Direct ink writing of metals and metal-based heterostructures

Three-dimensional (3D) printing of metals is generally achieved via laser or electron beam melting of powder beds, and the technology has progressed well over the past decade. However, powder bed fusion (PBF) has some challenges, such as limited control over the evolution of microstructure, and the technique is unable to print metal-nonmetal components. Also, due to the high-energy beam system and stringent environmental conditions, printing equipment and corresponding maintenance costs of PBF are high. To address these limitations and challenges, here we demonstrate the printing of various metals and dissimilar material interfaces using direct ink writing-based 3D printing. Several material systems comprising copper, copper-iron, and copper-graphene are printed using metal powder inks stabilized with small concentrations of nanoclay as a rheology modifier, and the sintered 3D metallic and multi-material parts show desirable mechanical and electrical properties. The printing process and post-sintering have been done in succession to obtain complex architecture from metals and dissimilar metal–metal, metal-nonmetal interfaces. The technique allows vast flexibility in multi-material metal printing, which could lead to various applications involving hetero-interfaces between different materials.