Abstract: Bioinspired superhydrophobic surfaces have been used for drag reduction. However, the secondary structures and the air cushions on these surfaces could be destructed in a flow, losing the effect of drag reduction. Here, a stainless-steel surface with mushroom-like cross-section (SMC) and diamond cavities (SMC_D) having a drag reduction rate up to 19.37% is developed by 3D printing. The concealed re-entrant structures in SMC_D prevent the infiltration of water into the chamber and form gas cushions, which converts the sliding friction at liquid-solid interface into rolling friction at liquid-gas interface, realizing the drag reduction. Meanwhile, 98.3% of air can be maintained in the chamber in a flow with Reynolds number (Re) of 9?×?10⁵, ensuring the drag reduction in a high-velocity flow. Moreover, the continuous top stainless-steel surface and the supporting mesh network protect the critical re-entrant structures, ensuring the robustness of SMC. With the bioinspired design and one-step additive manufacturing process, SMC holds great potential for large-area production and applications requiring robust drag reduction.

Key words: Additive manufacturing')">Additive manufacturing, Bioinspired, Re-entrant structure, Hydrophobicity, Drag reduction