NIST scientists have devised and modeled a unique optical method of sorting microscopic and nanoscopic particles by size, with a resolution as fine as 1 nm for particles of similar composition.

A stream of particles of various sizes enters the system at a single point, but the particles exit the system at different places, depending on their size. The process does not alter the particles in any way, so those with dimensions of interest can be readily separated and analyzed. The sorting operates on a continuous input of particles, with the particles moving through the system in only a couple of seconds.

That kind of capability is of significant interest to climate scientists studying atmospheric chemistry and airborne contaminants, as well as to professionals in national security and healthcare. “For example, if you wanted to know whether someone had released spores or bacteria or even viruses into the air in a closed space, such as a subway system, you could dramatically speed up the investigation by sorting, because a cubic centimeter of air can contain thousands of nanoparticles,” says John Curry of NIST’s Physical Measurement Laboratory (PML).

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