Fig. 5. Workflow of hydrogel formation via UV-light and treatment with DAS prior to two-photon micropatterning and post-treatment for visualization. (a) Disulfide-crosslinked PEG hydrogels were formed by photoinduced TEC upon irradiation with UV-light. (b) Thereafter, hydrogels were swollen in PBS, (c) before being soaked in solutions of DAS. (d) The activated hydrogels were then two-photon micropatterned using a fs-pulsed laser. (e) Microchannels were visualized by confocal microscopy, after swelling in fluorescing dextran. (f) The presence of the two-photon active DAS is crucial for effective cleavage of disulfide linkages by two-photon irradiation. PI denotes a photoinitiator fragment.