Stereolithography (SL) is emerging as an attractive alternative to soft lithography for fabricating microfluidic devices due to its low cost and high design efficiency. Low molecular weight poly(ethylene glycol)diacrylate (MW = 258) (PEG-DA-258) has been used for SL 3D-printing of biocompatible microdevices at submillimeter resolution. However, 3D-printing resins that simultaneously feature high transparency, high biocompatibility, and high resolution are still lacking. It is found that photosensitizer isopropyl thioxanthone can, in a concentration-dependent manner, increase the absorbance of the resin (containing PEG-DA-258 and photoinitator Irgacure-819) by over an order of magnitude. This increase in absorbance allows for SL printing of microdevices at sub pixel resolution with commercially available desktop printers and without compromising transparency or biocompatibility. The assembly-free, rapid (<15 h) 3D-printing of a variety of complex 3D microfluidic devices such as a 3D-fluid router, a passive chaotic micro-mixer, an active micro-mixer with pneumatic microvalves, and high-aspect ratio (37:1) microchannels of single pixel width is demonstrated. These manufacturing capabilities are unavailable in conventional microfluidic rapid prototyping techniques. The low absorption of small hydrophobic molecules and microfluidic labeling of cultured mammalian cells in 3D-printed PEG-DA-258 microdevices is demonstrated, indicating the potential of PEG-DA-based fabrication of cell-based assays, drug discovery, and organ-on-chip platforms.
Keywords: 3D printing; microfluidic; poly(ethylene glycol)diacrylate; rapid prototyping; stereolithography.