US scientists have developed a first aid kit for electrical systems that could stop circuits failing and lead to safer, longer lasting batteries. 

Jeffrey Moore, at the University of Illinois at Urbana-Champaign, and colleagues made microcapsules with robust walls and filled them with carbon nanotubes (CNTs). They then ruptured the microcapsules using vigorous stirring and measured the contents' ability to conduct electricity between two electric probes separated by around 100 micrometres. As the team swept the applied voltage from minus to plus 50 volts, the CNTs migrated towards the probe tips. They aligned with the electric field and completed the circuit, enabling the current to flow. 

They found the best capsules were between 280 and 350 micrometres - smaller ones were too difficult to break and larger ones broke too easily. 

'Battery safety and lifetime are two problems that may benefit from this approach,' says Moore. 'You may want to restore electrical conductivity of damaged battery electrodes. On the other hand, if battery electrodes short circuit, the battery becomes dangerous and has the potential to explode. One may thus want to coat the electrodes with a resistive material to shut down a run-away battery. Exploring these ideas are some of our future plans.'

'I think it is a neat approach that can become very useful if taken further,' comments Vsevolod Rostovtsev, a nanotube expert at DuPont, Wilmington, US. 'The capsules need to become smarter so that their precise and accurate placement could be effected. The broken microcapsule shell needs to be removed from the electronic device to reduce contamination.'

Charlotte Beard

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