Bending Effect on Magnetoresistive Silicon Probes

In vivo experiments to detect the neuronal magnetic field require high-sensitivity magnetoresistive sensors incorporated in micromachined silicon probes that do not damage the organic tissues and enhance the sensors proximity to the signal sources. When in touch with the tissues, the probe experiences a mechanical stress induced by an unavoidable bending moment. To evaluate its impact on sensor performance, the transfer curves and the noise level were measured for different applied stresses. A saturation field reduction (increase) was observed upon a compressive (tensile) stress as a consequence of the magnetostrictive effect, while the magnetoresistance value remained constant. Besides the clear influence of magnetostricition in the sensor transfer curves, no significant changes in the noise level were obtained, which will not affect the experiment feasibility.