|Michael Panhorst, Monika Brzeska, Jörg Schotter, Günter Reiss, and Hubert Brückl
Department of Physics, University of Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany
Commercially available magnetic microbeads can be functionalized and used as markers for molecule detection. An additional advantage of the magnetic markers is the possibility to manipulate them by magnetic fields. We demonstrate on-chip manipulation of paramagnetic beads and the possibility of single molecule detection via these markers with highly sensitive magnetoresistive sensors.
Conducting lines were patterned on a Si wafer and embedded in Si oxide. A current flow of up to 50 mA produces magnetic fields acting on the magnetic beads. Thus, the beads can be positioned on the chip. Calculations show that forces up to 500 pN can be applied to the magnetic beads and exerted on molecules bound to the beads. Supported by computer simulations the current work aims for a variable 2D positioning system.
In addition to the manipulation system, magnetoresistive sensors are intended to be incorporated on the chip which are capable to detect single beads or respectively molecules. Estimations show that beads of about 50 nm diameter can be detected with a tunnelling magnetoresistive sensors of 1 µm ×1 µm size. We proved already the detection of molecules by larger sized sensors.