Impact of the Undersaturation Level on the Longevity of Superhydrophobic Surfaces in Stationary Liquids.

Although the longevity of superhydrophobic surface (SHS) induced by diffusive gas transfer has been extensively studied, the scaling relation between SHS longevity and undersaturation level of the liquid is still an open question. In this study, we address this question by performing experiments where the plastron decay is visualized by a nonintrusive optical technique based on light reflection, the gas diffusion is introduced by using liquid with low dissolved gas concentrations, and the SHS longevity is measured based on the status of gas on the entire surface. We find that the SHS longevity ( t f ) follows a scaling relation: t f ∼ (1 - s )-2 , where s is the ratio of the gas concentration in liquid to that in the plastron. This scaling relation implies that as the gas is dissolving into the liquid, mass flux J reduces with time as J ∼ t -0.5 . Furthermore, we find that the diffusion length L D reduces as the undersaturation level increases, following the scaling relation of L D ∼ (1 - s )-1 . Lastly, we show that an SHS with a greater texture depth has a longer longevity and a larger L D . Our results provide a better understanding of SHS longevity in undersaturated liquid.