A first-of-its-kind demonstration suggests a greener future is possible for the electronics industry
Engineers at Duke University have created the world’s first fully recyclable printed electronics that replace the use of chemicals with water in the manufacturing process. By avoiding the need for harmful chemicals, this demo shows the path the industry can take to reduce its environmental footprint and human health risks.
The study was published online on February 28 in the journal Nano Letters.
One of the major challenges facing electronics manufacturers is stacking and protecting multiple component layers on top of each other. This is essential for creating complex devices. Sticking these layers together can be a frustrating process, especially for printed electronics.
“Putting layers on top of each other is not as easy as putting them on top of each other, but if you want to build electronic devices in print, you have to.”
Aaron Franklin
“If you’re making a peanut butter and jelly sandwich, it’s easy to put a layer on either slice of bread,” explains Aaron Franklin, Addy Professor of Electrical and Computer Engineering at Duke, who led the research. To do. “But if you put the jelly first and then try to spread the peanut butter on top, forget about it. It’s not as easy as that, but if you want to use printing to build electronic devices, you should.”
In previous work, Franklin and his group demonstrated the first fully recyclable printed electronics. The device used his three carbon-based inks: semiconducting carbon nanotubes, conducting graphene, and insulating nanocellulose. When trying to adapt the original process to use only water, carbon his nanotubes presented the biggest challenge.
To create a water-based ink in which the carbon nanotubes do not clump together and spread evenly over the surface, detergent-like surfactants are added. However, the resulting ink does not create a sufficiently dense layer of carbon nanotubes for large currents of electrons to travel.
“You want the carbon nanotubes to look like al dente spaghetti on a flat surface,” says Franklin. “But with water-based ink, it looks like you took one piece at a time and threw it against the wall to check the doneness. You can print it over and over again, but water doesn’t. After 100 iterations, it’s still as dense as it was at the beginning.”
This is because the surfactant used to prevent the carbon nanotubes from clumping together prevents additional layers from sticking to the first layer. In traditional manufacturing processes, these surfactants are removed using very high temperatures that require a lot of energy or harsh chemicals that pose risks to human and environmental health. Franklin and his group wanted to avoid both.
In this paper, Franklin and his group develop a cyclical process in which the device is rinsed with water, dried at relatively low temperatures, and printed again. By also reducing the amount of surfactant used in the ink, the researchers show that the ink and process are fully functional, fully recyclable, and capable of creating fully water-based transistors.
“If you are using chemicals, you can print over and over and over again until you have enough nanotubes. It remains dense.”
Aaron Franklin
Compared to resistors and capacitors, transistors are relatively complex computer components, used in devices such as power controls, logic circuits, and sensors. Franklin explained that by demonstrating the transistor first, he hopes to let other fields know that there are viable avenues for making some electronics manufacturing processes greener. doing.
Franklin has already demonstrated that nearly 100% of the carbon nanotubes and graphene used in printing can be recovered and reused in the same process, with little loss of viability of the material or its performance. Because nanocellulose is made from wood, it can be easily recycled or biodegraded like paper. The process uses large amounts of water, but not as much as is required to handle the toxic chemicals used in traditional manufacturing methods.
The United Nations estimates that less than a quarter of the millions of pounds of electronic equipment discarded each year are recycled. And as the world finally upgrades to his 6G devices and the Internet of Things (IoT) continues to expand, the problem will only get worse. Therefore, it is important to pursue the dent in this ever-growing pile of e-waste.
“While the performance of our thin film transistors does not match the best available today, we all need to do more to make these processes more environmentally friendly. competitive enough to show the research community that there is
Aaron Franklin
More work is needed, but Franklin says the approach could be used to make other electronic components, such as the screens and displays that are ubiquitous in society today. All electronic displays have a thin film transistor backplane similar to the one shown in the paper. Current manufacturing techniques are high energy and rely on hazardous chemicals and toxic gases. The entire industry has been warned by the US Environmental Protection Agency of the need for immediate attention.
“While the performance of our thin film transistors does not match the best available today, we all need to do more to make these processes more environmentally friendly. competitive enough to show the research community that there is
Original: Fully recyclable printed electronics dumps toxic chemicals into the water
Than: Duke University Pratt School of Engineering
