Thinking small could pay off big

Researchers see a potential revolution if they can harness the energy in microscopic yet stronger-than-steel carbon nanotubes and put it to work

Without fanfare, Carol Livermore pulled out a clear plastic case.

Inside were two small black cubes, each the size of a Chiclet. Take a closer look: Each one is pitch black, and appears lightly tufted. Come in closer still - say with the help of an electron microscope - and you would see strands of carbon, each perfectly formed by an array of atoms arranged in a tube.

The individual strands are carbon nanotubes, a microscopic material with unique properties. The clusters in the plastic case are dubbed, quaintly, "nanotube forests." Each individual nanotube acts like a tiny spring, and Livermore thinks that if you combine billions of them, they could do things that no steel spring could achieve.

Nanotechnology, the science of tiny materials, has already yielded practical applications for everything from clothing to insulation. But Livermore, an assistant professor of mechanical engineering at the Massachusetts Institute of Technology, believes these stronger-than-steel nanotubes could open new possibilities for energy generation and storage.

"It is well known that you can store energy in the deformation of a spring," said Livermore. "The main challenge with storing energy in springs is most don't store a lot of energy per unit of weight or volume. Carbon nanotubes are great because they can stretch incredibly far without breaking."

The nanotubes work like expansion springs - pull them and they stretch, release them and they pop back to their original shape, releasing energy. Think of them as tiny Slinkies.

While this has been shown with individual nanotubes, Livermore wants to combine the tubes into bundles that can be seen with the naked eye, and prove that the bundles have the same remarkable qualities.

The forests are her raw material. They are provided by John Hart, an assistant professor of mechanical engineering at the University of Michigan. Hart has developed a novel way to flow heated gases containing carbon over a silicon substrate. The carbon atoms join together at just the right spots to "grow" into tubes that can be seen. He is one of many researchers developing ways of growing longer and more uniform carbon nanotubes.

Livermore envisions taking bunches of nanotubes, squishing them together so they are denser, and then interweaving the ends with other bunches, gradually adding length to the bundle. A variety of molecular forces will hold the bundles together, she said.

"These nanotubes want nothing more than to stick to each other," she said.

With a grouping of nanotubes as long as an inch or two, it will be possible to test the qualities of the carbon nanotubes in a visible experiment. One end could be clamped or glued to a fixed point, and the other pulled. Instruments could measure the amount of force used, and the amount of energy returned when the spring contracts.

"If you clump them together in a disordered mess," said Livermore, "there won't be good energy transfer among the nanotubes. We're working for a well-ordered assembly in which the tubes are aligned and have lots of contact with their neighbors."

What could these tiny tubes be used for?

Leon Sandler, executive director of the Deshpande Center at the Massachusetts Institute of Technology, cautioned against predicting exactly how the carbon nanotube springs might be used.

"Commercial lasers initially came out for just a few applications, like scanning bar codes," said Sandler. "But then all kinds of uses popped up. If this nanotube technology is made available, all sorts of entrepreneurs will find ways to incorporate it into their designs. What we like about this nanotube technology is that it's sufficiently different. It's not an incremental advance over current methods."

One possibility is a high-end mechanical watch that might only need winding once a month. Buyers of high-end mechanical timepieces appreciate new technology as it is applied to the centuries-old art of clock making.

Livermore said another potential application would be a regenerative braking device for bicycles, in which mechanical energy is captured during braking, and can then be used to provide extra power for getting over hills. Systems currently on the market convert the mechanical energy to electricity, and then use the electricity to power a motor. But whenever energy is converted from one form to another, some is lost. Capturing mechanical energy - the energy of movement - and reusing it in the same state could make the device more efficient.

She is also thinking of ways in which the nanotube springs could replace some kind of batteries. Batteries tend to lose their charges over time, and stop working after a certain number of recharges. They don't work well when it's too hot or too cold. Theoretically, the nanotube springs can retain their energy indefinitely and work anywhere.

The few consumer products available that make use of carbon nanotubes don't really exploit the unique properties of the material, said Ahmed Busnaina, director of the Center for High-rate Nanomanufacturing at Northeastern University. Coatings and films, in which the bulk properties of the nanotubes - like conductivity - are useful, he said.

But a device like Livermore's nanotube powered watch would be a breakthrough, he said, and might work best in a high-end market in which consumers are willing to pay to own unique technology.

Like Livermore, others are entranced by the microscopic tubes, each so small it would take about a billion together to match the thickness of a single human hair.

"I love the sheer elegance and simplicity of the carbon nanotubes," said Lori Pressman, a director of Harris & Harris Group Inc., a publicly traded venture capital firm specializing in "tiny technology."

Pressman said development cycles for nanotechnology businesses are likely to be lengthy, like biotechnology, in which it often takes 15 years for a discovery to become a drug in a pharmacy.

"This work is more likely to resemble the biotech model, in which there will be more partnering with larger companies and intellectual property will be used to understand the relative contribution of partners," said Pressman, who has advised Livermore as an informal "catalyst" through the Deshpande Center for Technological Innovation at MIT. The center, which promotes commercialization of technology developed at MIT, has awarded Livermore two $50,000 grants to advance her research on the nanotubes.

Livermore has worked on a variety of nanotech projects, including tiny electro-mechanical systems. Working with Timothy F. Havel, a research scientist, and graduate student Frances Hill, she expects to fabricate a carbon nanotube "super spring" within weeks.

"If a grouping of overlapped strands is as strong as one single nanotube, that would be a home run," said Livermore.

Jeffrey Krasner can be reached at krasner@globe.com.