Single Emulsion Microfluidic Production Of Coreshell/Janus Microspheres And Helical Microfibers

Microfluidics is an emerging technique that studies the design, fabrication and operation of fluids at the microscale within microscopic channels. The fabrication process of microspheres by using microfluidic technology can generally be divided into two steps. Firstly, after the immiscible fluids are injected into microchannels, droplets are gained due to shear force and interfacial tension; secondly, the prepared droplets are solidified by photo polymerization, ionic crosslinking and solvent diffusion etc. to produce solid microspheres.Previous reports on microfluidic fabrication of core-shell or Janus particles often need multi-channel microfluidic devices with the use of small molecular surfactants and organic solvents. The removal of these surfactants and organic solvents in the following steps is often complicated and may cause many adverse effects. In this paper, simple single emulsion capillary microfluidic device and a polymerizable macromolecule emulsifier are used to solve these problems. Liquid MMA monomer containing polymerizable macromolecule emulsifier is used as the oil phase, PVA aqueous solution is used as the water phase without using any other organic solvent. Monodisperse solid, Janus or core-shell microspheres can be easily fabricated by off-chip polymerization under various UV irradiation conditions due to polymerization induced phase-separation.On the other hand, until now, there are only limited reports on production of polymeric helical microfibers using microfluidic technique. In this synthesis, based on a simple single emulsion capillary microfluidic device, helical dextran microfibers can also be prepared with the combination of mass transfer and buckling. Aqueous solution of dextran and liquid low molecular weight PEG are used as the inner and outer phase, respectively. The size and morphology of the obtained fibers can be finely controlled by easily adjusting various parameters such as the flow rates, concentration of dextran, and the length of the outlet channel. The whole experiment process does not need addition of organic solvent and surfactant, and is ecologically friendly. These results show a new way for fabrication of polymeric helical hydrogel microfibers.