Reducing particle loss in a critical orifice and an aerodynamic lens for focusing aerosol particles in a wide size range of 30 nm — 10 μm

Abstract

Most studies on particle focusing using an aerodynamic lens concentrate on loss and focusing performance of the lens itself without accounting for the critical orifice that acts as the actual inlet. If the newly proposed design for an aerodynamic lens capable of focusing particles over a wide range of 30 nm — 10 μm is integrated into the critical orifice, this will result in a huge loss of super-micron particles (> 1 μm in diameter), and the downstream aerodynamic lens will no longer have an advantage. CFD simulations were performed to investigate the loss of particles in the critical orifice and a new converging-diverging critical orifice was proposed instead of the conventional flat critical orifice to reduce the particle loss. By optimizing the angle of the converging and diverging sections as well as the relaxation chamber design, we derived an optimal design for the final aerodynamic lens and integrated system. As a result, we can generate particle beams of less than 1 mm with more than 80% penetration efficiency for particles in the 50 nm -7 μm range, and a 60% penetration efficiency for particles of 30 nm and 10 μm.