Ion Mobility Spectrometer on a Microchip
Trace molecules can be telltale signs of explosives in a briefcase or disease-revealing proteins in blood. Now, researchers at Pacific Northwest National Laboratory and Owlstone Nanotech in Cambridge, England, have dramatically improved the ability to detect and identify such molecules. Ion Mobility Spectrometer on a Microchip overcomes limitations of previous instruments by shrinking a key component — a channel through which such molecules must travel.
The dime-sized microchip is based on Field Asymmetric waveform Ion Mobility Spectrometry. Also called FAIMS, the method uses strong versus weak electric fields to separate electrically charged atoms or molecules called ions as they zoom through an instrument. In previous FAIMS systems, the distance ions raced ranged from 15 to 55 millimeters — even so, they took too long for the desired performance. "We needed to shorten the racetrack," said PNNL chemist Alex Shvartsburg.
But a shorter racetrack requires more intense electric fields to separate the pack of ions. So the team developed a FAIMS microchip with 0.3 millimeter-long channels that were only 35 micrometers wide. The short, narrow channels allow ion separation 100 to 10,000 times faster than previous instruments. Other design features improve the instrument's ability to measure both abundant and rare compounds in the same sample. Because the tiny FAIMS system was destined for use with mass spectrometry, the team then integrated and optimized the microchip with mass spectrometers at DOE's Environmental Molecular Sciences Laboratory at PNNL, as well as demonstrated how the new system can be used. The project was funded by the National Institutes of Health, DOE's Office of Science and PNNL.