Self-Activating Metal-Polymer Composites for the Selective Electroless Metallization of 3D Printed Parts
Authors: Bernasconi Roberto , Credi Caterina , Levi Marinella , Magagnin Luca 
Published: November 2022

Nowadays, polymer based additive manufacturing (AM) is widely recognized as a powerful technology for the fabrication of complex three-dimensional objects of virtually any shape in a time, material, and cost effective way. Thanks to their characteristic advantages over conventional manufacturing strategies, AM technologies are the subject of relevant research efforts. In particular, great attention is placed on developing novel 3D printable materials characterized by improved properties and, among all, by novel functionalities, such as magnetic [1] and conductive properties [2]. In order to do this, the most common strategy relies on doping polymeric matrices with nanoparticles, obtaining thus functional 3D printable polymeric composites.
Metal containing composites, in particular, can be exploited for their magnetic properties or for their mechanical behavior but also for their potential capability to trigger electroless deposition. It is well-known that electroless plating requires the presence of a catalytic surface, which can be constituted by the metallic particles embedded in the 3D printed composite. In this way, the need to activate the surface of non-conductive polymeric 3D printed parts can be avoided [3]. In addition, metallization can be carried out selectively by fabricating parts in a multi-material printing process [4] with both metal loaded and non-loaded materials. Since only the layers that contain the particles can metallize, conductive regions can be alternated with insulating zones to create metallic functional patterns on the surface of printed parts. This approach can enable the 3D printing of selectively self-metallizing parts, with possible applicability in the production of flexible and highly tridimensional electronic circuits, radiofrequency devices, microelectromechanical systems or microfluidic setups.
The present work focuses on the development of a stereolithography (SLA) printable composite based on an acrylate resin loaded with nickel microparticles and its application as self-catalytic material for electroless metallization. This approach, unprecedented for SLA resins, eliminates the need of noble metal activation of the surface. Moreover, the usage of Ni is of great interest also due to the other properties that it can potentially impart to the printed parts: improved mechanical properties, high thermal conductivity, magnetizability. The SLA printability of the metal-loaded resin is assessed and the morphological properties of the 3D printed composites are investigated. Subsequently, the functional properties of the composites are determined, placing a particular emphasis on their capability to trigger NiP and Cu electroless deposition. Finally, the possibility to selectively metallize only specific areas is successfully demonstrated by metallizing a Ni-loaded pattern printed on a Ni-free base.
[1] Huber et al.; Appl. Phys. Lett. 109, 162401 (2016)
[2] Postiglione et al.; Compos. Part A Appl. Sci. Manuf. 76, 110-114 (2015)
[3] Bernasconi et al.; J. Electrochem. Soc. 164, B3059–B3066 (2017)
[4] Choi et al.; J. Mater. Process. Technol. 211, 318–328 (2011)