Novel coil-less room-temperature resettable magnetic-bead manipulation by using thermomagnetic tracks

[Display omitted] •We demonstrate a novel thermomagnetic-track-guided magnetic bead manipulation.•Cooling to 5℃, tracks become ferromagnetic and thus can guide the bead motion.•Heating to 50 °C, tracks become paramagnetic and thus cannot guide the bead motion.•This achieves a coil-less room-temperature resettable magnetic bead manipulation.•This provides an alternative magnetic-bead-manipulation for biomedical systems. In this paper, we report a novel coil-less room-temperature resettable magnetic bead manipulation by using thermomagnetic Gd tracks. When comparing to conventional magnetic-track-guided magnetic bead motion, the thermomagnetic Gd tracks (whose Curie temperature is at room temperature) not only can guide the bead motion (as well as the conventional tracks) but also can be reset (demagnetized) in room temperature range without use of any conventional reset coil (i.e., superior than the conventional tracks). The operation and reset principles are described below. When a Gd track is cooled (by a thermoelectric generator, TEG) lower than its Curie temperature (for example: 5 °C), the Gd track becomes ferromagnetic. Furthermore, under a magnetic field, the ferromagnetic Gd track enables the magnetic-track-guided magnetic-bead manipulation. Oppositely, when the Gd track is heated (by the TEG) higher than its Curie temperature (for example: 50 °C), the Gd track becomes paramagnetic. Thus, under the magnetic field, the paramagnetic Gd track cannot attract the bead. This achieves the track resetting/demagnetizing through a coil-less room-temperature approach and thus disables the magnetic-track-guided magnetic bead manipulation. Furthermore, according to above principles, we can sequentially use TEGs to cool and heat different Gd tracks to guide the bead moving across different tracks, and also reset/demagnetize any track anytime during the bead motion through our approach. These results would be important fundamental elements to provide an alternative magnetic-bead-manipulation for biomedical MEMS systems.