Microstructure and compression properties of 3D powder printed Ti-6Al-4V scaffolds with designed porosity: Experimental and computational analysis

The osseointegration of metallic implants depends on an effective balance among designed porosity to facilitate angiogenesis, tissue in-growth and bone-mimicking elastic modulus with good strength properties. While addressing such twin requirements, the present study demonstrates a low temperature additive manufacturing based processing strategy to fabricate Ti-6Al-4V scaffolds with designed porosity using inkjet-based 3D powder printing (3DPP). A novel starch-based aqueous binder was prepared and the physico-chemical parameters such as pH, viscosity, and surface tension were optimized for drop-on-demand (DOD) based thermal inkjet printing. Micro-computed tomography (micro-CT) of sintered scaffolds revealed a 57% total porosity in homogeneously porous scaffold and 45% in the gradient porous scaffold with 99% interconnectivity among the micropores. Under uniaxial compression testing, the strength of homogeneously porous and gradient porous scaffolds were ~47MPa and ~90MPa, respectively. The progressive failure in homogeneously porous scaffold was recorded. In parallel to experimental measurements, finite element (FE) analyses have been performed to study the stress distribution globally and also locally around the designed pores. Consistent with FE analyses, a higher elastic modulus was recorded with gradient porous scaffolds (~3GPa) than the homogenously porous scaffolds (~2GPa). While comparing with the existing literature reports, the present work, for the first time, establishes 'direct powder printing methodology' of Ti-6Al-4V porous scaffolds with biomedically relevant microstructural and mechanical properties. Also, a new FE analysis approach, based on the critical understanding of the porous architecture using micro-CT results, is presented to realistically predict the compression response of porous scaffolds.