Ultra-light nanocables may replace copper for chip interconnects and power lines

September 8, 2011

A power cable made entirely of iodine-doped double-walled carbon nanotubes is just as efficient as traditional power cables at a sixth the weight of copper and silver, according to Rice University researchers (credit: Yao Zhao/Rice University)

Rice University researchers have fabricated iodine-doped, double-walled carbon nanotube cables with specific electrical conductivity (conductivity/weight) higher than copper and aluminum. The cables exhibit high current-carrying capacity of 10,000 to 100,000 amperes per square centimeter and can be joined together into arbitrary length and diameter, without degradation of their electrical properties.

They demonstrated their practical use by partly replacing metal wires in a household light bulb circuit. The conductivity variation as a function of temperature for the cables is five times smaller than that for copper. The high conductivity nanotube cables could find a range of applications, from low dimensional interconnects to transmission lines.

Highly conductive nanotube-based cables could be just as efficient as traditional metals at a sixth of the weight, said Enrique Barrera, a Rice professor of mechanical engineering and materials science. They may find wide use first in applications where weight is a critical factor, such as airplanes and automobiles, and in the future could even replace traditional wiring in homes.

The cables developed in the study are spun from pristine nanotubes and can be tied together without losing their conductivity. To increase conductivity of the cables, the team doped them with iodine and the cables remained stable.

The few centimeters of cable demonstrated in the present study seems short, but spinning billions of nanotubes (supplied by research partner Tsinghua University) into a cable at all is quite a feat, Barrera said. The chemical processes used to grow and then align nanotubes will ultimately be part of a larger process that begins with raw materials and ends with a steady stream of nanocable, he said. The next stage would be to make longer, thicker cables that carry higher current while keeping the wire lightweight. “We really want to go better than what copper or other metals can offer overall,” he said.

Ref. Yao Zhao, Jinquan Wei, Robert Vajtai, Pulickel M. Ajayan, and Enrique V. Barrera, Iodine doped carbon nanotube cables exceeding specific electrical conductivity of metals, Nature Scientific Reports, September 2011