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The main challenge in magnetic drug targeting lies in steering the magnetic particles, especially in deeper body layers. For this purpose, linear Halbach arrays are currently in focus. However, to the best of the authors' knowledge, the impact of the magnetization angle between two neighboring magnets in Halbach arrays has not been investigated for particle steering so far. Therefore, in this paper, a systematic numerical parameter study of varying the magnetization angle of linear Halbach arrays is conducted. This is completed by undertaking a typical magnetic drug targeting scenario, where magnetic particles have to be steered in an optimized manner. This includes the calculation of the magnetic flux density, its gradient, the total magnetic energy, and the resulting magnetic force based on a fitting function for the different Halbach constellations in the context of examining their potential for predicting the particle distribution. In general, increased magnetization angles result in an increased effective range of the magnetic force. However, as there is a trade-off between a weak force on the weak side of the array and a simple manufacturing process, a magnetization angle of 90 ∘ is recommended. For evaluating the steering performance, a numerical or experimental evaluation of the particle distribution is mandatory. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles offer numerous promising biomedical applications, e.g. magnetic drug targeting. Here, magnetic drug carriers inside the human body are directed towards tumorous tissue by an external magnetic field. However, the success of the treatment strongly depends on the amount of drug carriers, reaching the desired tumor region. This steering process is still an open research topic. In this paper, the previous study of a linear Halbach array is extended by an additional Halbach array with different magnetization angles between two adjacent magnets and investigated numerically using COMSOL Multiphysics. The Halbach arrays are arranged with permanent magnets and generate a relatively large region of a moderately homogeneous, high magnetic field while having a strong gradient. This results in a strong magnetic force, trapping many particles at the magnets. Afterwards, to avoid particle agglomeration, the Halbach array is flipped to its weak side. Therefore, the magnetic flux density, its gradient and the resulting magnetic force are computed for the different Halbach arrays with different constellations of magnetization directions. Since the calculation of the gradient can lead to high errors due to the used mesh in Comsol, the gradient was derived analytically by investigating two different fitting functions. Overall, the array with a 90 ∘ shifted magnetization performs best, changing the magnetic sides of the array easily and deflecting more particles. Besides, the results revealed that the magnetic force dominates directly underneath the magnets compared to the other existing forces on the SPIONS. Summarized, the results depict that the magnetic force and, thus, the region where the particles are able to get washed out, can be adjusted using low-cost permanent magnets. [ABSTRACT FROM AUTHOR]