Nano-centipedes get a grip

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 they believe could act like Velcro, holding together composite materials.

The centipedes consist of nanowires of cadmium tellurium (CdTe), made by attaching individual nanoparticles of CdTe to a capping ligand, mercaptosuccinic acid.

The complex tends to organise itself into a stack, lining up the CdTe particles to form a continuous wire, several hundred nm to 10 μm long. A coating of mercaptopro-pyl(trimethyloxysilane), and a bath in a solution of tetraethyl-orthosilicate, forms bristles of silica along the surface of the wires.

’We were initially dumbfounded by the formation of the centipedes,’ says Nick Kotov of the University of Michigan. ’The topology of the nanowires is very interesting - it 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.

The CdTe wires that form the backbone of the centipedes are both semiconducting and luminescent, Kotov explains, and can polarise absorbed and emitted light. ’Imagine a 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,’ notes Kotov.

These modified centipedes could also form the basis for thin-film fluorescence sensors.

Stuart Nathan