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The mask, called EBCare for 'exhaled breath condensate' could, for instance, monitor asthma patients for levels of nitrite, a chemical that indicates airway inflammation.
"Monitoring a patient's breath is something that is routinely done, for example, to assess asthma and other respiratory conditions. However, this has required the patient to visit a clinic for sample collection, followed by a waiting period for lab results," says Wei Gao, the lead investigator of a new study describing the mask in the journal
Science.
"Since Covid-19, people are wearing masks more. We can leverage this increased mask use for remote personalised monitoring to get real-time feedback about our own health in our home or office. For instance, we could use this information to assess how well a medical treatment may be working."
Gao had already developed wearable sensors that analysed metabolites and protein levels in sweat, but breath came with new challenges. The breath first needed to be cooled and condensed into a liquid so that it could be analysed—in the lab this is done with buckets of ice or refrigerated coolers, but Gao's new mask is self cooling. A passive cooling system uses hydrogel evaporative cooling with radiative cooling.
"The mask represents a new paradigm for respiratory and metabolic disease management and precise medicine because we can easily get breath specimens and analyze the chemical molecules in breath in real time through daily masks," says Wenzheng Heng, lead author of the study and a graduate student at Caltech. "The breath condensate contains soluble gases as well as nonvolatile substances in the form of aerosols or droplets, such as metabolic substances, inflammatory indicators, and pathogens."
Once the breath has been cooled into a liquid, a series of capillaries draw it into sensors for analysis, which then transmit the results to a smartphone or computer. "We learned from plants how to transport the water," says Gao. "Plants use capillary forces to draw water upward from the ground."
"The smart mask can be prepared at a relatively low cost," says Gao. "It is designed to cost only about $1 in materials." In tests with human subjects, the mask could detect nitrite in asthma patients, and could also accurately detect blood alcohol levels.
"These first studies are a proof of concept," says Gao. "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."
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