New technique recovers nearly 100% of fully carbon-based transistors while retaining future materials functionality – sciencedaily

Engineers at Duke University developed the world’s first fully recyclable printed electronics. By demonstrating a crucial and relatively complex computer component – the transistor – created with three carbon-based inks, the researchers hope to inspire a new generation of recyclable electronics to help fight the growing global epidemic of electronic waste.

The book appears online on April 26 in the journal Electronic Nature.

“Silicon-based computer components will probably never go away, and we don’t expect easily recyclable electronic components like ours to replace technology and devices already in widespread use,” said Aaron Franklin, Addy Professor of Engineering. electrical and IT at Duke. . “But we hope that by creating new, fully recyclable and easily printable electronic components and showing what they can do, they could be widely used in future applications.

As people around the world embrace more electronics in their lives, there is an ever-growing stack of discarded devices that no longer work or have been ditched in favor of a newer model. According to a United Nations estimate, less than a quarter of the millions of pounds of electronic products discarded each year are recycled. And the problem will only get worse as the world moves to 5G devices and the Internet of Things (IoT) continues to grow.

Part of the problem is that electronic devices are difficult to recycle. Large factories employ hundreds of workers who hack bulky devices. But while scrap copper, aluminum and steel can be recycled, the silicon chips in the heart of devices cannot.

In the new study, Franklin and his lab demonstrate a fully recyclable and fully functional transistor made from three carbon-based inks that can be easily printed onto paper or other flexible and environmentally friendly surfaces. Carbon nanotubes and graphene inks are used for semiconductors and conductors, respectively. While these materials are not new to the world of printed electronics, Franklin says, the path to recyclability has been opened with the development of a dielectric insulating ink derived from wood called nanocellulose.

“Nanocellulose is biodegradable and has been used in applications such as packaging for years,” Franklin said. “And while people have long known about its potential applications as an insulator in electronics, no one has yet figured out how to use it in printable ink. This is one of the keys to making these fully recyclable devices functional.

Researchers have developed a method to suspend nanocellulose crystals extracted from wood fibers which – along with a little table salt – yield an ink that works admirably as an insulator in their printed transistors. Using all three inks from an aerosol jet printer at room temperature, the team is showing that their all-carbon transistors perform well enough to be used in a wide variety of applications, even six months after the initial printing.

The team then demonstrates how recyclable their design is. By immersing their devices in a series of baths, gently vibrating them with sound waves, and centrifuging the resulting solution, carbon nanotubes and graphene are sequentially recovered with an average yield of nearly 100%. Both materials can then be reused in the same printing process while losing very little of their performance viability. And since nanocellulose is made from wood, it can simply be recycled along with the paper it was printed on.

Compared to a resistor or capacitor, a transistor is a relatively complex computer component used in devices such as power or logic control circuits and various sensors. Franklin explains that by first presenting a fully recyclable multifunctional printed transistor, he hopes to take a first step towards commercially sought-after technology for simple devices. For example, Franklin says he could imagine that the technology used in a large building requires thousands of simple environmental sensors to monitor its energy use or custom biosensing patches to track medical conditions.

“Recyclable electronics like this aren’t going to replace a half-trillion dollar industry by any means, and we’re certainly a long way from printing recyclable computer processors,” Franklin said. “But the demonstration of these types of new materials and their functionality is hopefully a stepping stone in the right direction for a new kind of electronic life cycle.”

This work was supported by the Congress-led Medical Research Program of the Department of Defense (W81XWH-17-2-0045), National Institutes of Health (1R01HL146849) and the Army Scientific Research Office air (FA9550-18-1-0222).

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Material provided by duke university. Original written by Ken Kingery. Note: Content can be changed for style and length.

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