Effects of surfactant, pressure, temperature, domain size, and texture geometries on the longevity of superhydrophobic surfaces

We experimentally investigated the longevity of underwater superhydrophobic surfaces caused by gas diffusion under various conditions. The SHS was created on polydimethylsiloxane and had an array of micro-holes and micro-posts. Using a non-intrusive optical method, the SHS longevity was determined based on the percentage of surface area covered by gas. First, we found that with increasing surfactant concentration, the SHS longevity increased, suggesting that the accumulation of surfactant at the gas-liquid interface reduced the mass flux. Second, with increasing temperature, the SHS longevity reduced due to the increased diffusion coeffective. Third, with increasing pressure, the longevity of SHS gradually reduced due to an increased concentration gradient at the interface according to the Henry’s law. However, when the pressure is larger than a critical value, the SHS experienced a sudden transition to Wenzel state, probably due to the surface energy minimization. Moreover, the SHS longevity increased by changing texture geometries, including the texture height and the percentage of solid-liquid surface area (or solid fraction). Final, we found that the SHS longevity increased when reducing domain size. Overall, our results help to predict SHS longevity and inform the design of long-life SHS.