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International Journal of Bioprinting Cell viability in printing structured inks

Figure 1. Overall schematic introduction of structured ink-based 3D printing and relevant analysis of fluid forces considering cell viability. (A) Schematic
of structured ink-based 3D printing starting from printing materials to constructing structures. (B) Advantages of structured inks and considerations
of cell viability in structured ink design. (C) Fluid force parameters and cell distribution in structured inks, as well as the software interface for CFD
simulation. (D) Comparative analysis of fluid force with conventional printing. (E) Equivalent analysis of fluid force with homogeneous inks.

distribution of extruded fibers. Input parameters for conventional printing methods to some extent. Kang
simulations included material properties such as viscosity, et al. mentioned the utilization of structured ink for
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density, and velocity vectors at the respective structured constructing structures with 4-symmetric fiber cross-
ink and homogeneous ink inlets. Due to the components sections using an 18G nozzle with inner diameter of 0.84
of structured inks being extruded simultaneously from the mm. They also mentioned that conventional printing
same piston within the ink cartridge, input velocity vectors with a 27G nozzle can fabricate the same structure. This
for different material phases of structured inks were set is possible if the printing path is planned appropriately,
to be identical. Volume fractions were involved in the taking into consideration material parameters such as
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validation of the CFD models to assess the distribution of resolution and flowability. As a result, this structure
material phases within the cross-section of extruded fibers. was chosen as a representative example in structured
Fluid force parameters, including average and maximum ink geometry design. Similarly, 2-symmetric inks can
fluid pressure, as well as average and maximum shear stress be used for comparative analysis when the viscosities
(at walls and material phase interfaces), were calculated and densities of the two materials were not significantly
to evaluate the suitability of this printing method different. Additionally, vascular-like and hepatic lobule
for cell-loaded bioinks. Specifically, for comparative analogue-like inks were selected (Figure 1D). These
analysis, fluid force analysis was conducted based on the related structures can be fabricated using conventional
following structured inks: 2-symmetric, 4-symmetric, printing with multiple printheads in a stepwise manner.
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vascular-like, and hepatic lobule analogue-like inks. For The structures of vascular and hepatic lobule analogue 36
equivalent analysis, the material properties of equivalent were referenced in the design. Symmetric and core–shell
homogeneous inks, which were derived using structured inks were designed for equivalent analysis due to their
inks (symmetric and core–shell inks), were assessed. simplicity, which we had previously analyzed based on the
material phases of extrusion fibers. We found that when
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2.3. Geometric design of structured inks the height of structured inks exceeds 30 mm, it becomes
The design requirements involved the development of difficult to control the interfacial characteristics of the
structured inks capable of constructing heterogeneous structures. Therefore, the height of all structured inks in
structures, which could also be assembled using this research was set to 30 mm.

Volume 10 Issue 4 (2024) 241 doi: 10.36922/ijb.2362