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

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.

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.

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.