Japanese researchers have proposed an idea to use stretchy circuits made from rubber and nanotubes to create an "e-skin", which will be flexible enough to completely cover a robot without limiting its movement.

"Without human skin-like sensitivity, robots cannot be used in everyday life. Imagine the danger if a robot did not recognise when it had accidentally bumped into a young child," New Scientist magazine quoted Takao Someya of the University of Tokyo as saying.

He has already developed a rubbery conductor, that can be stretched by 38 per cent without any drop in its conductivity.

He says that a net of it was still working after being stretched by 134 per cent, though with a drop in conductivity.

Someya has revealed that the new material is made by mixing conducting carbon nanotubes with rubber.

To prevent the nanotubes clumping together, the researchers have devised a technique that uses an iconic liquid, consisting of charged ions and not molecules like most liquids.

The novel technique allows the researchers to add more nanotubes without fear that a high density of them would form lumps.

The final material is around 20 per cent nanotubes by weight, and current flows through it by hopping from nanotube to nanotube.

Someya says that the time during which a route across the material exists when it is stretched and the tubes are pulled apart is maximised by using long nanotubes.