Rubbery muscle motors to make robots more lifelike: The muscles themselves are electroactive structures consisting of two layers of conducting carbon grease separated by an extremely stretchy insulating polymer film, says Anderson. "It can stretch by more than 300 per cent."
When a voltage is applied, the configuration behaves like a capacitor, with positive and negative charges accumulating on either side of the insulator. As the opposite charges attract one another the insulator is squashed between them and flattens and stretches. Turn the voltage off and it contracts again to its original size.
The motor looks rather like a bicycle wheel, with the elastic muscles stretched between the edge of the wheel and the centre, like flat spokes. To turn a shaft, six of the muscles work in concert, contracting one after the other.