Paris: Scientists in the Netherlands have said they have made a four-wheeled molecule that measures just a billionth of a metre -- 60,000 times smaller than the thickness of a human hair -- and moves in response to a burst of electrons.

The nanometre-sized molecule comprises a central body to which four rotary units, each comprising a few atoms, are attached.

The nanocar is propelled and steered thanks to energy input from a tunnelling electron microscope.

By firing electrons, the microscope induces a change in the interaction between the rotors and a copper surface. As a result, the rotors move around like paddle wheels and drive the wee molecule forward.

The research, reported in the journal Nature, is headed by Ben Feringa, a professor at the University of Groningen.

It marks a new step in a field that developed about half a dozen years ago and sees practical outlets in medicine and nanoscale engineering.