Aerosol flow through a long and tapered micro-capillary (MC) for direct write (DW) technology is typically used with small particles of sizes ranging from 0.2 μm to 10 μm at velocities up to 100 m/s. Earlier research showed that the particles coming through a long MC experience Saffman force that moves the particles towards the center of the beam other than the geometric convergence (due to Stokes drag); thus creating a collimated aerosol beam. It was also established that the additional Saffman force becomes more effective with certain particle diameters and velocities. Therefore, for experimental validation, it is important to accurately measure the particle size distribution and velocities coming out of the long MC. However, the current sizing methods are incapable of measuring particles less than 5 μm due to optical limitations. The current paper presents results using a micro-shadowgraphy system from LaVision Inc. to characterize the flow field. A modification of the particle-sizing algorithm is proposed to measure particles of sub-micron sizes. The modified algorithm can be used to accurately size particles of 1μm diameter.

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