Contact angle, adhesion and friction properties of micro-and nanopatterned polymers for superhydrophobicity

Abstract

Superhydrophobic surfaces have considerable technological potential for various applications due to their extreme water-repellent properties. A number of studies have been carried out to produce artificial biomimetic roughness-induced hydrophobic surfaces. It is not clear whether microstructures or nanostructures or their certain combination on the surface, are required for superhydrophobicity. A variety of micro- and nanopatterned surfaces of two different polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), were fabricated. We show how static contact angles vary with micro- and nanopatterns on the polymer surfaces. Based on the experimental data and a numerical model, the trends are explained. Tribological properties play an important role in many applications requiring water-repellent properties. Therefore, it is important to study the adhesion and friction properties of these surfaces that mimic nature. An atomic/friction force microscope (AFM/FFM) was used for surface characterization and adhesion and friction measurements. To further examine the effect of meniscus force and real area of contact, scale dependence is considered with the use of AFM tips of various radii. The effect of relative humidity is also investigated to study the environmental effects on adhesion and friction.