Nanocar

For the automobile manufactured by Tata Motors, see Tata Nano.

Chemical structure of a nanocar. The wheels are C₆₀ fullerene molecules.^[1]

The nanocar is a molecule designed in 2005 at Rice University by a group headed by Professor James Tour. Despite the name, the original nanocar does not contain a molecular motor, hence, it is not really a car. Rather, it was designed to answer the question of how fullerenes move about on metal surfaces; specifically, whether they roll or slide.

The molecule consists of an H-shaped 'chassis' with fullerene groups attached at the four corners to act as wheels.

When dispersed on a gold surface, the molecules attach themselves to the surface via their fullerene groups and are detected via scanning tunneling microscopy. One can deduce their orientation as the frame length is a little shorter than its width.

Upon heating the surface to 200 °C the molecules move forward and back as they roll on their fullerene "wheels". The nanocar is able to roll about because the fullerene wheel is fitted to the alkyne "axle" through a carbon-carbon single bond. The hydrogen on the neighboring carbon is no great obstacle to free rotation. When the temperature is high enough, the four carbon-carbon bonds rotate and the car rolls about. Occasionally the direction of movement changes as the molecule pivots. The rolling action was confirmed by Professor Kevin Kelly, also at Rice, by pulling the molecule with the tip of the STM microscope.

Independent early conceptual contribution

The concept of a nanocar built out of molecular "tinkertoys" was first hypothesized at the Fifth Foresight Conference on Molecular Nanotechnology (November 1997).^[2] Subsequently an expanded version was published in Annals of Improbable Research.^[3] These papers supposed to be a not-so-serious contribution to a fundamental debate on the limits of bottom-up Drexlerian nanotechnology and conceptual limits of how far mechanistic analogies advanced by Eric Drexler could be carried out. The important feature of this nanocar concept was the fact that all molecular component tinkertoys were known and synthetized molecules (alas, some very exotic and only recently discovered, e.g. staffenes, and notably – ferric wheel, 1995), in contrast to some Drexlerian diamondoid structures that were only postulated and never synthesized; and the drive system that was embedded in a ferric wheel and driven by inhomogeneous or time-dependent magnetic field of a substrate – an "engine in a wheel" concept.

Electrically driven directional motion of a four-wheel molecule on a metal surface

Kundernac et al. described a specially designed molecule that has four motorized "wheels". By depositing the molecule on a copper surface and providing them with sufficiently energy from electrons of a scanning tunnelling microscope they were able to drive some of the molecules in a specific direction, much like a car, being the first single molecule capable to continue moving in the same direction across a surface. Inelastic electron tunnelling induces conformational changes in the rotors and propels the molecule across a copper surface. By changing the direction of the rotary motion of individual motor units, the self-propelling molecular 'four-wheeler' structure can follow random or preferentially linear trajectories. This design provides a starting point for the exploration of more sophisticated molecular mechanical systems, perhaps with complete control over their direction of motion.^[4]

Motor Nanocar

A future nanocar with a synthetic molecular motor has been developed by Jean-Francois Morin et al.^[5] It is fitted with carborane wheels and a light powered helicene synthetic molecular motor. Although the motor moiety displayed unidirectional rotation in solution, light-driven motion on a surface has yet to be observed. Motility in water and other liquids can be also realized by a molecular propeller in the future.

See also

• Molecular motor
• Molecular propeller
• Nanoputian
• Nanodragster
• Synthetic molecular motors

References

1. ^ Shirai, Y. et al. (2005). "Directional Control in Thermally Driven Single-Molecule Nanocars". Nano Lett. 5 (11): 2330–4. doi:10.1021/nl051915k. PMID 16277478. 
2. ^ M T Michalewicz Nano-cars: Feynman's dream fulfilled or the ultimate challenge to Automotive Industry. Publication abstract. The Fifth Foresight Conference on Molecular Nanotechnology, Palo Alto (1997 November 5–8)
3. ^ M.T. Michalewicz Nano-cars: Enabling Technology for building Buckyball Pyramids, Annals of Improbable Research, Vol. IV, No. 3 March/April 1998
4. ^ Kudernac, Tibor; Ruangsupapichat, Nopporn; Parschau, Manfred; MacIá, Beatriz; Katsonis, Nathalie; Harutyunyan, Syuzanna R.; Ernst, Karl-Heinz; Feringa, Ben L. (2011). "Electrically driven directional motion of a four-wheeled molecule on a metal surface". Nature 479 (7372): 208–11. doi:10.1038/nature10587. PMID 22071765. 
5. ^ Morin, Jean-François; Shirai, Yasuhiro; Tour, James M. (2006). "En route to a motorised nanocar". Org. Lett. 8 (8): 1713–6. doi:10.1021/ol060445d. PMID 16597148. 

External links

• Rice University press release
• A New Model Nanocar on the Showroom Floor – Article covering the development of the second generation nanocar at Rice University including an interview with Professor Kevin F. Kelly.
• Click here to drive the Nanocar online – You can drive a NanoCar in the free NanoQuest Serious Game project