Recyclable vitrimer-based printed circuit boards for sustainable electronics
Printed circuit boards (PCBs) are ubiquitous in electronics and make up a
substantial fraction of environmentally hazardous electronic waste when
devices reach end-of-life. Their recycling is challenging due to their use
of irreversibly cured thermoset epoxies in manufacturing. Here, to tackle
this challenge, we present a PCB formulation using transesterifcation
vitrimers (vPCBs) and an end-to-end fabrication process compatible
with standard manufacturing ecosystems. Our cradle-to-cradle life-cycle
assessment shows substantial environmental impact reduction of the vPCBs
over conventional PCBs in 11 categories. We successfully manufactured
functional prototypes of Internet of Things devices transmitting 2.4 GHz
radio signals on vPCBs with electrical and mechanical properties meeting
industry standards. Fractures and holes in vPCBs are repairable while
retaining comparable performance over multiple repair cycles. We further
demonstrate a non-destructive recycling process based on polymer swelling
with small-molecule solvents. Unlike traditional solvolysis recycling,
this swelling process does not degrade the materials. Through dynamic
mechanical analysis, we fnd negligible catalyst loss, minimal changes in
storage modulus and equivalent polymer backbone composition across
multiple recycling cycles. This recycling process achieves 98% polymer
recovery, 100% fbre recovery and 91% solvent recovery to create new vPCBs
without performance degradation. Overall, this work paves the way for
sustainability transitions in the electronics industry.
Art Credits: Carmen Casado
Photo Credits: Mark Stone/University of Washington
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UW UbiComp Lab
UW Iyer Lab
Vashisth Research Lab