Thin, flexible material generates electricity when stretched

Scientists have developed a thin, flexible material that generates electricity when stretched or compressed, an advance that may pave the way for smart clothing or self-powered pacemakers.

The specially designed rubber, developed by researchers at Swiss Federal Laboratories for Materials Science and Technology ( Empa) is able to convert mechanical movements into electrical charges.

The trick behind the generated current is the internal polarisation which changes when the rubber film is mechanically stressed, scientists said.

This effect is used in sound pick-ups on analogue record players, for instance: the needle is guided through the grooves in the record in such a way as to generate mechanical vibrations.

In a piezoelectric crystal, these vibrations are converted into electrical impulses, which in turn can be amplified and transformed into sound waves.

For a long time, the piezoelectric effect was only known for crystals. As these are heavy and solid, the effect could only be used in certain applications.

However, researchers have now succeeded in giving elastomers piezoelectric properties. Nevertheless, the new material is not easy to produce.

The rubber is a composite material made of polar nanoparticles and an elastomer - silicone in the prototype.

There is a wealth of potential applications for the novel rubber film. It could be used to construct pressure sensors, for example. If the material is compressed, an electrical impulse is produced that can be received and "understood" by devices.

This can be used to develop a novel type of control buttons, but also a sensitive skin for robots that can feel (pressure) touches. Moreover, the film might be useful in clothing to either monitor the wearer's activities or generate electricity from their movements.

"This material could probably even be used to obtain energy from the human body," said Dorina Opris researcher at Empa.

"You could implant it near the heart to generate electricity from the heartbeat, for instance," Opris said.

This could power pacemakers or other implanted devices, eliminating the need for invasive operations to change the battery.