## 4 Conclusions  
In summary, this study reported on the study of the laser structuring of CP Ti surfaces using a picosecond laser with various laser processing parameters to fabricate surfaces with different surface morphologies, optical properties, surface chemistry, and wettability behaviours. After laser structuring, it was noted that a laser fluence of 0.2 J/cm\({}^{2}\) generates HSFLs which are perpendicular to laser polarization and with periods in a range from 439 nm to 476 nm. The other laser fluences generate NC-LIPSS which are perpendicular to laser polarization and with periods in a range from 722 nm to 764 nm on the surface of the CP Ti material. The NC-LIPSS were decorated with nanodroplets. The morphologies at the ablated regions showed no signs of molten materials within its vicinity, hence the process at this low fluence can be described as a gentle ablation process. The EDX analysis reveals that the laser-structured surfaces had thin oxide films which increase as the laser fluences increase. The Raman analysis established that the thin oxide films formed on the surfaces of the laser-processed samples had a rutile-like phase of TiO\({}_{2}\), as shown by the established peaks, while the polished sample had no notable peaks. As the laser fluences increase, the intensity of the E\({}_{\text{g}}\) and A\({}_{\text{1g}}\) vibrational modes increases too. The optical examinations show that different structural colours were produced in different regions. These colours have been attributed to the existence of various LIPSS generated on the laser-processed surfaces and/or titanium oxides present on the surfacesof the laser-processed regions. Different LIPSS with various periods can produce different structural colours. It can also be stated that, after laser processing of CP Ti, the wettability of the substrate changes from a hydrophilic to a hydrophobic state. It was observed that the laser fluence increases with the CA and vice versa while for the hatching distance and/or scanning velocity, the CA reduces as the hatching distance increases. The SFE reduces as the laser fluence increases and vice versa. After immersion in seawater, the wetting behaviour changes to hydrophilic. After storage in ambient conditions, the sample transitioned again to a hydrophobic state. The surface structures and carbonaceous materials present play a major role in the wetting transition behaviour and depend on the storage conditions and time. With this study, we have further enhanced the possibility of modifying the surface morphology, surface chemistry, optical properties, and wetting behaviour of CP Ti material directly through ultrafast laser surface structuring for different and tailored industrial applications such as wettability applications, anti-fouling control, corrosion control, decorations, photovoltaic cells, etc. In future work, optimizing and controlling the laser structuring of the surface towards a specific application can be considered. Further studies would be recommended to fabricate and evaluate the durability of the superhydrophobic surfaces on CP Ti substrate in real environments. Another piece of future work is to carry out more research to establish the contributions quantitatively of LIPSS, oxide films, and nanostructures to the colourization of metal surfaces after laser structuring. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14083164/s1](https://www.mdpi.com/article/10.3390/app14083164/s1)]([https://www.mdpi.com/article/10.3390/app14083164/s1](https://www.mdpi.com/article/10.3390/app14083164/s1)). Figure S1: SEM micrographs of ps laser-structured CP Ti surfaces of regions shown on each image. The laser processing parameters indicated in Table 1 were applied to these regions. Figure S2: SEM images showing LIPSS on the laser-processed CP Ti surfaces of regions shown on each image after immersion.