A generalized correlation for predicting microdroplet sizes in a squeezer T-junction microfluidic device with various squeezer types

This paper describes an extensive study on the dynamic behaviors of droplet formation in a Squeezer T-junction Microfluidic Device (STMFD) with various squeezers. The effects of squeezer size (Ws), squeezer location (Ls), water fraction (wf), and capillary number (Ca) on the droplet formation in this device were explored. The two-phase fluid flow in the microchannel is captured using the two-dimensional finite volume method and the volume of fluid model. This study aims to determine the squeezer shape, size, and position to expand the stable droplet formation region and generate uniform-sized droplets efficiently. Consequently, the droplet formation regime, droplet size, and droplet generation frequency are affected significantly by the presence of the squeezers. A rectangle-shaped squeezer design shows the most effective generation in the squeezing mode among the shapes considered. Then, phase diagrams of the droplet formation are constructed elaborately for this squeezer-shaped design. Particularly, a generalized correlation as a function of four important parameters (Ws, Ls, wf, and Ca) is first proposed to quickly and effectively predict the droplet size in the STMFD for various squeezer types. These results enhance the understanding of microdroplet dynamics in T-junction devices, offering potential applications in biomedical and drug delivery systems.