Page 263 - IJB-10-4

International Journal of Bioprinting Cell viability in printing structured inks

When the core layer radius was 2.8 mm, the equivalent cell viability. Despite a systematic proposal of a workflow
viscosity was 3.70 Pa·s when cells were in the flow domain (encompassing the design, preparation, and processing of
of the shell layer, and was 1.72 Pa·s when cells were in the structured inks) for 3D printing in previous work, there
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flow domain of the core layer. is a glaring oversight in considering cell forces during
Next, the equivalent average shear stress was validated. material design. To address this negligence, the workflow
As shown in Figure 12C, when the core layer radius was augmented to enhance considerations at the material
was 2.8 mm, the average shear stress at the wall and at design stage, as illustrated in Figure 13.
the interface of material phases was 7.401e+0 Pa and The intricacies of determining material design
3.366e+0 Pa, respectively. The corresponding shear stress parameters lie in the considerations made to optimize for
of the equivalent homogeneous inks was 7.282e+0 Pa both extruded fiber cross-sections and cellular viability. Key
and 3.385e+0 Pa (Figure 12D) when cells were in the steps include pre-determining material design parameters
flow domain of the shell layer and core layer, respectively. based on extruded fiber cross-sections, validating fluid
Like symmetric inks, this scenario was not unique; the forces on cells, establishing equivalent homogeneous inks,
average shear stress obtained for other inks with different and experimentally assessing cell viability. Following this,
core layer radii was also comparable to the corresponding preparation and 3D printing of structured inks occur.
structured inks. Notably, CFD simulations detailed in sections 3.2 and 3.3

3.7. Material design workflow and analyzed the impact of geometric parameters on extrusion
further considerations fiber cross-sections, pre-determining geometric parameters
While E3DP enables the construction of high-resolution of structured ink patterns resembling vascular structures
tissue structures, ensuring post-printing cell viability in and hepatic lobules analogues. Subsequent examination
bioinks poses a significant challenge due to fluid forces, of both the maximum and average pressure, as well as the
including pressure and shear stress, leading to cell death. maximum and average shear stress experienced by cells,
The use of structured inks as a promising method has facilitates qualitative predictions of cell viability. This
proven effective in mitigating these forces and enhancing process guides the selection of equivalent homogeneous

Figure 12. Equivalent analysis of core-shell inks considering fluid forces. (A) Maximum shear stress in the wall and material phase interface within the
nozzles. (B) Corresponding equivalent homogeneous inks with different viscosity when the cell was in different fluid domains of the material phases. (C)
Average shear stress in the wall and material phase interface within the nozzles. (D) Validation of equivalent shear stress within the nozzles using equivalent
homogeneous inks.

Volume 10 Issue 4 (2024) 255 doi: 10.36922/ijb.2362