Researchers have discovered how to weld together single-walled carbon nanotubes that could pave the way for controlled fabrication of molecular circuits and nanotube networks.

Pulickel Ajayan, professor of materials science at Rensselaer, and his colleagues in Germany, Mexico, the U.K., and Belgium used irradiation and heat to form the welded junctions to connect the pure carbon cylinders that have remarkable electronic properties.

This is the first time single-walled nanotubes have been welded together, although multi-walled nanotubes with junctions previously have been created using growth techniques. The electrical properties of single-walled nanotubes surpass those of multi-walled tubes, which is why so many researchers have been anxious to try this experiment, Ajayan says.

“No one knew if junctions could be created,” Ajayan adds. “Single-walled carbon nanotubes are perfect cylinders without any defects, but in order to create junctions between them, intertube carbon-carbon bonds need to form. The irradiation and heating process we use creates just enough defects for these bonds to form without damaging their electrical properties.”

The results were obtained after several years of ongoing experimentation. The difficulty was finding nanotubes that cross and touch, which are critical for the initiation of intertube links. “Unfortunately, we can’t control this type of alignment just yet,” Ajayan notes.

The researchers used a special electron microscope that has the capability to irradiate and produce the heat necessary for the experiment. The high-voltage microscope, located in Stuttgart, Germany, is one of only a few worldwide.


Originally published in Rensselaer Magazine, Winter 2002

Published December 1, 2002