We investigate maneuvering superparamagnetic microparticles, or beads, in a remotely-controlled, automated way across arrays of few-micron-diameter permalloy disks. This technique is potentially useful for applying tunable forces to or for sorting biological structures that can be attached to magnetic beads, for example nucleic acids, proteins, or cells. The particle manipulation method being investigated relies on a combination of stray fields emanating from permalloy disks as well as

more »

... ing externally applied magnetic fields. Unlike previous work, we closely examine particle motion during a capture, rotate, and controlled repulsion mechanism for particle transport. We measure particle velocities during short-range motion—the controlled repulsion of a bead from one disk toward another—and compare this motion to a simulation based on stray fields from disk edges. We also observe the phase-slipping and phase-locked motion of particles engaging in long-range transport in this manipulation scheme.