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

Abstract

The fabrication of microfluidic devices with nonplanar microchannel design by micro-stereolithography (µSL) 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 µm 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, ≈130–80 µm 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.