Numerical Simulations on Aerodynamic Focusing of Particles in a Wide Size Range of 30 nm–10 μm

Abstract

Previous designs of conventional aerodynamic lenses have the limitation of a narrow range of focusable particle size, e.g., just one order of magnitude such as 30–300 nm or 3–30 nm. To enlarge the focusable size range to two orders of magnitude (30–3,000 nm), it is necessary to focus small particles and at the same time not to loose the large ones. From numerical simulations of size-resolved particle trajectories, we confirmed that the traveling losses of such large particles could be avoided only when the radial positions of particles approaching the orifice lenses were near the axes of the lenses. Hence, we designed a lens system consisting of seven orifices to fulfill the requirement. In particular, the orifices were aligned in such a way that their diameters would descend and ascend downstream. As a result, 30–2500 nm particles could be focused to produce particle beams with radii of 0.2 mm or less with a transmission efficiency of above 90% 40 mm downstream of the aerodynamic lens exit. Even 10 μm pa...