Inspired by biological structures like bones, wood and teeth, the production of artificial materials with site-specific and graded properties are under investigation [1]. Additive manufacturing technologies are especially promising for the fabrication of these materials since they allow the combination of complex geometries with locally adjusted properties [2]. Examples where precise geometry and tailored mechanical properties are required can be found in biomedical applications, for example, in airway stents [3]. Here we present a single-step laser powder bed fusion (LPBF) process that enables precise local adjustments of the mechanical stiffness within magneto-active composites [4]. By utilizing distinct laser parameters in specific regions of a composite containing thermoplastic polyurethane and atomized magnetic powder derived from hard magnetic Nd-Fe-B, the stiffness of the composite can be modified within the range of 2–22 MPa. The fabrication of graded mechanical properties is verified with nanoindentation of parts printed with different orientations toward the building direction. As an example of a biomedical application, a magnetically responsive airway stent with localized stiffness adjustment is presented. The position and diameter of the stent can be controlled remotely by an external magnetic field. Since the airway stent is fabricated with increased stiffness at the center, the structure is well adapted to the function of expanding force on a tumor. The proposed method using LPBF presents an approach for creating functionally graded materials, not only for magneto-active materials but also for various other structural and functional materials.

Acknowledgements
This work was financially supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project ID No. 405553726, TRR 270 and the RTG 2761 LokoAssist (Grant no. 450821862).

References
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