Analysis of flow behavior of bioinks outside the 3D-printing nozzles

Abstrakti

The major challenge in extrusion-based bioprinting for medical application is printability, which largely depends on the flow behavior of bioinks just outside the nozzle. This flow behavior is influenced by several factors, including nozzle dimensions, bioink density, bioink viscosity, surface tension of the bioink-air interface, and the desired printing speed and structure. Accurately predicting the flow behavior of bioinks outside the nozzle in advance can reduce the costs associated with experimental testing. In this work, Volume of Fluid (VOF) method under Finite Volume method (FVM) framework is used to study the flow behavior outside a single nozzle. Computational Fluid Dynamics (CFD) simulations are conducted to analyze the behavior of bioinks outside the printing nozzles and flow behaviors are compared with literature. Initial simulations are performed using water due to its well characterized rheological and physical properties, and its widespread use as a reference medium in bioink formulations. The effect of all process parameters on the flow outside the nozzle was analyzed using water as the working fluid. By applying two non-dimensional numbers, Reynolds number and Weber number, flow demarcation regimes are established for water. Furthermore, simulations are performed for boinks to predict their printability. The model predictions for the qualitative flow behavior of bioinks at different temperatures matches well with experimental data from the literature.