Robots photo

Human skin is primed for touch — even minuscule pressure from a fly is enough to make you flinch. This ability does not yet extend to artificial limbs, however, and robots are a long way from having sensitive tactile abilities.

Now two California research teams have announced pressure-sensitive artificial skin made of tiny circuits, both of which could lead to better artificial limbs and helper robots.

One artificial skin, made by researchers at Stanford University, is 1,000 times more sensitive than human skin and is based on organic transistors. It sandwiches an elastic rubber layer between two parallel electrodes, and can detect the slightest touch — even the ephemeral sensation of an alighting butterfly.

It works because it acts as a spring, according to Stanford’s news service. The rubber stores an electrical charge, and when it is compressed, the amount of charge is changed. The electrodes sense this change and then transmit how much pressure the skin is “feeling.”

The second artificial skin, made by researchers at the University of California-Berkeley, works in a similar manner although it is made of inorganic nanowire circuits.

To build the “e-skin,” the researchers printed nanowire hairs onto an 18-by-19 pixel square matrix measuring about 2.7 inches square. The nanowire transistors were then connected to a layer of conductive rubber, which changes its electrical resistance when compressed. The researchers say their fabrication process can potentially be scaled up to larger materials.

It can detect pressure from 0 to 15 kilopascals, which is the range of force required from typing to holding something in your hand. This range could help robots adapt to the amount of force required to grasp a range of objects — from fragile eggs to a heavy frying pan, the Berkeley researchers say.

Both types of artificial skin can register pressure in a tenth of a second over a large range, as the BBC notes. The numbers rival the response of human skin, meaning artificial limbs and flapjack-flipping robots will be a lot more sensitive in the future.

[Technology Review, BBC]