Lego-microfluidics generated magnetically responsive bifunctional microcapsules with encapsulated phase change material

We report an innovative Lego-microfluidic technology for room temperature synthesis of highly monodispersed bifunctional microcapsules enclosing phase change material (PCM), exhibiting magnetic and thermal energy storage properties. Iron (II, III) oxide (Fe₃O₄) nanoparticle-embedded microcapsules encapsulating hexadecane (HD) are synthesized without external heating or cooling in just ~80 s. The process involves forming oil-in-oil-in-water (O/O/W) double emulsion droplets with Norland Optical Adhesive (NOA) photopolymeric shell and consolidating them through on-the-fly shell polymerization using thiol-ene “click” chemistry. PCM content and magnetic properties were accurately manipulated by adjusting inner phase (PCM) flowrate and mass fraction of Fe₃O₄ nanoparticles in the middle (polymer) phase. Microcapsules with a shell thickness of 17.1 μm achieved a maximum PCM content of 63.3%. Thermogravimetric analysis (TGA) revealed significantly enhanced thermal stability of Fe₃O₄ nanoparticle-embedded microcapsules compared to pure PCM. Vibrating sample magnetometry (VSM) verified an increase in saturation magnetization and residual magnetization of microcapsules having higher Fe₃O₄ nanoparticle content. Notably, the sample containing 1% Fe₃O₄ nanoparticles exhibited excellent magnetic properties, showcasing a saturation magnetization of 0.194 emu/g. Concurrently, the PCM microcapsules demonstrated high magnetic responsiveness and maneuverability.