Fig. 4. Mechanical properties of the cellulosic hydrogels.

a Photographs of Ion-CB hydrogels formed in the different mold. b Photographs of Ion-CB hydrogels under various external forces. c Photographs of the Ion-CB hydrogel cut by a scissor. d Compressive stress-strain curves of the hydrogels. e Tensile stress-strain curves of the hydrogels. f Compressive modulus and toughness of the hydrogels. Data are presented as mean values ± SD, n = 3 independent samples. g, h Cyclic compressive stress-strain curves of Ion-CB hydrogel (g) and Ion-C hydrogel (h) with a maximum strain of 50%. i The mechanical properties of Ion-CB hydrogels and other reported cellulose-based hydrogels, including double network cellulose hydrogel⁴², nanocomposite cellulose hydrogel⁴³, chemically cross-linking cellulose hydrogel⁴⁴, physical cross-linking cellulose hydrogel⁴⁵, and bacterial cellulose hydrogel⁴⁶.