Droplet-based synthesis of microencapsulated phase change hydrogels via electro-coalescence

Hypothesis: Phase change materials (PCMs) based on inorganic hydrated salt has garnered considerable attention for their high energy storage density, non-toxicity, cost-effectiveness. However, conventional techniques mainly address the macroscopic deficiencies of their phase change performance, with limited focus on precise manufacturing and customized functionalities at microscale. Experiments: Herein, we propose an innovative concept of microencapsulated phase change hydrogels (MPCHs), synthesized through electro-coalescence in a feasible droplet-based microfluidic platform. A comprehensive analysis is conducted on the influence of hydrated salt and hydrogel concentrations, as well as electric and flow conditions. Findings: We achieve the precise manipulation of the merging dynamics over a wide range of hydrated salt and hydrogel concentrations under AC electric field. The three-dimensional network structure and hydrophilicity of hydrogels helps to reduce supercooling, minimize phase separation, improve the cyclic performance. The versatile fluidic configuration allows for on-demand control over different mechanical and phase change properties in realistic scenarios. MPCHs could not only be applied as a thermal interface material for flexible electronics but also functions as a microscale thermal modulator for temperature buffering in bacterial cultivation. The unique transparency allows them to be carriers for temperature-sensitive fluorescent dyes, enabling simultaneous temperature detection and analysis. This approach offers a new approach to improve the thermal performance of hydrated salt PCMs and broaden the application ranges via droplet microfluidics.