Bioinspired Rose-Petal-Like Substrates Generated by Electropolymerization on Micropatterned Gold Substrates

Surfaces with high water-adhesion properties are promising materials for different applications in the field of water treatment and management, such as for water-harvesting systems or oil/water separation membranes. Herein, we developed rose-petal-like substrates that demonstrate interesting parahydrophobic character. This bioinspired material mimics the natural substrate thanks to a combination of two fabrication steps: (1) micropatterning to create a microstructured gold-coated substrate consisting of square pillars and (2) an electropolymerization process generating nanostructures over the micropillars. Judicious choice of the micropatterning specifications (pillar diameter and pitch), the type of electropolymerizable monomer, and the electrochemical parameters produces a material with both extremely high water contact angles (up to 160°), while retaining a remarkably high water-adhesion level. Our study suggests that a composite interface is expressed by the existence of the Wenzel state on the micropillars and the Cassie-Baxter state between the pillars ("Cassie-filled nanostructure"), as observed during our contact-angle measurements. Indeed, we show that the pitch should be small to obtain the optimal micropillar surface density. Moreover, a relatively low deposition charge of approximately 50 mC cm^-2 is preferable for coating the square pillars exclusively with nanostructures.