Engineers at Duke University have 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.

According to a United Nations estimate, less than a quarter of the millions of pounds of electronics thrown away each year is recycled. And the problem is only going to get worse as the world upgrades to 5G devices and the Internet of Things (IoT) continues to expand.

Part of the problem is that electronic devices are difficult to recycle. While scraps of copper, aluminum and steel can be recycled, the silicon chips at the heart of the devices cannot.

A 3D rendering of the first fully recyclable, printed transistor.

In the new study, Franklin, the Addy Professor of Electrical and Computer Engineering at Duke, and his laboratory demonstrate a completely recyclable, fully functional transistor made out of three carbon-based inks that can be easily printed onto paper or other flexible, environmentally friendly surfaces. Carbon nanotubes and graphene inks are used for the semiconductors and conductors, respectively.

While these materials are not new to the world of printed electronics, Franklin stated, the path to recyclability was opened with the development of a wood-derived insulating dielectric ink called nanocellulose.

The researchers developed a method for suspending crystals of nanocellulose that were extracted from wood fibers that — with the sprinkling of a little table salt — yields an ink that performs admirably as an insulator in their printed transistors.

Using the three inks in an aerosol jet printer at room temperature, the team shows that their all-carbon transistors perform well enough for use in a wide variety of applications, even six months after the initial printing.

Researchers test a biosensor made out of fully recyclable, printed electronics.

The team then demonstrates just how recyclable their design is. By submerging their devices in a series of baths, gently vibrating them with sound waves and centrifuging the resulting solution, the 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 because the 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 control or logic circuits and various sensors.

Franklin explained that, by demonstrating a fully recyclable, multifunctional printed transistor first, he hopes to make a first step toward the technology being commercially pursued for simple devices.

For example, Franklin said he could imagine the technology being used in a large building needing thousands of simple environmental sensors to monitor its energy use or customized biosensing patches for tracking medical conditions.

The work appears online April 26 in the journal Nature Electronics. It was supported by the Department of Defense Congressionally Directed Medical Research Program (W81XWH-17-2-0045), the National Institutes of Health (1R01HL146849) and the Air Force Office of Scientific Research (FA9550-18-1-0222).

Engineers at Duke University have 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.

According to a United Nations estimate, less than a quarter of the millions of pounds of electronics thrown away each year is recycled. And the problem is only going to get worse as the world upgrades to 5G devices and the Internet of Things (IoT) continues to expand.

Part of the problem is that electronic devices are difficult to recycle. While scraps of copper, aluminum and steel can be recycled, the silicon chips at the heart of the devices cannot.

A 3D rendering of the first fully recyclable, printed transistor.

In the new study, Franklin, the Addy Professor of Electrical and Computer Engineering at Duke, and his laboratory demonstrate a completely recyclable, fully functional transistor made out of three carbon-based inks that can be easily printed onto paper or other flexible, environmentally friendly surfaces. Carbon nanotubes and graphene inks are used for the semiconductors and conductors, respectively.

While these materials are not new to the world of printed electronics, Franklin stated, the path to recyclability was opened with the development of a wood-derived insulating dielectric ink called nanocellulose.

The researchers developed a method for suspending crystals of nanocellulose that were extracted from wood fibers that — with the sprinkling of a little table salt — yields an ink that performs admirably as an insulator in their printed transistors.

Using the three inks in an aerosol jet printer at room temperature, the team shows that their all-carbon transistors perform well enough for use in a wide variety of applications, even six months after the initial printing.

Researchers test a biosensor made out of fully recyclable, printed electronics.

The team then demonstrates just how recyclable their design is. By submerging their devices in a series of baths, gently vibrating them with sound waves and centrifuging the resulting solution, the 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 because the 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 control or logic circuits and various sensors.

Franklin explained that, by demonstrating a fully recyclable, multifunctional printed transistor first, he hopes to make a first step toward the technology being commercially pursued for simple devices.

For example, Franklin said he could imagine the technology being used in a large building needing thousands of simple environmental sensors to monitor its energy use or customized biosensing patches for tracking medical conditions.

The work appears online April 26 in the journal Nature Electronics. It was supported by the Department of Defense Congressionally Directed Medical Research Program (W81XWH-17-2-0045), the National Institutes of Health (1R01HL146849) and the Air Force Office of Scientific Research (FA9550-18-1-0222).