*3.1. Surface Morphology and Wetting Behavior*

Figure 3 shows the surface morphologies and wetting behaviors of the SLM-ed SS samples treated with different parameters (Table 2). The polished original sample showed a smooth surface with only a few defects (Figure 3a), and the initial CA was 77◦ . Figure 3b shows the surface morphologies of the sample ablated by the femtosecond laser in air (FLAR). To describe the different samples concisely, a series of abbreviations were used (Table 3). The rough surface was covered by a large number of nanoparticles with a size of about 100 nm, and the CA was decreased to 9◦ . When the femtosecond laser processing was conducted in an argon (FLAN) atmosphere (Figure 3c), the surface with a CA of 10◦ showed an obvious periodic structure. The structure with a period of about 300 nm was perpendicular to the laser polarization direction. This periodic structure may be attributed to the interference between the plasma and the incident laser [17,18]. Moreover, argon can avoid the oxidation of materials during femtosecond laser texturing. After the laser processing in air and argon atmospheres, the surface roughness (Sa) was reduced from 1.709 µm to 1.299 µm and 1.108 µm (Figure 3e).

**Table 3.** Sample labels.


Preparing a periodic micro-nanostructure is usually necessary to obtain an SH surface. As shown in Figure 3d, with the increased laser fluence and scanning spacing, micro-scale grooves with a width of 10 µm were observed on the laser-ablated surface (Figure 3d). The textured surface manifested superhydrophilicity with a CA of nearly 0◦ . After the annealing process, the SH surface showed a high CA of 154◦ and a sliding angle of 3◦ (Figure 3d). The advancing and receding CAs were 151.03◦ and 146.18◦ , respectively, resulting in a CA hysteresis of 4.85◦ .

1.709 μm to 1.299 μm and 1.108 μm (Figure 3e).

**Figure 3.** Surface structures of (**a**) original, (**b**) FLAR, (**c**) FLAN, and (**d**) SH samples. (**e**) Crosssection dimensions of original, FLAR, and FLAN samples. (**f**) Wetting behaviors of original, FLAR, FLAN, and SH samples. **Figure 3.** Surface structures of (**a**) original, (**b**) FLAR, (**c**) FLAN, and (**d**) SH samples. (**e**) Cross-section dimensions of original, FLAR, and FLAN samples. (**f**) Wetting behaviors of original, FLAR, FLAN, and SH samples.

a smooth surface with only a few defects (Figure 3a), and the initial CA was 77°. Figure 3b shows the surface morphologies of the sample ablated by the femtosecond laser in air (FLAR). To describe the different samples concisely, a series of abbreviations were used (Table 3). The rough surface was covered by a large number of nanoparticles with a size of about 100 nm, and the CA was decreased to 9°. When the femtosecond laser processing was conducted in an argon (FLAN) atmosphere (Figure 3c), the surface with a CA of 10° showed an obvious periodic structure. The structure with a period of about 300 nm was perpendicular to the laser polarization direction. This periodic structure may be attributed to the interference between the plasma and the incident laser [17,18]. Moreover, argon can avoid the oxidation of materials during femtosecond laser texturing. After the laser processing in air and argon atmospheres, the surface roughness (Sa) was reduced from
