title: Filtration at the microfluidic level: enrichment of nanoparticles by tunable filters.
abstract: We present an electrohydrodynamic device for filtration of nanometre-sized particles from suspensions. A high-frequency electric field is locally generated through the action of mutually parallel microelectrodes integrated into a microfluidic channel. Due to the mechanism of ohmic heating, a thermal gradient arises above these electrodes. In conjunction with temperature-sensitive properties of the fluid, an eddy flow behaviour emerges in the laminar environment. This acts as an adjustable filter. For quantification of the filtration efficiency, we tested a wide range of particle concentrations at different electric field strengths and overall external flow velocities. Particles with a diameter of 200 nm were retained in this manner at rates of up to 100%. Numerical simulations of a model taking into account the hydrodynamic as well as electric conditions, but no interactions between the point-shaped particles, yield results that are similar to the experiment in both the flow trajectories and the particle accumulation. Our easy technique could become a valuable tool that complements conventional filtration methods for handling nanometre-scaled particles in medicine and biotechnology, e.g. bacteria and viruses.
authors.affiliation: Faculty Clinical Medicine, Saarland University, D-66421 Homburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Boettcher
authors.forename: S
authors.initials: S
authors.lastname: Schmidt
authors.forename: A
authors.initials: A
authors.lastname: Latz
authors.forename: M S
authors.initials: MS
authors.lastname: Jaeger
authors.forename: M
authors.initials: M
authors.lastname: Stuke
authors.forename: C
authors.initials: C
authors.lastname: Duschl
mesh_terms: D005374:Filtration / Q000295:instrumentation*; D057446:Hydrodynamics; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry*; D013535:Suspensions
chemical_list: D013535:Suspensions