Enhanced droplet formation in a T-junction microchannel using electric field: A lattice Boltzmann study

The electric field-driven droplet formation technique can effectively improve the formation throughput and control the droplet size, which is important for the application of microscale droplets in biopharmaceuticals and chemical analysis. In this paper, the droplet formation characteristics in T-junction microchannels under the action of electric field are investigated by coupling a three-dimensional lattice Boltzmann method (3 D LBM) with the leaky dielectric model, focusing on the effects of electric capillary number, a flow ratio, and a viscosity ratio on the droplet size. It is shown that as the electrical capillary number increases, the non-uniformly distributed electric force stretches the dispersed phase to form a Taylor cone and increases shear force at the interface of the two liquids to overcome the surface tension force. This facilitates the transition from squeezing to dropping and reduces the droplet size. At high flow ratios, increasing the electric capillary number leads to a pinning effect between the dispersed phase and the wall, which intensifies the compression of continuous phase on the neck of dispersed phase, resulting in a significant decrease in the droplet size. As the viscosity ratio increases, the vortex resistance caused by electrical force decreases, and thus, the electric field effect will dominate the droplet formation process.