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International Journal of Bioprinting Low-cost quad-extrusion 3D bioprinting system

Figure 6. A 2-channel placenta model for HTR-8 cell invasion studies with 4 different bioinks. (A) Side view of the 2-channel placenta model with 4
different bioinks. (B) Top view of the 3D-bioprinted 2-channel placenta model. (C) Top view of the 2-channel placenta model showing the requirement
of 4 different materials represented by 4 different colors (SC: separation channel). (D) FITC and TRITC fluorescence microscope images overlay showing
the top view of the HTR-8 cells in green and epidermal growth factor (EGF) in red. (E) FITC and TRITC overlay with the different bioink areas within
the bioprinted placenta model shown in different colors: Red dashed areas are the modules made of GelMA with EGF incorporated within; green dashed
area is the module made of HTR-8 cells laden GelMA; white dashed area is the control channel composed of only GelMA; yellow dashed areas are the
separation channels made of only highly crosslinked GelMA. (F) Close-up top view of the experimental channel composed of EGF-laden GelMA showing
the invasion frontline of the HTR-8 cells within this channel represented by the dashed blue line.

available in the literature and on the market. 20-26 For other present designs at such a low-cost range. Such
example, Kahl et al. were able to achieve a printing volume advantages enable microfluidic mixing and gradient
of approximately 20.66% with a single nozzle based on the printing that can be achieved with minor upgrades,
original stock 3D printer configurations. This is relatively thereby creating opportunities for a much wider range of
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small compared to the 95.5% printing volume achievable applications that can be targeted using such a system.
with the QEH design presented herein.
Regarding printing resolution and accuracy, although
This was achieved with careful design of the base where the 3D printer presents high mechanical stepper motor
the whole QES attached to the X-axis carriage is designed resolution, this does not necessarily help to enable the
to give the whole QES space to traverse the X-axis bar bioprinting of biological tissue constructs with high
beyond the physical limits existing at its extremities. It accuracy. This is because the printing accuracy and shape
is also noteworthy that the volume of the syringes that fidelity of soft materials and hydrogel-based bioinks not
can be mounted onto the QEH is 3 mL compared to the only depend on the printer’s stepper motor resolutions but
1 mL syringes implemented in other systems, providing also closely depend on the printed material’s rheological
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more volume capability to print larger structures at scale. and chemical properties. With the presented mechanical
Moreover, it is important to appreciate the advantages resolution of the system, the bioprinted material properties
conferred by the QEB at such a low price point. The large are the dominant factors affecting the structural fidelity of
printing volumes and multi-material printing capabilities the bioprinted outcomes. These outcomes can be assessed
provide this open-source design a great advantage over and evaluated either experimentally or computationally

Volume 10 Issue 1 (2024) 304 https://doi.org/10.36922/ijb.0159