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SMALLEST CAR IN THE WORLD?

In Uncategorized on November 14, 2011 at 11:44 am

Reduced to the max: the emission-free, noiseless 4-wheel drive car, jointly developed by Empa researchers and their Dutch colleagues, represents lightweight construction at its most extreme. The nano car consists of just a single molecule and travels on four electrically-driven wheels in an almost straight line over a copper surface. The “prototype” can be admired on the cover of the latest edition of Nature.

A number of chemists aim to use similar principles and concepts to design molecular transport machines, which could then carry out specific tasks on the nano scale. According to an article in the latest edition of science magazine “Nature,” scientists at the University of Groningen and at Empa have successfully taken “a decisive step on the road to artificial nano-scale transport systems.” They have synthesised a molecule from four rotating motor units, i.e. wheels, which can travel straight ahead in a controlled manner. “To do this, our car needs neither rails nor petrol; it runs on electricity. It must be the smallest electric car in the world — and it even comes with 4-wheel drive” comments Empa researcher Karl-Heinz Ernst.

The downside: the small car, which measures approximately 4×2 nanometres — about one billion times smaller than a VW Golf — needs to be refuelled with electricity after every half revolution of the wheels — via the tip of a scanning tunnelling microscope (STM). Furthermore, due to their molecular design, the wheels can only turn in one direction. “In other words: there’s no reverse gear,” says Ernst, who is also a professor at the University of Zurich, laconically.

According to its “construction plan” the drive of the complex organic molecule functions as follows: after sublimating it onto a copper surface and positioning an STM tip over it leaving a reasonable gap, Ernst’s colleague, Manfred Parschau, applied a voltage of at least 500 mV. Now electrons should “tunnel” through the molecule, thereby triggering reversible structural changes in each of the four motor units. It begins with a cis-trans isomerisation taking place at a double bond, a kind of rearrangement — in an extremely unfavourable position in spatial terms, though, in which large side groups fight for space. As a result, the two side groups tilt to get past each other and end up back in their energetically more favourable original position — the wheel has completed a half turn. If all four wheels turn at the same time, the car should travel forwards. At least, according to theory based on the molecular structure.

 

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