Next, characterizing the mechanical capabilities of the fabricated hydrogel structures, postswelling, compressive mechanical analysis was conducted. Figure shows a representative stress-strain curve of cast discs from each formulation, measured up to 50 wt.% strain. It should be noted that the 15 wt.% materials reached the force limit of the 5N load cell, therefore ending the measurement around 15 wt.% PEGDA + Alg 15 wt.% 0.5 wt.% 10 5 30 wt.% strain. The addition of alginate did affect the modulus of some material formulations, which could be attributed to the alginate affecting the mesh formation, causing weaker networks. Specifically, the 5 wt.% PEGDA and 5 wt.% PEGDA + Alg hydrogels had similar compressive moduli of 13 ± 4 kPa and 14 ± 4 kPa, while the 10 wt.% PEGDA and 10 wt.% PEGDA + Alg hydrogels had a distinct compressive modulus of 135 ± 36 kPa and 90 ± 24 kPa respectively, and the 15 wt.% PEGDA and 15 wt.% PEGDA + Alg hydrogels had a compressive modulus of 414 ± 87 kPa and 289 ± 121 kPa, respectively. Through modulating the weight percent of PEGDA, we demonstrate control of the mechanical properties of the gel, with detailed oscillatory rheometry shown in Supporting Figure . Furthermore, our findings underscore that the addition of alginate affects the network formation of stiff hydrogels, and that post-curing optimization may be needed for applications requiring high modulus constructs (>250kPa). To further characterize the material, we investigated how the addition of alginate would affect the equilibrium water content (EWC) of the chosen compositions (Figure ). At 5% PEGDA, the alginate had a statistically significant difference, decreasing the EWC from 97.9% ± 0.2% to 96.8 ± 0.3%, which is notably above the starting photopolymer formulation water content of 95% and 94.5%, respectively. A reduction in EWC following the addition of the secondary, non-crosslinked, alginate may be attributed to the increased concentration of total polymer fraction. The addition of alginate did not have a statistically significant difference in the EWC for the 10% and 15% PEGDA, however there was a slight increase and slight decrease when compared to the starting water content, 90.5% ± 0.9% to 91.2% ± 0.8% and 83.8% ± 0.6% to 84.1% ± 0.9%, respectively. The final material properties of the hydrogels are listed in Supporting Table .