Saving the touch-screen: the search for new nanotech crystals

Until the late 1980s, touch-screen technology was considered pretty flaky and imprecise, but in the era of smartphones and tablets, fast, accurate capacitive touchscreens are everywhere.

Such screens are based on transparent crystals that conduct electricity and mostly the compound used is indium tin oxide (ITO).

As a powder, indium tin oxide looks a pale yellow-green but when deposited as a thin film it becomes transparent and conducts electricity.

However, indium is running out and increasingly expensive. Internationally the race is on to find an alternative.

Whatever that turns out to be, it must be low cost, boast high conductivity and deliver good optical transparency.

Fujitsu pioneered the flexible polymer PEDOT. While this did not have anywhere near the conductivity of ITO and had questionable stability, it is improving with new formulations.

Silver nanowires could offer a way forward, as could graphene and a large number of other compounds, however, easily etchable zinc oxide is a likely candidate - if it can be made more stable. It would also be cheaper and more environmentally friendly.

Fulbright scholar and University of Canterbury PhD candidate Alexandra McNeill is travelling University of Wisconsin-Madison next month to join a cross-disciplinary team developing chemically-coated zinc oxide touch-screen alternatives.
"My research involves coating zinc oxide crystals in different chemicals to change how it behaves and then to find out if it could be a viable option for use as semiconductors in technology," McNeill says.
"Once I have tested a sample and found that the chemical coating has attached to the surface of the zinc oxide crystal, I then have to learn about its electronic properties with the help of physicists and engineers."

McNeill's PhD in Chemistry research has examined which chemicals will adhere to the zinc oxide crystals and how these samples behave. She has had to travel to Melbourne to use the Australian Synchrotron facilities to examine samples.

In the US, she hopes to discover which faces on the crystals might be better for successfully attaching chemicals and how the chemical coatings affect the crystals' conductivity.