New touchscreen technology based on low-cost materials

A team has come up with a new touchscreen display that doesn’t require rare and expensive raw materials such as indium.

Indium-tin-oxide (ITO) is normally used for the wafer-thin electrode under the glass surface of a touchscreen display – it’s excellent at conducting slight currents and lets the colours of the display show through clearly.

Unfortunately, the stuff is in very short supply, making a readily-available alternative something of a holy grail for the industry. The US Geological Survey reckons that the world supply will be exhausted by 2020 at the latest.

But the Fraunhofer team says it’s found an alternative that’s just as good – and vastly cheaper. Its main components are carbon nanotubes and low-cost polymers.

The electrode foil is composed of two layers. One is the carrier, a thin foil made of polyethylenterephthalate PET, the same cheap plastic used for making bottles. Then a mixture of carbon-nanotubes and electrically conducting polymers is added, forming a thin film as it dries.

This combination by itself isn’t particularly durable, because humidity, pressure or UV light put a strain on the polymers. But the carbon nanotubes harden on the PET to anchor the electrically conducting polymers.

“”he electrical resistance of our layer is somewhat greater than that of the ITO,” says project manager Ivica Kolaric. “But it’s easily enough for an application in electrical systems.”

Kolaric says there are many other applications for the foil, including photovoltaic foils that could line corrugated roofs or other uneven structures.