Lego-Microfluidics Generated Magnetically Responsive Bifunctional Microcapsules with Encapsulated Phase Change Material

Abstract

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 (Fe 3 O 4 ) 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) flow rate and mass fraction of Fe 3 O 4 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 Fe 3 O 4 nanoparticle-embedded microcapsules compared to pure PCM. Vibrating sample magnetometry (VSM) verified an increase in saturation magnetization and residual magnetization of microcapsules, having higher Fe 3 O 4 nanoparticle content. Notably, the sample containing 1% Fe 3 O 4 nanoparticles exhibited excellent magnetic properties, showcasing a saturation magnetization of 0.194 emu/g. Concurrently, the PCM microcapsules demonstrated high magnetic responsiveness and maneuverability.