Spiral inertial microfluidics for size based microalgae separation

The identifcation of toxic microalgae is essential for the sustainable management of activities, such as aquaculture, being also relevant for environmental monitoring and marine research purposes [1]. For these reasons, there is an increasing demand for in situ, reliable, portable, autonomous, low-cost and of easy operation technologies and devices able to detect early signs of potential toxic algal populations within the context of long term monitoring programmes. To this aim, a multisensory platform for in-situ phytoplankton quantifcation and taxonomic identifcation designed for underwater deployment and based on lab-on-chip (LoC) technology has been developed. It combines fow cytometry with optical and electrical measurements. The separation of microalgae based on cell size prior to analysis is key to reduce the complexity and heterogeneous nature of seawater samples while also ofering a degree of distinction between taxonomic groups. This work investigates and develops a simple inertial microfuidic device based on a spiral microchannel that achieves size-based separation of microparticles/ cells. The theoretical principle of their separation was analysed trough numerical simulations and experimental tests were also performed. Using a 5-loop spiral (300 μm width and 100 μm height), 20 μm and 40 μm polystyrene (PS) microparticles were successfully separated for a fow rate of 2000 μl/min, showing its potential for microalgae size-based separation. Furthermore, the simple structure and high throughout makes this technique suitable for integration in LoC devices [2, 3].Peer Reviewe