Creating Flexible Electronics Using Nanocellulose

Not long ago it would have been hard to imagine throngs of people walking around with tiny computers in their pockets, able to communicate with someone across the globe instantly just by tapping on a screen.

It can be equally as hard to imagine where these amazing technologies are headed next.  Ron Sabo, a research materials engineer at FPL, and his partners at the University of Wisconsin (UW) have a few ideas, and they’re looking to wood to make them happen. Wood at the nano-scale, that is.

“So far, most electronics are rigid and have glass coverings,” Sabo says. “There is interest in advancing electronics by making them flexible, and we’re finding nanocellulose could help make that happen.”

Nanocellulose is simply wood broken down to the incredibly tiny nanoscale. (A nanometer is approximately one-millionth the thickness of an American dime.) At the nanoscale, wood is incredibly strong, lightweight, and transparent, all attributes that could enhance electronics.

Flexible electronics present a wide range of possible applications, including displays, smart cards, solar cells, radio frequency tags, medical implants, and wearable computers. Research and development have been ongoing in this arena, but there have been some challenges along the way.

“The materials used to create these products must not only perform as intended,” explains Sabo, “but also hold up to harsh production processes that can include drastic changes in temperature and being washed in acid.”

High-speed flexible electronics are created by building a circuit on a very thin silicone membrane and then transferring it to a flexible substrate. Most research has used plastic as the substrate, but plastics can have drawbacks; namely, the large degree to which they expand and contract with changes in temperature.

Sabo, along with UW researchers Jung-Hun Seo and Zhenqiang Ma, are studying nanocellulose composites substrates as an alternative to plastic, and were recently able to successfully demonstrate the technology.

“We found there are several benefits to using nanocellulose composites in flexible electronics,” said Sabo.  “When heated, cellulose does not expand as dramatically as plastics do, and it is also a renewable resource which is important considering how prolific electronic devices have become.”

According to a U.S. Environmental Protection Agency report, in the United States alone, 129 million mobile devices were disposed of in 2009, and less than 12 million of those were recycled.  Electronic waste is a serious environmental concern that the use of biodegradable materials such as cellulose nanofibers can help address.

Sabo’s research is ongoing as the team works to refine the technology. They have improved upon their earliest work by coating the nanocellulose composite with a thin layer of epoxy on each side. The epoxy provided protection and created a smoother surface, improving the transfer of the circuit.

Further research will focus on continuing to improve the composite material, as well as testing to ensure the products developed will perform well under real-world conditions.

So are we looking at a future where televisions are high-tech wallpaper and tablet computers roll up and fit in your back pocket? Such developments are not out of reach, and wood could help us get there.

“Using cellulose nanofibers as a sustainable component for high-speed flexible electronics is extremely promising,” says Sabo.