Aiming to tackle the problems caused by electronic waste, a team led by Ting Xu, professor of materials science and engineering and of chemistry, and faculty senior scientist at Berkeley Lab, has developed a fully recyclable and bio-degradable printed circuit.
The researchers had previously created a biodegradable plastic material — embedded with purified enzymes such as Burkholderia cepacian lipase (BC-lipase) — that could be degraded by hot water. For their biodegradable circuits, the researchers used cheaper, shelf-ready BC-lipase instead of expensive purified enzymes to reduce costs and enable mass manufacturing. By doing so, they were able to develop a printable “conductive ink” composed of biodegradable polyester binders, conductive fillers such as silver flakes or carbon black, and commercially available enzyme cocktails. The ink gets its electrical conductivity from the silver or carbon black particles, and the biodegradable polyester binders act as a glue. The researchers then used a commercial 3D printer to print circuit patterns with the conductive ink onto various surfaces.
To test its shelf life and durability, the researchers stored a circuit in a drawer without controlled humidity or temperature. After seven months, the circuit conducted electricity just as well as it did before storage. Next, the researchers put the device’s recyclability to test by immersing it in warm water. Within 72 hours, the circuit materials degraded into its constituent parts. The silver particles completely separated from the polymer binders, and the polymers broke down into reusable monomers, allowing the researchers to easily recover the metals without additional processing. They determined that approximately 94% of the silver particles can be recycled and reused with similar device performance.
Learn more: Print, recycle, repeat: Scientists demonstrate a biodegradable printed circuit (Berkeley Lab); Conductive ink with circular life cycle for printed electronics (Advanced Materials)