The study of bubbles can be traced back to the time of Plato, but for hundreds of years, people have not formed a unified understanding of the definition of bubbles. American colloid chemist L·I·Osipow and Dow Corning's R·F·Smith defined the foam in terms of foam density; Ito Koichi of Japan defined the foam from the perspective of foam structure, but ignored the bubble The interrelationship between China and the famous surface physicist Professor Zhao Guoxi in China defines foam as: a foam is a dispersed system in which a gas is dispersed in a liquid, a gas is a dispersed phase (discontinuous phase), a liquid is a dispersed medium (continuous phase), and a liquid The bubbles in the liquid rise to the liquid surface, forming a small amount of liquid, which is a collection of bubbles separated by a liquid film. Scholars at home and abroad agree that the foam itself is a thermodynamically unstable system. When gas enters a solution containing a surfactant, a long-term stable foam system is formed.