Manipulating microscopic magnetic beads at MIT
MIT researchers found that arc-shaped magnetic nanotracks could be used most effectively to control the motion of magnetic microbeads across the surface of a silicon wafer. By combining these arcs, they produced configurations such as this, with two "reservoir" rings at top right and left, where the beads can be stored indefinitely, connected to tracks where they can be moved along as needed. In the center, a junction allows the bead's path to be altered, either continuing to the side or moving downward to another section of the wafer. By combining such structures, complex series of manipulations of the beads could be carried out.
Read more at MIT News: http://web.mit.edu/newsoffice/2012/magnetic-beads-lab-on-a-chip-0925.html