Production and characterization of hydrolyzed bacterial cellulose for extrusion-based 3D printing applications

Bacterial cellulose obtained through kombucha tea fermentation, is a promising renewable biomaterial and is purer than plant-derived cellulose. Hydrolyzed bacterial cellulose is widely used in research due to its crystallinity. This research focuses on assessing the mechanical and rheological properties of hydrolyzed bacterial cellulose, aiming to unveil its potential for 3D extrusion-based printing. Bacterial cellulose sheets were bio-synthetized from three different Kombucha starters and after a cultivation of 7 days underwent an alkaline washing. Untreated cellulose sheets were dried and mechanically tested with uniaxial tensile tests. A blend of bacterial cellulose flakes from the different cultures was subjected to 30%(v/v) H2SO4 hydrolysis for 4 hours at 70°C. Hydrolyzed bacterial cellulose was dried in sheets and underwent uniaxial tensile testing. Hydrolyzed cellulose suspensions at different concentrations (5%(w/v),9%(w/v),13%(w/v),17%(w/v)), were produced. Rheological analysis, including flow and oscillatory tests, were conducted on these suspensions to evaluate their suitability for extrusion-based 3D printing. Tensile properties of hydrolyzed bacterial cellulose sheets were aligned with those of untreated cellulose. Rheological analysis showed a shear-thinning behavior of hydrolyzed bacterial cellulose suspensions, thus a suitability for extrusion-based 3D printing techniques. Thixotropy tests showed a prompt recovery of hydrolyzed cellulose after high imposed deformations, mimicking nozzle extrusion during 3D printing processes. In conclusion, these findings on mechanical and rheological properties of a blend of hydrolyzed bacterial cellulose unlock avenues for its utilization in advanced applications, particularly in the field of additive manufacturing.