Complete conversion of the NB groups was observed under full exposure conditions, while the conversion for Gel-MA was found to be 50-80%. After physical gelation and photocrosslinking, Gel-MA hydrogels exhibited a higher storage modulus and a higher mass swelling ratio than Gel-NB hydrogels within the tested concentration range. The higher modulus was attributed to the different polymerization mechanisms: in the MA hydrogels, the growing radical macromer can span many Gel chains. In contrast, in the thiol-ene system each NB function can only connect to one other NB unit of the same or another Gel chain via the bifunctional DTT crosslinker. The lower mass swelling ratio in the Gel-NB system was attributed to the more hydrophobic nature of the NB functions inside the network and the more homogeneous network structure due to the high conversion. Upon 2PP excitation, 5% and 10% w/v Gel-NB rendered stable hydrogels with a 3fold lower laser power than Gel-MA hydrogels at the same concentration using Irgacure as photoinitiator. Using 10% w/v Gel-NB, scaffolds of 200 x 200 x 200 µm with pores of 30 µm could be laser written. In following studies, 10% w/v Gel-MA and Gel-NB hydrogels with 90-95% degree of functionality were compared. Using DTT as crosslinker, the gelation point in Gel-NB was achieved at 0.36 s or 9.18 s in contrast to 19.9 s or 49.5 s for Gel-MA with lithium-phenyl-2,4,6-trimethylbenzoylphosphinat (LAP) or Irgacure as photoinitiator, respectively. In 2PP processing, the required laser power to obtain a reproducible structure Gel-NB was 20-fold lower than in Gel-MA. Self-supportive scaffolds with a minimum feature-size of 50 µm were fabricated using Gel-NB, while Gel-MA scaffolds written at the same writing speed and laser power collapsed. In a different study, the printability of NB or AE-functionalized Gel was studied using a volumetric printer and a negative resolution of 100-200 µm was demonstrated. Other studies have also compared NB and MA systems, though they used systems with different polymer backbones and, therefore, their comparison is less informative. Shih et al. studied the photorheology of NB and MA functionalized poly(ethyleneglycol) (PEG). Precursor solutions of 10 %wt PEG4NB (20 kDa) or PEGDA (10 kDa) were used for the comparison. Athough the solutions contain the same number of functional groups, the internal polymer architecture is different as the PEG4NB precursor with the star structure generates double number of crosslinks than the linear PEGDA in the final network. Qui et al. used 1.5-3% NB-functionalized poly(vinyl alcohol) to print structures with a negative resolution down to 900 µm using volumetric printing. The hydrogel precursor solution was compared to 10% Gel-MA.