2609 マイクロバブルの安定性に及ぼす圧力変動の影響(S44-1 マイクロ気泡・粒子,S44 マイクロ・ナノフルイディクス)  [in Japanese] 2609 Influence of Pressure Variation on the Stability of Microbubbles  [in Japanese]

The shrinkage and growth of microbubbles under variation of a pressure field are observed with a CCD camera. The influence of gas diffusion on the stability of microbubbles is investigated. It is shown that when the ambient liquid pressure increases, a tiny microbubble with about 5μm in radius shrinks accompanied with large surface depression, and does not return to the initial size even after the pressure is reduced. The depression suggests the formation of multilayers of surfactant on the bubble surface. We constructed a bubble model by considering the permeation resistance of surfactant layers. The simulations are in good agreement with the experimental results for nearly spherical bubbles. The results show that the increase of the permeation resistance during bubble shrinkage stabilizes the microbubble.