Extend Plastron Longevity on Superhydrophobic Surface Using Gas Soluble and Gas Permeable Polydimethylsiloxane (PDMS)

The gas (or plastron) trapped between micro/nano-scale surface textures, such as that on superhydrophobic surface, is crucial for many engineering applications, including drag reduction, heat and mass transfer enhancement, anti-biofouling, anti-icing, and self-cleaning. However, the longevity of plastron is significantly affected by gas diffusion, a process where gas molecular slowly diffuses into ambient liquid. In this work, we demonstrated that plastron longevity can be extended using a gas soluble and gas permeable polydimethylsiloxane (PDMS) surface. Two types of surface textures: micro-posts and micro-holes, were fabricated on PDMS. The textured PDMS surfaces were immersed in an undersaturated liquid, and the longevity of plastron trapped on the PDMS was measured using an optical method. Our results showed that the plastron longevity increased with increasing the thickness of PDMS surface, suggesting that gas initially dissolved between the polymer chains was transferred to the liquid and delayed the wetting transition. Numerical simulations confirmed that a thicker PDMS material released more gas across the PDMS-liquid interface and resulted in a higher gas concentration near the plastron. Furthermore, we found that the plastron longevity increased with increasing pressure difference across the PDMS material, indicating that the plastron was replenished by the gas injected through PDMS. With increasing pressure, the mass flux caused by gas injection exceeded the mass flux caused by the diffusion of gas from plastron to liquid. Overall, our results provided new solutions to extend the plastron longevity and will have significant impacts to applications where a stable plastron is desired.