*3.1. Surface Characterization of Natural Leaves*

Figure 1 shows AFM images of the polished SS 316L control plate and *C. esculenta* and *C. aurea* natural leaves. AFM images of *S. molesta* could not be obtained due to the topographical features on the surface of the leaf, which prevented the tip from making close contact with the surface.

**Figure 1.** AFM images of a polished SS 316L (control) plate, *C. esculenta* and *C. aurea* leaves.

Contact angle measurements from the three natural leaves exhibited high hydrophobicity (contact angle > 120◦). The most hydrophobic leaf was *S. molesta*, followed by *C. aurea* and *C. esculenta* (Figure 2). The differences were statistically significant (*p* < 0.001).

**Figure 2.** Contact angle measurements of control (SS 316L) surface and natural leaves.

As for roughness of the natural leaves, *C. aurea* showed higher roughness than *C. esculenta* and the difference was statistically significant (*p* < 0.001, Figure 3). As already mentioned, roughness of *S. molesta* could not be determined by AFM.

**Figure 3.** Average roughness of control (SS 316L) surface and natural leaves.
