  Gaseous layers (plastrons) trapped on the surfaces of immersed hydrophobic
surfaces are critical for their function. Fibrillar morphologies offer a
natural pathway, yet they are limited to a narrow range of liquid-surface
systems and are vulnerable to pressure fluctuations that irreversibly destroy
the plastron. Inspired by the convexly grooved surfaces of water fern
(Salvinia) leaves that support their fibrous outgrowths, we study the plastron
formation on 3D-printed dual-scale surfaces with elliptical interconnected
microgrooves. The groove curvature stabilizes a seed gas layer (SGL) that
facilitates plastron formation and restoration for all immersed hydrophobic
surfaces. Computations and theoretical calculations reveal that the SGL storage
capacity that sets the plastron robustness follows from the liquid menisci
adaption to the groove geometry and pressure, and it can be further tuned using
separated grooves. Our study highlights groove convexity as a key morphological
feature for the design of multi-scale immersed surfaces for robust
superhydrophobicity.
