Laser-Printed "Papertronic" Circuits Deliver Environmentally-Friendly, Biodegradable Electronics

Researchers from the State University of New York at Binghamton's bioelectronics and microsystems laboratory have come up with a way to turn parchment paper into "papertronic" circuits — by drawing on them with a laser.

"My long-term vision has always been to create a complete, self-powered, disposable electronic system on paper," explains project lead and corresponding author Seokheun Choi of the team's work. "We started with the power source — the biobattery. Then we moved to sensors. The missing piece was the circuit itself: the resistors, capacitors, and interconnects that tie everything together. Imagine a bandage that monitors a wound for infection and wirelessly alerts your phone — and when you are done with it, you throw it in your compost bin. Or a shipping label that tracks temperature and humidity throughout a supply chain, then biodegrades in a landfill. That is where we are heading."

The team's work is based on parchment paper, which has a thin water-repelling layer of silicone on its surface. By blasting this layer away with a precise laser, sections of the paper can be made to more readily absorb liquids — in this case, channeling conductive inks to form not only circuit traces but functional components including resistors, capacitors, and working analog filter circuits.

"The laser essentially writes wettability onto an unwettable surface," Choi explains. "Wherever the laser touches, the paper becomes receptive to our functional inks. Everywhere else, the silicone coating acts as a natural insulator. We didn't just improve the resolution [beyond previous work on wax-coated paper] — we changed the physics of how the resolution is determined. With wax, you are fighting against molten wax spreading through the paper. With our laser approach, the pattern is defined by the laser spot size and stays exactly where you put it. There is no spreading, no blurring, no uncertainty."

The resulting circuits, which can be produced with features as small as 250 micrometers at 300-micrometer spacing, are environmentally-friendly: the inks are water-based with no toxic metals or solvents, and the whole circuit can be composted within a period of weeks — or burned to nothing but ash in seconds. For devices that need to survive longer periods in harsh conditions, a coating of fresh silicone can offer protection.

The team's work has been published in the journal ACS Applied Materials & Interfaces under open-access terms.