Aerosol classification by dielectrophoresis: a theoretical study on spherical particles.

The possibilities and limitations using dielectrophoresis (DEP) for the dry classification of spherical aerosol particles was evaluated at low concentrations in a theoretical study. For an instrument with the geometry of concentric cylinders (similar to cylindrical DMA), the dependencies of target particle diameter $$d_{{\text {P}}}^*$$, resolution, and yield of the DEP classification on residence time, applied electric field strength, and pressure of the carrier gas were investigated. Further, the diffusion influence on the classification was considered. It was found that $$d_{{\text {P}}}^*$$ scales with the mean gas flow velocity $$u_{{\text {gas}}}$$, classifier length L, and electric field strength E as $$d_{{\text {P}}}^*\propto (u_{{\text {gas}}}/L)^{0.5}E^{-1}$$. The resolution of the classification depends on the particle diameter and scales proportionally to $${d_{{\text {P}}}^*}^{1.3}$$. It is constrained by the flow ratio $$\beta $$ (i.e., sheath gas to aerosol flow), electrode diameters, and applied electric field strength. The classification yield increases with the ratio of the width of the extended outlet slit $$s_{{\text {e}}}$$ to the diffusion induced broadening $$\sigma _z$$. As expected, resolution and yield exhibit opposite dependencies on $$s_{{\text {e}}}/\sigma _z$$. Our simulations show that DEP classification can principally cover a highly interesting particle size range from 100 nm to $${10}\,\upmu \hbox {m}$$ while being directly particle size-selective and particle charge independent.