Fig. 2: The bulk mechanical properties of the designed hydrogels.

a A strip of the undeformed PAA-G8 gel was fixed to two rigid clamps on the top and the bottom. The hydrogel was stretched to 11 times its initial length in a tensile test. b A hydrogel with a precut notch (yellow line) was stretched to 5.5 times its initial length without fracture. c–e The stress–strain curves for the PAA, PEG-G8, and PAA-G8 hydrogels until break. f–h Representative stretching-relaxation curves for the PAA, PEG-G8, and PAA-G8 hydrogels. The curves are horizontally offset for clarity. The final strains are shown on the curves. Insets show the superposition of the stretching–relaxation curves at different strains. i–k Stress–strain curves for the PAA, PEG-G8, and PAA-G8 hydrogels at different initial deformation rates. l–n Fracture stress and Young’s modulus of the PAA, PEG-G8, and PAA-G8 hydrogels at different deformation rates. Error bars represent SD.