Femtosecond Laser-Fabricated Multibioinspired Gradient Functional Surfaces for Bubble Transport and Collection

The manipulation of underwater gas bubbles offers potential for addressing pressing challenges such as energy shortages and oxygen harvesting in space. While substantial progress has been made in 1D bubble transport on asymmetric geometric-gradient surfaces and 2D penetration based on "bubble diode" type Janus surfaces, the integration of these functions, particularly for complex bubble manipulation under microgravity or against buoyancy, remains a challenge. Inspired by the hierarchical wettability gradients of cactus spines and the upper/lower surfaces of lotus leaves, we herein design and fabricate a directional transport channel with unidirectional penetration channels for gas bubbles. The influence of structural parameters on bubble motion and the performance of these channels under antibuoyancy conditions is systematically investigated. Moreover, a multifunctional integrated surface was developed through a simple fabrication strategy, enabling the simultaneous capture, directional transport, and collection of bubbles, and realizing complex 3D manipulation of bubbles in aqueous environments. In addition, the surface effectively captures, transports, and collects bubbles generated during water electrolysis. This work presents an integrated surface design for underwater bubble capture, transport, and collection, and offers a potential approach to bubble management in microgravity environments.