Detecting molecules in air is more difficult than in liquids. That's why hospitals draw blood, and even at-home COVID tests require the addition of liquid. One reason is the low concentration. The number of particles of interest, such as viruses, in the air can be as low as one in a trillion. This is a difficult task for a device, and previously, large and expensive equipment was required.
Scientists have come up with a way to liquefy air to make it easier to analyze. Their setup consists of several parts. First, a pump draws in air. Then, a humidifier adds water vapor, and a small cooling system lowers the temperature. This causes the air to turn into droplets, which trap the desired particles. These droplets flow down a smooth surface into a small reservoir. From there, instruments can easily measure how many molecules are contained in the liquid using standard liquid analysis equipment.
When creating the device, the scientists weren't sure whether they would be able to capture certain rapidly evaporating molecules, known as "volatiles." To test the idea, one of the scientists used a cup of coffee. He injected the steam into the system to see if it could be collected and detected. When the liquid condensed, it was clear the experiment had been a success—it smelled of coffee.
In subsequent tests, the scientists were able to measure exhaled sugar levels, detect E. coli in the air, and identify signs of inflammation in the cells of mice with compromised gut flora. They named their system ABLE, or "airborne biomarker localization system."
The technology will be useful in medicine, for example, by allowing non-invasive monitoring of biomarkers and improving the care of premature babies.
Scientists still need to determine which molecules to search for for different purposes. For example, they are currently exploring the possibility of detecting signs of inflammatory bowel disease through breathing. They also plan to make the device smaller and more comfortable to wear. One of the developers expects this work to lead to new discoveries in physics and to study how airborne contaminants affect physical processes.
