Controllable in-situ hydrogels membrane formation using microfluidics

This paper reports a novel method for the in-situ hydrogel membrane fabrication in a simple PDMS channel. We used two separate solutions of 0.0625 wt% of H₂O₂ in PBS with the 5.2 wt% of the Tetronic-succinic anhydride-tyramine (Tet-SA-TA), and 0.0625 mg/ml of horseradish peroxidase (HRP) in PBS with the same concentration of Tet-SA-TA. These two solutions were introduced into the typical microfluidic channel and the mixing of these solutions spontaneously formed the in-situ crosslinked hydrogels membrane in the microfluidic channel. The width of the membrane can be controlled quantitatively by adjusting gelation time and the velocity of microfluidics. Moreover, by using the formed inner-channel membrane, the permeation of chemical molecules through the membrane was observed and its quantitative value was analyzed with multiphysics modeling. The parallel hydrogel membranes were also formed using a time-dependent procedure, and, in addition, this separated channel by the hydrogel membranes was applied for the generation of stable concentration gradients into the microchannel. These results can be used to realize the complicated diffusive 3D structure, such as biomimetic blood vessels.