Big Wheels for Little Cars

by Steve Cross Steve Cross

The most prolific car manufacturer on the planet resides in a Rice University laboratory in Houston, where chemist James Tour and his colleagues have built one trillion trillion nanoscopic cars. The tiny four-wheeled vehicles are only four billionths of a meter wide-25,000 of them parked side by side would be about as thick as a piece of paper. Not just another nano-gimmick, Tour´s cars could one day carve tiny channels in silicon, creating more-powerful computer chips.

Although other groups have made nanocars that slip or slide across a surface, Tour´s team is the first to construct ones with actual rolling wheels. To get the cars moving, scientists either heat an atomically smooth gold roadway (the temperature difference incites the wheels to spin) or use a scanning tunneling microscope to emit a beam of electrons that drags the car along by static electricity. In the future, Tour hopes to install an active propulsion system. What we want to do now is put an internal motor in there and drive the thing, he says.

Several different motors are in the works, including a photon-powered version [see illustration below]. Tour is also fine-tuning new 2006 models, including a nanotruck capable of transporting molecules, such as oxygen. Before long, he says, we´ll have a little Daytona 500.

Inside the Nanocar:

1. Engine: Some cars will use light-powered motors. Photons strike a paddle-wheel-like molecule in the chassis, creating a reaction that turns the wheels.
2. Suspension: The wheels are made of carbon spheres known as buckyballs. Hydrocarbon axles rotate perpendicular to the ground so the wheels can ride over bumps.
3. Trunk space: The truck model will include a molecule in its center that acts as a cargo bed to transport other molecules.
4. Road: A heated gold surface enables the carbon wheels to rotate freely.