Microfluidic fabrication of smart micro gels from macromolecular precursors
Microuidic emulsication of a semidilute solution of crosslinkable pNIPAAm precursors in water (schematic). Subsequent gelation of the monodisperse droplets, achieved through crosslinking the polymer chains by dimerization of pendant reactive side groups, forms monodisperse microgel particles.
Microuidic templating of anisotropic microgels with two distinguishable sides (“Janus microgels”). (A) Optical micrograph of a microuidic device forming aqueous droplets from three separate semidilute pNIPAAm solutions. In the rst junction, these three solutions meet and form a laminar, co-owing stream. In the second junction, this stream is broken to form monodisperse droplets by ow focusing with parafn oil. For demonstration purposes, two of the three polymer phases are tagged with either red or green uorescent dyes while the third phase is untagged; however, note that the color in Panel A was added digitally, because the true color of these polymer solutions is visible only through uorescence. To visualize the ow pattern with greater clarity, the inset micrograph shows a similar experiment with a center phase that is doped with iron oxide nanoparticles (from Ref. ). Right after their formation, the droplets enter a wide basin channel, where they are gelled by UV exposure. (B) Fluorescence micrographs of the resultant microgel particles. Varying the ow rates of the two tagged outer polymer phases, the untagged center polymer phase, and the emulsifying oil phase from 105:105:30:500 mL h1 (upper row of micrographs) to 30:30:180:500 mL h1 (lower row of micrographs) yields particles with different inner morphology. All scalebars denote 100 mm.
1. S. Seiffert, D.A. Weitz, "Microfluidic fabrication of smart microgels from macromolecular precursors", Polymer 51 (2010) 5883-5889