Synthesis, Self-assembly and Integration of Multisegment Nanowires

Zhiyong Gu, Chemical Engineering 

Synthesis and fabrication of nanomaterials has been one of the most exciting and rapidly growing areas in the past decade. At the nanometer scale, many material properties may alter, for example, optical, mechanical, electrical and magnetic properties due to higher surface-to-volume ratio. However, in order to enable nanotechnology to fully manipulate and utilize nanomaterials to make nanodevices, nanoelectronics, or nano-products in general, new assembly and integration strategies have to be developed or created since the conventional microfabrication process is approaching its limit in terms of size and cost-effective mass production.

This study represented an effort in fabricating and assembling one of the most promising nano-building blocks – nanowires (nanorods), and the integration of nanowires into ordered structures that may find applications in electronics and medicine. Electrodeposition in nanoporous templates has been used to synthesize one- and multi-component nanowires in the diameter range of 15-200 nm and length up to 20 µm. Metallic, polymeric and hybrid nanowires have been fabricated in very large quantity (109-1010 wires/cm2) in this way. Two techniques have been described to assemble and integrate nanowires into ordered one-dimensional (1D), 2D and 3D structures. The first technique utilized surface tension driven self-assembly in a fluidic medium, in which the nanowires were selectively functionalized and then permanently bonded via a polymerizable adhesive. The second technique involved the utilization of nanoscale solder to bond nanowires. Chemical and electrical characterizations were conducted for the solder interconnects formed between nanowires. 

Two examples demonstrated how the aforementioned strategies can be incorporated into device fabrication. One is the fabrication of a nanowire-based analog integrator using magnetic assembly and nanoscale soldering. The other is preliminary results from a recent development in using nanowire networks as selective biosensors.