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Home > News > Waste not

Waste not

Fall 2022 Berkeley Engineer magazine
November 7, 2022
This article appeared in Berkeley Engineer magazine, Fall 2022
  • In this issue
    Artist’s rendering of a human base on a new planet, aerial view.

    Taking up space

    Lydia Sohn holding a petri dish containing small sensing deices in her lab.

    The power of simplicity

    A 3D-printed, trifurcated microtubule model alongside a gnat

    The Big Picture

    Dean Tsu-Jae King Liu speaks at a CHIPS and Science Act press event

    Dean's note

    Upfront

    • Waste not
    • Aiding Chernobyl
    • Just for you
    • Next-gen lasers
    • Fired up for the future
    • Digging deep
    • Into the drink

    New & noteworthy

    • Transfer student success
    • Lighting up Hollywood
    • To infinity and beyond
    • Farewell
    • With flexibility comes possibility
  • Past issues

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.

Ph.D. student researcher Junpyo (Patrick) Kwon demonstrates a biodegradable printed circuit

Photo by Marilyn Sargent/Berkeley Lab

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)

Topics: Sustainability & environment, Materials science, Research
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