fig2

Figure 2. Measure the fracture energy of polyacrylamide/Ca-alginate hydrogel specimens containing incisions of different diameters. (A) Introduce a circular hole to a sheet of hydrogel; (B) Cut a crack from the edge of the hole; (C) Pure shear fracture test; (D) The stress-stretch curve of pure shear specimens without incision; (E-G) The stress-stretch curves of specimens with incision diameters D = 0.2, 0.4 and 1.1 mm. The insets show the incision tips observed by an optical microscope.