Navigation with magnetic nanoparticles: Magnetotactic bacteria and magnetic micro-robots

Magnetotactic bacteria navigate in the magnetic field of the Earth by aligning and swimming along field lines with the help of special magnetic organelles called magnetosomes. These organelles contain magnetic nanoparticles and are organized into chain structures in cells. Here we review recent work on the formation of these chains and provide some estimates of the magnetic interaction energies and the corresponding forces involved in this process. In addition, we briefly discuss the propulsion of synthetic micro- or nanopropellers based on magnetic nanoparticles.