Fig. 5.

Robustness of the superhydrophobicity of the surface with covalent bonding and vulnerability of the superhydrophobicity of the surface without covalent bonding. (a) Before any rubbing, a water droplet could easily slide down off the covalent bonded superhydrophobic silicone elastomer membrane wrapping a finger, as indicated by the yellow arrows in different frames and the yellow circle in the last frame. (b) Rubbing was performed, making sure that the superhydrophobic elastomer received large amount of shear stress. (c) After the rubbing process, the superhydrophobicity of the elastomer membrane was kept, as shown the fast sliding of water droplet dispensed on the membrane. (d) Before rubbing, water droplet could slide down off the non-covalent bonded superhydrophobic elastomer membrane. (e) A same rubbing process to that in (b) was conducted. (f) After the rubbing process, water droplets with the same volume to that in (d) stuck firmly to the post-rubbed surface, indicating compromised superhydrophobicity.