Fig. 6. Microchannels were fabricated by two-photon degradation of disulfide-based hydrogels in presence of two-photon initiator DAS (0.5–2.0 mM). Individual x,y-planes were either scanned once or twice. Thereafter, hydrogels were soaked in a solution of high molecular weight fluorescent dextran (FITC2000) and microchannels were visualized by confocal microscopy. (a) 8arm-d,l-HCys 120 could be fully degraded in presence of 2.0 mM DAS in a single scan. At lower concentration double scanning was required for complete erosion. (b) Microchannel fabrication in stiffer 8arm-l-HCys 100 hydrogel required double scanning in presence of 2.0 mM DAS for complete erosion. When 1 mM DAS was used, channels could only be visualized using lower molecular weight dextran (FITC500), indicating localized softening of the material. Images display orthogonal cross sections (y,z-plane) of micro channels. Scale bar 20 μm.