Ferromagnetic Ring-Shaped Biosensors
T. Mitrelias, J. Llandro, T. Hayward, F. van Belle, J. Ziling, W.S. Lew, Z. Wang and J. Pulfreyman
University of Cambridge, UK
ferromagnetic rings, MR sensors, magnetic beads
Convergence between nanotechnology and biomedicine in the last years has led to extensive research for the development of sensitive, low cost, miniaturised biosensors. The concept of designing biological assays using libraries of microbead functionalised with biochemical probes is very powerful since it can lead to the development of high throughput biosensors capable of detecting many biomolecules simultaneously, provided that an ultra-sensitive sensing element is utilised. Here, we describe the development of an advanced magnetic biosensor, the novelty of which is in the use of an annular magnetoresistive element to detect single magnetic microbeads. Advantages of ferromagnetic ring sensors include the good flux-matching between the ring shape and the bead, as well as the highly abrupt switching between the stable states of the rings in response to an external magnetic influence. It is expected that magnetic moments of around 10-12 emu could be detected with good signal to noise ratio. We will present results on the characterisation of magnetic beads of various sizes and simulation results of the effects on properties of rings of the position of current injection contacts and of various magnetic beads at increasing separation from the ring. A dynamic bead manipulation system will also be described.
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Nanotech 2005 Conference Program Abstract