Scanning Magnetoresistance Microscopy for Imaging Magnetically Labeled DNA Microarrays

We demonstrate the use of a magnetic tunnel junction (MTJ) sensor as a probe for non-contact scanning microscopy of magnetically labeled DNA microarrays. Induced magnetic stray fields from 2.8 mum diameter magnetic particles are detected using the MTJ sensor, while two dimensional scanning generates the magnetic map of the DNA microarray with a spatial resolution of 1 mum over a large scan area exceeding 1 cm
²
. Current particle-sensor spacing of ~20 mum results in a detection resolution of ~30 magnetic particles within each 100 mum diameter DNA spot. Our results highlight the use of scanning magnetoresistive microscopy as a convenient and powerful technique for the accurate detection and identification of biomolecules tagged with magnetic particles.