Optimizing Process Parameters in Commercial Micro-Stereolithography for Forming Emulsions and Polymer Microparticles in Nonplanar Microfluidic Devices

The fabrication of microfluidic devices with nonplanar microchannel design by micro-stereolithography (mu SL) for oil-in-water (O/W) and water-in-oil (W/O) single emulsion as well as oil-in-water-in-oil (O/W/O) and water-in-oil-in-water (W/O/W) double emulsion formation is presented. By investigating separation distance, printing direction and voxel compensation in X,Y-plane as key printing parameters, microflow cells with channel cross-sections varying from 500 to 75 mu m are printed, which are thus truly similar to those yielded by conventional stamped microfluidics. Without the need of controlling microchannel wettability, these flow cells are employed for forming O/W and W/O microdroplets, approximate to 130-80 mu m in diameter and narrow size distribution of 2%, and at frequencies of up to 2.9 kHz. The as-formed emulsion droplets are then utilized as templates for preparing hydrophobic and hydrophilic polymer microparticles, respectively. Likewise, O/W/O and W/O/W double emulsions are prepared in a single microflow cell to extend the applicability of nonplanar, 3D-printed microfluidic devices. For each set of experiments, the same single flow cell is used to prove the reusability and robustness of the 3D-printed flow cells compared to microfluidic flow cells fabricated by conventional, combined photo- and soft-lithography.