Tough tubes -- Carbon nanotubes endure heavy wear and tear

July 2, 2007
Nanotube Block -- Before Compression
A two-millimeter square block of carbon nanotubes, made up of millions of individual, vertically aligned, multiwalled nanotubes. Credit: Rensselaer/Victor Pushparaj

The ability of carbon nanotubes to withstand repeated stress yet retain their structural and mechanical integrity is similar to the behavior of soft tissue, according to a new study from Rensselaer Polytechnic Institute.

When paired with the strong electrical conductivity of carbon nanotubes, this ability to endure wear and tear, or fatigue, suggests the materials could be used to create structures that mimic artificial muscles or interesting electro-mechanical systems, researchers said.

Carbon Nanotube Block - After Compression
The same carbon nanotube block after being compressed more than 500,000 times. Even after this stress, there is virtually no difference in the block’s shape, mechanical integrity or electrical conductivity. This resistance to wear and tear is similar to the behavior of soft tissues such as a shoulder muscle or a stomach wall.Credit: Rensselaer/Victor Pushparaj

The report, “Fatigue resistance of aligned carbon nanotube arrays under cyclic compression,” appears in the July issue of Nature Nanotechnology. Despite extensive research over the past decade into the mechanical properties of carbon nanotube structures, this study is the first to explore and document their fatigue behavior, said co-author Victor Pushparaj, a senior research specialist in Rensselaer’s department of materials science and engineering.

“The idea was to show how fatigue affects nanotube structures over the lifetime of a device that incorporates carbon nanotubes,” Pushparaj said. “Even when exposed to high levels of stress, the nanotubes held up extremely well. The behavior is reminiscent of the mechanics of soft tissues, such as a shoulder muscle or stomach wall, which expand and contract millions of times over a human lifetime.”

Pushparaj and his team created a free-standing, macroscopic, two-millimeter square block of carbon nanotubes, made up of millions of individual, vertically aligned, multiwalled nanotubes. The researchers then compressed the block between two steels plates in a vice-like machine.

The team repeated this process more than 500,000 times, recording precisely how much force was required to compress the nanotube block down to about 25 percent of its original height.

Even after 500,000 compressions, the nanotube block retained its original shape and mechanical properties. Similarly, the nanotube block also retained its original electrical conductance.

In the initial stages of the experiment, the force needed to compress the nanotube block decreased slightly, but soon stabilized to a constant value, said Jonghwan Suhr, an assistant professor of mechanical engineering at the University of Nevada in Reno, who received his doctorate from Rensselaer in 2005, and with Pushparaj contributed equally to this report.

As the researchers continued to compress the block, the individual nanotube arrays collectively and gradually adjusted to getting squeezed, showing very little fatigue. This “shape memory,” or viscoelastic-like behavior (although the individual nanotubes are not themselves viscoelastic), is often observed in soft-tissue materials.

While more promising than polymers and other engineered materials that exhibit shape memory, carbon nanotubes by themselves do not perform well enough to be used as a synthetic biomaterial. But Pushparaj and his fellow researchers are combining carbon nanotubes with different polymers to create a material they anticipate will perform as well as soft tissue. The team is also using results from this study to develop mechanically compliant electrical probes and interconnects.

Source: Rensselaer Polytechnic Institute

Explore further: Self-assembling, biomimetic membranes may aid water filtration

Related Stories

Carbon nanotube speakers play music with heat

July 28, 2015

Troy Bouman reaches over, presses play, and the loudspeaker sitting on the desk starts playing the university fight song. But this is no ordinary loudspeaker. This is a carbon nanotube transducer—and it makes sound with ...

Short wavelength plasmons observed in nanotubes

July 28, 2015

The term "plasmons" might sound like something from the soon-to-be-released new Star Wars movie, but the effects of plasmons have been known about for centuries. Plasmons are collective oscillations of conduction electrons ...

Wafer-thin material heralds future of wearable technology

July 27, 2015

UOW's Institute for Superconducting and Electronic Materials (ISEM) has successfully pioneered a way to construct a flexible, foldable and lightweight energy storage device that provides the building blocks for next-generation ...

Recommended for you

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

Meet the high-performance single-molecule diode

July 29, 2015

A team of researchers from Berkeley Lab and Columbia University has passed a major milestone in molecular electronics with the creation of the world's highest-performance single-molecule diode. Working at Berkeley Lab's Molecular ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.