Submersed in a slow-flowing liquid, a dense bundle of nanotubes develops a voltage that ranges up to 10 millivolts and increases with flow speed, according to Ajay Sood and his colleagues at the Indian Institute of Science in Bangalore.

The tiny turbine "is made of single-wall carbon nanotubes," Sood told NewsFactor. "Measurements are reported in Sciencexpress, showing the generation of voltage by fluid flow."

When 8 Times the Size of the National Debt Means Ultra-Small

A nanotube is so small that a bundle the size of a sesame seed contains about 50 trillion tubes -- eight times the size of the U.S. national debt. As various fluids, from hydrochloric acid to water, flowed over a nanotube bundle mounted between metal electrodes, Sood and his team measured the generated voltage.

Hydrochloric acid produces voltages about five times that of purified water and 60 times that of methanol, Sood observed. Methanol and water are poorly ionized liquids, while hydrochloric acid contains abundant hydrogen ions. Imbalances that develop between positive and negative charges as liquids flow over the tubes probably cause the voltage to develop, Sood hypothesizes. More ions create a greater charge difference and hence a greater voltage.

Fantastic Change of Pace

Charge-generating nanotubes may find applications in micro-machines that work in a fluid -- and futuristic -- environment. While nano-explorers have yet to be invented, inner-space journeys, such as that envisioned by Harry Kleiner and Isaac Asimov in "Fantastic Voyage," might become possible with nanotube-powered micro-submarines that use flowing blood as both a power source and a medium of transport.

In the nearer future, nanotube turbines might power a new, lightweight line of heart pacemakers that need neither heavy battery packs nor recharging.

"It sounds great that this is emerging pacemaker technology that avoids a battery," said Dr. Nieca Goldberg, chief of the Cardiac Rehabilitation and Prevention Center at Lenox Hill Hospital in New York. "It would reduce the need for surgical procedures to change the pacemaker battery, which is usually required at an average time of five years," Goldberg told NewsFactor.

Radical Batteries

Rolled nanotubes also lend themselves to three-dimensional batteries that can be made extra small.

"The electrodes in today's small batteries are made flat (or as multilayer sandwiches of flat electrodes at best)," said UCLA engineering professor Chang-Jin "CJ" Kim, a micro-fabrication and nanotechnology expert. "With the recent advances in micro-machining technologies and emerging nanotechnologies, we are exploring a new concept of using three-dimensional electrodes in designing small batteries, a radical departure from the existing practice of mating two flat plates," Kim told NewsFactor.

Confident that nanotubes will set the pace for many new technologies, Dr. Sood said he is "in the process of patenting the concept in both India and the United States."