Micromagnet Conductors for High-Resolution Separation of Magnetically Driven Beads and Cells at Multiple Frequencies

Abstract

We demonstrate a separation method for complex mixture of superparamagnetic beads using half-disk pathways, under an in-plane rotating magnetic field, which is highly sensitive to the bead size and magnetic susceptibility. The non-linear dynamics of the beads moving along the half-disk pathways at multiple frequencies can be divided into three regimes: a phase-locked regime at low driving frequencies, a phase-slipping regime above the first critical frequency f c1 , and a phase-insulated regime above the second critical frequency f c2 in which the beads just hop at the gaps between two half-disks. Hence, based on the dynamical motions, the beads with varied sizes or heterogenic magnetic properties can be separated efficiently. Furthermore, a bio-selective separation of bead plus human monocytic leukemia (THP-1) cell complexes from bare beads has been achieved due to the increased drag force on the complexes, resulting in a decreased critical frequency.