The effect of surface microstructures and surface compositions on the wettabilities of flower petals

The investigation of the surfaces of various flower petals indicates that most of the flower petals possess hierarchical micro- and nano-structures except for a few which possess only a smooth structure. However, their surface wettabilities are different, exhibiting from super-hydrophobic, hydrophobic to super-hydrophilic. SEM and XPS analysis demonstrate that such difference results from both the surface microstructures and surface chemical compositions. Surface roughness can effectively enhance the surface wettability, i.e., change hydrophobicity to super-hydrophobicity, and hydrophilicity to super-hydrophilicity. Surface chemical composition is also important to the surface wettability, i.e., materials with different surface energies can induce different surface properties.