Ultrahigh Efficient Collection of Underwater Bubbles by High Adsorption and Transport, Coalescence, and Collection Integrating a Conical Arrayed Surface

Abstract

The capture and utilization of underwater fuel bubbles such as methane can alleviate the greenhouse effect, solve the global energy crisis, and possibly improve the endurance of underwater equipment. However, previous research routinely failed to achieve the integrated process of continuous adsorption, transportation, and collection of bubbles limited by the trade-off between the bubble adhesion and transport efficiency dependent on interfacial pinning, tremendously hindering the direct capture and utilization of underwater fuel bubbles. To break through this bottleneck, a magnetic-guided conical arrayed surface (CAS) associated with a laser etching technique is fabricated conveniently to realize superhydrophobicity. The bubbles on laser-etched CAS have higher adhesiveness and low-pinning transport compared with those on the nonlaseretched surface. Intriguingly, the gas film adsorbed within the CAS seems to be a gas channel, which accelerates the bubble coalescence and fast spreading to eventually realize the integration of transport, coalescence, and collection. The dynamic behaviors of bubble adsorption, transportation, and coalescence on CAS are probed to reveal the mechanism of the gas filmgenerating process within conical arrays. Furthermore, a novel underwater bubble-collecting device with multiangled CAS is proposed to achieve multidirectional capture, highly efficient transportation, and collection of rising bubbles. The results advance our understanding of dynamic behaviors of bubbles at solid−liquid interfaces and facilitate design and manufacturing of an apparatus for bubble collection.

Drag reduction and antifouling of a spontaneous fast moving air film

“…Thus, the first problem to be solved here is how to obtain the spontaneous high-speed transportation of a single air bubble. Actually, there were several methods to realize the spontaneous transportation of an air bubble, such as using 3D structures, 30–33 slippery grooves, 34–37 rectangular patterns, 38–40 and wedge-shaped patterns. 41–44 However, the transportation distance and velocity for the air bubble on those surfaces were not long or fast enough.…”

“…To confirm that our proposed SBP had faster transportation velocity than existing spontaneous air bubble transportation methods, we compared the SBP with these methods, as shown in Figures 2(e) and S11 . 30–44 It was surprising that the transportation velocity of the air bubble on the SBP was almost 1.4–296 times as high as those on 3D structures, slippery grooves, rectangular patterns, or wedge-shaped patterns, which meant that the transportation velocity of the air bubble on the SBP was the fastest among the existing spontaneous air bubble transportation methods. Specifically, the details of the above spontaneous air bubble transportation methods are shown in Table S4†.…”