At about 100 times the strength of steel at one sixth the weight and with impressive electrical conductive properties, carbon nanotubes (CNTs) have promised much since their discovery in 1991. The problem has been translating their impressive nanoscale properties into real-world applications on the macro scale. Researchers have now unveiled a new CNT fiber that conducts heat and electricity like a metal wire, is very strong like carbon fiber, and is flexible like a textile thread.

Building on ten years of research, the team, consisting of scientists from Rice University, Dutch firm Teijin Aramid, the Air Force Research Laboratory (AFRL) and the Technion-Israel Institute of Technology, relied on a “wet-spinning” chemical process using chlorosulfonic acid to dissolve clumps of raw nanotubes in a liquid before they were squirted through tiny holes to form long strands. These strands, with trillions and trillions of tightly packed carbon nanotubes all aligned in the same direction, were then spun into a macroscopic thread the researchers say boasts the highest conductivity ever reported for a macroscopic CNT fiber.

“We finally have a nanotube fiber with properties that don’t exist in any other material,” said lead researcher Matteo Pasquali, professor of chemical and biomolecular engineering and chemistry at Rice. “It looks like black cotton thread but behaves like both metal wires and strong carbon fibers.”

A spool with around 50 m (164 ft) of the new threadlike carbon nanotube fiber

“The new CNT fibers have a thermal conductivity approaching that of the best graphite fibers but with 10 times greater electrical conductivity,” adds study co-author Marcin Otto, business development manager at Teijin Aramid. “Graphite fibers are also brittle, while the new CNT fibers are as flexible and tough as a textile thread. We expect this combination of properties will lead to new products with unique capabilities for the aerospace, automotive, medical and smart-clothing markets.”

Pasquali says the specific electrical conductivity of the fibers is on a par with copper, gold and aluminum wires, but is much stronger, which gives them advantages over metal wires for data and low-power applications.

“Metal wires will break in rollers and other production machinery if they are too thin,” Pasquali said. “In many cases, people use metal wires that are far more thick than required for the electrical needs, simply because it’s not feasible to produce a thinner wire. Data cables are a particularly good example of this.”

To demonstrate the fibers’ impressive properties, the researchers have used it to suspend an LED light bulb while also supplying it with power. This can be seen, along with a description of the fiber's production, in the video below.

The researchers detail an industrially scalable process for making the threadlike CNT fibers in their paper published in Science.

Source: Rice University