3D printing of lignin-based supramolecular topological shape-morphing architectures with high strength, toughness, resolution, and fatigue resistance

The design and fabrication of customized and sustainable elastomers with supramolecular frameworks remain a central focus of scientific research. 3D printing represents an advanced manufacturing technology that has garnered significant attention. Lignin, a naturally abundant polymer, fits well with 3D printing due to its unique aromatic-rich structures that can provide rigidity and structural support. However, challenges persist in developing UV-curable lignin-based inks and fabricating high-strength lignin-based composite hydrogels with tailored shapes and structures through vat photopolymerization (VPP) printing techniques, largely due to lignin's inherent heterogeneity, fragility, and poor fluidity. Here, we successfully developed a unique lignin-based photosensitive macromonomer resin tailored for VPP 3D printing. Using an ethanol/water fractionation process, heterogeneous lignosulfonate (LS), a by-product of the pulp and paper industry, was treated to isolate highly reactive lignin fractions rich in phenolic hydroxyl and sulfonic groups. These fractions were then chemically modified to synthesize a lignin-based macromonomer known as urethane acrylated lignosulfonate (UALS). The resulting lignin-based macromonomer (15-35 wt%) exhibits excellent compatibility with photosensitive resin formulations, enabling effective VPP 3D printing. The 3D-printed lignin-based supramolecular composite hydrogels exhibit high strength (tensile strength of similar to 2.12 MPa, an elongation at break of similar to 220.13 %), high resolution, fatigue resistance (up to 10000 cycles), and moisture-induced responsive behavior. The development of 3D-printed lignin-based supramolecular elastomers with defined shapes and patterned structures significantly advances the discovery of robust and environmentally sustainable soft materials with potential applications in soft robotics and tissue engineering.