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Xu, et al.
2.2.6. Customized software enables the application of structures, the printing effects of the developed system in
the desired print control terms of temperature-sensitive biological ink, photosensitive
This software system is divided into two control modes, biological ink, high-temperature stent printing, high-
(i) standard mode: first select the 3D model (external temperature stent and hydrogel composite printing, coaxial
source or built-in model), then perform layering, then printing, and suspension printing will be verified. The related
printing parameters of the extrusion cell printing process,
explore process parameters, and finally print the structure such as nozzle diameter, printing speed, ejection speed,
and (ii) Quick mode: prestore the optimized data model printing path spacing, and height, affect the formability of
containing printing process information in the common the cell printing ink and the cell survival rate, as shown
database so that users can skip redundant steps and in a previous article [59,60] . Therefore, this research will not
quickly start the repeated printing of the model when perform further exploration in this area. Initial experiments
they use it for the 2 time. The printer software interface
nd
enables the input of required printing parameters and and prefabricated printing results are described below.
the automatic generation of g-codes to appropriately 3.1. Printing thermosensitive hydrogels
move and trigger the motion system and nozzles. The
temperature and UV control interface allow one to set the To print a 3D complex cell structure with high-resolution,
nozzle’s temperature, UV curing intensity, and duration. the cell printing ink needs to improve the gel capacity
of the bioink by increasing the viscoelasticity of the
2.2.7. Integrated technology for modular and printing ink to maintain the mechanical properties of the
collaborative printing stacked structure. However, as the viscoelasticity of the
cell printing ink increases, the shear force that the cells
Nozzles that can be quickly replaced are an important
foundation for modular combinations of nozzles. The are subjected to during the printing process increases,
thereby reducing the survival rate of the cells. Therefore,
print head often contains functions such as temperature controlling the viscoelasticity of the cell printing ink
control and extrusion control, so the connection between
the print head and the main body of the printer has not only during the printing process and finding the appropriate
a mechanical connection but also an electronic interface. viscoelastic interval of the cell printing ink are important
The common mechanical connection method is screw steps to achieve good cell 3D printing (good formability
connection. The connection is firm, but it is inconvenient and biological performance). Temperature can control the
to disassemble. Therefore, this study intends to explore temperature-sensitive material in the gel or sol state and
a way to quickly replace and combine multifunctional then affects the viscoelasticity of the material.
The rheological properties of gelatin, silica gel,
nozzles. A quick-release joint (a fixed method of
magnetic attraction and POGO PIN electronic interface) GelMA, and PF127 were tested before printing to
was used to connect the motion system and achieve the determine the optimal printing temperature of the
signal transmission. When using the magnetic attraction materials (Figure 6A-D). Various structures were
method of plane bonding, if the magnetic attraction is too printed using 10% (w/t)gelatin at 22°C and as shown
small, the nozzle will easily shake naturally, resulting in Figure 6E. About 40% (w/t) PF127 (Pluronic F-127,
in poor stability. If the magnetic attraction is too large, Dow Corning) was printed at 18°C to verify the printer’s
it is not easy to assemble the nozzles. Therefore, in this ability to print complex structures (Figure 6F). Gelatin,
silica gel, nanocellulose, and PF127 material were used
study, a “⅂”-shaped suspension mode was designed. The
“convex” shape designed on the top of the back plate to print (motor-driven piston-based microextrusion) the
matches the “concave” shape structure on the back of complex shape of the human ear structure, as shown
the nozzle, which not only provides nozzle upward force in Figure 7A. The pneumatic-based microextrusion
support but also limits the possibility of swinging from nozzle was also tested using PF127, GelMA to print
side to side. Using the combination design of magnets mesh (Figure 7B[i]), cervical stent (Figure 7B[ii]), and
and the matching design of the POGO PIN, the nozzle spinal cord (Figure 7B[iii]) structures. The above results
can be quickly connected and removed from the motion show that the printed model maintains a high fidelity.
A mixed bioink containing 10% (w/t) gelatin, 1% (w/t)
system (within 3 s).
sodium alginate, and cells (1 × 10^6 cells/mL) mL)(the
3. Initial experiments and prefabrication rheologicalparameters as shown in Figure 6G was used
printing results of a single nozzle to print the mesh structures (Figure 6H), and the survival
rate of printed cells (A549, HeLa, NIH3T3 and HUVECs)
To further explore the capability of this multifunctional was tested afterward. After printing, the cell survival rate
modular 3D bioprinting system, the printability, fidelity, and exceeded 80% (Figure 6I-M), meeting the requirements
resolution were subsequently evaluated. To achieve soft and for further use. Actin staining results of HeLa cells as
hard materials, multiscale fiber filaments, and multiscale shown in Figure 6N.

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