The affect of bias voltage to the DC test of GMR spin valve biosensors

This paper presents the fabrication process of a GMR spin-valve biosensor, and discusses the general design rules of the plane structure of the biosensor. The resistance variation of the sensor is studied versus the magnetic excitation field when 1ul solution of nanoparticles (150nm in diameter) with a concentration of 25mg/ml is directly dropped on the surface of the sensor. The experimental results show that the sensor´s resistance had a non-zero change when the magnetic excitation field (H_f) equals zero, and it reaches the minimum when a particular negative magnetic excitation field (H_f) is applied. The detection accuracy of our biosensor is tested using a Wheatstone bridge circuit, and the results indicates that the fringe field of nanoparticles in 1μl solution with a concentration of 0.25μg/ml can be detected when the excitation field is -9Oe, but it is undetectable with a zero field.