRapid Acceleration of Diagnostics Radical (RADx-rad) programme.

“In many ways, masks are the perfect ‘wearable’ sensor for our current world,” says Jesse Jokerst, professor of nanoengineering at the UC San Diego Jacobs School of Engineering and principal investigator of the project. “We’re taking what many people are already wearing and repurposing them, so we can quickly and easily identify new infections and protect vulnerable communities.”

The test strips, that can be put on any mask, are being designed to detect the presence of protein-cleaving molecules, called proteases, produced from infection with the SARS-CoV-2 virus.

The idea is that as the user breathes through the mask, particles – including SARS-CoV-2 proteases if the user is infected – will accumulate in the test strip. At the end of the day or during a mask change, the user will conduct the test. The test strip is equipped with a blister pack that the user squeezes, releasing nanoparticles that change colour in the presence of the SARS-CoV-2 proteases. A control line on the test strip will show what a positive result should look like. This would be similar to checking the results of a home pregnancy test.

“Think of this as a surveillance approach, similar to having a smoke detector in the house,” said Jokerst. “It would just sit in the background every day and if it gets triggered, then you know there’s a problem and that’s when you would look into it with more sophisticated testing,”

The test strips can be easily mass produced via roll-to-roll processing to keep costs down to a few cents per strip.

“We want this to be affordable enough for daily testing,” Jokerst said. “This would allow facilities at high risk such as group homes, prisons, dialysis clinics and homeless shelters to monitor for new infections earlier and more frequently to reduce spread.”

Jokerst is teaming up with researchers at UC San Diego School of Medicine to test the strips first on Covid-19-positive saliva samples, then on patients and healthcare workers at Veterans Affairs San Diego Healthcare System.

“The proteases we’re detecting here are the same ones present in infections with the original SARS virus from 2003 as well as the MERS virus, so it would not be too far of a stretch to imagine that we could still benefit from this work later on should future pandemics emerge,” he said. “Even with vaccination efforts underway, this surveillance approach could be deployed in parts of the world where vaccines are not yet available or still limited in distribution.