Flow-induced synthesis of polystyrene-block-poly(ethylene glycol) vesicles on the interface of a laminated microflow

This paper presents a microfluidic synthesis of polymeric vesicles (PVs) by employing flow-induced self-assembly of polystyrene-block-poly(ethylene glycol) (PS-b-PEG) in a double flow-focusing microchannel (DFFM). The DFFM can solve the limitation of a large size distribution of produced PVs caused by clogging issues in general microchannel synthesis. By adding an attenuation layer between the polymer-dissolved solution and water, it is determined that rapid self-assembly of the polymers can be controlled. The hollow PVs are synthesized with a narrow size distribution and the size controllability is also examined for the ratios of the inlet flow rates and the polymer concentration. The produced PVs are characterized by using transmission electron microscopy, scanning electron microscopy and dynamic light scattering. It is newly visualized that the self-assembly occurs mostly in the attenuation layer owing to the diffusion through the interfaces of the five parallel laminar flow formed in the DFFM. This finding can provide a significant clue to understand the inflow-induced synthesis of the PVs in microchannels. Also, the uniform PVs can be applied to the development of drugs and biomedical researches.