Controllable penetration of underwater bubble via an integrated Janus mesh

Abstract

Underwater bubble dynamics and manipulation have emerged as an important research hotspot for boiling heat transfer, as well as bubble transport and collection. However, achieving switchable and controllable penetration of bubbles remains a challenge. In this work, by using laser etching and post-modification, Janus meshes with four pore sizes ranging from micron to millimeter sizes were prepared for unidirectional penetration of bubbles. Although typical unidirectional penetration was observed in these Janus meshes of four pore sizes, they all exhibit easy passage of bubbles without the desired controllable and switchable properties for penetration behaviors. The Janus mesh (with a pore size of ∼930 μm) is respectively superimposed with hydrophilic meshes of different pore sizes as integrated meshes. Interestingly, the integrated meshes take a penetration behavior transition of the bubbles from prohibited to a critical state, and easy permeation by changing the pore size and thickness of the hydrophilic mesh. The controllable permeability of the integrated mesh is attributed to different levels of resistance (i.e., the gas pressure at the upper interface, Pup) before acquiring a Laplace pressure. The integrated mesh can function as a bubble switch, offering a flexible and effective strategy for controllable penetration of underwater bubbles.