In this work, we describe a straightforward approach to produce monodisperse Janus and core-shell particles by using organic solvent free single emulsion droplet-based microfluidic device combining with off-chip polymerization. To accomplish this, methyl methacrylate(MMA) was used as both the oil phase and solvent to dissolve a polymerizable PEGbased macromolecular surfactant, instead of traditional surfactant, and the photo-initiator. Janus particles can be easily obtained by off-chip UV polymerization due to polymerization induced phase separation between PEG and the formed poly(methyl methacrylate). At the same time, core-shell particles can also be easily attained by inverting the original collecting tube several times and then exposing to UV light. These results may extend the scope of microfluidic technology and the studies on polymerization induced self-assembly/phase-separation into easy fabrication of various new functional materials. In this work, we describe a straightforward approach to produce monodisperse Janus and core-shell particles by using organic solvent free single emulsion droplet-based microfluidic device combining with off-chip polymerization. the oil phase and solvent to dissolve polymerizable PEG based macromolecular surfactant, instead of the traditional surfactant, and the photo-initiator. Janus particles can be easily obtained by off-chip UV polymerization due to polymerization induced phase separation between PEG and the formed poly methacrylate). At the same time, core-shell particles can also be attained by inverting the original collecting tube several times and then exposing to UV light. These results may extend the scope of microfluidic technology and the studies on polymerization induced self-assembly / phase-separation into easy fabrication of various new functional materials.