Based on a porous polymer film, highly-sensitive sensors can detect trace compounds in breath or toxins in air
The result of research by chemists and biomedical engineers at the University of Illinois at Urbana-Champaign, the sensors are made from films of semiconducting plastics. They are capable of detecting molecules in breath at levels far too low to smell, but which are significant for human health.
Other attempts at making sensors from these materials have not achieved the required sensitivity, but Prof Ying Diao’s group discovered that the reactive sites in the material were not on the surface, but buried inside the polymer’s structure.
To allow the target molecules to reach these sites, the team devised a method of making the films so that they had a porous structure.
“We developed this method to directly print tiny pores into the device itself so we can expose these highly reactive sites,” Diao said. “By doing so, we increased the reactivity by ten times and can sense down to one part per billion.”
In their first demonstration of the technique, described in a paper in the journal Advanced Materials, the team made a film that can detect traces of ammonia in breath: a marker for kidney diseases. By changing the composition of the sensor, it could be made sensitive to other compounds; they have also made a sensor to detect formaldehyde, which is found in the air in new or refurbished buildings and poses health hazards.
“We would like to be able to detect multiple compounds at once, like a chemical fingerprint,” Diao said. “It’s useful because in disease conditions, multiple markers will usually change concentration at once. By mapping out the chemical fingerprints and how they change, we can more accurately point to signs of potential health issues.”
Diao explained that such small, cheap sensors could be a boon for healthcare. “In the clinical setting, physicians use bulky instruments, basically the size of a big table, to detect and analyse these compounds. We want to hand out a cheap sensor chip to patients so they can use it and throw it away,” he said.