An experimental and numerical study of a miniature high resolution isopotential DMA

A miniaturized version of an isopotential nano-differential mobility analyzer (DMA) [Labowsky, M., & Fernández de la Mora, J. (2006). Novel ion mobility analyzers and filters. Journal of Aerosol Science, 37, 340–362] has been tested experimentally and simulated by means of the commercial code COMSOL® to take into account Brownian diffusion. Compared with the prototype tested by [Martínez-Lozano, P., & Fernández de la Mora, J. (2006). Resolution improvements of a nano-DMA operating transonically. Journal of Aerosol Science, 37, 500–512.] this model is half the size and weights 920 g. Resolution, defined as the inverse of the relative full width at half height (FWHH), has been improved by a 50%, attaining a maximum resolution of 75 operating at a Reynolds number (Re) of ∼47,000, measuring ions of equivalent mobility diameter ∼1 nm. The maximum diameter theoretically measurable by this DMA is 15 nm. The predictions of the numerical simulations are in reasonable agreement with experiments with respect to resolution and the device constant, which provides an estimation of the measurable size range. The model suggests future approaches to improve resolution and to extend the measurable size range.