Conversely, said postdoctoral researcher Yu Zhu, lead author of the new paper, fine metal meshes show good conductivity, but gaps in the nanowires to keep them transparent make them unsuitable as stand-alone components in conductive electrodes.
But combining the materials works superbly, Zhu said. The metal grid strengthens the graphene, and the graphene fills all the empty spaces between the grid. The researchers found a grid of five-micron nanowires made of inexpensive, lightweight aluminum did not detract from the material's transparency.
"Five-micron grid lines are about a 10th the size of a human hair, and a human hair is hard to see," Tour said.
Tour said metal grids could be easily produced on a flexible substrate via standard techniques, including roll-to-roll and ink-jet printing. Techniques for making large sheets of graphene are also improving rapidly, he said; commercial labs have already developed a roll-to-roll graphene production technique.
"This material is ready to scale right now," he said.
The flexibility is almost a bonus, Zhu said, due to the potential savings of using carbon and aluminum instead of expensive ITO. "Right now, ITO is the only commercial electrode we have, but it's brittle," he said. "Our transparent electrode has better conductivity than ITO and it's flexible. I think flexible electronics will benefit a lot."
In tests, he found the hybrid film's conductivity decreases by 20 to 30 percent with the initial 50 bends, but after that, the material stabilizes. "There were no significant variations up to 500 bending cycles," Zhu said. More rigorous bending test will be left to commercial users, he said.
"I don't know how many times a person would roll up a computer,"
|Contact: David Ruth|