Effects of surface wettability on gecko adhesion underwater

- A theoretical model is established in order to explain the abnormal gecko adhesion on different substrates underwater.
- It is found that gaseous capillary force dominates gecko adhesion underwater.
- Robust adhesion on hydrophobic substrates but weak adhesion on hydrophilic ones could be realized by geckos underwater.
- The multiple fibrillar adhesion structure can enhance gecko adhesion on both dry and wet surfaces.