Anisotropic, Strong, and Thermally Insulating 3D-Printed Nanocellulose-PNIPAAM Aerogels

Cellulose is a promising candidate for the fabrication of superinsulating materials, which would be of great interest for thermal management applications as well as for the scientific community. Until now, the production of strong cellulose-based aerogels has been dominated by traditional manufacturing processes, which have limited the possibilities to achieve the structural control and mechanical properties seen in natural materials such as wood. In this work, we show a simple but versatile method to fabricate cellulose aerogels in intricate geometries. We take advantage of the 3D printing technique direct ink writing to control both the shape and the thermal-mechanical properties of the printed cellulose-based hydrogel inks. Moreover, the shear forces involved in the extrusion process allow us to impart an anisotropic nanostructure to the printed samples. By solvent exchange and supercritical drying, the hydrogel parts are then transformed into stable aerogels. Using X-ray diffraction analysis, mechanical tests and thermal conductivity tests, our 3D printed aerogels are shown to exhibit directionally dependent thermal-mechanical properties higher than those reported for earlier cellulose-based aerogels. These characteristics enable us to fabricate customized structures that can be precisely tailored for their application as load-bearing insulating materials for thermal management.