A microfluidic device for size-based microplastics and microalgae separation

Phytoplankton are microscopic marine algae that constitute the foundation of the aquatic food web. They are essential to drive life in the oceans but can also be harmful in the form of algae blooms, either by producing phytoplankton toxins or massive biomass proliferation. Microalgae cell size is a relevant morphologic trait that can help identifying species responsible for these blooms at early stages. Sorting microalgae based on cell size reduces the complexity of the sea water samples, making identification easier, and allows enrichment of the target size. This work reports the study and optimization of an inertial microfluidic device for size-based separation and concentration of microparticles/microalgae. It is demonstrated the suitability of the device for sorting and separation of microparticles/microalgae of varying sizes. Furthermore, the enrichment of microalgae was also demonstrated, achieving a 2.5-fold increase fluorescence detection with only one spiral passage. This method is well suited for integration in monitoring devices due to its easy fabrication and integration in miniaturized systems and has potential as a pre-sorting and enrichment step prior to analysis. In addition, it can be used to improve the monitoring performance of early harmful algal blooms, or detection of microplastics in the water.