One of the most attractive techniques currently under development in the sector of additive manufacturing is the 3D printing of metallic objects. Parts realized with pure metals or alloys present many useful functional and aesthetic properties: electrical and thermal conductivity, metallic luster, high mechanical properties. Many techniques, including selective laser sintering (SLS) or electron beam melting (EBM), are able to yield good quality results [1]. All metal 3D printing techniques are however characterized by common drawbacks that limit their applicability: poor surface quality, residual porosity and inability to reach extremely low feature sizes (useful in the so called additive microfabrication).

Another approach that can be followed to obtain parts presenting metallic properties is the surface metallization of polymeric 3D printed objects. Polymers are easier to print than metals and some techniques, like stereolithography, are able to reach micrometric feature sizes. Metallic layers can be in principle applied using many different techniques, but electroless plating in particular presents important advantages in terms of cost per unit and flexibility.

Methods to electroless metallize stereolithography printed parts are available in literature [2], but the influence of different pretreatment routes on the quality of the final metallic layer was never fully investigated. In the present work, three stereolithography resins were pretreated following three different methods. The first one was based on the use of an acidic etching solution, the second was based on an alkaline etching, while the latter saw the application of atmospheric plasma to the pretreatment of the resins. Evolution of surface properties for the different pretreatment routes was investigated employing SEM, contact angle measurements, compositional analysis and FT-IR. Following surface preparation, resins were metallized with electroless copper. By doing this, the influence of the pretreatment on coating quality and adherence was evaluated.

[1] I. Gibson, D. W. Rosen, B. Stucker, Additive manufacturing technologies, Springer (2010)

[2] R. Bernasconi, C. Credi, M. Tironi, M. Levi, L. Magagnin, Electroless Metallization of Stereolithographic Photocurable Resins for 3D Printing of Functional Microdevices. J. Electrochem. Soc. 164, B3059–B3066 (2017)