US Patent 9415398 Magnetic fluid manipulators and methods for their use

One aspect of the invention provides a device for sorting non-magnetic particles. The device includes: (a) a fluid holding chamber comprising an inner and outer surface; (b) a fluid in contact with the inner surface of the fluid holding chamber, said fluid containing a dispersion of magnetic particles and at least two sets of non-magnetic particles; and (c) at least two sources of magnetic fields positioned in close proximity to, or inside of, the fluid holding chamber. The at least two sources of magnetic fields produce a changeable pattern of magnetic field minima and maxima regions thereby causing said non-magnetic particles in the fluid to be transported towards the magnetic field minima regions by magnetic force. At least one of said sources of magnetic fields comprises an array of magnetizable features on a micrometer or nanometer length scale.