Patent ID: 7048890

Claim:
A magnetoresistive sensor device for determining a presence or an areal density of magnetic nanoparticles being directly or indirectly coupled to a target, the magnetoresistive sensor device comprising: a substrate; an elongate probe element arranged on the substrate and including at least one binding site able to selectively bind a target, the probe element having first and second opposite end regions defining a length therebetween and extending in a first direction; and a magnetoresistive sensor arranged in association with the probe element for detecting a magnetic field of magnetic nanoparticles at least when coupled to the target, wherein the magnetoresistive sensor comprises at least one pair of discrete, elongate first and second magnetoresistive sensing elements, each arranged only partially under the probe element, the first and second magnetoresistive elements each having a length and extending in the first direction such that the first and second magnetoresistive elements are parallel to the probe element, the first magnetoresistive element being arranged under the first end region of the probe element and the second magnetoresistive element being arranged under the second end region of the probe element such that the first and second magnetoresistive elements are separated and spaced apart from one another in the first direction, whereby outputs of the first and second magnetoresistive elements are fed to a comparator circuit which determines the presence or the areal density of magnetic nanoparticles coupled to the target bound to the at least one binding site of the probe element.