Theoretical Investigation of Capture, Collection, and Targeted Transfer of Underwater Gas Bubbles Using Janus‐Faced Carbon Cloth

Recently, a straightforward method for the preparation of a Janus carbon cloth (Janus‐CC) is reported. The method relies on polydimethylsiloxane (PDMS) coating, followed by flame exposure of one face of the PDMS‐coated CC. The nonexposed to the flame face of the Janus‐CC is superhydrophobic, while the exposed to the flame face is superhydrophilic. Underwater, the superhydrophobic face shows superaerophilicity, while the supherhydophilic face shows superaerophobicity. A tethered gas bubble onto the superhydrophobic face has a paraboloid of revolution shape due to the cohesion force between the bubble and the gaseous film. Herein, the geometrical parameters of underwater tethered gas bubbles onto the Janus‐CC are obtained, and the tendency of Janus‐CC for capturing of bubbles is interpreted based on the derived Gibbs free‐energy change equation. It is experimentally observed that a small sited bubble moves toward the bigger one through the formed gaseous film, but this observation cannot be interpreted based on the classical Young–Laplace equation because here the smaller bubble has bigger curvature radius. Herein, a modified Young–Laplace equation is derived and applied for interpretation of the movement of a small bubble toward the bigger one. Also, the buoyancy force for a sited bubble on the gaseous film is discussed.