2.9 Combination of two step crosslinking
GelMA solution was added to one side of the mold (Fig. 3A). After crosslinked for 10 s, the solution was added to the other side and crosslinked for 100s to form a two-step crosslinked sample. GelMA solution was added to both sides of the mold and directly crosslinked for 100s was used as one-step crosslinked sample as a control.
Two-step crosslinked and one-step crosslinked samples were loaded in Instron mechanical tester (Model 5533, Instron Corporation, Norwood, Ma, USA), and tensile tests were conducted with a maximum value of 10N load cell.
Two-step crosslinked samples were observed by scanning electron microscope (SEM) to analyze the pore size and the integrity of connections.