Selective laser sintering (SLS) enables the fabrication of complex geometries with the intricate and controllable internal architecture required in the field of tissue engineering. In this study hydroxyapatite and poly--caprolactone, considered suitable for hard tissue engineering purposes, were used in a weight ratio of 30:70. The quality of the fabricated parts is influenced by various process parameters. Among them Four parameters, namely laser fill power, outline laser power, scan spacing and part orientation, were identified as important. These parameters were investigated according to a central composite design and a model of the effects of these parameters on the accuracy and mechanical properties of the fabricated parts was developed. The dimensions of the fabricated parts were strongly dependent on the manufacturing direction and scan spacing. Repeatability analysis shows that the fabricated features can be well reproduced. However, there were deviations from the nominal dimensions, with the features being larger than those designed. The compressive modulus and yield strength of the fabricated microstructures with a designed relative density of 0.33 varied between 0.6 and 2.3 and 0.1 and 0.6 MPa, respectively. The mechanical behavior was strongly dependent on the manufacturing direction.

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Abstract.Selective laser sintering (SLS) has the potential to fabricate bioresorbable polymer / ceramic composite scaffolds with pre-designed external and internal architecture that can be used for bone tissue engineering applications. Scaffolds were fabricated using poly-c-caprolactone as the base material. The effect of 15 and 30 wt% of hydroxyapatite (HA) addition was investigated in terms of compressive properties, accuracy, surface topology, and wettability. Fabricated dimensions of PCL microstructures showed great deviations from their nominal values. Average surface roughness was found to be Ra=25±4 gm. Increased HA content had no statistically significant effect on accuracy and surface roughness. However the addition of HA had a significant influence on compressive properties, hydrophobicity and wettability of the samples. Addition of 30 wt% HA improved initial compressive modulus of pure PCL scaffolds from 1.31±0.08 MPa to 1.58±0.18 MPa. Yield strength values increased from 0.14±0.07 MPa to 0.17±0.01 MPa by adding 15 wt% of HA, but decreased with further HA addition. Yield strain for all compositions was over c=0.06. Increased HA content decreased hydrophobicity and increased wettability of scaffold surfaces. The study demonstrated the ability of SLS to fabricate tissue engineering scaffolds, and the positive effect of HA particle reinforcement in terms of compressive mechanical properties and surface characteristics.

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