UV-assisted direct ink writing of fully bio-derived photopolymer composites with high cellulose loadings

This work presents a plant oil-derived acrylate resin system with high loadings of microcrystalline cellulose (MCC), enabling high-viscosity, sustainable additive manufacturing via UV-assisted extrusion direct ink writing (DIW) 3D printing. In contrast to prior bio-based vat photopolymerization AM systems, which typically rely on low-viscosity oligomers, the present approach combines a bio-based carbon fraction with mechanical reinforcement and extrusion compatibility. The proposed resin exhibits shear-thinning behavior, making it suitable for syringe-based extrusion, and cures rapidly under UV irradiation, ensuring dimensional fidelity and layer integrity. The mechanical response of the printed composites is tunable through formulation and post-curing. In the UV-cured state, the materials remain tough and flexible, with elastic moduli below 60 MPa and elongation at break exceeding 50%. Thermal post-curing increases the elastic modulus to 594 MPa and raises the tensile strength to 15 MPa at the optimized cellulose content. Thermogravimetric analysis shows that varying cellulose content does not significantly alter the thermal stability, while thermal post-curing shifts the decomposition onset by 3°C–5°C to higher temperatures. Collectively, the developed ink formulations and processing strategy establish a new path for green composite AM, advancing the state of the art and positioning bio-based photopolymers as viable candidates for industrial AM applications.