3D printing of concentrated nanocellulose material: The critical role of substrates on the shape fidelity and mechanical properties

Abstract

This paper presents a breakthrough in the shape fidelity and mechanical strength of 3D-printed high-concentration nanocellulose structures, demonstrating a record flexural strength of 149 ± 2 MPa and a flexural modulus of 15 ± 0.8 GPa. These findings replace the previous method of 3D printing on conventional substrates with wood substrates for highly concentrated nanocellulose (HCNC) structures. The HCNC structures are 3D-printed using extrusion and processed under controlled drying conditions (Relative humidity: 60 % and 45 %, Temperature: 25 °C) to achieve outstanding mechanical properties without sacrificing structure shape fidelity/retention. It was noticed that the drying phenomenon of HCNC structures on the conventional substrates is responsible for the adhesion issues between the printed layers resulting in low shape fidelity/retention. In contrast with conventional substrates, the wood substrates offer an increased drying rate from the bottom side of printed HCNC structures due to its hydrophilicity and wicked nature, which helps maintain the shape fidelity without using additional crosslinkers, resulting in improved shape fidelity/retention and mechanical properties. The 3D-printed nanocellulose structure bears twice the load compared to a commercial poly lactic acid 3D-printed one. These features open a new horizon for fabricating 3D-printed nanocellulose structures for advanced environmentally friendly structural applications.