Magnetic steering of a distributed ferrofluid spot towards a deep target with minimal spreading

In magnetic drug targeting, where drugs are attached to magnetic nanoparticles and external magnets are then used to focus the therapy to, for example, solid tumors, there is a need to better control and focus the distribution of particles (the ferrofluid) to deep targets. This paper considers a key next question: how to move a single spot of ferrofluid to a deep target with minimal spreading. The problem is challenging since the applied magnetic forces have a natural tendency to stretch the ferrofluid spot. A control policy is designed and verified by simulations to optimally control multiple electromagnets in concert to move a single spot of ferrofluid from the edge of a domain to a deep central target with minimal spreading.