Controlled Latent Heat Phase-Change Microcapsules for Temperature Regulation.

Microencapsulation of phase-change materials (PCMs) is of great value and significance for improving energy efficiency and reducing carbon dioxide emissions. Here, highly controllable phase-change microcapsules (PCMCs) with hexadecane as the core material and polyurea as the shell material were developed for precise temperature regulation. A universal liquid-driven active flow focusing technique platform was used to adjust the diameter of PCMCs, and the shell thickness can be controlled by adjusting the monomer ratio. In synchronized regime, the droplet size is only related to the flow rate and excitation frequency, which can be accurately predicted by the scaling law. The fabricated PCMCs have uniform particle size with a coefficient of variation (CV) under 2%, smooth surface, and compact structure. Meanwhile, under the good protection of a polyurea shell, PCMCs exhibit fair phase-change performance, strong heat storage capacity, and good thermal stability. The PCMCs with different sizes and wall thickness show obvious differences in thermal properties. The feasibility of the fabricated hexadecane phase-change microcapsules in phase-change temperature regulation was verified by thermal analysis. These features indicate that the developed PCMCs by the active flow focusing technique platform have broad application prospects in thermal energy storage and thermal management.