Researchers have installed a molecular engine into a 鈥渃ar鈥� just a few billionths of a metre long. Measuring just 3 by 4 nanometres, around 20,000 of the cars could be parked on the tip of a human hair.
Jim Tour and colleagues at Rice University in Houston, US, built a chassis and wheels for a nano-car from organic molecules at the end of 2005. The engineless model could only be powered remotely 鈥� using a heated gold surface to stop its wheels sticking and an electromagnetic field to drag it forwards. But the new model should be able to propel itself 鈥� using a motor fuelled entirely by light.
The nano-car鈥檚 molecular motor contains a pair of bonded carbon molecules that rotate in one direction if illuminated by a specific wavelength of light. After fixing the molecular engine to the car鈥檚 chassis and shining a light on it, Tour鈥檚 team confirmed that the engine was running by using nuclear magnetic resonance to monitor the position of the hydrogen atoms within it.
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But the car was not released to drive itself along. 鈥淚t鈥檚 analogous to building a race car and putting it up on blocks,鈥� Tour said. 鈥淣ow it鈥檚 a question of getting it out on the track.鈥� The motor should function as a fifth wheel to drive the car along.
Seeing is believing
Tour estimates that the car could travel two nanometres per minute but says his team has yet to find a way to watch their molecular automobile in action. 鈥淲e think the car would drive along, but we wouldn鈥檛 be able to see it and I don鈥檛 think people would believe us,鈥� he says.
The previous version of the nano-car moved along a flat gold surface. But this would stop the new motor from working as the energy collected from light would drain into the gold molecules.
A non-metal track should allow the engine to work, but this makes observing the car in action problematic as the scanning tunnelling microscope normally used needs a metal base. Other forms of microscopy either do not have the power to resolve the car properly, Tour says, or require the use of other surfaces that are unsuitable.
鈥淭his is shows a general problem with nanotechnology right now,鈥� Tour says. 鈥淲e only have crude tools and that slows development down.鈥�
