Ion-linked double-network hydrogel with high toughness and stiffness

In this paper, a facile one-pot method was developed to fabricate ion cross-linked calcium-alginate/poly(acrylamide) (PAAm) double-network hydrogels with excellent toughness and stiffness. In comparison to the sodium alginate/PAAm hybrid gel, the as-fabricated calcium-alginate/PAAm gel demonstrated superior mechanical properties. After soaking in calcium chloride (CaCl2) solution, the size of the as-synthesized hybrid gel can be well controlled without observable volumetric swelling through manipulating the equilibrium between shrinkable elastic energy from ionic (Ca2+) bonds and swelling osmotic energy. This material design and processing technology are promising to fabricate complicated-shaped cartilage with high geometric fidelity. After soaking in 8 wt% CaCl2 solution for 2 h, compressive strength of calcium-alginate/PAAm gel was significantly improved by 92 % compared to PAAm single network hydrogel, meanwhile the size and shape of calcium-alginate/PAAm gel were nearly changed and deformed, respectively.