Tribology of water on graphene and silicon superhydrophobic nanostructured surfaces

Since the advent of the centrifugal adhesion balance, it was recently shown by Tadmor et al. that the lateral force required to slide a drop placed on a surface is a strong function of the drop/surface contact time prior to sliding. In other words, the lateral retention force increases with the resting time. The reason for such observation was related to the Shanahan–de Gennes deformation occurring at the three-phase contact line, which favors a stronger intermolecular interaction between liquid and solid molecules. Tribological studies on (1) graphene/water and (2) nanostructured superhydrophobic/water systems are presented in this chapter. The first system shows no variation in lateral force with increasing resting time. We attribute this behavior to its chemical homogeneity and stability. The second system gives a confirmation of surface deformation at the three-phase contact line for rigid surfaces as displayed by the decrease in hydrophobicity or increase in retention force with the accumulative resting time.