Computational Fluid Dynamics Assessment of the Effect of Bioprinting Parameters in Extrusion Bioprinting.

Wall shear stress is the most critical factor in determining the viability of cells during the bioprinting process, and controlling wall shear stress remains a challenge in extrusion bioprinting. We investigated the effect of various bioprinting parameters using computational simulations on maximum wall shear stress (MWSS) in the nozzle to optimize the bioprinting process. Steady-state simulations were done for three nozzle geometries (conical, tapered conical, and cylindrical) with varying nozzle diameters (0.1 mm-0.5 mm) at different inlet pressure (0.025 MPa-0.25 MPa) as inlet conditions. Non-Newtonian power law was used to model the bioink rheology and four different bioinks with power-law constants ranging from 0.0863 to 0.5050 were examined. To capture the dynamic behavior of the bioink and the thread profile of the extruded bioink, transient simulations were carried out. Our results indicate that although the MWSS is lowest in the cylindrical nozzle, this stress condition lasts for a longer portion of the nozzle and for the same inlet pressure and nozzle diameter, the mass flow rate is lower compared to the tapered conical and conical nozzle, contributing to lower cell viability.