Patent ID: 7682837

Claim:
A device for forming an array of magnetic particles, the device comprising: a substrate comprising a plurality of magnetic regions having gaps between them, wherein the substrate comprises a surface, wherein the magnetic regions have a maximum length parallel to the surface of the substrate and a maximum width parallel to the surface of the substrate with the maximum length being greater than the maximum width, and wherein the magnetic regions produce a plurality of localized magnetic fields when magnetized, and wherein adjacent magnetic regions are so aligned with one another in the directions of their maximum length that the localized magnetic fields are sufficient to trap a magnetic particle between adjacent magnetic regions with a trapping energy at least three times greater than the thermal energy of the particle at room temperature and the gaps are available for fluid flow among them and are also available for occupancy by magnetic particles prior to introduction of magnetic particles to the device so that forces generated by the localized magnetic fields between adjacent regions can trap magnetic particles in the gaps between them, wherein the magnetic regions project above the surface of the substrate, and wherein the magnetic regions comprise a layer of magnetic material and a layer of nonmagnetic material, wherein the layer of nonmagnetic material is located between the substrate and the layer of magnetic material.