3D printed micro-cyclones with improved geometries for low-cost aerosol size separation

The impact of suspended particles on health, climate, and industrial applications is highly size-dependent. Thus, regulations are typically based on particles with diameters below a specific size, such as particulate matter less than 2.5 μm (PM_2.5). For over a century, cyclones have been employed to isolate particles below a certain diameter by removing large particles from a gas stream, but cyclones are typically relatively large, heavy, and expensive to fabricate compared to objects made with low-cost 3-dimensional (3D) printers. Herein, we present one-piece 3D-printed micro-cyclones (PM_2.5 and PM₁) to isolate particles smaller than a specific diameter. The collection efficiencies and 50% cut-off diameters (d₅₀) of multiple cyclones were evaluated with both monodisperse and polydisperse standards ranging from 0.1 to 3 μm, as well as ambient aerosol. By altering the inlet orientation relative to the micro-cyclone centerline (orthogonal, 50% offset, and fully offset), we show that shifting the inlet radially outward increased the steepness of the transmission curve resulting in a sharper cut-point. The d₅₀ also decreased below the designed for diameter, (PM₁ = 1.4, 1.0, and 0.9 μm; PM_2.5 = 3.2, 2.0, 1.9 μm), which was attributed to imperfect models, internal surface roughness, and print errors versus machining. These single piece, 3D-printed cyclones provide a cheaper (< $1), faster, and more accessible approach to manufacture micro-cyclones for use in a range of aerosol applications.