Self-healing method readies nanotubes for flexi electronics

US researchers have developed a way to heal gaps in wires too small for even the world’s tiniest soldering iron.

Prof Joseph Lyding has developed a way to join carbon nanotubes to turn them into more efficient transistors.

The “nano-soldering” method was created by engineers at the University of Illinois as a way of joining carbon nanotubes for use in flexible electronic components as an easier-to-manufacture alternative to traditional silicon transistors.

The researchers claim the technique, which involves using gases to deposit metal molecules on the nanotubes as they heat up, improves the performance of nanotube devices by an order of magnitude.

Creating single nanotubes to serve as transistors is very difficult, the researchers said, and arrays of separate nanotubes slow down the flow of current as it jumps between them.

But traditional soldering methods are far too clumsy to join such tiny molecular structures (carbon nanotubes are one-atom-thick cylinders of carbon).

Instead the researchers used the established process of chemical vapour deposition (CVD) to cause a chemical reaction between the nanotubes and gases containing metal molecules.

‘It occurred to me that these nanotube junctions will get hot when you pass current through them,’ said research leader Prof Joseph Lyding, in a statement. ‘We use these hot spots to trigger a local chemical reaction that deposits metal that nano-solders the junctions.’

Once the links are made the current flows more easily and as the electrical resistance drops so does the temperature, ending the reaction.

‘It would be easy to insert the CVD process in existing process flows,’ said Lyding. ‘CVD technology is commercially available off-the-shelf. People can fabricate these transistors with the ability to turn them on so that this process can be done. Then when it’s finished they can finish the wiring and connect them into the circuits. Ultimately it would be a low-cost procedure.’

Lyding’s team is now examining ways to improve the process. The research has so far been funded by the US National Science Foundation and Office of Naval Research.