If the current spate of molecular motors being constructed by scientists is anything to go by then we can expect interesting things from the emerging science of nanotechnology.

Watch an animation of the Cornell motor

The late physicist Richard Feynman once wrote that there was "plenty of room at the bottom", meaning that atoms are so small compared with living things that machines made of atoms and molecules could find many applications.

Some visionaries speculate that such machines could travel through the body releasing tiny doses of drugs to, for example, kill cancer cells.

Two molecular motors, composed of just a few dozen atoms, are described in the current edition of the scientific journal Nature. Now scientists at Cornell University in New York have described another one in the journal Nanotechnology.

They say it demonstrates the feasibility of extremely small, self-propelled bionic machines that could travel inside plant and animal cells, including those in humans.

Fabrication on a tiny scale

The engineers have combined a molecule made by a bacterium with one chemically synthesised in the lab. The result is a motor consisting of the enzyme ATP and an engineered molecule that is its moving component.

This is actually a central protein shaft (or rotor, in electric-motor terms) that rotates in response to electrochemical reactions with charged parts of ATP molecule.

The motor ran for 40 minutes at three to four revolutions per second.

Besides demonstrating that an organic molecular motor and an inorganic, nanofabricated device can be integrated, the Cornell engineers note, their system provides a platform for studying how ATP operation works.

Future possibilities

The ATP molecules were produced by modified E. Coli bacteria. With further genetic manipulation, it is hoped that the altered bacteria will produce ATP molecules with tiny propellers as well as other useful structures.

Although this progress is impressive, it is still early days for nanotechnology.

"We have a long way to go before it's safe to turn these little machines loose in the human body. But we believe this is a significant step toward the seamless integration of nanoscale technologies into living systems," Cornell's Carlo Montemagno says.