Sustainable, Robust, and Electrothermal Metal Yarns with Fully Recycled Polystyrene/Polyethylene Terephthalate for Smart Textiles

In this study, we report a sustainable fabrication strategy for electrothermally active metal yarns using fully recycled polystyrene (re-PS) and polyethylene terephthalate (re-PET) as core materials. Hybrid nanofiber yarns were produced via dual-nozzle electrospinning, combining the processability of re-PS and the mechanical reinforcement of re-PET. Electroless copper plating was subsequently performed under ambient conditions following surfactant-assisted activation and palladium seeding, resulting in uniform and continuous metallic coatings. The Cu-plated hybrid yarns exhibited high electrical conductivity with a resistance of 2.84 Ω and showed efficient Joule heating, reaching 153.3 °C at a low applied voltage of 1.2 V. Stable temperature output (∼96 °C) was maintained during continuous 1 h operation, and rapid heating–cooling response was retained over 300 cycles under both flat and bent configurations, confirming mechanical and thermal durability. This approach presents a scalable method for converting plastic waste into high-performance functional textiles. The fabricated metal yarns are lightweight, flexible, and conductive, showing strong potential for integration into wearable heaters and next-generation smart textile systems.