Centipedes in space
19 Feb 2004
The next generation of spacecraft could be powered by materials whose structures are halfway between a centipede and a dressmaking accessory - but thousands of times smaller.
Teams from the Universities of Michigan and Purdue University in the US, and the University of Vigo in Spain, have developed what they call 'bristled nano-centipedes' which could act as molecular velcro, and may also form the basis for new types of gas sensor.
The centipedes are made from nanowires of a semiconductor, cadmium tellurium (CdTe). These are made by attaching individual nanoparticles of CdTe to a capping ligand, mercaptosuccinic acid, then allowing these complexes to self-assemble into wires, several hundred nanometres to 10 microns long. A coating of an organic primer and a bath of a silica source, tetraethyl orthosilicate, and an ammonia catalyst encouraged silica bristles, around 30nm long, to be deposited on the surface of the wires.
'We were initially dumbfounded by the formation of the centipedes,' says Nick Kotov of the University of Michigan. 'Their topology could be exceptionally useful for the design of optically active and remarkably strong nanocomposites, due to the Velcro effect.'
Such ultra-strong optical materials could have far-ranging applications, such as thin-film solar cells. 'Imagine space station with large area plastic solar batteries,' Kotov says. 'They need to be both strong and photoactive.'
Closer to home, industry could also benefit from the discovery. 'The bristled morphology of the centipedes could be useful for sensor applications, because it provides a very large surface with multiple attachment sites,' he says.
