Concept for an electrostatic focusing device for continuous ambient pressure aerosol concentration
Abstract. We present a concept for enhancing the concentration of
charged submicron aerosol particles in a continuous-flow stream using in situ
electrostatic focusing. It is proposed that electrostatic focusing can
enable the continuous, isothermal concentration of aerosol particles at
ambient pressure, without altering their chemical composition. We model this
approach theoretically and demonstrate proof of concept via laboratory
measurements using a prototype. The prototype design consists of a
nozzle-probe flow system analogous to a virtual impactor. The device was
tested in the laboratory using submicron, monodisperse stearic acid
particles. Particles were charged using a unipolar charger then
concentrated using a cylindrical electrostatic immersion lens to direct the
charged submicron particles into the sample probe. Under applied lens
voltages ranging from 0 V to 30 kV, aerosol concentration increased up to
15 %. Observed particle enrichment varied as a function of voltage and
particle diameter. These results suggest that an imposed electric field can
be used to increase aerosol concentration in a continuous flow. This
approach shows promise in increasing the effective enriched size range of
virtual impactors or other continuous-flow methods of collection.