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Custodio, et al.
Table 2. 3D printing parameters for FDM printing of PLA/HAp 2.9. In vitro biomineralization
composites. The bioactivities of the 3D printed scaffolds were
Parameters Settings assessed through immersion in SBF. The scaffolds were
Layer height 0.2 mm immersed in an SBF solution having a composition
Infill density 100% similar to what Rodriguez and Gatenholm reported , to
[16]
Infill pattern Grid (45°, −45°) determine the effect of increasing HAp powder loading
Printing temperature 210°C to their biomineralization activity as a function of time.
Build plate temperature 60°C A liter of SBF solution was prepared by dissolving the
Print speed 45 mm/s analytic grade reagents (< 99%) in distilled water in the
Extrusion width (nozzle diameter) 0.6 mm following order shown in Table 3.
PLA, polylactic acid; HAp, hydroxyapatite; FDM, fused deposition In preparing the SBF solution, each reagent was
modeling. added after the previous reagent has dissolved completely.
The solution was prepared at 36.5°C under constant
features and textures, depth profile, and fractured cross stirring. The pH of the solution was also adjusted to pH
section of the 3D printed PLA/HAp composites, as well 7.4 using 1 M HCl solution and was kept refrigerated
as the resulting scaffolds immersed in simulated body at 4°C before usage. The SBF is similar to the human
fluid (SBF) solutions. The samples were observed from blood plasma ionic concentration and composition. The
30× to 500× range. samples were immersed in 15 mL of SBF solution and
placed inside a dedicated oven set at 37°C for 24, 48,
2.6. Chemical composition and 72 h to assess the growth and deposition of apatite
species on the scaffold [17,18] . The SBF-immersed samples
Attenuated total reflectance-Fourier transform infrared were retrieved from the solution and dried in the oven
(ATR-FTIR) spectra were recorded across the 4000– overnight, and finally characterized through digital
600 cm frequency range, with 1–2 µ penetrating depth, microscopy, gravimetric analysis, and XRD.
−1
and with 20 scans per sample at room temperature (23°C)
using a Frontier FTIR spectrometer (PerkinElmer, USA). 3. Results and discussion
The synthesized HAp and 3D printed PLA/HAp composites
were subjected to ATR-FTIR scans to determine the 3.1. 3D printed PLA/HAp prototype
functional groups within the composite material.
Figure 2 shows the digital micrographs of the 3D printed
2.7. Crystallinity PLA/HAp composites at different magnification levels,
including the depth profile analysis. The top view of
The diffraction patterns were obtained using a LabX X-ray pure PLA (PLA/0H) was characterized by well-defined
diffraction (XRD)-6000 X-ray diffractometer (Shimadzu, individual print beads, as the grid could be clearly seen
Japan), with a Cu Kα radiation source at 40 kV operating both from 30× to 200× (Figure 2A and B), and even at the
voltage. The scanned range for all samples was from 2° to depth profile (Figure 2E-F). However, as the HAp loading
60° (2θ) with a step size of 1°/min. The synthesized HAp, was increased from 5 wt% to 15 wt%, the print beads were
3D printed PLA/HAp composites, and the biomineralized slowly disappearing and became less defined. Likewise,
scaffolds were subjected to XRD characterization to the surface finish oh PLA/5H, PLA/10H, and PLA/15H
confirm the presence of apatite species and their influence were more irregular and rougher than PLA/0H. The same
to the composite. visual trend could be seen at the depth profile, whereas the
print bead gaps were slowly closing in and disappearing
2.8. Mechanical properties (Figure 2L, R and X). Hence, the 3D printed PLA/HAp
As adopted from ASTM D638, the tensile tests were composites were becoming more irregular as the HAp
carried out using a universal testing machine (Instron loadings were increased. Nonetheless, hydroxyapatite
5585H, USA), with a 10 kN static load cell, at a gauge powders were seen from the composite surface with
length of 50 mm, and a strain rate of 5 mm/min. Tensile increasing frequency in accordance to the increasing
tests were done to determine the elastic modulus and tensile HAp loading, although the distribution were irregular and
strength of the 3D printed PLA/HAp biocomposites. Five agglomeration was present (Figure 2H, J, N, P, T and V).
trials were tested for each sample, the average values Porosity and density are also some physical
reported, and the representative samples were plotted. properties that must be considered, especially with polymer
Width and thickness of the test specimens were measured matrix composites. These properties can provide useful
using a Mitutoyo digital caliper before testing. The tests information in the prediction of the material’s behavior,
were performed at room temperature and 54% relative for instance, under mechanical stimuli. A denser material
humidity. is usually a stronger one, and a porous material is usually

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