A nanoelectromechanical infrared sensing workflow has shown that submicrometer aerosol chemistry can be measured from nanogram-scale samples, reducing collection times that often stretch across days or weeks to as little as minutes.
The approach, developed by researchers at TU Wien, EPFL, and Invisible-Light Labs, combines nanoelectromechanical systems with Fourier transform infrared spectroscopy (NEMS-FTIR). Instead of relying on conventional filter collection, airborne particles are deposited onto ultrathin silicon nitride resonators that act as both sampling substrate and detector.
The membrane-based method extends infrared detection to very low particle masses. When particles on the membrane absorb infrared light, they heat slightly, changing the membrane’s vibrational frequency. That photothermal response can then be used to quantify chemical components such as organic functional groups, ammonium sulfate, and equivalent black carbon.
In the study, the team applied NEMS-FTIR to submicrometer atmospheric aerosols, an analytically difficult fraction because of its small size and low mass. Calibration experiments showed strong agreement between NEMS-FTIR spectra and reference measurements for ammonium sulfate and organic functional groups. Reported detection limits for organic functional groups ranged from 1.3 to 5.4 ng, roughly three orders of magnitude lower than previous PTFE-filter FTIR methods.
That sensitivity translated into much shorter sampling times. In urban conditions, the researchers estimate that 15–20 minutes of sampling is enough to exceed detection limits, while low-mass Arctic aerosol environments can be characterized on timescales of hours rather than week-long filter collections.
Field demonstrations in Vienna, Sion, and Greenland showed that the method could capture short-term changes in aerosol composition. At Villum Research Station in Greenland, the compact sensor was also deployed on a tethered balloon, allowing chemical profiles to be measured above the surface layer.
“Thanks to the high sensitivity of our method, Julia Schmale’s team can analyze the chemical composition of particles with high temporal resolution,” said Josiane Lafleur, CEO of Invisible-Light Labs, in a recent press release. “It is now possible, using tethered balloons, to observe how the chemical composition of aerosol particles changes over short timescales and how it varies between ground level and higher altitudes – something that was practically impossible with previous methods.”
Further validation across more aerosol types and field conditions will help determine how broadly NEMS-FTIR can complement established aerosol mass spectrometry and filter-based spectroscopy methods.
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