Highly compliant planar Hall effect sensor with sub 50 nT sensitivity

Next generation of flexible appliances such as soft robots aim to become fully autonomous and will require ultra-thin and flexible navigation modules, body tracking and relative position monitoring systems, which typically include magnetic field sensors as key building blocks. Although there is a great progress in the field of shapeable magnetoelectronics [1], there is no technology available which can enable sensitivities to magnetic fields lower than 1 μT (below the geomagnetic field) in a mechanically compliant form factor. To address this challenging task we introduced a new fundamental effect towards magnetic field sensing --the planar Hall effect (PHE) [2-5]-- in the field of shapeable magnetoelectronics. We demonstrate that even when prepared on mechanically imperceptible 6-μm-thick polymeric foils, magnetic field sensors based on the planar Hall effect have a remarkable sensitivity of 0.86 V/T and are capable of detecting magnetic fields in the range of sub 50 nT. Furthermore, these sensors can be bent to a radius of 1 mm without any degradation of their electrical resistance and shows excellent cyclic bending performance with only 0.3% resistance variation after more than 150 bending cycles. The application potential of the device is showcased in two examples of an angle and proximity sensors. For the latter, we demonstrate that the compliant PHE sensor is able to detect small magnetic stray fields of magnetically functionalized objects as needed for conventional metrology as well as point of care diagnostics. High sensitivity of the prepared sensing devices combined with a remarkable simplicity of fabrication, is a step forward in the realization of cost efficient flexible magnetoelectronic devices, with possible application in soft robotics, interactive devices for virtual- and augmented reality [6,7] and point of care platforms for the detection of magnetic objects [8].
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[5] V. Mor, Journal of Applied Physics, Vol. 111 (2012)
[6] G. S. Cañón Bermúdez, Science Advances, Vol. 4 (2018)
[7] M. Melzer, Nature Communications, Vol. 6 (2015)
[8] G. Lin, Lab Chip, Vol. 14, p.4050 (2014)