Metastable and Ultimate Stable States of Underwater Superhydrophobicity

Underwater superhydrophobic surface has many great performances, which are attributed to a gas cushion entrapped in the microstructures. However, many factors lead to the wetting transition and collapse of the gas cushion. In the current work, we explore the underlying mechanisms of wetting transition of underwater superhydrophobicity and demonstrate the existence of an ultimate stable state on underwater superhydrophobic surfaces.

In situ observations are used to quantify the whole wetting transition process. The metastable state is obtained. A diffusion-based mode is developed to predict the evolution process and the longevity of the metastable states. We theoretically demonstrate a both mechanically and chemically equilibrated superhydrophobic state, which is denoted as an ultimate stable underwater superhydrophobic state. The long-term stable underwater superhydrophobic state is achieved experimentally under different liquid pressures and moderate flow rates. Moreover, with experiments on fresh lotus leaves, we prove that the ultimate stable state can also be realized on randomly rough superhydrophobic surfaces. The finding here contributes to a better understanding of the fundamental mechanism of wetting transition and long-term stability of underwater superhydrophobicity.