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High-throughput selective particle separation by dielectrophoretic filtration in open porous ceramic structuresWednesday (07.10.2020) 14:40 - 15:00
Dielectrophoresis (DEP), motion of polarizable matter in inhomogeneous electric fields, gives a unique opportunity for material selective separation challenges. It is applied to divide «target» cells/particles against millions of «background» ones, for example live and dead cells or blood cells according to type. The vast fraction of DEP separation techniques is limited to small channel sizes. The application of DEP in open porous microstructures (DEP filtration) facilitates the scale up by broadening the effective channel cross section and, thereby, enlarging the throughput by orders of magnitude.
Here we report fundamental experiments to elucidate the DEP filtration mechanism. A porous media was located in-between two macroscopic electrodes. The small pores (200-500 µm) in this material are highly interconnected. Electric field scattering at the pore walls locally induces spatial field gradients and thus causes a highly inhomogeneous distribution inside the sample.
It was found that property dependent sorting is possible due to differences in particle polarizability. We extracted design rules outlining the influence of fundamental parameters on DEP filtration in the broad variety of porous filters. Further, by varying the fluid conductivity we show that particle retention is evidently dependent on the particle polarizability. With this, we were able to create a selective DEP filter that only retains target particles and further allows their easy resuspension by switching of the excitatory field. Since pore sizes are much larger than particle sizes, there is no noticeable filter fouling. For a further improvement, we study enhancing of local field gradients by functionalizing the surface of the filter pores.
Due to the ease of scaling up DEP filters, this is a potential avenue to implementations of material selective retention on industrial scale from applications in biotechnology to metal recycling and thus showing solutions for current challenges in the field of microparticle separations.