fig6

Figure 6. (A) Schematic of the force measurements between two bubbles using AFM bubble probes; (B) Force-separation curves between two air bubbles in different pH conditions; (C) The measured pH range of bubble coalescence for different types of gases; (D) Time variation of the force between two bubbles (radius ~65 μm) at an approach velocity of 1 μm·s^-1 and the theoretical fitting results; (E) The disjoining pressure in a thin liquid film between two approaching bubbles caused by surface interactions; (F) The profiles of two approaching bubbles as the function of separation distance. The open symbols are the experimental data, and the solid curves are the theoretical data. Reproduced from ref.^[79] for (A-C), Copyright 2011, John Wiley & Sons, Inc.; and from ref.^[80] for (D-F), Copyright 2017, John Wiley & Sons, Inc. AFM: Atomic force microscope.