Digital light processing (DLP) of photopolymerizable inks and hydrogels typically uses (meth)acrylated formulations crosslinked via the chain-growth process of photoinitiated radical polymerization (Figure ). A limitation of radical polymerization for DLP printing is its oxygen sensitivity. To counteract oxygen inhibition, higher photoinitiator concentrations and higher light doses are typically applied, which can lead to phototoxicity in bioprinting contexts. Photopolymerizable precursors based on radical thiol-ene photopolymerization are interesting alternatives to radical (meth)acrylate polymers. The radical thiol-ene reaction involves the addition of a thiyl radical to a vinyl group to form a thioether (Figure ). The polymerization proceeds via a step-growth mechanism and the resulting networks show higher homogeneity than (meth)acrylate networks polymerized by radical polymerization (Figure ). The radical thiol-ene reaction is not sensitive to oxygen as the generated peroxy radical readily abstracts a hydrogen atom from a thiol which can then proceed in the thiol-ene reaction. Moreover, the kinetics of the addition of the thiyl radical can be tuned by the chemical design of the ene: faster with electron rich or strained vinyl groups like vinyl ether (VE), allyl ether (AE) or norbornene (NB) groups and slower for electron poor vinyl groups or vinyl groups where the intermediate radical is stabilized as in methacrylate (MA). The thiol-ene reaction offers higher conversions than the radical polymerization of (meth)acrylates , leading to lower generation of reactive oxygen species and higher cell viability in bioprinting applications. A few examples in the literature have compared the final properties of thiol-ene vs. MA photopolymerized hydrogels. Van Hoorick et al. studied the gelation reaction and the DLP of 5-15% w/v gelatin (Gel) functionalized with NB (Gel-NB) or MA (Gel-MA) at 65% functionalization degree using two photon polymerization (2PP). Dithioerithrol (DTT) was used as crosslinker in the thiol-ene system. Photorheology demonstrated a 24-fold shorter gelation time for Gel-NB.