Analysis of oxygen inhibition in photopolymerizations of hydrogel micropatterns using FTIR imaging

UV photopolymerizations are a versatile polymerization technique and are thus utilized in a variety of applications. Photopolymerizations are often free-radical polymerizations, and these reactions (e.g., final conversion and reaction rates) can be inhibited by the presence of oxygen. In particular, oxygen inhibition can play a critical role in polymerization process occurring in thin films and micro/nanoscale structures where oxygen is able to rapidly transport through the short diffusion paths. Since patterned polymer micro- and nanostructures are of high interest in a variety of applications (e.g., biomedical microdevices), there is a need for methods to characterize polymerization processes at the small scale. Here, a novel method was applied to fabricate thin film of hydrogel microstructure on gold surface by using microcontact printing. The photopolymerization reaction of the patterned hydrogel was studied in situ and spatially resolved in real time with FTIR imaging techniques. The effect of oxygen inhibition during photopolymerization was also analyzed using FTIR imaging. The oxygen inhibition during polymerization was reduced by increasing the amount of photoinitiator or increasing UV intensity. This novel fabrication and characterization method will facilitate the optimization of integration processes of patterned hydrogel films.