Functionalized superparamagnetic beads are the biomedical industry workhorse for tagging, manipulating, and detecting chemical and biological species in a fluid environment. This work makes a significant step forward in the field of on-chip magnetic bead handling by using magnetic domain walls as mobile traps for beads. We show that the bead-DW magnetostatic interaction enables transport along specifically designed track structures, and that a bead trapped by a sinsusoidally-driven DW in such a track exhibits a magneto-mechanical resonance frequency characteristic of its size and susceptibility. This interaction between bead and domain wall provides a means to sense and characterize magnetic beads without the need for specific chemistry. The integration of transport and measurement on chip coupled with chemical non-specificity is a step toward the development of multifunctional precision magnetic lab-on-bead devices. This work bridges the fields of physics and biomedical device engineering.
E. Rapoport, D. Montana, and G. S. D. Beach, “Integrated Capture, Transport, and Magneto-Mechanical Resonant Sensing of Superparamagnetic Microbeads Using Magnetic Domain Walls,” Lab Chip. 12, 4433-4440 (2012). (view pdf)
E. Rapoport and G. S. D. Beach, “Dynamics of Superparamagnetic Microbead Transport Along Magnetic Nanotracks by Magnetic Domain Walls,” Appl. Phys. Lett. 100, 082401 (2012). [cover story] (view pdf)
E. Rapoport and G. S. D. Beach, “Magneto-mechanical Resonance of a Single Superparamagnetic Microbead Trapped by a Magnetic Domain Wall,” J. Appl. Phys. 111, 07B310 (2012). (view pdf)
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