Manipulation of Magnetic Beads by Magnetic Fields of Narrow Metallic Wires for Use in Biosensors

In this paper, we investigated a means to manipulate small magnetic beads using the magnetic fields of current-carrying wires. Narrow metallic wires were fabricated with optical lithography and vacuum deposition methods. As we applied 20-40 mA of current, the magnetic beads could be collected on the wire. Depending on the magnitude of the currents, the velocity of the beads was 2-20 mum/s. In addition to the motion of the beads by the interaction with the fields, we also observed drift of the beads caused by the local heating of the wire and the resulting temperature gradient. We also demonstrated transfer of beads between wires by switching the current between the wires. We consider that this simple device can be used to transfer the beads to the locations of the sensors and that it can increase the reaction probability between beads and magnetic sensors.