Nanowire Self-Assembly

Assembly of the nanowires be controlled by the application of a small magnetic field H ~ 1 Gauss. Since the isolated wires all align parallel to H, their tendency to aggregate in a random way due to the complicated angular dependence of the dipolar forces between randomly oriented wires is prevented, and instead the interwire interactions cause the wires to form head-to-tail chains along the magnetic field lines. As shown in Figure 3, these chains become quite long, and can ultimately extend over hundreds of microns.

The left-hand figure above shows four video-microscope still-frames filmed as two nanowires come together due to their mutual magnetic attraction. The wires were pre-aligned in a small external field. The right-hand figure shows the end-to-end wire separation as a function of time. The four large circles (a)-(d) correspond to the four video frames on the left. The solid line through the data is a fit based on a dynamic model that includes both magnetic and viscous drag forces.