Interface-controlled capture, transport, and collection of underwater bubbles: current research and applications

The capture, transport, and collection of underwater methane and other fuel gases are essential for addressing global environmental and energy challenges. Methane, a potent greenhouse gas, has a global warming potential that is 25 times greater than CO₂, making underwater methane leaks a severe threat to climate stability and global health, and a challenge to China's dual carbon targets. In addition, as the US, Europe, and Japan advance their strategic goals for ocean exploration robots, China urgently needs to develop its underwater robots. Current equipment, reliant on cables and/or batteries limits endurance, Nonetheless, capturing underwater fuel gases offers opportunities for energy self-sufficiency and extended operational capabilities. The capture and utilization of underwater methane and other gases are vital for reducing greenhouse gas emissions, promoting environmental health, addressing energy shortages, and enhancing the endurance of underwater equipment.

Recent advances in bubble capture, transport, and collection stem from interdisciplinary research merging micronanotechnology, material science, and fluid mechanics. Researchers have employed noncontact techniques, including electric fields, magnetic fields, and sound waves, to improve bubble stability and optimize their movement. Studying bubble physicochemical properties has helped overcome challenges such as rupture, coalescence, and trajectory oscillations caused by external disturbances, including fluid flow and temperature changes. Micronanotechnology has enabled precise manipulation over bubble interfacial behavior by leveraging surface structures and interfacial energy. Techniques such as using hydrophobic surfaces and capillary forces have improved bubble capture, whereas microstructured surfaces and optimized fluid channels allow precise, efficient transport. Advanced materials, including responsive polymers, further improve dynamic control of bubble flow paths, increasing overall efficiency. Notable progress has been made in gas collection. Porous materials and functionalized membranes now enable efficient gas separation and aggregation. Biomimetic structures inspired by natural systems, along with superhydrophobic surfaces, have improved bubble capture and stability, presenting promising solutions for integrated gas recovery systems.

Despite these advancements, considerable challenges remain. Bubbles in underwater environments are highly vulnerable to external disturbances, making their stable capture and efficient transport difficult. Furthermore, interactions between bubbles of varying sizes during transport can reduce separation efficiency and directional control, whereas inconsistent aggregation during collection further limits overall efficiency. Future research should address these challenges by integrating nanomaterials and advancing interfacial modification techniques for improved selectivity and precision of bubble capture in complex environments. Analyzinging the relationship between bubble properties and environmental factors through simulations and experiments can refine strategies for trajectory control, size classification, and stability. Moreover, the development of novel materials, including superhydrophobic and multifunctional surfaces, combined with innovations in external field applications (electric, magnetic, and optical), offers tremendous potential to revolutionize underwater gas recovery systems. These approaches, combined with advancements in theoretical models and experimental techniques, hold the promise of groundbreaking improvements in the efficiency and controllability of gas capture, transport, and collection processes. These efforts will support sustainable energy utilization and contribute to mitigating climate impacts and advancing ocean exploration technologies.