Metal-plastic hybrid 3D printing using catalyst-loaded filament and electroless plating

The metallization of local areas of 3D-printed plastic structures has attracted a significant amount of attention. However, metal and plastic additive manufacturing technologies are incompatible with each other due to the significant difference in their associated process temperatures. This paper proposes and demonstrates a plastic 3D printing technology that adopts electroless plating, a form of chemical metal deposition. The technology is capable of metalizing selected areas of 3D-printed plastic structures made of acrylonitrile butadiene styrene (ABS). Because electroless plating is triggered by a palladium (Pd) catalyst, this study designed and custom-fabricated an ABS filament that contains palladium chloride (PdCl₂) as a catalyst precursor, which can be used in a fused filament fabrication (FFF) 3D printer. The 3D printer has two nozzles. One produces the main component of the ABS 3D structure using a regular filament (i.e., pure ABS without PdCl₂), and the other deposits a PdCl₂-loaded ABS layer onto a selected area of interest using the custom filament. Then, the 3D-printed structure is directly immersed in a nickel (Ni) electroless plating bath. The Ni coats the selected area with strong adhesion. The proposed plastic 3D printing technology coupled with electroless plating does not require any etching (which often uses chromic acid, a very toxic chemical) or roughening of the ABS structure, which are necessary for conventional electroless plating on plastic structures for strong adhesion. Overall, the proposed 3D printing technology has several advantages, namely area-selective metallization, compatibility with regular FFF 3D printing, no damage to the printed structure, and environmental friendliness.