Flexible Magnetoresistive Sensors Designed for Conformal Integration

This paper reports on the integration of magnetic tunnel junction (MTJ) sensing devices with magnetoresistance responses above 150% on flexible substrates. The sensors are integrated in a fabrication process based on polyimide materials, and demonstrate sensitivities up to <inline-formula> <tex-math notation="LaTeX">$250~\mu \text{V}$ </tex-math></inline-formula>/Oe for bias currents in the 100-<inline-formula> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> range. Assessment of the sensors performance is done under controlled mechanical load conditions, and the magnetoresistance is only slightly affected (1% variation) while sensitivity changes by 7.5% when the bending radii reduce down to 5 mm. The results demonstrate the high potential of the MTJ sensors to be used in applications requiring bending and conforming to non-planar geometries, bringing magnetoelectronic technologies to hard-to-reach regions of space.