Numerical simulation of droplet dynamic behaviors in a convergent microchannel

Microfluidic devices are of high efficiency for the coalescence and manipulation of monodispersed droplets. Numbers of microfluidic applications involve the control of droplets through networks of convergent or divergent junctions. The convergent microchannels are widely applied in transporting DNA and controlling other chemical and biological reactions. But there are still some problems unsolved such as that how to merge droplets more efficiently and how to guarantee the stability of the droplet in a convergent microchannel. In this work, numerical method is used to investigate the dynamic properties of the water microdroplets suspended in the convergent microchannel filled with oil. The moving of microdroplets in the convergent microchannel is driven by the initial droplet velocity. The surface tension is taken into account in the Navier-Stokes equations. The microchannel size parameter Da is firstly proposed to describe the convergent microchannel geometric characteristics and through which a regime map is created to classify droplets states into total coalescence regime, partial coalescence regime and no coalescence regime respectively. The dynamic behaviors of the droplets suspended in the convergent microchannel are discussed in detail. This work would contribute to the design of convergent microchannels for better biochemical analysis.