Recyclable Printed Electronics Dumps Toxic Chemicals for Water

Duke University engineers produced the world’s first fully recyclable printed electronics, replacing chemicals with water in the fabrication process. The industry could substantially reduce its environmental footprint and human health risks by eliminating hazardous chemicals. The research appeared online Feb. 28 in the journal Nano Letters.

Electronics manufacturers secure several layers of components on top of each other to make complex devices. Getting these layers to stick together is challenging, especially for printed electronics.

The researchers previously demonstrated the first fully recyclable printed electronics using three carbon-based inks: semiconducting carbon nanotubes, conductive graphene, and insulating nanocellulose. The carbon nanotubes presented the biggest challenge in trying only to use water. They add a surfactant to create a water-based ink in which the carbon nanotubes don’t clump together and spread evenly on a surface. The resulting ink’s layer of carbon nanotubes is not dense enough for a high current of electrons to travel across.

The surfactant that keeps the carbon nanotubes from clumping also prevents additional layers from adhering. In the paper, the team developed a cyclical process in which the device is rinsed with water, dried in relatively low heat, and printed on again. When the amount of surfactant used in the ink is also tuned down, the researchers show that their inks and processes can create fully functional, fully recyclable, fully water-based transistors.

They proved that nearly 100% of the carbon nanotubes and graphene used in printing can be recovered and reused in the same process, losing little of the substances or their performance viability.

The approach could be used to manufacture other electronic components like screens and displays.