## 2 Results and Discussion  
### Characterization  
The morphological properties and surface elemental compositions of four kinds of wires were characterized by SEM, EDS, and XRD. As can be seen in Figure 1(a1), the pristine wire had a smooth surface with few grooves. After hydrothermal digestion in strong acids at a high temperature, some small holes appeared, the surface was scattered with flower-like TiO\({}_{2}\) nanostructures in Figure 1(b1), and the increase in roughness led to an increase in adsorption sites in the extraction. Further chemical modification with a low surface energy caused an observed decrease in surface wettability, which formed a superhydrophobic surface in Figure 1(c1). After UV irradiation for Ti wire \(c\), the superhydrophobic surface transformed to superhydrophobic in Figure 1(d1). As seen in the cross-section of the wires in Figure 1(a2), no coating was observed for the smooth pristine wire. For the modified wires, the thickness of the coating was thin due to the formation of multiple layers of nanoflowers on the surface in Figure 1(b2-d2). There were some internal and external gaps in the nanoflower clusters. This coating morphology probably increases its specific surface area, improving the mass transfer and extraction efficiency. Figure 1: SEM for the pristine wire (**a1,a2**), the superhydrophilic wire (**b1,b2**), the superhydrophobic wire (**c1,c2**), and the UV-irradiated superhydrophobic wire (**d1,d2**). EDS further proved the elemental changes for four kinds of Ti wires in Figure 2. The pristine Ti wire was mainly composed of Ti and O elements (a). After chemical etching, the oxygen element content increased from 27.7 to 50.2% (b). Carbon, silicon, and fluorine elements were observed after further modification of FOTS, which demonstrated thin organic films surrounding the Ti wire surface (c). Further UV irradiation led to the formation of hydrophilic domains on the TiO\({}_{2}\) surface. When photosensitive TiO\({}_{2}\) on the wire surface is irradiated by UV light, pairs of electron holes appear on its surface, which can react with lattice oxygen to form surface oxygen vacancies. More monolayers and multilayers of water molecules can be kinetically attached to these vacancies by molecular adsorption. It was proven by the increase in oxygen element from 42.8 to 50.0% (d). XRD was used to investigate the crystal structure and phase of four kinds of Ti meshes. Figure 3 presents the XRD patterns of Ti substrates with different surface wettabilities. The samples were in the anatase phase, and the diffraction peaks were indexed to that of anatase (JCPDS No. 21-1272) [32]. No characteristic peaks from impurities were detected within experimental error, indicating the formation of anatase nanostructures. Figure 3: XRD patterns of Ti substrates. Symbol identification: **(a)** the pristine mesh, **(b)** the superhydrophobic mesh, **(c)** the superhydrophobic mesh, and **(d)** the UV-irradiated superhydrophobic mesh. Figure 2: EDX for the pristine wire (**a**), the superhydrophobic wire (**b**), the superhydrophobic wire (**c**) and the UV-irradiated superhydrophobic wire (**d**). In the 20 scan range 10\({}^{\circ}\)-100\({}^{\circ}\), all show characteristic peaks of Ti(100), Ti(002), Ti(101), Ti(102), Ti(110), Ti(103), Ti(112), and Ti(201) at 35.1\({}^{\circ}\), 38.4\({}^{\circ}\), 40.2\({}^{\circ}\), 53.0\({}^{\circ}\), 62.9\({}^{\circ}\), 70.6\({}^{\circ}\), 76.2\({}^{\circ}\), and 77.3\({}^{\circ}\), respectively. These data for the pristine (a) are in good agreement with the Ti crystallographic data (Reference code:00-001-1198).