A Robust Hybrid Skeleton for Omnidirectional Underwater Bubble Collection

Underwater bubble capture using superhydrophobic surfaces (underwater superaerophilicity) is vital for the survival of certain aquatic organisms and has great potential for application in industry. However, surface-exclusive coatings often demonstrate limitations in bubble capture efficiency since they are restricted to single-direction capture and face a trade-off between capture and mobility on the same surface. Additionally, this kind of coating usually fails due to the irreversible transition from the Cassie-Baxter state to the Wenzel state, leading to wetting. Current research mainly focuses on metals and polymers, which lack the durability to endure harsh underwater environments and thus limits their real-world applications. Organisms with a bone-muscle structure exhibit multifunctionality and high durability. Inspired by this, we report for the first time a superhydrophobic hybrid skeleton─featuring a bone-like support of in situ-grown mullite whiskers and a muscle-like functional phase of heat-solidified silicone oil─for underwater bubble collection. This hybrid skeleton demonstrates excellent chemical, thermal, and mechanical stability since it can retain superhydrophobicity even when submerged in strong base, acid, or salt water for 8 h, heated at 450 °C for 4 h, or crushed into powder. Our findings demonstrate that the hybrid skeleton enables omnidirectional underwater bubble collection and even resists buoyancy to facilitate continuous bubble capture and transport. Furthermore, the hybrid skeleton features a pore size of ∼1 μm, more than 100 times smaller than previously reported values, which extends the liquid entry pressure from a few centimeters to approximately 30 m. This study provides a practical solution for underwater bubble collection, overcoming the constraints of surface-only modifications and the material limitations of polymers and metals prevalent in current research.