Copper Nanofilm Can Replace Rare Earth in Digital Displays

A flexible film made of copper nanowires and plastic conducts electricity illuminating a small light bulb. (Ben Wiley, Duke University)

Research chemists at Duke University in Durham, North Carolina have developed a film made of copper nanowires that could replace expensive rare earths now used in digital displays. The discovery by Duke chemistry professor Ben Wiley and grad student Aaron Rathmell appears online in the journal Advanced Materials (paid subscription required). Wiley has also started a company to take his research findings to market.

Wiley and Rathmell devised a method of organizing copper atoms in water to form nanoscale wires — 1 nanometer equals 1 billionth of a meter. The wires can then be arrayed into films and coated on glass or plastic, like those used in displays for computers, tablets, and smart phones, as well as solar cells that convert sunlight into electric power.

Spread out on a surface, the nanowires overlap and chemically bind to each other, creating a conductive path for electrons. Few wires are needed to overlap in order to make a conductive path, so a thin coating of nanowires can make an impact on conductivity without significantly affecting the transparency of the film.

Current electronic screens are made of indium tin oxide, which is transparent and performs well, but is slow and expensive to produce. The material also cracks easily, which limits its use to well-protected, stationary environments.

In their research, Wiley and Rathmell found copper nanowires to be much more flexible that indium, and could be bent 1,000 times without breaking or losing their conductivity. Indium tin oxide, on the other hand, broke after a few bends.

But copper is an abundant material, widely available and inexpensive —  about $3.25 a pound today on world markets, with the price falling over the six months.

Indium, on the other hand, is a rare earth metal, with more than half of the world’s supply coming from China. Earlier this month, the New York Times reported that China — for economic and environmental reasons — is restricting supplies of its rare earth metals, which will put even more upward pressure on prices. Indium sells for about $360 per pound on world markets, a price that has risen by more than 40 percent over the past year.

Wiley co-founded a company, NanoForge Corp. in Durham, to commercialize his research on copper nanowires. The company plans to produce the nanowires suspended in a water-based solution that can be applied as inks or films to substrates.

Read more: U.K. Grant Awarded to Develop Non-Rare Earth Electric Engine

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