Nanowires of copper, silver, and gold may bring more flexible and longer-lasting displays to smartphones and large screens in the next few years. This is why
You’re running to the train, or the bus, or the car. You are trying to pull yourself together, and just as you reach the door, you bump into someone coming from the left or the right. Your phone slips out of your pocket or your hand and darts to the pavement. All hope is lost. The world is ending. That you’re five minutes late already to pick up your son from Judo doesn’t matter anymore. Your real baby, your iPhone 6s, has a cracked screen. Call the in-laws to pick him up, because you’re in mourning.
Well, those days will soon be in the trash can of history thanks to the advent of metallic nanowire touch screens, hitting stores near you at some point in the next decade. The nanowires mesh together in a thin coating, mimicking the strength of glass with the flexibility of plastic. The reflective nature of the metals in the screens magically makes them transparent, conducting electricity and projecting light in cheaper combinations than tin and glass.
It’s been a long time coming says Professor Gil Markovich, head of nanochemistry at Tel Aviv University. His startup project is in the early research phase, but already has the ear of manufacturing giants BASF and 3M. His research team also has a working agreement with South Korean firm Nepes to develop transparent conductive coating for flat panels.
What’s interesting about Markovich’s displays are the use of precious metals, whose properties for electricity conduction are known but whose prices are often too expensive. Markovich and his team of researchers have a concept of silver and gold interwoven together to form the most advanced (and practical) use of silver and gold in recent history. But in the quantities required for these displays, Markovich’s startup project can intersect silver and gold wires to create a flexible, stable and clean (more on that in a moment) display screen.
“The gold is important for the particular self-assembly chemical process leading to the growth of the nanowires. Gold is also more oxidation resistant than silver, so it is better as a building material for the nanowire film infrastructure.”
Flexible technology for bendable screens
One research report has estimated a $3 billion transparent conductor market. The nanotech industry is looking at explosive growth, up to $75.8 billion by 2020. Other companies in the nanowire space — silver specifically — include Minnesota Wire, Sea Shell Technology Novarials, US Nano, Nanostructured & Amorphous Materials Inc, Kemix, ACS Material, Nano Composix, and RAS Materials.
But why go nano?
Current phone screens — as well as plasma displays, solar cells and LEDs — use glass and a certain compound called indium tin oxide (ITO). Indium, while far cheaper than gold, is one of the 17 so-called rare earth metals that have found new importance in consumer electronics. China is the world’s leading indium producer, followed by Canada, Japan, and South Korea. But with supplies dwindling, the race is on to an alternative.
Companies like Cambrios (an MIT spinout founded by Evelyn Hu and Angela Belcher) and Blue Nano are already marketing their silver nanowire materials. A Stanford spinout called C3Nano has raised about $22 million for producing transparent electrode ink. There are other labs at Duke University and the University of Akron still experimenting with (cheaper) copper nanowires.
One thing is for sure. All the teams claim better electrical conductivity than ITO. And despite the inclusion of gold, the costs are still extremely cheap.
Markovich’s Midas touch is a major point of differentiation. “The amount of metal is very small,” says Markovich. “Around 100-200 micrograms (millionths of a gram) gold and a slightly larger amount of silver.” Pure gold is highly conductive and extremely malleable, or bendable; This is why the gold in your engagement and wedding rings are usually between 10 and 14 karats out of 24. The silver strands (90% of the material used) reinforce the gold (10%), while the gold and a custom polymer protect the silver from tarnishing, or oxidation.
Metallic nanowiring is one of the methods being used to create flexible screens. Samsung debuted a model for a bendable screen made of graphene in 2014 and LG has debuted several models in the last few years, including an 18″ OLED screen on display at CES. But these are all still prototypes.
“Today you’re watching an 18-inch prototype, but then imagine you have a larger size, maybe larger than a 55-inch,” KJ Kim of LG told the BBC last week at CES 2016. “Then you can roll up your TV when you don’t need and you can still look at your beautiful interior or wallpapers.”
Perhaps more important than the use of gold is Markovich’s printing technique. While Cambrios produces its wires and mixes it into its patented ClearOHM coating ink, Markovich’s technology would directly make the wires on the printing surface.
“In our process the wires are formed directly on the surface of choice. This is possible only using gold as the primary component. Our wires are also much thinner” than Cambrios’ cords, which have to be thicker “to survive the dispersion of the wires in a liquid,” according to Markovich. “When the wires are formed directly on a surface, they can survive even if they are much thinner and longer due to the stabilization by the supporting surface.”
“If one would like to deposit the nanowire films by printing techniques like inkjet printing in order to pattern the films as in the case of touch panels, where the film has to be patterned into fine lines, then an ink made of very long nanowires will be hard to print through the very small nozzles used for inkjet printing.”
We are still some time away from having a fully-functioning and durable nanowired screen in our pockets if recent prototypes from other companies are any indication. But the abundance of options should make us optimistic that sometime soon, a dropped phone doesn’t mean living with a cracked screen for months on end.