Controlled Porosity of Ceramic Scaffold by Directional Freeze Casting and Scaffold Printing

The objective of this work is to produce a 3-dimensional scaffold with hierarchical porosity produced with automated manufacturing control. In this paper we present a two-step manufacturing process: solid freeform fabrication (SFF) of a polymer scaffold, followed by freeze casting, a directional solidification technique, of composite slurry. This combination allows for the production of composite scaffolds with well defined, gradient porosity in two directions. Transverse porosity is created by immersing a printed alginate scaffold in a chitosan (CS)-hydroxyapatite (HA) slurry which is freeze cast to produce a scaffold with highly aligned porosity in the longitudinal direction. The combination of these two processes, printing and freeze casting, provides engineering control over chemical, structural and mechanical cues of the interconnected microenvironment within the scaffolds over several length scales, including features like overall porosity, pore size and shape as well as the choice of material and for example the ratio of polymer to ceramic within the highly porous composite material. Thus, the material’s structure and architecture can be custom-designed by the fabrication processes to regulate diffusion throughout the scaffold as well as to potentially direct cell proliferation and migration.