NMR magnets for portable applications using 3D printed materials.

In this paper, we introduce 3D printing as a possibility for realizing lightweight, yet high-precision NMR magnets. Using a commercially available filament containing steel particles allows for the realization of critical components of NMR magnets such as pole pieces and even the flux-conducting yoke. In contrast to shimming structures made of iron, 3D printed structures made of the lightweight filament allow for a robust and inexpensive way of realizing high-performance NMR magnets for future portable NMR applications. We demonstrate the versatility and achievable high performance of the proposed solution with two different H-shaped NMR magnets. In the first magnet, the 3D-printed filament is used to realize the yoke that guides the magnetic flux inside the magnet, providing the potential for a substantial weight reduction compared to a conventional iron yoke. In the second magnet, we use the 3D-printed material to realize arbitrarily shaped passive shim structures. Numerical size and shape optimizations using non-uniform rational basis splines (NURBS) have been applied to obtain the optimal geometry. The two manufactured magnets achieve measured NMR spectral line widths of 54 ppm and 250 ppm, respectively. Our results clearly demonstrate the efficiency and versatility of the proposed design and optimization approach.