US Patent 7892817 - Magnetic nanoparticle biosensor

http://www.freepatentsonline.com/7892817.html

This patent from Philips Electronics teaches using the detection of nanoparticle rotational movement to achieve 3D resolution imaging of molecules. Claim 1 reads:

1. A sensor device for distinguishing a specific binding from a less specific binding between at least one polarizable or polarized nanoparticle label and a surface of another entity, the sensor device comprising:

at least one electric or magnetic field generator for applying an electric or a magnetic field to a sample fluid containing polarized or polarizable nanoparticle labels; at least one magnetic sensor element; and

a detector for detecting a parameter related to nanoparticle rotational or motional freedom while the nanoparticle labels are attached to the surface for distinguishing a specific binding from a less specific binding between said nanoparticle labels and the surface of the other entity,

wherein the electric or magnetic field generator generates a rotating magnetic field.