3D Printing Super Strong Hydrogel for Artificial Meniscus

3D printing of artificial meniscus affords the great potential to overcome the supply shortage of transplantation; however, inferior mechanical properties pose as a huge roadblock for this potential. This paper demonstrates 3D printing of superstrong hydrogel for eliminating this barrier. Specifically, a multiple-ingredient ink consisting of cellulose nanocrystal (CNC), hard phenyl acrylate (PA), and soft acrylamide (AAm) components was developed to print super strong hydrogel toward artificial meniscus application. The effect of cellulose nanocrystal fraction on the printability of the complex ink was investigated, and >8% cellulose nanocrystal was found to be required for adjusting the ink viscosity and thus making the ink printable. As-printed inks were cross-linked to form interpenetrated polymer network via UV irradiation, which resulted in numerous randomly distributed hard PA-rich regions and soft AAm-rich regions in an interpenetrated gel network. The synergistic effect of hard and soft phases on mechanical performance was studied. Hydrogels printed with a PA/AAm ratio of 4:2 exhibited exceptional tensile strength of ∼16.5 MPa but poor toughness of ∼1.8 MJ m-3 due to the too high PA molar ratio. The hydrogel with a PA/AAm ratio of 3:2 demonstrated a tensile strength of ∼4.4 MP and toughness of ∼6 MJ m-3, which are equivalent to or even superior to the performance of human meniscus. Finally, printing of such hydrogel-based artificial meniscus was demonstrated, and the printing precision was studied.