Method of making high efficiency magnetic sensor for magnetic particles

摘要

A method of making a high efficiency magnetic sensor for determining the presence or amount of an analyte in a test sample. The method typically includes providing a sensing device with a magnetic sensing element, exposing the sensing device to a fluid test medium suspected of containing an analyte and monitoring the resistance of the magnetic sensing element to detect any change in the electrical resistance of the magnetic sensing element in response to the immobilization of a magnetizable particle. The magnetic sensing element comprises at least one planar layer of electrically conductive ferromagnetic material having an initial state in which the material has a circular magnetic moment within the plane of the layer, a means to immobilize a magnetizable particle at a point along an axis that is perpendicular to the plane of the layer and passes through the center of the circular magnetic moment, and a means for detecting the change in the electrical resistance of each magnetic sensing element. The magnetic sensing element has molecules of a first specific binding member attached to it. The relative size of the magnetic particle and the magnetic sensing element are selected so that when the magnetic particle becomes immobilized with respect to the magnetic sensing element, the radial fringing field of the magnetic particle causes the magnetic moment of at least one layer of electrically conductive ferromagnetic material to shift from circular to radial, thereby causing a detectable change in the electrical resistance of the magnetic sensing element.