A polydimethylsiloxane (PDMS) microfluidic chip with well-interconnected microfibrous channels was fabricated by using an electrospun poly­(ε-caprolactone) (PCL) microfibrous matrix and 3D-printed pattern as templates. The microfiber-templated microfluidic chip (MTMC) was used to produce nanoscale emulsions and spheres through multiple emulsification at many small micro-orifice junctions among microfibrous channels. The emulsion formation mechanisms in the MTMC were the cross-junction dripping or Y-junction splitting at the micro-orifice junctions. We demonstrated the high throughput and continuous production of water-in-oil emulsions and polyethylene glycol-diacrylate (PEG-DA) spheres with controlled size ranges from 2.84 μm to 83.6 nm and 1.03 μm to 45.7 nm, respectively. The average size of the water droplets was tuned by changing the micro-orifice diameter of the MTMC and the flow rate of the continuous phase. The MTMC theoretically produced 58 trillion PEG-DA nanospheres per hour without high shear force. In addition, we demonstrated the higher encapsulation efficiency of the PEG-DA microspheres in the MTMC than that of the microspheres fabricated by ultrasonication. The MTMC can be used as a powerful platform for the large-scale and continuous productions of emulsions and spheres.

A microfluidic device with microfibrous channels was prepared using perfluoropolyether (PFPE) and poly(ethylene glycol) diacrylate (PEG-DA). PFPE was chosen as a major material for the device due to its excellent solvent resistance. PEG-DA was used in the device to improve its hydrophilicity. Microfibrous channels with different diameters (approximately 12 and 17 μm) were developed using an electrospun disc as a template. Compared to a polydimethylsiloxane microfluidic device, the PFPE microfluidic device exhibited a significantly lower swelling ratio. The continuous production of poly(ε-caprolactone) (PCL) microspheres with dexamethasone was achieved using the oil-in-water (O/W) emulsification and solvent evaporation methods. The microsphere size was decreased with the use of smaller microfibrous channels at a higher flow rate of the continuous phase. PCL microspheres prepared by the PFPE microfluidic device showed higher encapsulation efficiency than conventional homogenization. The addition of poly(ethylene glycol) (PEG, 5 wt %) in the discontinuous phase enhanced the encapsulation efficiency to 39.4%. PCL microspheres with PEG showed more sustained release profiles than PCL microspheres without PEG. These results indicate that the PFPE microfluidic device with microfibrous channels can be used as a platform for the continuous production of drug carriers.

No abstract