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Smart mask for monitoring chemicals in exhaled breath

The EBCare mask can collect and analyze chemicals in breath in real time. Caltech / Wei Gao and Wenzheng Heng

Recent respiratory disease epidemics and pandemics, such as COVID-19, have brought renewed attention to what’s in the breath we exhale. Beyond viruses, exhaled breath contains several compounds that can provide information about a person’s health. But there are currently limited tools for analyzing human breath. Typically, breath analysis requires the breath first be condensed into a liquid, known as exhaled breath condensate (EBC). The time and costs associated with this step have limited the use of such analysis.

A research team led by Dr. Wei Gao at the California Institute of Technology has developed a facemask-based system for monitoring EBC in real time. They call the system EBCare (an acronym for exhaled breath condensate analysis and respiratory evaluation). EBCare consists of a mask that continuously condenses exhaled breath and collects and analyzes the resulting EBC. The development of EBCare was funded in part by NIH. The device and its capabilities were described in Science on August 29, 2024.

EBCare forgoes the ice buckets and refrigeration systems that are usually used to condense exhaled breath. Instead, it relies on passive cooling mechanisms. The device reflects sunlight while allowing heat radiation to escape. Meanwhile, the evaporation of water from a hydrogel layer helps the mask to cool. This combination allowed EBCare to stay up to 18°F cooler than an ordinary face mask while indoors or outside at night. In the sun, the difference could be as much as 36°F.

The mask relies on capillary action, or the tendency of water to flow through a narrow space, to collect and transport the EBC to the sensors. The researchers designed a series of microscopic channels to direct the flow of EBC through sensors within the mask. These could continuously analyze EBC even while the wearer was lying on their back.

To demonstrate the mask's ability to analyze EBC, the team added an array of sensors for alcohol, nitrite, ammonium, pH, and temperature. The sensor could wirelessly send the results of the analysis to a smartphone for readout.

The team conducted various pilot studies to test the masks’ capabilities. In one study of 72 people, the team measured nitrite in EBC from smokers, people with asthma or COPD, and people who had recently recovered from COVID-19. Nitrite is a marker of airway inflammation, which people in these groups would be expected to have. As expected, these groups had higher nitrite levels than healthy people. This shows that EBCare could be a reliable way to diagnose, track, and manage airway inflammation.

In another study, the researchers measured alcohol levels following alcohol consumption. They found that EBCare measurements tracked with blood alcohol levels measured by a commercial breathalyzer. A third study showed that ammonium levels in breath tracked with blood urea levels. Urea is a by-product of protein metabolism that increases in the blood as kidney function declines. Thus, EBCare might be used to monitor and manage kidney disease.

 “These first studies are a proof of concept,” Gao says. “We want to expand this technology to incorporate different markers related to various health conditions. This is a foundation for creating a mask that functions as a versatile general health–monitoring platform.”

—by Brian Doctrow, Ph.D.