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

Objective: 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.

Methods: 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.

Results: 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.