Thermal inkjet 3D powder printing of metals and alloys: Current status and challenges

This article reviews the current status and contemporary challenges involved in 3D inkjet powder printing of metallic biomaterials. The process physics, comprising of drop-on-demand methodology and binder-powder interaction are briefly discussed. For the later, various dimensionless numbers (Re, Oh and We) are emphasized as they govern the morphology and travel of the binder droplet. The post-impact interaction with powder particles are described into three sequential stages as, impact driven, capillary driven and equilibrium attainment. A review of several binder formulations to 3D print metallic biomaterials is presented along with the guidelines. Non-destructive 3D structural analysis, using advanced X Ray micro-computed tomography (XCT) technique is emphasized for porous architecture assessment (pore volume fraction, pore shape and size distribution, % inter-connectivity) and dimensional tolerance. Finally, the processing and post-processing related challenges in terms of the suitable models for real time powder-binder interaction study, limitations in depowdering, heat treatment strategy, surface roughness are emphasized.