Enhancing mechanical performance of elastomeric vat-photopolymerized resins via functionalized cellulose nanocrystals

Vat photopolymerization (VP) additive manufacturing enables precise, reproducible fabrication of complex biomedical devices, yet elastomeric resins with robust mechanics remain scarce for constrained surgical settings. Cellulose nanocrystals (CNC) are appealing reinforcements owing to high strength, biodegradability and biocompatibility, but their hydrophilicity limits compatibility with hydrophobic resins and drives agglomeration at higher loadings. Acrylated CNC (ACNC) was synthesised to increase hydrophobicity and promote interfacial bonding. Elastic resins with varied CNC or ACNC loadings were 3D printed by VP and characterised by tensile testing, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and rheology. Both fillers increased tensile strength, modulus, elongation and toughness relative to the neat resin, with the maximum improvement observed at 0.01 phr; ACNC consistently outperformed CNC. TEM showed relatively well-dispersed nanofillers at low concentration, whereas higher levels agglomerated and reduced reinforcement. FTIR and rheology indicated stronger covalent interactions and enhanced network formation in ACNC composites, yielding superior interfacial adhesion. Although interfacial bonding rose with filler level, agglomeration ultimately governed performance. These results demonstrate the feasibility of CNC-based nanofillers in VP elastomers and highlight ACNC as a sustainable route to high performance, patient-specific biomedical materials with clear practical relevance to constrained surgical environments.