## 3 Results and Discussion
### The Effect of SBF Immersion Time on the Microstructure of the HA/WS Skeleton  
The morphological comparison of the three-dimensional porous HA/WS skeleton before and after immersion in SBF solution is illustrated in Figure 9. The surface of the three-dimensional porous HA/WS skeleton exhibited a relatively dense biomineralized layer after being immersed in 1.5 \(\times\) SBF for 21 days, as depicted in Figures 5-9. After conducting further observations of the local area, it was discovered that the generated apatite exhibited a thin sheet structure, and this formation was found to be closely associated with the crystallographic characteristics and orientation of apatite crystals. The sheet has a diameter of approximately 2 \(\upmu\)m, with a thickness ranging in the dozens of nm. It is intricately interwoven and intertwined. The deposition of hydroxyapatite in simulated body fluids within the HA/WS three-dimensional porous skeleton can be observed in Figure 9, demonstrating a three-dimensional directional growth. Furthermore, the biological mineralization process leads to the formation of apatite nanoparticle crystals within the cavities, walls, and inner surfaces of the three-dimensional porous HA/WS skeleton. The biomineralization process being dynamic in nature, the osmosis gradually progresses inward as the simulated body fluid comes into contact with the three-dimensional porous HA/WS skeleton and the infiltration time increases. The internal cavity structure becomes intricate due to variations in the SBF contact environment. As immersion progresses, the biomineralization process differs across these environments, resulting in the  
Figure 8: Morphology of the 90 HA/10 WS scaffolds obtained via micro-CT analysis. (**a**) Front view; (**b**) top view; (**c**) side view; and (**d**) inside cutting-surface view. formation of distinct types of apatite nanocrystals during mineralization. The internal micropore structure of the implant skeleton may require redesigning based on bone cell preferences and regeneration needs. Therefore, it is necessary to investigate the changes in the internal micropore structure after different durations of SBF soaking. In this study, a three-dimensional porous HA/WS skeleton was immersed in 1.5 \(\times\) SBF solution for varying periods (1 day, 3 days, 7 days, 14 days, and 21 days) under identical culture conditions. After each immersion period, excess impurities were removed from the surface via cleaning with deionized water followed by drying at room temperature. The effect of simulated body fluid immersion time on the microstructure of the three-dimensional porous HA/WS skeleton was observed using scanning electron microscopy. The microstructure of the three-dimensional porous HA/WS skeleton after being immersed in simulated body fluids for 1 day is depicted in Figure 10. The observation from Figure 10a reveals that following a 1-day immersion period, only a few apatite nanocrystals grow on the three-dimensional porous HA/WS skeleton surface within certain grooves. This can primarily be attributed to the short duration of immersion, which corresponds to an early stage in the biomineralization process and consequently results in a slow crystal growth rate. Upon further certification (Figure 10b), a lake-like distribution of apatite nanocrystals surrounded by a WS glass phase becomes apparent. The smooth region surrounding it represents the high-temperature-formed glass phase composed of WS while the area consisting of the central nanocrystal sheet signifies the cluster of apatite nanosheets formed through biomineralization. The subsequent magnification of the three-dimensional porous HA/WS skeleton surface provides clearer evidence that solely formed apatite nanocrystals are distributed within fluted areas. Based on experimental findings, it can be concluded that under a 1-day immersion time, there is a greater inclination for apatite nanoparticles to form within grooves present on the three-dimensional porous HA/WS skeleton surface.