Step-by-step : A microfluidic (PDMS) staircase device for size sorting microparticles down to 25 µm using a 3D-printed mold

Microparticles are ubiquitous and span from living matter to microplastics to inorganic materials. Their detection and identification must be more accessible and time efficient. Microfluidic devices can filter microparticles from liquids, but fabricating microfluidics with lateral resolutions of a few tens of microns is complex, lengthy, and outside the reach of most scientists researching microparticles. In this article, we show how to use height features in a channel instead of relying on lateral elements for separating particles. The height features can be as small as 25 µm, along the Z axis, using consumer-grade 3D printers. We show the potential of such microfluidic devices for size-sorting parasite eggs such as Schistosoma haematobium, microplastics, and zooplankton.