The conical inner electrode of a recently described differential mobility analyzer (DMA), covering at resolution >50 the size range up to 60 nm, has been modified by increasing its radius at the outlet slit from 1 cm to 1.6 cm, and decreasing its convergence angle from 3° to 0.5°. The cylindrical outer electrode radius is maintained at 2 cm, while other critical dimensions are only slightly modified. The classification voltage for fixed flow rate of sheath gas and particle diameter decreases almost fourfold, extending the size range theoretically spanned at high resolution well beyond 120 nm. Tests with multiply charged polystyrene latex spheres 200 nm in diameter confirm the actual ability to cover this wide size range. A resolution above 100 (with no corrections for instrument or particle nonidealities) is demonstrated with rotavirus double-layered particles (DLPs), whose mobility diameter is found to be near 60 nm. The DLP has several configurations that complicate its use for DMA characterization, but occasionally presents mainly one conformer, with singularly narrow relative mobility width FWHM < 1/150. Two broad range instruments with slightly different axial lengths have been developed and tested, both reaching resolving powers of 100. Copyright © 2023 American Association for Aerosol Research.

This work has been partially supported by grants 786945 (COSMIC) from the European Union (Horizon 2020 Program) to Fernando Almazán and grant FA9550-22-1-0097 from the US AFOSR to Yale University.

Peer reviewed