  Within this work a passive and wireless magnetic sensor, to monitor linear
displacements is proposed. We exploit recent advances in 3D printing and
fabricate a polymer bonded magnet with a spatially linear magnetic field
component corresponding to the length of the magnet. Regulating the magnetic
compound fraction during printing allows specific shaping of the magnetic field
distribution. A giant magnetoresistance magnetic field sensor is combined with
a radio-frequency identification tag in order to passively monitor the exerted
magnetic field of the printed magnet. Due to the tailored magnetic field, a
displacement of the magnet with respect to the sensor can be detected within
the sub-mm regime. The sensor design provides good flexibility by controlling
the 3D printing process according to application needs. Absolute displacement
detection using low cost components and providing passive operation, long term
stability and longevity renders the proposed sensor system ideal for structural
health monitoring applications.
