Figure 4.

An example of good mechanical properties of a 3D printed double network polymers. A) Schematic diagrams of the tough double‐network hydrogel, ionically crosslinked alginate with of Ca²⁺ and covalently crosslinked poly (ethylene glycol) (PEG). Reproduced with permission.^{[ 147 ]} Copyright 2015, John Wiley and Sons. B) Various 3D constructs printed with the double network hydrogel. C) A printed pyramid undergoes a compressive strain of 95% while returning to its original shape after relaxation.