This electronic circuit degrades on demand into recyclable components

Sample of the biodegradable electronic circuit created by Berkeley researchers — © Marilyn Sargent / Berkeley Lab

Notoriously difficult to recycle, old electronics clutter our landfills. American scientists have recently developed an innovative process, allowing them to be degraded on demand and thus easily recover the precious materials they contain.

Efficiently recycle e-waste

The recycling of the’electronic represents today a major environmental challenge. While they contain precious metals like gold and silver, these devices are generally not designed to be recycled, meaning that most of them end up in landfills, where they can release toxic chemicals into the body. environment. To avoid such a scenario, researchers turn to transient electronics, degrading after a certain time or when subjected to a specific trigger like heat or water.

In the context of work published in the journal Advanced materialsBerkeley scientists have designed printed circuits that can be broken down into reusable materials on demand.

The approach builds on the team’s previous research, which had created biodegradable plastics with embedded enzymes that break down into polymer chains in hot water or soil within days. In order to prevent degradation from occurring under other conditions, the researchers had used a molecule called RHP, which disperses the enzymes in clusters in the plastic.

electric circuit
– Roman Sakhno / Shutterstock.com

This time, the American researchers turned to inexpensive enzymes, in order to streamline production and reduce costs. Their biodegradable plastic was used as a substrate, on which electronic circuits made of conductive ink were printed. This is made up of silver flakes or carbon black particles to ensure electrical conductivity, polyester binders holding it together, and cocktails of enzymes capable of degrading them.

Impressive properties

In order to assess the entire life cycle of such circuits, the researchers placed them for seven months in a drawer, where they were exposed to daily fluctuations in temperature and humidity, before being crossed by a continuous electric current for one month. According to the team, after the experiment, the circuits performed as well as their new counterparts, indicating that they had not started to degrade prematurely.

Their biodegradability was assessed by letting them sit in hot water for a few days. Within 72 hours, the silver particles had separated from the polymers, having themselves broken down into monomers. According to the team, 94% of the silver in these circuits could be recycled, just like the monomers.

If biodegradable, conductive ink worked equally well on soft plastic and fabric, paving the way for its use to create wearable electronic devices, the next step will be to create an entire microchip that is completely biodegradable.

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