Using Magnetic Particle Trapping and Transport to Investigate Magnetism at the Micro-Scale

We study the guided transport of fluid-borne micro-scale spherical particles about grids of permalloy disks, driven by varying, weak (<100 Oe) magnetic fields. These microspheres, made of iron oxide encased in polystyrene, are designed for bioseparation of cells, proteins, DNA, and RNA, whereas they can be specifically bound to these targets allowing for field gradients to separate the particles from a mixture. We investigate phenomena that arise during transport of individual particles, for example variation in particle motion with external fields and transition from orderly phased-locked motion to less predictable phase-slipping behavior. We use results from these experiments to guide development of computer models for understanding magnetic characteristics of both the microparticles (i.e. susceptibility) as well as the permalloy disks (i.e. magnetization landscapes). Furthermore, we discuss recent updates to o?ur lab's transport apparatus, including methods for minimizing unwanted surface adhesion and increased magnetic field stability.