3D printing is transitioning from a rapid prototyping tool to an industrial production technology. State-of-the-art 3D printing technologies manufacture objects with a wide range of materials. Currently, there is no integrated technology to print dissimilar materials within the same part. Bonding dissimilar parts creates interfaces with debilitating stress concentrations. Overall, part performance is compromised. Therefore, there is value in 3D printing multi-material and functionally graded objects. In this thesis, we propose a novel binder jetting approach using nanoparticle inks to build composites. The approach deposits nanoparticle inks containing physical/chemical bonding agents to bind polymer powders into an object;​ by switching between different nanoparticle inks (metal/graphene/conductive polymers), a functionally graded composite with non-distinct interfaces is built. To this end, a novel system for robustly ejecting nanoparticle ink is developed, and a graphene oxide (GO) ink was formulated and printed onto polyvinyl alcohol (PVOH) powder to build a 0.5vol% GO/PVOH composite.