Direct Surface-Exposed Nucleation Site Development via a Dip-Coated Filament Strategy for Facile Functional Metallization in Material Extrusion-Based Plastronics

Functional conductive coatings on polymer substrates are essential for the next generation of plastic-based electronics, facilitating reliable electrical interconnections, embedded circuitry, energy-harvesting modules, and the seamless integration of wearable and sensing systems, while preserving the inherent advantages of polymeric materials, including lightweight, manufacturing flexibility, and cost-effective production. Material extrusion (MEX)-based 3D-printing offers geometric flexibility for such components; however, effective area-selective metallization in MEX has primarily relied on composite filaments with high wt % conductive fillers, followed by electroless plating (ELP). In these systems, conductive particles often remain embedded beneath the printed polymer layers, necessitating additional postprocessing to expose them for ELP, yet even then, the electrical performance remains limited. This study presents an advanced dip-coating strategy for producing Cu-coated ABS filaments, enabling the direct formation of surface-exposed nucleation sites during MEX printing. The acetone-mediated Cu deposition process yielded filaments with an electrical resistivity of 2.075 × 10 –3 Ω·cm, while preserving extrusion performance. Printed circuitry pathways exhibited continuous, surface-exposed Cu regions that served as preferential sites for Pd accumulation during brief Pd/Sn activation, thereby intrinsically enabling area-selective ELP without any additional selective treatment of the pathways. Subsequent Cu deposition achieved electrical conductivity up to 85.77% of bulk copper while maintaining strong metal–polymer adhesion (ASTM D3359 ratings of 4B–5B). By integrating AM with targeted surface functionalization, this approach offers a scalable and sustainable route to fabricate highly conductive, adherent coatings on polymeric structures, advancing functional coating technologies for plastronics and related applications.