Why nanobubbles collapse?

Nanobubbles can implode or collapse due to several factors, including diffusion of gas from the bubble into the liquid, coalescence with other bubbles, and the presence of external forces or disturbances.

One of the main factors that can cause nanobubbles to collapse is diffusion. Because nanobubbles have a very small volume and surface area, the gas molecules inside the bubble can easily diffuse into the surrounding liquid, causing the bubble to shrink and eventually collapse. This process is accelerated by higher temperatures, pressure changes, or changes in the chemical composition of the liquid.

Another factor that can cause nanobubbles to collapse is coalescence, which occurs when two or more bubbles come into contact and merge into a larger bubble. This can happen due to the natural movement of bubbles in the liquid or due to external forces such as shear stresses or turbulence.

Finally, external forces or disturbances, such as acoustic waves, can also cause nanobubbles to collapse. When a high-intensity acoustic wave passes through a liquid containing nanobubbles, the wave can generate microjets that can cause the bubbles to collapse. This effect is called cavitation, and it is a key mechanism by which ultrasonic irradiation can be used to produce and control nanobubbles.

In summary, nanobubbles can implode or collapse due to several factors, including diffusion of gas from the bubble into the liquid, coalescence with other bubbles, and the presence of external forces or disturbances. The ability to control the formation, stability, and collapse of nanobubbles is an active area of research with many potential applications in fields such as environmental remediation, food processing, and medical imaging.