A novel zero-drift detection method for highly sensitive GMR biochips

In this paper, we present a novel drift compensation mechanism for highly sensitive biodetection based on giant magnetoresistive (GMR) sensors and magnetic nanoparticles. Micromagnetic simulations showed the quantitative detection ability of this new method. The proposed detection scheme uses both ac current sources and ac magnetic fields along with two dc bias states. Experiments were carried out to detect Miltenyi Biotec (MACS) magnetic nanoparticles on the spin-valve sensor (0.2 mu m x 4 mu m). The experimental results show that sub-microvolt drifts can be achieved by this dual bias-double modulation (DBDM) method.