Microfluidic production of snowman-shaped Janus hydrogel particles

We present a simple microfluidic-based synthesis protocol to fabricate snowman like Janus hydrogel particles of poly(N-isopropylacrylamide) (PNIPAM) in micron length scale. Particles are synthesized by emulsifying a hydrogel solution (water (w)/oil (o)) followed by partial solvent evaporation. Solvent evaporation allows the hydrogels to concentrate within the droplet and phase separate into a monomer-abundant and a sparse phase. Due to the difference in interfacial tension and chemical properties of the two phases, emulsion droplets are deformed into snowman like Janus droplets. After cross-linking the monomer by UV irradiation, the particles are transferred into water. The resulting Janus colloids exhibit thermo-responsive behavior and form self-assembled structures.