Self- Magnetization-Switchable Micro-Magnetic-Track Based Magnetic-Bead Manipulation

Abstract

In this paper, we report a self-magnetization-switchable magnetic-track based magnetic-bead manipulation on a silicon wafer. The manipulation approach consists of a thermomagnetic NiCu micro-disc track (which is deposited on the silicon wafer), micro magnetic bead, a thermoelectric generator (TEG; which is placed beneath the silicon wafer), and four external electromagnets (which are used to produce a directional magnetic field). The Curie temperature of the NiCu micro-disc track is approximate room temperature. Due to this, when the TEG cools the NiCu micro-disc track lower than its Curie temperature (i.e., lower than room temperature), the track becomes ferromagnetic. However, when the TEG heats the NiCu micro-disc track higher than its Curie temperature (i.e., about or higher than room temperature), the track becomes paramagnetic. Therefore, by alternative cooling and heating, the track is switched between ferromagnetic and paramagnetic (i.e., magnetic moment is changed between normal and very small). This achieves on-chip self-magnetization-switchable track. Furthermore, when a directional magnetic field is applied to the track which becomes ferromagnetic, the track can guide the bead manipulation. Alternatively, when the track becomes paramagnetic, the track cannot guide the bead manipulation. This novel self-magnetization-switch able magnetic-track-guided bead-manipulation provides an important alternative bead-manipulation for biomedical MEMS/NEMS systems.