Hybrid 3D printing technique prints both plastic and metal

A new hybrid 3D printing technique can print both plastic and metal, producing objects with combinations of both.

Developed at Waseda University in Japan, the technique aims to overcome the limitations of the most popular 3D printing process.

In fused filament fabrication, plastic or metal is melted and extruded through a small nozzle by a printer head, before immediately solidifying and fusing with the rest of the piece. However, because the melting points of plastics and metals are very different, the technology has been limited to creating objects of either metal or plastic – until now.

“Even though 3D printers let us create 3D structures from metal and plastic, most of the objects we see around us are a combination of both, including electronic devices,” said Professor Shinjiro Umezu, who led the study. “We thought we would be able to expand the applications of conventional 3D printers if we managed to use them to create 3D objects made of both metal and plastic.”

In the conventional approach for combining plastic and metal in 3D-printed objects, plastic objects are printed before being submerged in a solution containing palladium (Pd), which adheres to the object's surface. The piece is then submerged in an electroless plating bath that, using the deposited Pd as a catalyst, causes dissolved metal ions to stick to the object.

While the researchers said that approach is technically sound, they said it produces a metallic coating that is non-uniform and adheres poorly to the plastic structure.

In the new hybrid method, a printer with a dual nozzle is used – one nozzle extrudes standard melted plastic (acrylonitrile butadiene styrene, or ABS) and the other extrudes ABS loaded with PdCl². By selectively printing layers using one nozzle or the other, specific areas of the 3D object are loaded with Pd. Electroless plating is then used to finish the object, giving a plastic structure with metallic coating over selected areas.

The team found the adhesion of the metal coating to be much higher when using their approach. Unlike the conventional method, the new approach does not require roughening or etching of the ABS structure to promote the deposition of the catalyst.

The researchers said the technique, which is compatible with existing fused filament printers, could be used to create 3D electronics for Internet of Things applications.

The work was published in Additive Manufacturing.

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