Researchers at Princeton University have developed a new type of energy-harvesting rubber film that could harness natural body movements such as breathing and walking to help power pacemakers, mobile phones and other electronic devices.

The material, which uses the power generated from ceramic nanoribbons embedded onto silicone rubber sheets to create electricity when flexed, is highly efficient at converting mechanical energy into electrical energy.

Published in the journal Nano Letters (DOI: 10.1021/nl903377u), the study has shown how piezoelectric ceramics can generate an electrical charge or voltage when materials experience stress or strain, with the efficiency of the energy conversion using these new materials shown to be significantly highly than other flexible piezoelectric materials such as quartz.

The research team, led by Michael McIntyre, have focused on developing a reliable power source for portable electronics and medical devices, and are the first to successfully combine silicone and nanoribbons of lead zirconate titanate (PZT), a ceramic material which is able to convert 80% of the mechanical energy applied to it into electrical energy.

The ribbons generate power due to the stress of the bending motion, while electrodes route the generated electrical current, which can be used, for example, to power an iPod or cell phone. The PZT nanoribbons are so narrow that 100 of them could fit side-by-side in the space of a millimeter. The team has demonstrated that these ceramics can be transferred in a scalable process onto rubber or plastic, rendering them flexible without any sacrifice in energy conversion efficiency.

As McIntyre states, the “silicone rubber is lightweight and bio-compatible, and already used for cosmetic implants and medical devices. So power-harvesting devices made of our piezo-rubber could be implanted in the body to perpetually power medical devices, and the body won't reject them.”

Sheets of the material could also be used in shoes, to use the natural movement of walking and running to power electrical devices, and to take advantage of the continual motion of the lungs to power pacemakers. This latter process has the further advantage of replacing batteries, as well as the need for invasive surgery keep them operational.

The team are now looking to create a fully functional device, while ensuring that its performance would be sufficient to power handheld portable electronics. It is crucial that the technology is scalable, with continual improvements made to the chips allowing for increasingly larger sheets that can harvest even more energy.