Wiley and his students, PhD candidate Aaron Rathmell and undergraduate Stephen Bergin, grew the copper nanowires in a water-based solution. "By adding different chemicals to the solution, you can control the assembly of atoms into different nanostructures," Wiley said. In this case, when the copper crystallizes, it first forms tiny "seeds," and then a single nanowire sprouts from each seed. It's a mechanism of crystal growth that has never been observed before.
Because the process is water-based, and because copper nanowires are flexible, Wiley thinks the nanowires could be coated from solution in a roll-to-roll process, like newspaper printing, which would be much more efficient than the ITO production process.
Other researchers have produced copper nanowires before, but on a much smaller scale.
Wiley's lab is also the first to demonstrate that copper nanowires perform well as a transparent conductor. He said the process will need to be scaled up for commercial use, and he's got a couple of other problems to solve as well: preventing the nanowires from clumping, which reduces transparency, and preventing the copper from oxidizing, which decreases conductivity. Once the clumping problem has been worked out, Wiley believes the conductivity of the copper nanowires will match that of silver nanowires and ITO.
Wiley, who has applied for a patent for his process, expects to see copper nanowires in commercial use in the not-too-distant future. He notes that there is already investment financing available for the development of transparent conductors based on silver nanowires.
"We think that using a material that is a hundred times cheaper will be even more attractive to venture capitalists, electronic companies and solar companies who all need these transparent electrodes," he said.
|Contact: Karl Leif Bates|