Synthesis of uniform polymeric microparticles via droplet microfluidics

Synthesis of uniform polymeric microparticles via droplet microfluidic

Highly porous magnetic Janus microparticles with asymmetric surface topology

Monodispersed magnetic Janus particles composed of a porous polystyrene portion and a nonporous poly(vinyl acetate) portion with embedded oleic acid-coated magnetic nanoparticles were generated using microfluidic emulsification followed by two distinct phase separation events triggered by solvent evaporation. The template droplets were composed of 2 wt% polystyrene, 2 wt% poly(vinyl acetate) and 0.5-2 wt% n-heptane-based magnetic fluid dissolved in dichloromethane (DCM). The porosity of polystyrene compartments was the result of phase separation between a non-volatile non-solvent (n-heptane) and a volatile solvent (DCM) within polystyrene-rich phase. The focused ion beam cross-sectioning and SEM imaging revealed high surface porosity of polystyrene compartments with negligible porosity of poly(vinyl acetate) parts, which can be exploited to increase the wettability contrast between the two polymers and enhance bubble generation in bubble-driven micromotors. The porosity of the polystyrene portion was controlled by varying the fraction of n-heptane in the dispersed phase. The particle composition was confirmed by scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The fabricated particles were successfully magnetised when subjected to an external magnetic field, which led to their aggregation into regular 2D assemblies. The particle clusters composed of 2-4 individual particles could be rotated with a rotating magnetic field. Microfluidic generation of highly porous Janus particles with compositional, topological, and magnetic asymmetry provides a cost-effective, easy-to-implement yet highly robust and versatile strategy for the manufacturing of multifunctional smart particles

In-vitro oral digestion of microfluidically produced monodispersed W/O/W food emulsions loaded with concentrated sucrose solution designed to enhance sweetness perception

Monodispersed W1/O/W2 emulsions consisting of sunflower oil droplets containing a single large internal droplet or numerous small internal droplets of concentrated sucrose solution were prepared by microfluidic emulsification. The external droplet interface was stabilized by waxy rice starch, which hydrolyzes during oral processing thereby releasing the encapsulated sucrose solution to the proximity of taste receptors imparting a higher sweetness perception compared to adding the same amount of sugar to the bulk phase. The sucrose release was tracked by adding NaCl to the internal phase as a conductivity tracer. Core/shell droplets containing 50 wt% sucrose and 1.5 wt% NaCl in the internal phase, 1.40–2.86 wt% polyglycerol polyricinoleate (PGPR) in the middle phase, and 4 wt% gelatinized waxy rice starch in the external phase were produced with 100% encapsulation efficiency and showed stability against coalescence for at least two months, because the gelatinized starch acted as a highly efficient Pickering stabilizer. The sucrose release from the inner droplets during in-vitro oral processing at 37 °C for 30 s with 50 U/mL α-amylase increased from 16% to 49% when the PGPR concentration in the oil phase was reduced from 2.86 wt% to 0.7 wt%. Core/shell droplets were less stable during storage when the surface-active molecularly dissolved octenyl succinic anhydride (OSA) modified starch was selected as stabilizer although the oil droplets were smaller due to the lower interfacial tension at the external interface. W1/O/W2 emulsion consisting of numerous internal droplets coalesced during storage in one day and released 91% of sucrose during in-vitro oral processing