Randy Wind/Martin Roelfs

ScienceShot: Nano Car Is World's Tiniest

Sure, nature created motor proteins used in synthesizing chemical energy and flexing muscles. And scientists have come up with synthetic molecules that do everything from walk down a prelaid path to spin a metal whisker like a helicopter blade. But now researchers from the Netherlands and Switzerland have outpaced them all. The group fashioned what looks like a molecule-sized car, made of a few dozen atoms, with four-wheel drive. The wheels work like molecular ratchets to all spin in a common direction when fed a fuel of energized electrons from a scanning tunneling microscope. The only difficulty is that lots of the cars don't actually work because when deposited on a copper surface they land on their roofs or sides. That, and even the ones that do drive, don't have much room for groceries.

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