MANHASSET, N.Y. — Immersing vertically-grown carbon nanotubes into a liquid organic solvent and allowing them to dry allows the nanotubes to compress into a dense bundle, researchers in the U.S. have discovered.

The technique boosts tube bundle density by as many as 25 times. And the higher the density of carbon nanotube density, the better they can conduct electricity.

A carbon nanotube bundle before (left) and after (right) densification.

James Jian-Qiang Lu, associate professor of physics and electrical engineering, and his research associate Zhengchun Liu of Rensselaer Polytechnic Institute (RPI, Troy, N.Y.) detailed the results of the post-growth densification project on Wednesday (June 6) at the International Interconnect Technology Conference (Burlingame, Calif.).

Lu attributed the densification process to capillary coalescence, the same physical principle that allows moisture to move up a piece of tissue paper when dipped into water.

The tightly packed bundles are said to be efficient conductors, and could one day replace copper as the primary interconnects used on computer chips, according to Lu.

The RPI researchers also said the technique could hasten the transition to next-generation, three-dimensional stacked chips.

"It's a significant and critical step toward the realization of carbon nanotube interconnects with better performance than copper," claimed Lu, adding "there's still a lot of work to do before this technology can be integrated into industrial applications.

Alternative energy advocates such as the late Richard Smalley have long pointed to carbon nanotubes as a key technology for future power generation.