Magnetic trapping and self-assembly of multicomponent nanowires

TLDR

Magnetic nanowires in fluid can be assembled and ordered by exploiting their shape anisotropy. The authors introduce a magnetic trapping method that captures a single nanowire between lithographically patterned microelectrodes. The trapping dynamics are governed by the balance of magnetic forces and fluid drag at low Reynolds number, and the technique uses patterned microelectrodes to hold the wire. They demonstrate that electrodeposited Ni nanowires (350 nm × 12 µm) can be aligned into chains hundreds of micrometers long under a ~10 G field, and that three‑segment Pt–Ni–Pt nanowires form low‑resistance Ohmic contacts with the electrodes, suggesting utility for nanoscale magnetic device fabrication.

Abstract

Magnetic nanowires suspended in fluid solutions can be assembled and ordered by taking advantage of their large shape anisotropy. Magnetic manipulation and assembly techniques are demonstrated, using electrodeposited Ni nanowires, with diameter 350 nm and length 12 μm. Orienting suspended nanowires in a small magnetic field H≈10 G promotes self-assembly of continuous chains that can extend over several hundred μm. The dynamics of this process can be described quantitatively in terms of the interplay of magnetic forces and fluid drag at low Reynolds number. In addition, a new technique of magnetic trapping is described, by which a single magnetic nanowire can be captured between lithographically patterned magnetic microelectrodes. The use of three-segment Pt–Ni–Pt nanowires yields low resistance, Ohmic electrical contacts between the nanowires and the electrodes. This technique has potential for use in the fabrication and measurement of nanoscale magnetic devices.