RESUMEN
Understanding the wetting properties of chemically modified inorganic surfaces with random nanoscale topographies is of fundamental importance for diverse applications. This issue has hitherto continuously been the subject of considerable controversies. Herein, we report a thorough investigation of the wettability-topography-chemistry balance for a nanostructured surface with random topography, the main challenge being decoupling topography from surface chemistry. For this purpose, we use a superficially nanostructured aluminum substrate chemically modified by fatty acid monolayers. From atomic force microscopic data, we extract a variety of parameters describing the surface topography by means of variogram calculations, a method originally developed by geostatisticians to explore large surfaces. Moreover, by using log and power transforms, we establish a consistent relationship relating wettability, topography, and surface chemistry. Interestingly, we demonstrate that the water contact angle comprises a contribution due to the surface composition, originating from hydrophobization through alkyl chains, and a contribution due to the surface topography, particularly its stochastic feature. This model is valid in the Wenzel region; it provides guidelines for tuning the wetting properties of inorganic surfaces with random nanoscale topographies.
RESUMEN
Herein, we report the coating of a surface with a random nanoscale topography with a lipid film formed by an anchoring stearic acid (SA) monolayer and phospholipid (DPPC) layers. For this purpose, different procedures were used for phospholipid coating, including adsorption from solution, drop deposition, and spin-coating. Our results reveal that the morphology of the obtained lipid films is strongly influenced by the topography of the underlying substrate but also impacted by other factors, including the coating procedure and surface wettability (modulated by the presence of SA). These coated surfaces showed a remarkable antifouling behavior toward proteins, with different yields of repellency (Yrp) depending on the amount/organization of DPPC on the nanostructured substrate. The interaction between the proteins and phospholipids involves a partial detachement of the film. The use of characterization techniques with different charcateristics (accuracy, selectivity, analysis depth) did not reveal any obvious vertical heterogenity of the probed interface, indicating that the lipid film acts as a nonfouling coating on the whole surface, including the outermost part (nanoprotrusions) and deeper regions (valleys).
