Experimental study of microbubble coalescence in a T-junction microfluidic device

This study presents the microbubble coalescence process in a confined microchannel. Triple T-junction microfluidic devices with different main channel size were designed to generate monodispersed microbubble pairs with air/n-butyl alcohol-glycerol solution as the working system. The head-on collision of microbubble pair was realized in the microfluidic devices. Three collision results including absolute coalescence, probabilistic coalescence, and non-coalescence were distinguished. The effects of liquid viscosities and two-phase superficial velocities on the coalescence behavior were determined. The results showed that microbubble coalescence process in the confined space was slightly faster than in the free space. Increasing liquid viscosity apparently prevents coalescence. In the probabilistic coalescence region, higher two-phase superficial velocity could reduce the percentage of coalescence events. Two characteristic parameters representing the bubble contact time and film drainage time have been introduced to analyze the microbubble coalescence behaviors and a linear correlation could clearly distinguish the coalescence and non-coalescence region.