Research on the flow behavior of bio-ink inside the extrusion nozzle during printing.

Nozzle shape greatly affects the activity of cells and growth factors inside bio-ink, which is easy to be ignored. In this research, the finite element simulation software based on fluid dynamics theory was used to simulate the extrusion flow behavior of the bio-ink inside the printing needle. By establishing the flow models of two commonly used needles (cylindrical and conical needles), taking sodium alginate solution as bio-ink, the extrusion flow behavior of bio-ink inside the printing needle was simulated. Following, taking steady pressure, flow rate, and fluid shear stress as the research objectives, the response effects of nozzle geometry parameters, including shape, size, and feeding pressure, on the flow behavior of bio-ink were analyzed. Finally, a method based on the idea of integration for evaluating the cumulative damage to the active substances inside bio-ink has been proposed. Results show that the wall shear stress is the main stress suffered by bio-ink in the bio-printing process. Smaller inlet pressure and larger nozzle outlet diameter are beneficial for reducing wall shear stress. Compared with the cylindrical nozzle, although the maximum wall shear stress of the conical nozzle is higher than that of the cylindrical nozzle under the same inlet pressure and outlet nozzle diameter, the time of bio-ink subjected to the wall shear stress is shorter. The cumulative damage of the cylindrical nozzle is 29.65 Pa·s, and that of the conical nozzle is 18.25 Pa·s, which indicates that the conical nozzle has better biofriendliness and less damage to the active substance inside the bio-ink. [ABSTRACT FROM AUTHOR]