Bach Seat

The website Tested asks if tech users can go back to the days of keyboards and mice. They speculate that the day may be coming when we have to dump touchscreens. They point out the transparent conductor ceramic material indium tin oxide (ITO) used in touchscreen is running out fast. The website says that at the current pace, the known supply of ITO will be gone by 2020 warns Yale University’s Thomas Graedel.

Telecom Circle says a capacitive touch screen panel consists of an insulator such as glass, coated with a transparent conductor (mostly indium tin oxide). The touchscreen must be touched by a human finger. Since the human body is also a conductor, touching the surface of the screen distorts the body’s electrostatic field, generating a measurable change in capacitance.  Some of the advantages of a capacitive touch screen include:

• Higher clarity display (up to 90% optical transparency)
• Supports multi-touch
• High touch resolution
• High sensitivity

Replace indium tin oxide in touchpanels

The Tested author says that researchers are already hunting for new materials to replace indium tin oxide and for methods to use the current supply more efficiently.

The article lists a number of potential solutions, but so far most of them are held up by one problem or another. Zinc oxide (yes the stuff you put on your nose in the summer) for example, is a similar material, and it’s far cheaper than indium tin oxide. It’s also more brittle, less transparent, and a poor conductor. And since ITO is barely conductive enough to power capacitive touchscreens, zinc oxide’s not going to cut it according to Tested. Another option the article suggests is a cadmium oxide material that uses far less indium (the expensive, rare part of indium tin oxide) than ITO, but is 3-4 times more conductive. Unfortunately, cadmium is also highly toxic.

Radical solutions

Since materials like ITO don’t seem to be ideal solutions, Tested reports that some scientists are turning to more radical solutions that could eventually pay off. A team at Princeton is working with conducting polymers, which are nowhere near as brittle as ITO. But they suffer from degradation due to UV light and oxygen. Other options the Tested article cites are graphene which is a great conductor and carbon nanotubes that show remarkable durability and conductivity.

Manchester University Professor Andre Geim who won the 2010 Nobel prize for physics for his work on graphene described it to the UK’s Telegraph, as having “a range of superlatives which no other material can be proud of”, including its incredible thinness and conductive qualities which see electric currents passing 100 times faster than copper manages. The Telegraph reports that since the iPhone made buttons unfashionable, touchscreen interfaces for smartphones, tablets, and even computer monitors have proved extremely lucrative for many consumer electronics companies. Samsung believes graphene could be perfect for the company’s many touchscreen devices.

Carbon nanotubes (CNTs) are tiny hollow cylinders of carbon with tremendous electrical and optical properties. CNT’s are attractive to touchscreen manufacturers because they can be as thin as 10 or 20 nanometers, transparent to visible light, and can conduct enough electricity to make them useful for touch screens according to Physorg.com. Carbon nanotubes are remarkably robust and flexible. The material can be applied 50 times faster than ITO films, and are almost unbreakable when flexed, tapped, strained, or smashed with a hammer.

Researchers predict that the first commercial applications for these transparent CNT films will be as the electrodes in touch screens. Physorg.com says this is because they already meet all technical requirements, and ITO has an issue in that it tends to crack after repeated use, thus degrading the touch screen response. By the end of the year, CNT films will begin to replace ITO in touch screens. As the technology continues to improve it will continue to take market share from ITO.

Carbon Nanotubes have their issues as well. Physorg.com has a discussion about health concerns over the new technology and transferring electrons from tube to tube proved difficult. These issues led a team of researchers at HP to ditch nanotubes and go with silver nanowires instead. Researcher Jonathan Coleman of Trinity College in Dublin, who works in collaboration with Hewlett-Packard is quoted in Gizmodo, “When we started, industry thought that carbon nanotube films would be it – but no longer.” After trying various ideas to get around the problem of high resistance between the tubes, the team changed paths,  “We realized that, if instead of nanotubes you had metal nanowires, then where they touch you might get some bonding, giving electron transfer between them,” he says.  Experimenting with silver nanowires, his team discovered that they could get transparency of 85 percent and a conductivity only a fraction behind that of ITO. “Optically and electrically, the silver was almost identical to high quality commercially available ITO, but totally flexible,” Coleman told Gizmodo. “Hewlett-Packard is now looking at silver nanowires as a material of choice,” Coleman concludes.

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There are a few years left for researchers will find a replacement for indium tin oxide. Since most of the indium mines are located in China there are likely to be exorbitant price hikes long before the supply’s completely exhausted. What will Apple do to produce a better, cheaper, stronger iPad?

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.