Robot skin stretches to the task

October 22, 2003

THE skin of a robot has to fulfil two apparently opposing needs: it must be elastic enough to lend the robot human-like dexterity, and yet carry enough wiring to allow it to sense its environment.

If engineers connect the robot's sensors to metal wires these will break when the skin stretches. An emerging answer might be to embed a broad corrugated metal film in an elastic covering instead.

Electrical engineers Sigurd Wagner and Stephanie Lacour at Princeton University have developed a kind of connector incorporating broad metal strips that, unlike wires, can stretch up to twice their length and still conduct electricity. They think it will be ideal for use in robot skin.

Metal films are normally quite brittle, snapping when stretched more than 1 per cent of their length. Wagner and Lacour say their elastic metal film connectors- based on gold film just 25 nanometres thick- can stretch by at least 15 per cent in the rubbery silicone membrane in which they are embedded. This is because the gold film is corrugated, so it can be flattened out or compressed and still conduct electricity.

And it stretches even more than they expected. A mystery Wagner and Lacour can't yet explain is how some of their contacts conduct even when stretched to twice their original length. Wagner speculates that the ribbons might break apart when pulled too far- but that points on the torn golden shards still remain in contact with each other and conduct (see Graphic).

The researchers plan to demonstrate their connectors at a robotics conference next week in Las Vegas, Nevada, and hope soon to have a handmade elastic circuit they can blow up like a balloon. Wagner says their conducting skins could allow sensors to be placed all over a robot's body. "The goal is to enable robots to become cautious," he says, as the droids will be more aware of their environments.

A factor hampering progress, the pair say, is the sheer pliability of their strip-like connector devices, which are proving difficult to handle owing to the extreme flimsiness of their first prototypes. They hope to develop an automated way of fabricating a conducting robot skin within three years.
Author: Charles Choi

New Scientist issue: 25th October 2003


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