UNC-CH Study Shows Carbon Nanotubes Display Remarkable Strength, Flexibility

The research, conducted at the University of North Carolina at ChapelHill, for the first time used a unique computer-linked microscope to bend andrecord properties of carbon nanotubes.

Researchers create the materials -- a form of soot -- by arcingelectricity between two sticks of carbon. About six years ago, Japanesescientist Sumio Iijima discovered the tiny tubes, which are proving to bestiffer and stronger than any other known substance.

"Carbon nanotubes are a new material that scientists around the worldhave been studying intensively," said Michael R. Falvo of UNC-CH. "What we havefound is that under large strains, they have the extraordinary property of beingone of the stiffest materials known, while also being able to bend withoutbreaking and then be bent back into their original shape. This is unique."

Falvo is a doctoral student working under the direction of Dr. RichardSuperfine, assistant professor of physics and astronomy.

A report on the research appears as the cover story in Thursday's issue(Oct 9) of the journal Nature. Besides Falvo and Superfine, authors of thereport are graduate student Gregory J. Clary; Russell M. Taylor II, researchassistant professor of computer science; Vernon Chi, director of themicroelectronics systems laboratory; Dr. Frederick P. Brooks Jr., Kenanprofessor of computer science; and Dr. Sean Washburn, professor of physics andastronomy.

The UNC-CH scientists used a device they invented and called thenanoManipulator to bend the nanotubes, which are extremely light, and thenmeasure the curvature of the bends. They also studied the tubes' bucklingbehavior -- whether or not they buckled under pressure like drinking straws in achild's hands and stayed bent and damaged.

"We found that most of the bending was reversible, and that's excitingbecause it was not known before," Falvo said. "Even after repeated bending andstraightening of the nanotubes, they did not break. In fact, we have neverobserved a tube fail after repeated bending."

The unique nanoManipulator combines a commercially available atomicforce microscope with a force-feedback virtual reality system. The formeremploys an atomically small probe capable of bending and otherwise manipulatingmolecule-sized particles. The latter allows the scientists to see and feel arepresentation of the surface a million times bigger than its actual size.

Carbon fibers already are used in graphite composite tennis rackets andother products because of their strength and lightness, Falvo said. The UNC-CHexperiments indicate that carbon nanotubes are significantly stronger thancarbon fibers and hundreds of times stronger than steel.