For many load bearing biomedical applications, development of mechanically strong hydrogels are needed to act as supporting structures. Due to their extreme strength and toughness, Double-network (DN) composite hydrogels have emerged as a hot research topic. Herein, we prepared cellulose nanofiber (CNF) reinforced poly(acrylamide-co-Alginate) (P(AAm-co-Alg)) double network composite hydrogel via in situ polymerization. Based on the double-network P(AAm-co-Alg)/CNF-Fe³⁺ composite hydrogel structure formed by the covalently cross-linked acrylamide network and non-covalently COO−-Fe³⁺ ionic coordination act as a secondary crosslinking network. The development of Cellulose nanofibril (CNF) and Fe3+-based anisotropic functional tough composite hydrogel construct, presenting the development and physical characterisation (shape morphing, swelling potential and rheology) of the composite structure. By incorporating CNF and Fe³⁺, the tensile properties such as tensile strength and toughness of the P(AAm-co-Alg) composite hydrogel were improved by 300% and 250%, respectively. The loading of FE³⁺ also enhanced the energy dissipation in loading and unloading tests.

Here, we also proposed the 3D printed multilayer composites, printed in nature inspire hierarchical laminate fashion, to fabricate a functional porous composite construct. We implement the finite element (FE) modelling to analysis the pre-programmed anisotropic functional composite structure with the computer simulation. It shows how the improved physical, mechanical and biological functionality of the hydrogel fiber reinforced composite printed scaffold can be programmed by varying cellulose fibers/fibrils orientation and matrix compliance, making it suitable for load-bearing biomedical applications. Our novel design approach, based on DN composite hydrogel with enhanced anisotropic mechanical, physical and antibacterial properties of the printed construct, offers new perspectives for application in the area of electronic skin,, drug delivery and tissue engineering.