Highly conductive ultrathin film on skin between clips. Credit: Sam Yoon/Korea University
An ultrathin film that is both transparent and highly conductive to electric current has been produced by a cheap and simple method devised by nanomaterials researchers from the Uni of Illinois at Chicago and Korea University. The film – actually a mat of tangled nanofiber, electroplated to form a “self-junctioned copper nano-chicken wire” – is also bendable and stretchable, offering potential applications in roll-up touchscreen displays, wearable electronics, flexible solar cells and electronic skin.
The new film establishes a “world-record combination of high transparency and low electrical resistance,” the latter at least 10X greater than the previous existing record, said Prof Sam Yoon, Korea University. The film also retains its properties after repeated cycles of severe stretching or bending, an important property for touchscreens or wearables.
Manufacture begins by electrospinning a nanofiber mat of polyacrylonitrile, or PAN. The fiber shoots out like a rapidly coiling noodle, which when deposited onto a surface intersects itself a million times, Yarin said. “The nanofiber spins out in a spiral cone, but forms fractal loops in flight,” Yarin said. “The loops have loops, so it gets very long and very thin.” The naked PAN polymer doesn’t conduct, so it must first be spatter-coated with a metal to attract metal ions. The fiber is then electroplated with copper – or silver, nickel or gold.
The electrospinning and electroplating are both relatively high-throughput, commercially viable processes that take only a few seconds each. “We can then take the metal-plated fibers and transfer to any surface – the skin of the hand, a leaf, or glass,” Yarin said. An additional application may be as a nano-textured surface that dramatically increases cooling efficiency.
Yoon said the “self-fusion” by electroplating at the fiber junctions “dramatically reduced the contact resistance.” Yarin noted the metal-plated junctions facilitated percolation of the electric current – and also account for the nanomaterial’s physical resiliency. “But most of it is holes,” he said, which makes it 92 percent transparent. “You don’t see it.”
https://news.uic.edu/new-nanomaterial-offers-promise-in-bendable-wearable-electronic-device
Recent Comments