*2.4. Soft Lithography*

For the three experimental groups, the corresponding natural leaves were cut in 5.0 cmdiameter segments. These fragments were located at the bottom of silicone containers with the lamina of the leaf facing upward. Polydimethylsiloxane (PDMS, Silastic T-2, Dow Corning Corporation, Midland, MI, USA) was used to duplicate the topography of each leaf. To obtain the stamp, PDMS was prepared according to the manufacturer and was poured to cover each fragment. Polymerization for 24 h was allowed, followed by further heat treatment at 80 ◦C for 3 h to finish the process. PDMS stamps containing the topography from each leaf were obtained. To transfer the topography from each stamp to the corresponding SS 316L plate, a drop of 7 μL of silica sol was placed on the SS surface, the stamp was placed on top of the drop and gentle pressure was applied to distribute the sol throughout the surface. Gelation was allowed for 4 h at RT and then the stamp was removed. The plates from the experimental groups were subjected to heat treatment at 450 ◦C for 30 min. After this procedure, three experimental groups were obtained (one group per topography).
