Stability of interfacial nanobubbles.

Interfacial nanobubbles (INBs) on a solid surface in contact with water have drawn widespread research interest. Although several theoretical models have been proposed to explain their apparent long lifetimes, the underlying mechanism still remains in dispute. In this work, the morphological evolution of INBs was examined in air-equilibrated and partially degassed water with the use of atomic force microscopy (AFM). Our results show that (1) INBs shrank in the partially degassed water while they grew slightly in the air-equilibrated water, (2) the three-phase boundary of the INBs was pinned during the morphological evolution of the INBs. Our analyses show that (1) the lifetime of INBs was sensitive to the saturation level of dissolved gases in the surrounding water, especially when the concentration of dissolved gases was close to saturation, and (2) the pinning of the three-phase boundary could significantly slow down the kinetics of both the growth and the shrinkage of the INBs. We developed a one-dimensional version of the Epstein-Plesset model of gas diffusion to account for the effect of pinning.