Rheological Indicators for 3D-Printed Hydrogels: Spotlight on Chitosan
Chitosan as a key material for bio-based 3D printing inks
Additive manufacturing - especially 3D printing of hydrogels - requires materials that are not only formable and biocompatible but also precisely tunable. A recent study investigated hydrogels based on chitosan, graphene, and titanium dioxide to optimize printability and shape fidelity.
The goal was to identify rheological indicators that can predict so-called bead spreading - the tendency of printed filaments to flow after deposition.
Tan delta as a decisive parameter
The researchers demonstrated that the viscoelastic properties - particularly the ratio of storage to loss modulus (tan δ) - play a central role in the structural stability of printed parts. Tan δ values ≤ 1 proved optimal: in this range, hydrogels behaved more “solid-like” and retained their shape better during printing.
Which chitosan was used?
The hydrogels were formulated with medium molecular weight chitosan (190-310 kDa) with a degree of deacetylation of 75-85%. This type of chitosan combines good solubility in weakly acidic media with sufficient chain length for mechanical stability - ideal characteristics for 3D printing applications.
Note: Our own chitosan products are manufactured with a narrower specification, ensuring even higher consistency and reproducibility in hydrogel formulations and additive manufacturing.
Alternatives and outlook
Other types of chitosan could also provide interesting properties in such systems:
- Low molecular weight chitosan (<100 kDa): better solubility but less mechanical stability.
- High molecular weight chitosan (>400 kDa): very robust structures but more difficult to process.
- Highly deacetylated grades (>90% DD): more positive charges and stronger crosslinking, but sometimes limited solubility.
The choice of the optimal chitosan strongly depends on the application - whether for biomedical implants, functional hydrogels, or as a carrier for catalysts.
Conclusion
This study provides valuable insights into how the interplay between the polymer matrix (chitosan) and functional fillers (graphene, TiO₂) affects the printability of hydrogels. For additive manufacturing, it opens new possibilities to use chitosan not only as a biocompatible base material but also as a precisely tunable functional material.
References
Heinze, D. A., Thale, S., Yao, Y., Reynolds, J. P., Ballentine, M. L., Griggs, C. S., Williams, C. B., & Bortner, M. J. (2025). Rheology indicators for assessing bead spreading of hydrogels with functional rheology modifiers for direct ink writing: A case study for chitosan-graphene-titanium dioxide. ACS Applied Polymer Materials. https://doi.org/10.1021/acsapm.5c02887
First published on 25th of September2025
Revised on 25th of September 2025