To carry out mechanical work, one usually turns to engines, which transform chemical, thermal or electrical energy into kinetic energy in order to, say, transport goods from A to B. Nature does the same thing; in cells, so-called motor proteins such as kinesin and the muscle protein actin carry out this task. Usually they glide along other proteins, similar to a train on rails, and in the process "burn" ATP (adenosine triphosphate), the chemical fuel, so to speak, of the living world.
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.
Range per tank of fuel: still room for improvement
The downside: the small car, which measures approximately 4x2 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
|Contact: Prof. Dr. Karl-Heinz Ernst, Empa Nanoscale Materials Science|
Swiss Federal Laboratories for Materials Science and Technology (EMPA)