So what other options do we have to indium? Finding a material that is transparent, light and conducts electricity as efficiently as ITO is a big challenge, but there are some candidates. So-called non-stochiometric tin oxides, which use the far more abundant aluminium, are one option that could be incorporated fairly easily into current manufacturing set-ups. The problem is that they do not perform as well as ITO and that tin is itself running out, with reserves estimated to last another 20-40 years.
Researchers in Germany and Japan are working on a flexible polymer-based material called PEDOT, which when doped with various chemicals becomes more transparent and a better conductor. Again, the polymer relies on non-renewable oil or coal supplies.
What’s desperately needed is a sustainable alternative, and the best solution could come in the shape of a remarkable material called graphene, the subject of a recent Nobel Prize. Like pencil-lead and diamonds, graphene is yet another form of carbon, one of the most abundant elements on Earth. Graphene's carbon atoms are arranged in a flat sheet of hexagons, like chicken wire, and this structure makes it the strongest known material and can conduct electricity as well as copper. And because graphene is just one atom thick, it is almost transparent.
Graphene may be one of the most versatile materials ever discovered – with an endless list of possibilities ranging from miniaturised computer chips to high-capacity batteries (and believe it or not for making extra-strong vodka). But one of its most-desired applications is to roll it up into carbon nanotubes and use it in touchscreens, as it offers several advantages over ITO. Graphene is more stable, so it will survive better in applications where the product will be subjected to constant physical force, such as regular finger-pounding. And graphene's superior flexibility means that it can be shaped in various configurations – you could create a spherical touchscreen, for example.
So why have we not already moved from ITO to carbon? Mark Hersam, a carbon nanotubes pioneer at Northwestern University in Illinois, believes we're waiting for an industry tipping point. "There's tremendous inertia in the electronics sector because the entire industry is modelled around ITO. Big companies like Apple are wedded to the ITO manufacturing processes and will need to invest substantially to start using carbon," he says. However, as the price of indium goes up and it becomes harder to get hold of, there is likely to be a switch."
With solar cells and electronics all competing for the same rare metal, industry is already under increasing pressure to start using a different material, whether that's another metal oxide or novel carbon chicken-wire. Looking through the breathless coverage of the iPad 3 launch on my phone, one thing is for sure: our unwavering enthusiasm for touchscreen/display-screen technologies means we desperately need to find alternatives soon.