How does the packing density of a metal screen affect the mechanism for catching highly charged nanoparticles

Highly charged aerosol nanoparticles of a molecular size (< 5 nm) exhibit complex behaviors caused by random (Brownian) motion and electrostatic interactions (image force) with solid surfaces. The classical single fiber theory, however, can only partially describe the complex filtration mechanism of highly charged nanoparticles. We began this study by employing the Langevin Dynamics (LD) Method to simulate the random motion and deposition of highly charged nanoparticles on a single fiber. The single fiber efficiencies predicted by the LD simulation did not agree with data from experiments using electrosprayed highly charged molecular ions. To explain this mismatch and search for other factors that could potentially affect the capturing mechanism, we investigated the influence of the mesh structure. While the image force exerted a significant influence as the packing density decreased, the influence tended to oppose the theoretical predictions. These results suggested that the fiber-fiber interaction in a wire screen with high packing density significantly influences the collection of multiply charged molecular ions. A new theoretical model describing the influence of inter-fiber interaction will be required to clarify how highly charged molecular ions are captured by image force.