Micron-scale additive manufacturing of binary and ternary alloys by electrohydrodynamic redox 3D printing

Across disciplines and length scales, alloying of metals is a common and necessary strategy to optimise materials performance. While the manufacturing of alloys in bulk and thin film form is well understood, the fabrication of alloyed 3D nanostructures with precise control over the composition remains a challenge. Herein, we demonstrate that electrohydrodynamic redox 3D printing from mixed metal salt solutions is a versatile approach for the 3D nanofabrication of alloys. We propose that the droplet-by-droplet nature of the electrohydrodynamic redox printing process allows straightforward electroplating of alloys with composition solely controlled by the composition of the electrolyte solution, independent of the reduction potential of the involved cations. As a demonstration of the direct control of composition, we deposit binary and ternary alloys of Ag, Cu and Zn. TEM microstructure analysis indicates homogeneous alloying at the nanoscale and the formation of a metastable solid-solution phase for Ag-Cu and a two phase system for Ag-Cu-Zn alloys. The straightforward approach to alloying with an electrochemical technique promises novel opportunities for optimisation of properties of 3D nanofabricated metals.