Researchers from the US have created smart nanocomposite films whose potential applications range from self cleaning sensors to fuel efficient transport.

Liming Dai at the University of Dayton, Ohio, and co-workers prepared composites of vertically aligned carbon nanotubes and a temperature responsive polymer. Above a critical temperature, the polymer chains exist in a collapsed conformation, and recede beneath the surface, then on cooling the chains expand and protrude from the surface.

Carbon nanotubes have been used in a variety of sensing applications and the ability of a sensor surface to clean itself - the expanding polymer chains push debris away from the surface - means that the useful lifetime of the sensor can be extended. But this is not the only potentially useful feature. If something is trapped in the polymer, the change in conformation can be used to release it in a controlled fashion.

'Vertically aligned carbon nanotube composites are more difficult to prepare that the non-aligned versions that are often used,' said Dai. 'Some of our other research efforts have been directed to the problem of aligning nanotubes more efficiently as this will be an important step in achieving our long term goals for these materials.'

Dai and his colleagues have big plans for this technology. And by big, you need to think on the macro-scale. 'What if we could keep a boat so clean that there was much less drag acting on it as it travels?' asked Dai.

'The multi-functionality of these composites is very impressive,' said Christopher Li, a professor of materials science and engineering from Drexel University in Philadelphia, US. 'The future holds many challenges that are dependant on the specific direction the research takes. For large scale applications, it will be important to develop methods to prepare these films on a very large scale. If controlled release is the goal, it would be nice to be able to release several different agents in a controlled way from one device.'

Stephen Davey