Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: Wetting, Micro and nanofluidics II

CPP 39.7: Vortrag

Freitag, 30. März 2012, 11:15–11:30, C 243

Rotating magnetic field assisted microfluidics — •Frank Wittbracht¹, Bernhard Eickenberg¹, Alexander Weddemann², and Andreas Hütten¹ — ¹Thin Films and Physics of Nanostructures, Bielefeld University, Bielefeld, Germany — ²Research Laboratory of Electronics/LEES, MIT, Cambridge, United States

Superparamagnetic beads suspended in a liquid show characteristic behavior when immersed in a homogenous external magnetic field. Due to the inhomogeneous character of the stray field of the beads, magnetic agglomerates are formed. The dimensionality of these magnetic superstructures can be adjusted by rotating the external magnetic field. This allows especially for the formation of highly ordered two-dimensional clusters consisting of magnetic beads [1]. Time scales for the cluster formation are studied with respect to a dependence on the rotation frequency of the magnetic field [2]. We present a microfluidic device, which utilizes the interaction between magnetic agglomerates and channel walls in order to perform colloidal separation. The magnetic agglomerates may also act as dynamic free-flowing micro-stirrers which enhance the effective diffusion at the interface of a two fluid streams. At the chosen system parameters an increase in the diffusivity of 32 was obtained and a separation efficiency of about 80% at flow rates up to 0.4 mm/s was achieved.

[1] A. Weddemann, F. Wittbracht, B. Eickenberg, A. Hütten, Langmuir, 26, 19225 (2010)

[2] F. Wittbracht, B. Eickenberg, A. Weddemann, A. Hütten, J. Appl. Phys., 109, 114503 (2011)