Novel nano-film for better bendable, wearable devices

Nano material researchers from the University of Illinois at Chicago (UIC) and Korea University have invented a cheap ultra-thin film that is both transparent and highly conductive to electric current, offering promise for bendable, wearable electronic devices like smart watches.

The film — a mat of tangled nanofibre — is also bendable and stretchable, offering potential applications in roll-up touchscreen displays, wearable electronics, flexible solar cells and electronic skin.

“It is difficult to make materials that are both transparent and conductive,” said Alexander Yarin, distinguished professor of mechanical engineering at UIC.

The new film establishes a “world-record combination of high transparency and low electrical resistance, the latter at least 10-fold greater than the previous existing record,” informed Sam Yoon, professor of mechanical engineering at Korea University.

The film also retains its properties after repeated cycles of severe stretching or bending — an important property for touchscreens or wearables.

The manufacturing begins by electrospinning a nanofibre mat of polyacrylonitrile or PAN, whose fibres are about one-hundredth the diameter of a human hair.

The fibre shoots out like a rapidly coiling noodle, which when deposited onto a surface intersects itself a million times.

The fibre 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, according to the researchers.

“We can then take the metal-plated fibres and transfer to any surface — the skin of the hand, a leaf, or glass,” Yarin added in a paper reported in the journal Advanced Materials.

An additional application may be as a nano-textured surface that dramatically increases cooling efficiency, he noted.