Synthesis of uniform polymeric microparticles via droplet microfluidics

Particles, including micro particles, spherical and non-spherical, play important roles in many fields. The major goals in designing these particles include controlling particle monodispersity, chemistry, porosity, shape and size. Therefore, there is a continuous demand for controllable technologies and equipment for the engineering of such particles. Despite the traditional methods for particles production, droplet microfluidics technique is promising method for the production of monodisperse emulsion droplets one at a time with tailored sizes, shapes and morphologies. These emulsion drops can be used for the precise manufacturing of novel particles, such as microcapsules, Janus or patchy particles and porous particles with tailored internal structures. In general, highly monodisperse emulsion droplets are produced in microfluidic device and are used as templates and then solidified to form microparticles by solidification methods. For example, single emulsion drops can be a template for microspheres and double emulsion can be a template for coreshell microparticles, Janus and other morphologies.

In this study, two-phase and three-phase glass capillary microfluidic devices were utilized for the formation of single emulsions and double emulsions respectively. Solidification methods used were photopolymerisation of photocurable monomer/polymer and solvent evaporation. Single emulsions of O/W and W/O were used as templates for the fabrication of porous and non-porous microspheres and Janus microparticles. Whereas double emulsions were used as templates for the formation of core-shell microparticles. The size of the produced droplets, the frequency of droplet generation and the size distribution were precisely controlled by adjusting fluids flow rates and orifice diameter of the collection capillary. In addition, to add functionality to the microparticles, nanoparticles such as TiO₂ , magnetic Fe(II,III)Oxide and graphene were added separately to the polymer solutions. Two droplet formation modes were observed during droplet generation process in the microfluidic devices, dripping and jetting where uniform droplets (CV < 3%) were produced in the dripping mode.

Microparticles fabricated in this work were: microspheres and core-shell microparticles of TiO₂ /poly(HDDA) and graphene/poly(HDDA), PS/PVAC magnetic Janus microparticles and PEGDA , TiO₂ /PEGDA and graphene/PEGDA microgels.

The fabricated microparticles were characterised using SEM, ATR-FTIR, DSC, XRD, FIB and confocal microscopy.