Cancelling stray magnetic fields to render magnetic nanobots autonomous

Magnetic nanobots are of great technological importance due to their benign actuation method, bio-compatibility and medium-independent behaviour. They can be driven to propel in a particular direction using external magnetic fields. They can also be self-propelled under certain conditions where orientations of the nanobots remain independent of the energy input, implying individual entities behave independently of each other. The latter requires a precise magnetic field design, which, as we show here, is non-trivial experimentally. Specifically, the induced or stray magnetic fields in the plane of the nanobot motion can hinder autonomous motion altogether. We address the technique used to eliminate these unnecessary magnetic fields in two ways and especially highlight a method based on analyzing the trajectories of the nanobots.