Observing and Simulating Magnetic Microparticle Hopping on Permalloy Disks

Magnetic microspheres are commercially-available, fluid-borne particles made of iron oxide encapsulated in polystyrene. These microspheres 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 study the transport of these particles about grids of permalloy disks, driven by varying, weak (<100 Oe) magnetic fields. Recent work has been done in the development of surface-based transport schemes and methods of applying tunable magnetic forces, showing promise for use in on-chip devices. I will discuss some of the applications of this chip-based technique as well as phenomena that arise during transport, for example variation in particle speed with external fields and transition from ordered to disordered transport. We use results from these experiments to develop competing computer models for the purpose of understanding magnetic characteristics of both the microparticles (i.e. susceptibility) as well as the permalloy disks (i.e. magnetization landscapes).