Unlocking the potential of a 3D extrusion-based printer as a capillary rheometer

Capillary rheometry is one of the most widely used techniques for measuring the viscosity of fluids at high shear rates. It is commonly employed to replicate industrial conditions, particularly in polymer processing. Notably, capillary rheometers rely on the same pressure-driven extrusion principles found in many 3D bioprinters. In this study, we explore the potential of using a commercial 3D bioprinter—an increasingly widespread and accessible technology—as a cost-effective and versatile capillary rheometer for measuring nonlinear rheological behaviour at high shear rates. Beyond its practical simplicity, this setup enables the extraction of key rheological parameters, such as viscosity and shear rate, through a straightforward mathematical analysis of the extrusion data. To demonstrate the feasibility of the approach, three model fluids—polydimethylsiloxane (PDMS), aqueous solutions of κ-carrageenan, and cetylpyridinium chloride— each one with a distinct and peculiar rheological behaviour, were emplyed. The resulting shear viscosity versus shear rate curves obtained from the 3Dprinter show good agreement with those of a conventional rotational rheometer, with an average deviation of approximately 5%. This study highlights the scientific relevance of the method, which combines affordability, ease of implementation, and adaptability to real-world applications, thereby positioning extrusion-based 3D printers as promising tools for rheological characterization.