Tensile properties of GelMA, GelMA/DbPE, and GelMA/TbPE hydrogels were characterized by an Instron 5542 tensile tester. 120 µL precursor solution was transferred into a rectangular PDMS mold (18 mm × 4.5 mm × 1.5 mm) and exposed to UV light (302 nm, 8 W) for photocrosslinking. The hydrogel samples were affixed to the machine tension grips with double-sided tape and stretched with an extension rate of 6 mm•min -1 . Ultimate stress was the maximum stress that a hydrogel sample could withstand before fracture, and its corresponding strain indicated its extensibility. Young's modulus was determined by computing the slope of the linear region of the stress-strain curves (Figure ). Toughness was calculated by integrating the area under the stress-strain curve, wherein the strain is unitless.