could be formed into tiny springs capable of storing as much energy, pound for pound, as state-of-the-art lithium-ion batteries - and more than 1,000 times as much as steel springs - and potentially do so more durably and reliably.

Why it matters: Ultimately, such springs might be used for such applications as an emergency backup power supply or alarm system that can be left in place for many years without losing its "charge," portable mechanical tools like leaf blowers that work without the noise and fumes of small gasoline engines, or devices to be sent down oil wells or into other harsh environments where the performance of ordinary batteries would be degraded by the extremes of temperature.

How they did it: Livermore and her team did a combination of mathematical analysis and small-scale laboratory testing to determine the potential of carbon nanotubes to be used as springs for energy storage.

Next steps: Livermore says that to create devices that come close to achieving the theoretically possible high energy density of the material will require plenty of additional basic research, followed by engineering work. Specifically, the initial lab tests used long fibers of individual carbon nanotubes joined end-to-end, but creating a practical energy storage device will require assembling nanotubes into longer, thicker fibers without losing their key advantages.

Source: "Storing elastic energy in carbon nanotubes," by F. A. Hill, Carol Livermore et al, in Journal of Micromechanics and Microengineering, Aug. 26, 2009, and "Modeling mechanical energy storage in springs based on carbon nanotubes," F. A. Hill, Carol Livermore et al, in Nanotechnology, June 3, 2009

Funding: Their work has been funded by the Deshpande Center for Technological Innovation Ignition grant and by an MIT Energy Initiative seed grant.

Source: MIT – 21.09.2009.