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International Journal of Bioprinting Medical regenerative in situ bioprinting

Similarly, Zhao et al. developed a six-DOF bioprinting redundant properties, ensuring high-precision printing
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system (Figure 2A), integrating a 3D scanner and a closed- with minimal intrusion. The redundant properties of the
loop visual system to facilitate rapid healing and high- robot means that the total freedom of each joint is greater
precision printing. The authors further proposed a seven- than the freedom of the end-effector, and the redundant
axis bioprinting system for in vivo underwater bioprinting, freedom enables obstacle avoidance and enhances
specifically designed to operate within the limited space flexibility during the printing process.
inside the amniotic sac. This seven-axis robot has The printing accuracy can also be enhanced using
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flexible robotic arms, which offer the advantages of not
being limited to the DOF of rigid robotic arms and using
fewer motors, resulting in smaller robotic arm volumes.
Shi et al. developed a flexible soft robotic arm for in situ
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bioprinting, whereby the manipulator can move freely in
3D space along Cartesian and curvilinear coordinates.
Moreover, this innovation facilitates the printing of
complex structures on curved wounds. For in situ printing
on a curved surface, the ink is required to be crosslinked
immediately. However, optical crosslinking may clog the
printhead during printing, which is the primary cause of
errors during the printing process. Therefore, achieving
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instant control of the exposure direction is essential to
mitigate this issue. Fortunato et al. developed an in situ
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printing system that is integrated with an automatically
activated optical crosslinking system to control the exposure
direction according to the print path, ultimately avoiding
the risk of needle clogging. Additionally, the potential
for printhead blockage also depends on the rheological
properties of the bioink. To minimize printhead blockage,
selecting a material with shear-thinning characteristics can
be advantageous.
2.1.3. Real-time tracking of the printing process
Imaging the tissue defect area is essential to determine
the wound structure and construct a model of the
implant, prior to printing with the computer-assisted
RASBS. The accuracy of the model based on pre-print
imaging data directly affects the degree of coincidence
between the structure and the target region. During the
printing process, mismatches between the printhead ink
extrusion and movement speeds can result in deposition
errors, thereby reducing the fidelity of the printed
structure. Furthermore, correction errors of the print
head, instability in the rheological characteristics of the
bioink, and control errors stemming from environmental
Figure 2. Robotic-assisted in situ bioprinting system (RASBS). (A) factors can also affect the fidelity of the structure. Hence,
Schematic of the multi-degree-of-freedom (DoF) bioprinting system.
(B) Application of laser-assisted bioprinting (LAB) to directly deposit it is essential to monitor and implement feedback
bioink-encapsulated cells in mice models. (C) The process of in situ control mechanisms in the printing process for accuracy
3D bioprinting. (C, i) Extruded hybrid hydrogel is photo-polymerized and consistency.
by the ultraviolet (UV) lamp; (C, ii) view of the 3D bioprinting system;
(C, iii) the bioprinting process; and (C, iv) the printed scaffold. (D) The printing procedure would make real-time
Treatment of large burn wounds. (D, i) Prior to in situ bioprinting, the adjustments according to the printed structures under
wound topography was obtained using a handheld 3D scanner; (D, ii) predefined 3D geometries through CAD and/or CAM
the printhead deposits regenerative materials to specified locations under
the guidance of the wound model. Adapted with permission from Zhao to regulate the spatial distribution of all regenerative
et al. (A), Keriquel et al. (B), Li et al. (C), and Albanna et al. (D). biomaterials. The calibration process is necessary to reduce
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Volume 10 Issue 5 (2024) 51 doi: 10.36922/ijb.3366