Adoption of appropriate scanning strategy on selective laser melting of stainless steel 316L to enable healthy mesenchymal stem cells response

In this study, an appropriate scanning strategy in selective laser melting [SLM, also known as laser powder bed fusion (LPBF)] was adopted to enhance the forming quality of stainless steel (SS) 316L for load-bearing implant applications, with a particular focus given to investigate the effect of argon flow velocity inside the build chamber. The biocompatibility of the resulting printed surfaces was evaluated by in vitro culturing of mesenchymal stem cells (MSCs) at different time points up to 96 h. Notably, it is one of the first studies to document the MSC response on SLM 316L surfaces. The results showed that highly dense parts (>99.8% density) can be produced by carefully selecting the interlayer rotation, scan vector length, and hatch distance. Microsized surface defects (i.e., balling) appeared after the SLM process. Their chance of occurrence and size were found to be related to the gas flow velocity inside the build chamber. The resulting printed surfaces were hospitable for MSCs, and healthy cell response was recorded throughout the 96-h culture periods. These findings can be instrumental in optimizing the surface features of SLM in order to improve the cell response.