Airborne nanoparticle analysis mini-system using a parallel-type inertial impaction technique for real-time monitoring size distribution and effective density

To elucidate the relationship between exposure to airborne nanoparticles (NPs; < 300 nm particles) and adverse health effects, two of their characteristics — size distribution and effective density— should be measured in real-time as they are key parameters that determine the particle deposition patterns in human airways. However, current lab-grade and portable instruments that assess airborne NPs only measure their size distribution; in addition, they are bulky and expensive, limiting their application to the analysis of individual NP exposure. To overcome these limitations, in this paper, we introduce and successfully demonstrate an NP analyzer realized in a mini-fluidic system whose main components were realized on two printed circuit boards (PCBs) that were subsequently adjoined. Our sensor could analyze the effective density and lognormal size distribution (number concentration, median diameter, and geometric standard deviation) of NPs in real time. Moreover, since an innovative NP analysis algorithm based on a parallel-type microfluidic inertial impaction technique is integrated in a miniature system, our sensor was portable (16.0 × 9.9 × 7.85 cm³, 980 g) and cost-efficient. In performance tests using synthesized NPs and in real-world environmental application tests, the performance of our sensor was comparable to that of conventional NP analysis systems. These results indicate that our mini-system is excellently suited to be used in hand-held sensors or distributed sensor networks for personal NP exposure monitoring, and toxicological studies.