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Permanent magnet systems are used for guiding superparamagnetic (nano)particles (SPP) on arbitrary trajectories over large volumes. The basic idea is to use two superimposed magnetic fields: one constant to magnetize and orient the particles, and the other with a constant gradient to exert a force. Changing the angle between them enables steering with constant force at a single angle/direction. The same instrument can also be used for magnetic resonance imaging (MRI) using the inherent contrast of the SPP.
The idea was realized by combining Halbach-cylinders of dipolar and quadrupolar configuration. Prototypes of various sizes and complexity were constructed for different applications (e.g. light-microscopy). An advanced system with two quadrupoles even allows canceling the force, hence stopping the SPP and moving them around sharp edges. This system also allows for MRI and some first experiments are presented. The velocity of SPPs under such conditions was also investigated and modelled.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009026, DOI: 10.18416/IJMPI.2020.2009026