## 4 Conclusions  
In summary, this study investigated the effects of heat treatment of SLM-fabricated Ti64 specimens on the surface morphology, areal surface texture parameters, and contact angles that are crucial in osseointegration and implant infections. The SEM images showed that the untreated Ti64 specimens primarily consists of microscale features, whereas the surface of a heat-treated specimen had a hierarchical structure consisting of microscale features and nanoscale features. The 3D surface height was measured using a laser confocal 3D profiler to determine the surface texture parameters. Values of S\({}_{\rm{a}}\) and S\({}_{\rm{q}}\) were not sensitive to the surface topography of the untreated or heat-treated Ti64 specimens; however, S\({}_{\rm{sk}}\) and S\({}_{\rm{ku}}\) revealed distinct differences between the two surfaces. The wavelet-based multi-resolution analysis was applied to investigate the characteristic length scales of untreated and heat-treated Ti64 specimens. Both Ti64 specimens revealed periodic oscillations for the height signals. The primary peak value significantly increased from 37.4 \(\pm\) 3.8 (untreated) to 45.6 \(\pm\) 6.9 \(\upmu\)m (heat-treated) primarily due to the formation of large-scale aggregations of Ti64 metal powder particles on the heat-treated surface. The contact angle measurements revealed all Ti64 specimens were found to be hydrophobic, where the contact angles for untreated and heat-treated Ti64 specimens were 126.4\({}^{\circ}\)\(\pm\) 1.4\({}^{\circ}\) and 130.7\({}^{\circ}\)\(\pm\) 2.3\({}^{\circ}\), respectively. Compared with untreated specimens, MG-63 cells attached to the heat-treated surface  
Figure 8: Fluorescence images of MG-63 cells attached to Ti64 specimens (cell nuclei stained with PI). (**a–c**)/(**d–f**) and (**g–i**)/(**j–l**) are the highest/lowest positions of MG-63 cells attached to untreated and heat-treated Ti64 specimens, respectively. Scale bar 30 \(\upmu\)m.  
showed a significant difference in proliferation after 4, and 24 h of incubation. The present results showed a strong influence of kurtosis (\(S_{\text{ku}}\)) on cell attachment; therefore, 3D surface texture parameters can be extended to explore the relationship between surface roughness and cell attachment. The potential biomedical context of this study is alveolar bone to Ti64 dental implant. We are currently using the proposed a continuous-wave laser-induced forward transfer (CW-LIFT) system [37] for cell printing on the untreated and heat-treated Ti64 specimens for tissue engineering applications, and these results will be reported in the near future.  
The following are available online at [[https://www.mdpi.com/2076-3417/11/5/2234/s1](https://www.mdpi.com/2076-3417/11/5/2234/s1)]([https://www.mdpi.com/2076-3417/11/5/2234/s1](https://www.mdpi.com/2076-3417/11/5/2234/s1)), Figure S1. The wettability of the untreated (left) and heat-treated (right) SLM-fabricated Ti64 specimens. Table S1. The areal surface texture parameters via the measured surface in the filtering presence for untreated and heat-treated Ti64 specimens. Video S1: The real-time fluorescence images of MG-63 cells attached to untreated Ti64 specimens (cell nuclei stained with PI). (AVI).  
Co-first author, [PERSON]; Conceptualization, T.-S.Y., P.-W.P. and J.-C.Y.; methodology, C.-M.C.; software, I.-J.C.; validation, C.H.; investigation, W.-F.L. and C.-Y.F.; writing--original draft preparation, T.-S.Y.; writing--review and editing, T.-S.Y. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability Statement: Data is contained within the article.  
The authors declare no conflict of interest.