Performance evaluation of a 3D-printed sharp-cut cyclone.

A sharp-cut cyclone with an aerodynamic cut-off diameter of 1 µm, when operated at a flow rate of 1 L min-1, was built by 3D-printing and tested against a metallic (aluminum) counterpart having the same design and dimensions. The penetration efficiency of both cyclones was experimentally determined using quasi-monodisperse aerosol particles having aerodynamic diameters from ca. 100 nm to 2 µm. The aerodynamic cut-off diameter for both cyclones was very similar and in accordance with the expected design value. The penetration efficiency curve of the 3D-printed cyclone was less steep compared to that of its metallic counterpart. This difference is most likely attributed to the higher surface roughness of the inner parts of the 3D-printed cyclone - as also indicated by the greater pressure drop it exhibits compared to the aluminum cyclone when operated at the same flow rate - and not by higher deviations from its design dimensions resulting from the tolerances of the 3D printer. Despite that, the substantially low cost, speed, and ease of manufacturing, make the 3D-printed cyclone a highly promising solution for applications in aerosol metrology.

Characterizing the Chemical Profile of Incidental Ultrafine Particles for Toxicity Assessment Using an Aerosol Concentrator.

Incidental ultrafine particles (UFPs) constitute a key pollutant in industrial workplaces. However, characterizing their chemical properties for exposure and toxicity assessments still remains a challenge. In this work, the performance of an aerosol concentrator (Versatile Aerosol Concentration Enrichment System, VACES) was assessed to simultaneously sample UFPs on filter substrates (for chemical analysis) and as liquid suspensions (for toxicity assessment), in a high UFP concentration scenario. An industrial case study was selected where metal-containing UFPs were emitted during thermal spraying of ceramic coatings. Results evidenced the comparability of the VACES system with online monitors in terms of UFP particle mass (for concentrations up to 95 µg UFP/m3) and between filters and liquid suspensions, in terms of particle composition (for concentrations up to 1000 µg/m3). This supports the applicability of this tool for UFP collection in view of chemical and toxicological characterization for incidental UFPs. In the industrial setting evaluated, results showed that the spraying temperature was a driver of fractionation of metals between UF (<0.2 µm) and fine (0.2-2.5 µm) particles. Potentially health hazardous metals (Ni, Cr) were enriched in UFPs and depleted in the fine particle fraction. Metals vaporized at high temperatures and concentrated in the UF fraction through nucleation processes. Results evidenced the need to understand incidental particle formation mechanisms due to their direct implications on particle composition and, thus, exposure. It is advisable that personal exposure and subsequent risk assessments in occupational settings should include dedicated metrics to monitor UFPs (especially, incidental).

A tunable high-pass filter for simple and inexpensive size-segregation of sub-10-nm nanoparticles.

Recent advanced in the fields of nanotechnology and atmospheric sciences underline the increasing need for sizing sub-10-nm aerosol particles in a simple yet efficient way. In this article, we develop, experimentally test and model the performance of a High-Pass Electrical Mobility Filter (HP-EMF) that can be used for sizing nanoparticles suspended in gaseous media. Experimental measurements of the penetration of nanoparticles having diameters down to ca 1nm through the HP-EMF are compared with predictions by an analytic, a semi-empirical and a numerical model. The results show that the HP-EMF effectively filters nanoparticles below a threshold diameter with an extremely high level of sizing performance, while it is easier to use compared to existing nanoparticle sizing techniques through design simplifications. What is more, the HP-EMF is an inexpensive and compact tool, making it an enabling technology for a variety of applications ranging from nanomaterial synthesis to distributed monitoring of atmospheric nanoparticles.