Stability mechanisms of surface nanobubbles

Surface nanobubbles, as nanoscale gaseous domains spontaneously formed at solid-liquid interfaces, exhibit significant potential applications in the biomedical field due to their unique nanoscale size effects, rapid dynamic response characteristics, and favorable biocompatibility. In ultrasonic imaging, surface nanobubbles enhance tissue acoustic contrast by generating strong harmonic scattering signals through nonlinear oscillation under stable cavitation. In antibacterial disinfection applications, the rupture of surface nanobubbles generates a transient high pressure, which synergizes with oxidative damage mediated by reactive oxygen species /hydroxyl radicals to achieve efficient bacterial inactivation. However, in physiological environments, blood flow shear stress and pH fluctuations may induce premature rupture of surface nanobubbles, leading to imaging signal attenuation or risks of non-specific tissue damage, rendering their stability a critical factor determining functional efficacy and biosafety. Notably, the experimental observation of surface nanobubble lifetimes (ranging from hours to days) significantly contradicts the dissolution behavior within microseconds predicted by classical thermodynamic theory, which urgently demands the construction of theoretical models of stability. Although existing theoretical modelshave elucidated the stability mechanisms of surface nanobubbles from multiple perspectives, they arelimited by the lack of intrinsic correlation and inherent limitations, thereby restricting targeted optimization of stability: the contamination barrier model emphasizes that surfactant adsorption inhibits gas diffusion; the dynamic equilibrium model explains that stability arises from the dynamic balance of gas exchange at the gas-liquid interface; the contact line pinning model reveals that substrate heterogeneity constrains the evolution of the three-phase contact line; the local supersaturation model proposes that local high-concentration gas layers formed by substrate adsorption delay dissolution; the interfacial charge enrichment model suggests that electrostatic pressure from the double layer counteracts the Laplace pressure driving dissolution; the internal high-density model assumes that the condensed high-density gas inside reduces diffusion rate and partially counteracts the Laplace pressure. This review systematically summarizes the research progress of the stability mechanisms of surface nanobubbles. It first reviews the discovery history of surface nanobubbles, then deeply analyzes the core mechanisms, intrinsic correlations, and limitations of the aforementioned theoretical models., Finally, it examines the technical challenges faced by surface nanobubbles with the application examples in the biomedical field, and proposes potential optimization strategies and future perspectives based on ther theoretical models of stability.