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A new technique allows nearly 100% recovery of all-carbon-based transistors while preserving future functionality.
Duke University engineers have created the first ever fully recyclable printed electronics. The researchers demonstrated a critical and complex computer component, the transistor. They used three carbon-based inks to create the transistor. This will help to encourage a new generation to recycle electronics and combat the global electronic waste epidemic.
The article in the journal Nature Electronics appears online today (April 26, 2021).
“Silicon-based components for computer components are likely never to go away,” stated Aaron Franklin, Addy Professor in Electrical and Computer Engineering at Duke. We hope that future applications will make them more widely available by creating new, recyclable, easily printed electronic components and demonstrating their capabilities.
Insulating cellulose is printed onto other carbon-based components to make the first fully recyclable printed transistor. Researchers hope to incite a new generation to recycle electronic waste to combat the global epidemic.
The number of electronics that people use every day is increasing worldwide. There’s a growing pile of old devices that are either no longer functional or have been discarded in favor of newer models. A United Nations estimate shows that less than 25% of the electronics thrown away yearly are recycled. As the world continues to upgrade to 5G devices and the Internet of Things (IoT), the problem will only get worse.
Electronic devices can be challenging to recycle. Many workers in large plants hack on bulky devices. While scraps of steel, aluminum, and copper can be recycled in some cases, silicon chips that make up the core of these devices cannot.
Franklin and his lab have demonstrated a fully recyclable, functional transistor made from three carbon-based inks. These inks can easily be printed on paper or any other flexible, eco-friendly surface. Graphene and carbon nanotube inks are used for the conductors and semiconductors. Franklin states that these materials are familiar in the world of printed electronics. However, Franklin believes the discovery of nitrocellulose, a wood-derived insulating dielectric, opened the door to recyclability.
Researchers have tested a biosensor made from fully recyclable printed electronics. Recycling almost 100% of materials is possible, and they retain very little performance.
Franklin stated that nanocellulose is biodegradable and has been used in packaging applications for many years. “While people have known for years that nanocellulose can be used as an insulator in electronic devices, no one has yet figured out how to print it. This is a crucial ingredient to making these fully recyclable devices work.
Researchers developed a method to suspend nanocellulose crystals from wood fibers. With a small amount of table salt, this ink acts as insulation in the transistors they print. The team demonstrated that all-carbon transistors could be used in many applications using the inks printed in an aerosol printer at room temperature.
The team then shows how easily their design can be recycled. The team submerged their devices in several baths and gently vibrated them with sound waves. Finally, they centrifuge the solution to recover the graphene and carbon nanotubes with an average yield close to 100%. The materials can be reused with the same printing process without losing their performance viability. Because nano cellulose is made of wood, it can be recycled with the paper that it was printed on.
A transistor, which is more complex than a resistor and capacitor, is used in various computer components such as power control, logic circuits, and sensors. Franklin explained that by first demonstrating a fully recyclable and multifunctionally printed transistor, he hopes to take the first step toward commercializing simple technology. Franklin says he can see the technology used in large buildings with thousands of environmental sensors to track energy consumption or custom biosensing patches to follow medical conditions.
Franklin stated that “recyclable electronics such as this won’t go out and replace an entire industry worth half-trillion dollars by any means” and that we aren’t even close to printing recyclable computer processors. But, demonstrating these new materials and their functionality can be a step in the right direction toward a new type of electronics lifecycle.
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