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International Journal of Bioprinting Simulation-based comparative analysis of nozzles for bioprinting

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Figure 4. Extruded volume (mm ) of pneumatic simulations. Extruded volume of piston-driven simulations is not shown in the figure because volumetric
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flow is set as simulation inlet (10 mm /s so the extruded volume in 10 s is 100 mm ).
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in bioink flow rate might be useful for faster bioprinting with the pneumatic simulation’s extruded volume
while maintaining a recommended dispensing pressure (Figure 4). The Cone needs an inlet pressure over 15 kPa
for this specifical bioink. Therefore, the use of Nozzle- to achieve the expected extruded volume while the Nozzle
type microextrusion head in pneumatic bioprinting could requires lower pressure to extrude the same volume. In
partially solve the current challenge of low printing speed this sense, the Cone inlet pressure is 1.76 times bigger
for bioprinting [2,7,8,26] . than the Nozzle pressure. According to Boularaoui et al. ,
[26]
Outlet pressure from piston-driven simulations shows a the lower the dispensing pressure, the better the cellular
similar evolution in values and times (Figure 3). Therefore, viability. Therefore, our results showed that the Nozzle
there were no relevant differences between the Nozzle and configuration is better for microextrusion bioprinting at
Cone maximum pressure values (2.41 and 2.27 kPa), the least when it comes to inlet pressure.
time when the drop falls (0.928 and 1.208 s) or the low- Our simulation results are also similar to Gómez-
pressure peak values (250 Pa lower for the Nozzle). Blanco et al. , who obtained maximum values in the
[50]
Comparing all simulations, the Nozzle geometry outlet range of 1.14–1.76 kPa for conical tips using 15 kPa as
pressure is higher than in the Cone in all cases. However, inlet pressure. Thus, the pressure values are in the range
if only piston-driven simulations are considered, the outlet for pneumatic simulations and Cone geometry but not for
[42]
pressure is nearly the same, as these simulations establish a the rest. Additionally, Reid et al. set the outlet pressure
fixed inlet volumetric flow. Hence, the input or dispensing to 1 atm (101 kPa) and obtained maximum inner pressure
pressure plays an important role when obtaining the outlet with an approximate value of 107 kPa. This value can be
pressure, but in all cases, they vary in a short range with a understood as the inlet pressure, but proper explanation
maximum variation of approximately 2.2 kPa. is missing in the article to assure this statement. In this
sense, although they obtained 6 kPa of inlet pressure,
The dispensing (or inlet) pressure was fixed by which seems better than our results, it is difficult to make
pneumatic simulations at 15 kPa, but piston-driven a fair comparison between both studies due to three
simulations, where the volumetric flow was fixed, resulted main differences in the methodologies. The first one is
in smaller pressure for the Nozzle (Figure 5). the selected extrusion material. While the rheological
Maximum inlet pressure values are 22.73 kPa and data of the material were properly detailed in this work,
12.95 kPa for the piston-driven Cone and Nozzle they used “a fluid with similar properties to blood” as the
geometries, respectively. The obtained values are consistent bioink without further information. Second, we set an inlet

Volume 9 Issue 4 (2023) 214 https://doi.org/10.18063/ijb.730