To study the mechanism of microbubbles generation in cross-shaped microchannels, numerical simulations of gas–liquid

two-phase fl ow in microchannels are carried out in this paper using the volume of fl uid method (VOF). By varying the twophase

fl ow rate, three diff erent fl ow regimes were obtained, including dripping regime, slugging regime and threading regime,

and the relationship between the two-phase fl ow rate and the fl ow state was plotted. Meanwhile, the phase interface, pressure

and velocity of microbubbles in three diff erent fl ow regimes were studied, and the evolution of the gas–liquid interface in

microbubbles formation was analyzed. It is found that the microbubbles diameter decreases and the frequency increases as

the viscosity of the continuous phase gradually increases. As the wall contact angle decreases, the adhesion of the liquid

phase to the wall at the channel interaction increases and the microbubbles diameter increases. The increase in interfacial

tension greatly increases the cohesion between molecules on the surface of the gas fl ow, making it diffi cult to achieve force

equilibrium, which leads to a reduction in the shear stress required to dominate the interface to break the tip of the gas fl ow

and slower bubbles formation, resulting in a larger microbubbles diameter.