Simulation of species leakage in material encapsulation using compound droplets*

Compound droplets can be used in substance encapsulation and material compartmentalization. The shell of compound droplets can serve as a protective layer of the inner phase by minimizing the mass transfer between the core and the outer phase. This often relies on that the solubility of the species is low in the shell layer. However, it should be noted that the solubility of the species in the shell phase is not ideally zero. We simulate the leakage of material from the core to the continuous phase or from the continuous phase to the core phase. To reduce the spurious current at the interface, we used to ghost fluid method to consider the surface tension effect. To avoid the numerical diffusion for the mass transfer process, we used the particle tracking method. The mass transfer across the interface is simulated using a Monte Carlo concept. The method presented in this study can also be used in other mass transfer analyses across interfaces such as micro-extraction, micro-mixing, and micro-reaction.