Deterministic-hydrodynamic Size-, Shape- and Density Fractionation of Polydisperse Microparticles

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Throughout the last years the demand for industrially applicable fractionation methods for microparticles of less than 10μm diameter has been steadily growing. Where conventional approaches such as sieving, filtering, sedimentation, centrifugation and screening are pushed to its limits, microfluidic separation methods are capable to exert high hydrodynamic forces on micro- and submicron particles under laminar flow conditions. Especially passive microfluidic separation processes can be designed in a very compact and parallelized manner to increase throughput rates.The most successful microfluidic systems for size fractionation of microparticles are the Multi Orifice Fluid Fractionation (MOFF), fractionation in microfluidic serpentine channels and the Deterministic Lateral Displacement Fractionation (DLDF). In funding period 1, these were successfully used for size and density fractionation of model particles and are also suitable for multidimensional separation. Nevertheless, the separation of real particles according to multiple characteristics such as size, density and shape via aforementioned methods is still little understood. To gain a better understanding of these processes, complementary numerical and experimental studies shall be performed in funding period 2. A central goal of the planned project is to realize for the first time multidimensional separation of particles smaller than 1µm by a combination of targeted model particle and real particle experiments. For this purpose, existing channel geometries will be equipped with multiple flow outlets to separate and analyze partial streams after fractionation. This also allows testing multi-stage fractionation processes in cooperation with other project partners.Required numerical and experimental methods were successfully established in the first funding period. They allow studying the complex motion dynamics of microparticles in a temporally and spatially resolved manner. The complexity of the separation methods and the experimental restrictions to a few channel geometries require a close cooperation between simulation and experiment also in the second funding period. This includes numerical sensitivity studies of dominant forcing mechanisms in the systems but also numerically assisted designing of experiments and evaluation of results. Compared to the first funding period, only moderate extensions of numerical and experimental techniques are necessary to facilitate studies of the fractionation dynamics of particles smaller than 1 µm under Brownian molecular motion. In view of future industrial applications, fractionation under increasing throughput rates and higher particle concentrations is studied in particular to quantify the influence of particle interaction on the separation degree and the selectivity.