Steering magnetic nanoparticles (MNPs) in a desired trajectory has been proposed for guiding magnetically labelled drugs to clinical targets1. In order to steer MNPs to a desired location, a strong magnetic field and field gradient is necessary and the deeper the location, the stronger the magnetic force required. External permanent magnets can provide a strong magnetic field and gradient. We hypothesise that external magnetic field/field gradient arrays of 1.1T can be designed to capture MNPs into tumors. Brain tumors are one of the most difficult cancers to treat due to the complex anatomy of the brain. Therefore, we are developing a 3D printed brain tumor model to investigate trapping of MNPs into a tumor using Halbach arrays.