Thin, Transparent Nanotube Sheets

NANOMATERIALS

Using a solid-state process, researchers have found a way to transform a carbon nanotube "forest" into strong, ultrathin, transparent carbon nanotube sheets or ribbons with exceptional mechanical and physical properties. The process, they say, appears to be scalable for continuous high-rate production, opening the door to a variety of potential applications such as artificial muscles, flexible organic light-emitting displays, low-noise electronic sensors, solar cells, and electricity-conducting appliqués (Science 2005, 309, 1215).

"When you have a remarkable material, it's easy to find applications that look attractive," says team leader Ray H. Baughman, a chemistry professor and director of the NanoTech Institute at the University of Texas, Dallas.

By pulling on the edge of a forest of naturally "sticky" nanotubes, Baughman and colleagues draw out 5-cm-wide, meter-long, transparent sheets at rates exceeding 7 meters per minute. Initially, the sheets are highly porous aerogels, but they can be compressed into denser sheets that are stronger than steel sheets of the same weight. The nanotube sheets can be attached to plastic or silicone rubber sheets to fashion transparent, flexible electronic circuits. When used as electrodes to energize musclelike actuators, the sheets can be reversibly deformed without losing their conductivity.

Because the sheets absorb microwaves, becoming hot, they can be layered between Plexiglas plates and welded together to make transparent heating elements and antennas for car windows.

A voltage applied across a sheet leads to emission of polarized ultraviolet, visible, and infrared light for sensing, imaging, and other applications.

The work reported in the Science paper involves multiwalled nanotubes, but Baughman says the technology is transferable to single-walled tubes.

He and his colleagues, including Ken R. Atkinson of the Commonwealth Scientific & Industrial Research Organization, in Australia, plan to license the technology to firms.