## 3 Results
### Coatings' Characterization
#### 3.1.4. Wettability  
Due to the superhydrophobicity of coatings, the CA measurements on 3D samples (A1 and A2) have been impossible to be perform; the water droplets, in fact, do not retain on the surfaces but quickly glide away. Therefore, for A1 and A2 samples, the success of the coatings' application and then the superhydrophobicity of surfaces was assessed by observing that the water droplets slipped rapidly away from the A1 surface (right side of Figure 6), whereas they adhered to the AR surface (left side of Figure 6). The same behavior was observed for the A2 sample (data not shown for brevity). Instead, Figure 7 shows a representative picture of 3 \(\upmu\)L of water droplets on all flat surfaces, i.e., CR, C1, C2, SR, S1, and S2 samples. The CA measurements and the corresponding optimized values are listed in Table 2, whereas the SFE, W\({}_{\text{A}}\), and SP of coated and reference surfaces are displayed in Figure 8.  
Figure 6: Images sequences of water droplets dropping on AR (**left**) and A1 (**right**) surfaces.  
As reported in Table 2, all coated surfaces were superhydrophobic. However, some little difference in the wettability of the samples prepared by applying the same coating on different substrates could be noticed. In fact, the CA of S1 and S2 were slightly lower than those measured for C1 and C2, respectively. This could be ascribed to slightly different morphologies observed for C and S samples, also responsible for the different measured roughness (Figure 3). In fact, as reported in Section 3.1.3 and in Figure 5, in the C samples, the micro-aggregates emerge more than occurred for the S samples, thereby improving the roughness (Figure 3) and the Cassie-Baxter state, and reducing the wettability as a consequence. This is in line with that observed by other authors who found such increased contact angles with the increased surface roughness [34].  
The SFE of reference samples SR and CR were 35 mN/m (\(\gamma_{\mathrm{s}}\)P = 2 mN/m and \(\gamma_{\mathrm{s}}\)D = 33 mN/m) and 42 mN/m (\(\gamma_{\mathrm{s}}\)P = 5 mN/m and \(\gamma_{\mathrm{s}}\)D = 36.5 mN/m), respectively, whereas the values of 79 and 93 mN/m were found for the corresponding W\({}_{\mathrm{A}}\). After the application of the coating, we observed a reduction of 99% in SFE in the C samples (0.3 mN/m for both C1 and C2), and 95-98% for the S samples (1.6 mN/m for S1 and 0.8 mN/m for S2). Accordingly, the W\({}_{\mathrm{A}}\) was reduced by 93-94% for the C samples (6.8 mN/m for C1 and 5.5 mN/m for C2) and by 86-92% for the S samples (11.1 M/m for S1 and 6.3 mN/m for  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Contact Angle [DEG]** & \multicolumn{2}{c}{**H\({}_{2}\)O**} & \multicolumn{2}{c}{**CH\({}_{2}\)I\({}_{2}\)**} & \multicolumn{2}{c}{**HCONH\({}_{2}\)**} \\ \hline  & **Measured** & **Optimized** & **Measured** & **Optimized** & **Measured** & **Optimized** \\ \hline CR & \(70\pm 4\) & \(74\) & \(48\pm 6\) & \(46\) & \(62\pm 3\) & \(62\) \\ SR & \(82\pm 3\) & \(85\) & \(55\pm 5\) & \(52\) & \(69\pm 6\) & \(75\) \\ C1 & \(161\pm 7\) & \(155\) & \(146\pm 8\) & \(148\) & \(152\pm 8\) & \(153\) \\ S1 & \(157\pm 9\) & \(148\) & \(140\pm 10\) & \(130\) & \(136\pm 6\) & \(142\) \\ C2 & \(164\pm 6\) & \(157.5\) & \(141\pm 8\) & \(148.5\) & \(137\pm 10\) & \(141.5\) \\ S2 & \(161\pm 5\) & \(156\) & \(136\pm 7\) & \(139\) & \(139\pm 11\) & \(150\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Experimentally measured CA; the optimized values are also reported.  
Figure 8: SFE, WA, and SP of SR, S1, and S2 (a), and of CR, C1, and C2 (b) samples.  
Figure 7: Water CA measurements on CR, C1, and C2 (top) and SR, S1, and S2 samples (bottom).  
S2). With respect to CR, SP decreased by 75% and 100% in C1 and C2, from 12 to 3 and 0, respectively, whereas it was reduced by 83% and 17% for S1 and S2, from 6 to 1 and 5, respectively, with respect to SR.