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- Development of micro/nano cellulose-based biodegradable materials using 3D computational simulationPublication . Mendes, José António Silva; Curto, Joana Maria RodriguesThe dramatic increase in single-use plastic (SUP) made from fossil-derived materials that are not biodegradable has contributed to the emergence of pollution as an environmental issue. Concerns regarding the environment and the development of biodegradable products from renewable sources, specifically the development of sustainable packaging using cellulose fibers from different plant sources, represent a multidisciplinary challenge for this investigation. Fibers from bleached Eucalyptus globulus, unbleached Picea abies, and hemp fibers produced in the laboratory were selected for this study. The fibers were evaluated for their morphology and biometry, and structures were produced in the laboratory with different mixtures and mechanical treatments at the PFI. Its structural, mechanical, optical, and chemical properties were experimentally characterized using methodologies and following the respective ISO standards. The fibers and structures formed by them were simulated using 3D computer simulation models. Composting was used to conduct biodegradability tests using a methodology developed to be used both in the laboratory and later in the sector's industries, having collected data for this purpose. The comparison of the reference fibers revealed that softwood fibers are approximately three times longer than hardwood fibers. In terms of width, softwood fibers are about twice as wide as hardwood fibers. In general, the increase in refining resulted in a rise in fibrillation and fine elements within the sample. As a result, the handsheets' thickness was reduced by 62% (HW) and 60% (SW) compared to handsheets made with unrefined fibers. Higher compaction and increased interfiber bonds contribute to a more cohesive and reinforced structure, as evidenced by the exponential increase in refined structures' tensile index and elastic modulus. The characteristics of hemp fibers were similar to Picea abies fibers but a little longer. The tensile index increased by 62,33% and the elastic modulus by 40,50% in an optimized combination of hemp fiber and eucalyptus fibers. Furthermore, biodegradation studies evaluated the effect of composting after 28 and 60 days, indicating that the refined structures biodegraded more quickly than the remaining samples since their mass loss values were the highest. An optimized combination of a fibrous structure containing micro and nanoscale cellulose fibers produced a porous 3D matrix that could be used for innovative packaging. In this network, the microscale cellulose fibers provide resistance and stability. In contrast, the nanoscale cellulose fibers create a structure with more interfiber bonds, which may provide resistance and stability properties advantageous for the intended functions. The porous structural units formed by cellulose fibers in micro and nanoscale were represented by 3D computational simulation, considering the input values of the fiber characterization and the output values. Finally, the proposed experimental and computational methodology proved an excellent tool for developing and optimizing 3D structures for obtaining laboratory prototypes that could be used in more sustainable food packaging.