2606 気体圧力変動を利用した単一マイクロバブル発生法(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] 2606 Formation of single bubbles controlled with fluctuating gas pressure  [in Japanese]

A method of a bubble production, originally developed by Kariyasaki and Osaka [Trans. JSME, 68-674B (2002)], is further investigated experimentally. First, the acoustic characteristic of the pipe between audio speaker and nozzle is investigated. Then, a new type of fluctuation consisted of both increase and decrease in gas pressure is used to clarify the effect of the fluctuation. Shrinking motion of a capillary bridge connecting a bubble and a nozzle was observed in detail using high-speed photography. We also estimate the force balance on a bubble center based on a spherical bubble formation model. As results, it is clarified that the pipe between speaker and nozzle could regard as acoustic tube. Moreover, when gas pressure is decreased the capillary bridge is sucked down into a nozzle and upward added mass force is applied on a bubble center, both of which cause the detachment of a bubble from a nozzle.