One of the challenges with recycling electronics is that there are components inside that will never break down if tossed into a landfill. Even among electronics that are recycled, it’s very challenging to separate and recover valuable materials from discarded electronic devices. To help make recycling electronics easier, researchers from Duke University have developed what they call the world’s first fully recyclable printed electronics.
The printed electronics were demonstrated using a type of transistor that can be reduced to its original building blocks using water and soundwaves. The advance was created during experimentation with nanocellulose, material derived from plants and often created using wood waste. Researchers combined the nanocellulose with common printing techniques to produce flexible electronic circuits. The material is biodegradable and has been used in packaging for years.
Its potential applications as an insulator and electronics have been known about for years, but no one had previously figured out how to use it in a printable ink before. The Duke University researchers developed a way to incorporate nanocellulose into printable ink by reducing it to a crystalline form and adding in a little salt.
The resulting insulating dielectric ink was then combined with a conductive ink made using graphene and a semiconductor ink made with carbon nanotubes. The resulting ink formed an all-carbon transistor that can be printed onto a paper substrate using aerosol jet printing at room temperatures.
Recycling the transistors starts with a series of baths that vibrate the material gently using sound waves. The solution resulting from the bath process is added to a centrifuge allowing the carbon nanotubes and graphene to be recovered at a yield very close to 100 percent. Those materials can then be reused via the same printing process, while the nanocellulose can be recycled with the paper substrate.