Patent ID: 8092745

Claim:
A method for magnetic sensing using a magnetic sensor to detect a target substance in a sample, wherein the magnetic sensor comprises a magnetic field detecting element, wherein the method comprises detecting the target substance in the sample indirectly by immobilizing the target substance to a surface of the magnetic field detecting element, by making a labeling substance larger than the target substance bond with the target substance immobilized on the surface of the magnetic field detecting element, and by detecting a change of magnetic field using the magnetic field detecting element, the change of magnetic field being due to the target substance being immobilized to the magnetic field detecting element and consequently the target substance being close to the magnetic filed detecting element, wherein the labeling substance is a magnetic particle, wherein the surface of the magnetic field detecting element to which the sample is in contact comprises a first plurality of areas each of which has a substance that specifically captures the target substance, wherein each of the first plurality of areas is surrounded by a second area which does not have the substance that specifically captures the target substance, wherein a distance between respective ones of the first plurality of areas is larger than a diameter of the labeling substance, and wherein each of the first plurality of areas has a size such that only one molecule of the target substance is captured.