Noble-metal-free recyclable electronic nanoinks for wireless wearable sensors

Inappropriate disposal of electronic waste (e-waste) can pollute ecosystems and deplete mineral resources, highlighting the urgency to develop sustainable and recyclable electronics. While various metal nanoparticles have been tested in literature regarding built-in recyclability for electronics, it remains unclear on how recycling processes affect their properties, since oxidation and contamination of recycled nanomaterials may compromise the functional and reliable performance of remanufactured devices. This study aims to fill this knowledge gap by systematically investigating the behaviors of metal particles at different remanufacturing stages and by developing an effective, printing-enabled, remanufacturing route using fully recyclable, noble-metal-free, conductive inks. Recyclability of the printed conductors is investigated in terms of electrical properties across multiple reuse cycles, achieving ∼90% recovery of electrical conductivity after 3 reuse cycles (at least 1 order of magnitude higher than the regular "mill-to-print" approach). As proof of concept, a wireless strain-sensing platform is designed for real-time monitoring of small strains generated by the human body, highlighting potential for wearable human-machine interface applications.