Set-up of electrospinning and 3D printing processes for nanocellulose from lignocellulosic biomasses and bacterial fermentation to produce functional coatings for sustainable packaging

Cellulose, the most abundant natural polymer, presents a promising alternative to traditional oil-based synthetic polymers for creating sustainable and economically viable polymeric products. Current research in cellulose dissolution spans fundamental and applied aspects, emphasizing the mechanistic interactions between cellulose and solvents. Key areas of focus include developing innovative solvents, optimizing dissolution conditions, and preparing diverse cellulose-based prototypes. Recent advancements highlight the efficiency of ionic liquids (ILs) and deep eutectic solvents (DES) in dissolving cellulose, particularly when combined with ultrasonic and microwave-assisted heating. In this study, we investigated the performance of ILs—1-butyl-3-methylimidazolium acetate (BmimAc), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI), and 1-ethyl-3-methylimidazolium dicyanamide (EmimDCA)—and their solutions in gamma-valerolactone (GVL), focusing on the impact of ether linkages in the IL sidechains. Additionally, five DESs were examined, each comprising choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and various hydrogen bond donors (HBDs), including oxalic acid dihydrate, lactic acid, levulinic acid, propionic acid, and glycolic acid. These DESs were selected for their potential as eco-friendly, non-toxic, biodegradable alternatives to volatile organic solvents, as well as for their scalability and cost-effectiveness. The study employed rheological analysis, optical density measurements, and solvatochromism to evaluate the dissolution performance of ILs and DESs. Results indicated that ILs exhibited higher viscosity and greater efficiency in cellulose dissolution compared to DESs. For stable electrospinning, solution viscosity and electrical conductivity emerged as critical factors. By optimizing electrospinning parameters, cellulose fibers with reduced diameters, continuous formation, and enhanced pore size distribution were produced, improving their applicability in specialized fields. For 3D printing applications, cellulose-based inks were optimized by adjusting parameters such as cellulose concentration, viscosity, printer head temperature, and pressure. A cellulose concentration of 12.5% (w/w) improved the mechanical stability of 3D-printed structures, with BmimAc-dissolved cellulose proving particularly effective. The development process for extrusion-based 3D printing was examined, including cellulose hydrogel rheology, fiber entanglement, alignment, gelation, printability, shape fidelity, and processing conditions. Functionalization of 3D-printed cellulose materials was achieved either through surface modifications or incorporation of functional materials, paving the way for advanced applications. Lignin, known for its complex structure, was shown to significantly influence the pore structures of composites while imparting additional functionalities such as UV-blocking, antibacterial properties, adsorption, and catalytic activity. Research on functional films utilizing lignocellulose is gaining momentum, reflecting the growing interest in sustainable and multifunctional materials for cutting-edge applications.