Fabrication of gyroid-structured, hierarchically-porous hydroxyapatite scaffolds by a dual-templating method

Freeze-casting is a widely recognized method for producing porous materials. However, in the typical freeze-casting process, the pore morphology is single, and the pore size is mostly distributed at the micrometer scale due to the limitation of the nature of ice dendrites. In this study, ice template and the 3D-printed template we integrated to develop the dual-templating process to fabricate gyroid-structured, hierarchically-porous hydroxyapatite scaffolds. Microstructural characterizations by SEM and micro-CT demonstrated that the average diameter of macro-porosity, micro-porosity, and average porosity of the dual-scale gyroid scaffolds were 667.4 +/- 95.8 mu m, 20.8 +/- 5.7 mu m, and 66%, respectively. The fish scale-derived hydroxyapatite (HAp) powder was utilized as the raw material due to the advantages of hydroxyapatite, including eco-friendly, bio-compatibility, non-toxicity, and high ion removal ability. Assuredly, the dual-scale hydroxyapatite scaffolds have greatly improved the permeability (445.6 +/- 171.3 x 10(-13) m(2)) and Pb (II) ion adsorption efficiency (>98%) compared to traditionally freeze-casted, single-scale ones. In summary, the dual-scale, gyroid-structured hydroxyapatite scaffolds have great potential to be applied in the industrious wastewater treatment field.