Bone consists of a natural composite of organic (collagen) and inorganic (bone mineral Hydroxyapatite) phase with a highly porous structure. For bone regeneration in case of trauma or illness, researchers therefore try to mimic the hieratical, porous and/or material structure of bone. Artificial bone replacement materials should fulfill several requirements, such as: mechanical properties should match the original tissue, the applied material should be at least bioinert or better bioactive (i.e. dissolution of the material will enhance the self-healing properties of the surrounding tissue), and the geometry should mimic that of natural bone (i.e. high porosity coupled with high specific surface area and good mechanical strength). An open porous structure encourages cell adhesion, proliferation and the transport of nutrients. If mesoporous ceramic powders are employed a hierarchical porosity can be achieved, ranging from nanometer to mm pores.

Open macroporous scaffolds can be achieved by conventional processing, such as freeze casting, or by additive manufacturing, such as robocasting, laser-based powder bed fusion or stereolithography. We employed freeze casting to produce Bioactive Glass- Chitosan-Gelatin composite scaffolds with high porosity and good elastic properties. Freeze-casting is a cost-effective, easy to use technique for the fabrication of macroporous ceramics. It relies on the formation and subsequent sublimation of ice crystals that act as pore templates in frozen particulate dispersions. By variation of processing parameters, such as freezing rate and slurry composition pore size distribution and pore shape can be controlled.

Additive manufacturing on the other hand allows complete control over geometry, pore size, pore structure, and such factors, but requires equipment. For AM of pure ceramics and composites the ceramic powders are generally combined with organics, either as sacrificial or non-sacrificial binders.