nanocellulose

Nanocellulose denotes nanoscale cellulose materials derived from natural cellulose. It includes cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC). Nanocellulose exhibits high mechanical strength and stiffness relative to its weight, a large specific surface area, and tunable surface chemistry, while remaining biocompatible and renewable.

CNCs are short, rod-like particles produced by acid hydrolysis of cellulose, with high crystallinity and rigid geometry. CNFs are long, entangled nanofibers obtained by mechanical fibrillation of cellulose pulp, often aided by chemical pretreatments. BNC is produced as a hydrated, three-dimensionally networked material by certain bacteria during fermentation, yielding a pure, highly hydrated, and mechanically robust gel.

Common sources include plant-based celluloses from wood pulp, cotton, or agricultural residues for CNCs and CNFs; BNC comes from bacterial fermentation. Production methods include acid hydrolysis (for CNCs), mechanical defibrillation (for CNFs), TEMPO-mediated oxidation to introduce surface carboxyl groups, and enzymatic pretreatments. Surface chemistry and crystallinity are adjustable to suit applications.

Nanocellulose offers high tensile modulus and strength at low density, with high aspect ratios and large surface areas. CNCs are highly crystalline; CNFs provide entanglement and network-forming behavior; BNC forms dense hydrogels. All forms are hydrophilic and can be chemically modified; dispersion in matrices and moisture sensitivity are important considerations.

Applications include reinforcing fillers in biopolymer and conventional polymers, barrier films and coatings, rheology modifiers in paints and inks, aerogels and foams for insulation, and biomedical uses such as wound dressings and tissue engineering scaffolds.

Advantages include renewal and biodegradability, while challenges involve production costs, energy demand, scalability, dispersion and aggregation control, moisture sensitivity, and regulatory considerations for medical products.