Bubble adhesion dynamics on solid surfaces: Interfacial behavior, force, and energy perspectives using a self-developed dynamic force testing system

Bubble-solid surface adhesion is crucial for industrial processes such as wastewater treatment, and the separation of minerals, plastics, and biomass. In this paper, a novel dynamic force testing system was developed to provide a detailed understanding of bubble-solid adhesion dynamics by simultaneously collecting "time-displacementforce" signals and capturing real-time images. The interfacial behavior and force mechanisms of bubble adhesion to solid surfaces with varying hydrophobicity were investigated. Higher hydrophobicity results in more pronounced "snap-in" adhesion and greater adhesion strength. Instead of fully detaching, bubble breaks at the capillary neck and leaves a microbubble on the solid surface, whose size increases with hydrophobicity, indicating different interfacial behaviors in subsequent reaction. The evolution of Laplace force and surface tension force was further analyzed and the toroidal approximation shows over 60 mu N error in Laplace force calculation for large bubble deformations. Thus, for the first time, the "gorge" method was employed to calculate the bubble adhesion force in the presence of a capillary neck. Error analysis indicates that this method, while maintaining simplicity, achieved higher accuracy (lower error) by calculating the Laplace force based on the neck area and accounting for the surface tension force along the tangent at the neck. Energy analysis show that the detachment energies in the stretching and sliding phases correspond to the energy barrier to be overcome for detachment and the "effective work" of interfacial change, respectively. This provides new insights into detachment mechanisms and industrial process modelling, such as flotation.