Longevity of plastron layer in underwater vapor stable superhydrophobic surfaces under different atmospheric condition and drag measurements

The use of superhydrophobic surfaces for marine and submarine vehicles aids in drag reduction. The drag reduction is achieved due to the formation of a thin layer of air called a "plastron" inside the textured surface between the solid and liquid phases. But the plastron layer is unstable due to the effects of hydrostatic pressure, diffusion of air in water and instability due to the shear nature of the flow over the surface. It was attempted to make vapor stable surfaces by varying the surface morphology of micro, nano, hierarchical and re-entrant geometries, to increase the longevity of the plastron layer and reduce drag under flow conditions. A low-cost scalable fabrication method was utilized to make superhydrophobic surfaces with highly re-entrant geometry and hierarchical surface morphology. Fabricated surfaces showed increased longevity of the plastron layer at different pressures and temperature due to the increased stability of air or vapor in the textures. Initial results indicate significant drag reduction on these surfaces under laminar flow conditions at atmospheric pressure.