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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster: Micro- and Nanofluidics

CPP 35.19: Poster

Mittwoch, 16. März 2011, 17:00–19:00, P2

Microfluidic gate using self-assembling superstructures of superparamagnetic beads — •Bernhard Eickenberg, Frank Wittbracht, Alexander Weddemann, and Andreas Hütten — Universität Bielefeld, Bielefeld, NRW, Deutschland

The use of magnetic beads for microfluidic applications has been thoroughly studied during the last decades. The permanent magnetic moment allows for the controlled manipulation by external (inhomogeneous) magnetic fields and the detection by magnetoresistive sensors. Depending on the ligands that are used for the functionalization of the bead surface, they can furthermore be bound to various biomolecules.

Recently, the formation of reconfigurable, self-assembling structures from superparamagnetic beads has attracted a lot of interest. While in the absence of a magnetic field the inter-particle coupling is eliminated by thermal excitation, the presence of a homogeneous magnetic field leads to alignment of the magnetic moments of the particles, causing attractive forces between the particles and the assembling of one-dimensional, chain-like superstructures. When the magnetic field is rotated in-plane, the chains follow the movement of the field direction and start to rotate.

Based on this method of external manipulation of bead superstructures by rotating homogeneous magnetic fields, a microfluidic gate was developed that allows to actively sort the flowing particles into one of two diverging channels. At flow velocities below 90 m/s, an efficiency of 95% was achieved. Thus, the system allows for a highly effective flow control without the need for complex microstructuring.