FAQs about UC San Diego’s wearable mask sensor for COVID-19

Monitoring your potential exposure to COVID-19 could be as simple as wearing a sticker on your mask. Researchers at UC San Diego are developing test strips that can be stuck on N95, surgical or cloth masks and be used to detect the presence of SARS-CoV-2 in a person’s breath or saliva. 

This newly funded project has made headlines—and raised questions. For answers, we followed up with Jesse Jokerst, a professor of nanoengineering at UC San Diego who is leading the project. 

How is this approach different from other at-home tests for COVID-19? 

This approach is designed for daily COVID-19 surveillance in high-density settings where a lot of people are together indoors for prolonged periods of time, such as hospitals, nursing homes, shelters, prisons, dialysis centers, halfway houses, etc. Our goal is to facilitate early detection of COVID-19 infections in high-risk populations. This approach provides a simple way to do that by integrating daily detection onto something that people are already wearing (masks). The notion is that a new day means a new strip; with this constant nature of surveillance, we can stop outbreaks early in high-density settings before they escalate. And rather than requiring you to swab your nose or throat, this strip collects particles that you breathe in and out throughout the day. 

How do the stickers work?

The stickers are designed to detect the presence of protein-cleaving molecules called proteases—not the virus itself—that are produced from infection with the SARS-CoV-2 virus.

The idea is that a sticker would be worn on your mask, in front of your mouth.

Throughout the day, airborne particles that you inhale and exhale will accumulate in the test strip.

When you’re ready to activate the strip, you would peel the sticker off and squeeze the blister pack.

The blister pack releases a reagent that changes color (for example, pink to purple as illustrated here) in the presence of the SARS-CoV-2 proteases. The top line of the strip is the control line, the bottom line is your test line. A color change in the reagent at the bottom line would indicate a potential exposure; this means you should get tested for COVID-19.

You would then dispose the used sticker and replace with a new one.

Can I use the stickers in place of getting a COVID-19 test?

The stickers are not a replacement for getting a COVID-19 test. They are not as sensitive as diagnostic COVID-19 tests run in a lab. The stickers are meant to be used as a surveillance tool for monitoring COVID-19 exposure, which can be done on a daily basis. Diagnostic testing, on the other hand, is done occasionally or less frequently. That’s the difference between testing and surveillance.

The analogy I like to use here is that this is like having a smoke detector in your home. It sits in the background at the ready and when it goes off, it does not tell you exactly where the fire is or what kind of fire it is, but that there is a problem and you need to take action. With these stickers, we’re similarly creating a warning device to tell you that you may have been exposed to SARS-CoV-2, and that’s when you would seek formal testing.

Why would we need these stickers if we already have COVID-19 tests?

While diagnostic viral testing is a critical tool, it does not scale readily for daily monitoring of asymptomatic or pre-symptomatic individuals. The value of surveillance for infectious disease is that it is ongoing. Just like how your smoke detector is in the background and at the ready, the stickers would be working on something you’re already wearing and can be used daily. This approach would supplement other monitoring efforts like wastewater monitoring, which is currently happening at UC San Diego. The stickers would add to our arsenal in the fight against COVID-19 and help us identify outbreaks early before they have a chance to spread.

Does a positive result mean I am infected with COVID-19?

Just like your neighbor’s house fire could cause your smoke alarm to go off, a positive result does not necessarily mean that you have COVID-19. It does mean potential exposure, so you should move beyond the surveillance phase and seek active testing. This could help identify asymptomatic and pre-symptomatic cases early, and thus prevent outbreaks in high density settings. 

How will the sticker detect what’s in my breath or saliva if it’s placed outside my mask?

Most masks have some airflow (otherwise you would suffocate). The sticker has vents both at the back—that allow air to flow through from your mask—and at the front to sample air from the environment.

If the sticker is meant to work outside the mask, does this mean that masks are not protecting us from COVID-19?

Masks definitely prevent the spread of COVID-19. All masks have some degree of permeability. N95 respirators, for example, reduce particle spread by 95%, so 5% of airborne particles can go through. This is the permeability we are exploiting to sample the air.

Will the sticker also detect SARS-CoV-2 particles in the air around me?

We do not know yet but hope so. The sticker will accumulate aerosols that you breathe in and out. The sticker will sample the air in your environment—not just the air that you are exhaling. Our goal is that this would serve as surveillance of the environment and not just the person wearing the sensor.

Can I wear the sticker inside my mask instead of outside?

Yes, either should work but we suspect that the exterior would be more comfortable. 

Would wearing this sticker be a violation of privacy? 

No. The sticker does not change color spontaneously as the user is wearing it. The color change would occur when the user activates the strip, which would be done in private.

How long would I need to wear the sticker before performing the test? 

We designed this for use in high density settings where individuals are at high risk, like nursing homes, shelters and prisons. The goal is that at the end of each 8-hour shift, residents, patients and staff would activate their test strips. We are doing studies to determine if shorter time periods can activate the color change. 

Can I still use my mask after activating the test strip? 

Absolutely. Just peel off the sticker when you are done. 

When will this be available to the public? 

The stickers are still in development. We currently have the reagents (in the blister pack) validated with recombinant proteases and are now evaluating them in a variety of more complicated samples. One of our next steps is to test the strips on COVID-19-positive saliva samples. We will work with UC San Diego School of Medicine Professors Louise Laurent and Rob Knight, who have access to a biobank of these samples. 

One big question is: How much of these proteases accumulate on our face coverings? And that depends on how long we wear them on our faces and how much we speak. Once we have these questions answered, we will begin testing in a cohort of known positive and known negative subjects. This should be in the second quarter of 2021. 

Then, we will move on to testing on patients and healthcare workers at VA San Diego Healthcare System, in collaboration with William Penny, a professor of clinical medicine at UC San Diego School of Medicine and a cardiologist at VA San Diego Healthcare System. 

Could this work as a saliva test? 

If these do not work out as mask stickers, we will repurpose the strips as dipstick tests using saliva as a sample. Here, the user would simply expectorate into a tube and add a test strip containing the color-changing reagents. While not as simple, this type of test could also be performed daily and still have value as a surveillance approach.