Wear-resistant rose petal-effect surfaces with superhydrophobicity and high droplet adhesion using hydrophobic and hydrophilic nanoparticles

Surfaces exhibiting the so-called "petal effect" (superhydrophobicity with high droplet adhesion) have potential for applications such as the transport of small volumes of liquid. It is known that the microstructure pitch value and nanostructure density are important in achieving this effect, both in rose petals themselves and in synthetic petal-effect surfaces. However, the effect of the surface energy of materials on these values has not been systematically studied. In addition, wear resistance, which is critical for industrial applications, has rarely been examined for petal-effect surfaces. In this study, surfaces of varying microstructure pitch and nanostructure density were fabricated by depositing ZnO nanoparticles onto micropatterned substrates. The prepared surfaces were then modified with octadecylphosphonic acid (ODP) in order to hydrophobize the ZnO nanoparticles. The wettability of the surfaces was characterized both before and after ODP modification. The effect of hydrophobizing the nanostructure was examined with regards to the values of microstructure pitch and nanostructure density necessary to achieve the petal effect. In addition, to study wear resistance for industrial applications, a wear experiment was performed using an atomic force microscope (AFM).