Laser Surface Engineering of Hierarchy Hydroxyapatite Aerogel for Bone Tissue Engineering

Bioceramics with porous microstructure has attracted intense attention in tissue engineering due to tissue growth facilitation in the human body. In the present work, a novel manufacturing process for producing hydroxyapatite (HA) aerogels with a high density shell inspired by human bone microstructure is proposed for bone tissue engineering applications. This method combines laser processing and traditional freeze casting in which HA aerogel is prepared by freeze casting and aqueous suspension prior to laser processing of the aerogel surface with a focused CO₂ laser beam that forms a dense layer on top of the porous microstructure. Using the proposed method, HA aerogel with dense shell was successfully prepared with a microstructure similar to human bone. The effect of laser process parameters on surface and cross-sectional morphology and microstructure was investigated in order to obtain optimum parameters and have a better understanding of the process. Low laser energy resulted in fragile surface with defects and cracks due to low temperature and inability of laser to fully melt the surface while high laser energy caused thermal damage both to surface and microstructure. The range of 40–45 W laser power, 5 mm/s scanning speed, spot size of 1 mmm and 50 % overlap in laser scanning the surface yielded the best surface morphology and micro structure in our experiments.