Precise morphology control of all-organic core-shell droplets for synthesis of microencapsulated phase change materials through AC electric fields

Hypothesis: Complex emulsions usually consist of aqueous phases, like oil-in-water-in-oil (o/w/o) and water-in-oil-in-water (w/o/w), serving foundational roles in colloid science. Oil-in-oil-oil (o/o/o) emulsions offer new avenues for non-aqueous reagents but face challenges in balancing the forces between multiple organic phases. Experiments: In this work, we generate o/o/o emulsions by integrating an AC electric field with a double cross-junction microchannel. The characteristics of generating dynamics is observed and analyzed based on the interaction between the electric force, viscous force, and interfacial tension. Findings: We first establish an innovative evaluation theory to quantify the generation efficiency for complex emulsions. The results show that the electric effect improves the generation efficiency and monodispersity across a variety of high flow rates compared with conventional methods, enabling the flexibility in adjusting droplet sizes and core–shell structures. At low flow rates, the breakup of core–shell droplets can also be controlled by the electric force under different types of o/o/o emulsions. The inner phase could be substituted with alkane phase-change materials and processed into microencapsulated phase-change materials (MEPCMs). These organic MEPCMs could be integrated into electrolytes due to their ultra-low electric conductivity, which shows a significant temperature buffering effect in lithium batteries. This research not only enhances our understanding of colloidal systems but also fabricates core–shell structures with customized functionalities, paving the way for advancements in energy conversion and management, drug delivery, and materials engineering.