Fig. 2.

(A) Photograph of the double-network hydrogel through a Schiff-based reaction (primary cross-linking network) and UV crosslinking (second cross-linking network). (B) SEM images of GelMA, GelMA-O7 and GelMA-O5 hydrogels. (C) The swelling ratio of hydrogels. (D) The compression modulus. The Compressive modulus was defined as the compressive strength at 60% strain. (E) The rheological properties. G′ represents the storage modulus and G″ represents the loss modulus. (F) The hydrogel viscosity with frequency ranging from 0.1 to 100 Hz.