A high performance differential mobility analyzer for the masses

Abstract

A hand-held Differential Mobility Analyzer (DMA) weighting 4 kg is developed to operate laminarly at many hundreds of L/min, while covering at unusually high resolution the 1–200 nm size range. Coupled with a small and efficient portable vacuum cleaner pump requiring no cooling, a resolving power of 10 or more is obtained at mobility diameters above 1.4 nm. The resolving power at 200 nm is between 40 and 60. Certain design compromises have been made to enable the wide adoption of this instrument in conventional aerosol measurements, making it comparable to broadly used contemporary commercial DMAs in portability, complexity, and cost. Yet, the high flow rate capability provides drastic advantages in resolution, sensitivity and size range over more conventional DMAs. This DMA is nevertheless inferior in resolution to more specialized instruments developed for studies of either nanoparticles or viruses. The inner electrode is a 1° half-angle cone accelerating mildly the flow. Critical dimensions in mm are: outer radius R₂ = 19.58; inner radius at the outlet slit R₁ = 14.34; axial distance between slits L = 85.94.