Direct ink writing of porous Fe-HA metal-matrix composites (MMCs) with independently adjustable porosity and degradation rate for bone implant applications

The porosity and degradation rate are critical properties of biodegradable bone implants, as they facilitate the regeneration of bone tissues and ensure a gradual load transfer. Herein, porous iron-hydroxyapatite (Fe-HA) metal-matrix composites (MMCs) with independently adjustable porosity and degradation rate are fabricated through a 3D printing technique, i.e., direct ink writing (DIW). HA micro powders exhibit a significant acceleration effect on the degradation rate, which act as a variable that is independent of the porosity to regulate the degradation rate. The mass losses of Fe-HA MMCs with the porosities of 30%, 50%, and 70% after 21d in-vitro immersion increased by 26%, 38%, and 93%, respectively, with the rising of HA content from 0 to 7.5 wt%. The novel porous Fe-HA MMCs have an adjustable and wide porosity-degradation rate range, yielding great potential to match with varied porosity and regeneration rate among various bones of different people.