Airborne hazardous chemicals can be dilute, mobile and hard to trap. Yet, accurately measuring these chemicals is critical in protecting human health and the environment.
Now, a new, small, low-cost device, nicknamed ABLE, could make the collection and detection of airborne hazards much more efficient. The device, just four by eight inches across, was devised by Jingcheng Ma, assistant professor of aerospace and mechanical engineering at the University of Notre Dame, and researchers at the University of Chicago. The results of their work were published in Nature Chemical Engineering.
ABLE has immediate applications in hospitals, where viruses, bacteria and nanoplastics can be detected directly from the air - offering less invasive alternatives to blood draws, particularly for vulnerable infants in neonatal units.
"Many important biomarkers - molecules your body produces when it's dealing with pathogens - are very dilute in the air. They could be at the parts per billion level. Trying to find them is like locating six to seven people in the global population - very difficult," said Ma, the study's first author, who conducted the research as a postdoc at the University of Chicago.
Ma, whose graduate training was in thermal science and energy systems - a field in which the transfer of water from liquid to steam is central - wondered how airborne biomarkers might behave if condensed into liquid. Could these molecules be captured in water droplets? Would their concentration in liquid be the same as their concentration in air? Would different molecules condense differently?
If airborne biomarkers are tested in gas form, large, expensive machines - such as mass spectrometers - are usually necessary. However, if the researchers could convert the air into a liquid, an array of low-cost, accurate measuring tools became available - paper-based test strips, electro-chemical sensors, enzyme assays and optical sensors.
We discovered that many molecules can effectively enter water droplets even when their concentration is very low. We didn't need to develop any advanced chemical systems to capture these biomarkers in water. It's a very natural process."
Jingcheng Ma, assistant professor of aerospace and mechanical engineering, University of Notre Dame
The ABLE device, which can be made for under $200, sucks in air, adds water vapor and cools it. The air sample condenses into water droplets on a surface of microscopic silicon spikes - a process through which even tiny amounts of contaminant become highly concentrated. These droplets then slide into a reservoir where they are tested for biomarkers.
Ma's research group, the Interfacial Thermofluids Lab (ITL), is exploring ways to miniaturize ABLE, enabling it to fit into portable sensing systems or robotic platforms for environmental and healthcare monitoring. The group is also working with community partners to monitor the health of vulnerable infants in neonatal care.
"I like to do what I call 'budget research,' that is, use simple and low-cost components, but do something important that no one has achieved before. I like research that delivers something everyone can buy from the store," Ma said.