Stretchable Electronics to go on Electroactive Polymers

Arla Foods, the largest dairy products company in Europe, has been developing various smart packages including ones that have micropumps that suck down the plastic wrapping back on to cheese to preserve it in the home. Electroactive plastics change shape under the influence of an electrics field and another potential application of them would be to make the package of expired food change in texture to warn the partially sighted user. Micromuscle AB in Sweden is one of several companies developing electroactive polymers. Their products will be used as muscles, locks (for example on packages of hazardous chemicals) and even communication with the partially sighted and others by change of texture, perhaps using changeable Braille (see our article on Breakthroughs at Tokyo University for another organisation working on this). For example, the package could sense that it has been left out for too long and the Braille could change from giving an expiry date to saying EXPIRED DO NOT USE. Micromuscle pumps could be an environmental alternative to aerosols, if powerful enough printed batteries become available.

In most cases, very high volume use will call for the low cost and durability of printed electronics but those circuits must be able to stretch if they are to be deposited on electroactive polymers. So far, printed organic inks have been the nearest to meeting such a requirement and they are rarely stretchable enough.

Stretchable Electronics

In 2007, more suitable flexible electronic structures with the potential to bend, expand and manipulate individual electronic devices are being developed by researchers at the US Department of Energy's Argonne National Laboratory and the University of Illinois at Urbana-Champaign in the USA. The researchers say that these could find applications as sensors and electronic devices that can be integrated into artificial muscles or biological tissues. In addition to a biomedical impact, flexible electronics are important for energy technology as flexible and accurate sensors for hydrogen.

Argonne scientist Yugang Sun and a team of researchers at the University of Illinois led by John A. Rogers form single-crystalline semiconductor nanoribbons in stretchable geometrical configurations with emphasis on the materials and surface chemistries used in their fabrication and the mechanics of their response to applied strains.

"Flexible electronics are typically characterized by conducting plastic-based liquids that can be printed onto thin, bendable surfaces," Sun said. "The objective of our work was to generate a concept along with subsequent technology that would allow for electronic wires and circuits to stretch like rubber bands and accordions leading to sensor-embedded covers for aircraft and robots and even prosthetic skin for humans. We are presently developing stretchable electronics and sensors for smart surgical gloves and hemispherical electronic eye imagers."

The team of researchers has successfully fabricated thin ribbons of silicon and designed them to bend, stretch and compress like an accordion without losing their ability to function. Clearly, such technologies could be combined with printed electronics to create many other capabilities as well, including very tightly rollable electronics.

The Center for Nanoscale Materials at Argonne links nanoscale research with Argonne's existing capabilities in synchrotron X-ray studies, neutron-based materials research and electron microscopy with new capabilities in nanosynthesis, nanofabrication, nanomaterials characterization as well as theory and simulation.

www.anl.gov