Abstract:
This report details preliminary studies towards the development of a microfluidic
sensor that exploits ferromagnetic resonance, excited in magnetic bead labels, for signal
transduction. The device consists of a microwave circuit in which a slotline and a coplanar
waveguide are integrated with a biochemically activated sensor area. The magnetic beads are
immobilized in the sensor area by bio-specific reactions. A microwave signal applied to the
slotline is coupled to the coplanar waveguide only in the presence of magnetic beads at the
functionalized sensor area. Ferromagnetic resonance in the beads further enhances the coupling.
This inductive detection technique lends itself to miniaturization, is inexpensive to fabricate and
can be adapted for the detection of a wide range of molecules for which bio-specific ligands are
available.
Experimentally, the variation of the output signal as a function of the location of magnetic beads
was studied for the proposed technique. Subsequently, a prototype device was constructed by
biotinylation of the sensor area and integration with a microfluidic chip fabricated in
polydimethyl siloxane (PDMS). Preliminary experiments were conducted on this prototype using
streptavidin-functionalized magnetic beads as labels. It was shown that the magnetic beads,
immobilized at the sensor area by streptavidin-biotin linkage, produced a distinct ferromagnetic
resonance response easily discernible from the background signal.
