Page 110 - IJB-9-1

International Journal of Bioprinting Robotic in situ bioprinting

3.1.2. Articulated robots The replacement of machine elements is also relatively

Articulated robots with 360° rotating joints (Figure 3C) straightforward. In contrast, issues such as massive linkages
have been developed to overcome the limitations of fixed and singularity due to parallel linkages may exist in ordinary
[44]
axes. The number of rotary joints ranges from two to ten parallel robots . Zhu et al. employed a delta robot printer
or more, and these rotary joints are often powered by servo to print cell-laden hydrogels on live mice to investigate the
[45]
motors. Most robotic arms have three to six axes, which potential of bioprinting for wound healing . The method
allow biomaterials to be placed onto curved surfaces with also demonstrated feasibility in fabricating smart wearable
[34]
sophisticated profiles from all directions . Articulated devices directly on the human body (Figure 3F). Zhao
robots are more versatile and flexible than other platforms et al. developed a micro bioprinting platform that can be
as they have multiple axes and degrees of freedom. Other installed on an endoscope to enter the human body and
merits of this anthropomorphic technology include process bioprinting. A delta robot was leveraged as the
its deployable/foldable ability to reduce the footprint. configuration of the printing platform. The delta robot can
Moreover, the advanced kinematics algorithms also help fold itself down into smaller size when entering the patient’s
[46]
to improve the precision of movement . Particularly, as body and unfold before bioprinting .
[35]
demonstrated by the da Vinci surgical system, articulated The comparison of robot configurations for in situ
robots enable surgeons to perform delicate operations bioprinting is shown in Table 1.
through small incisions . Articulated robots can
[36]
also enhance in situ bioprinting for potential clinical 4. Three-dimensional bioprinted tissues
applications. One of the main concerns in the development and organs
of the articulated robotic system is the low intraoperative 4.1. Cartilage
[37]
correction ability if the controller fails . In addition,
a singularity (a robot end effector becomes blocked in Cartilage is an important structural component of
certain directions) may exist . Compared with Cartesian the human body. Cartilage injuries are very common,
[38]
robots, the controlling and programming of articulated affecting millions of people, and they may result in joint
robots are more complicated. For instance, redundancy dysfunction. Cartilage is firm but softer and much more
can be exploited to improve manipulability and achieve flexible than bone. However, blood vessels and nerves are
more dexterous motions, but it may complicate the inverse absent in the tissue. Hence, damaged articular cartilage
kinematics . Li et al. demonstrated the feasibility of using has poor self-healing capacity, and it is difficult to detect
[39]
the industrial 6-DOF robot for direct in situ 3D printing in early articular cartilage damage. Although autologous
living animal models for injury repair. The osteochondral chondrocyte implantation, mosaicplasty, and periosteal
defect in rabbits could be repaired in about 1 min . grafts have been widely adopted as conventional treatments
[40]
Zhao et al. used a novel design and an adaptive in situ for repairing chondral defects, the reproduction of
bioprinting robot for rapid biomaterial fabrication on an normal hyaline cartilage with long-term stability and
excisional wound in mice (Figure 3D). The 6-DOF robot reliable functionality must be improved. The direct
successfully provided immediate, precise, and complete repair of cartilage by developing large-scale biomimetic
wound coverage through stereotactic bioprinting . anisotropic constructs with structural integrity, mimicking
[41]
Zhang et al. equipped a printer with a 6-DOF robotic the native tissue, is challenging. Cui et al. developed a
arm, which enabled cell printing on 3D complex-shaped 3D bioprinting system with photopolymerization that
vascular scaffolds from all directions, and proposed an oil is capable of cartilage tissue engineering. For repairing
bath-based cell printing method to preserve the natural defects in osteochondral plugs, poly(ethylene glycol)
functions of cell after printing . dimethacrylate with human chondrocytes was printed
[42]
layer-by-layer, revealing the significance of direct cartilage
3.1.3. Parallel robots repair through bioprinting . Sun et al. demonstrated
[47]
Parallel robots or delta robots have multiple arms (usually anisotropic cartilage regeneration through 3D bioprinting
three) connected to a single base mounted above the dual-factor releasing and gradient-structured constructs.
workspace (Figure 3E). These robots employ articulated The fabricated anisotropic cartilage structures showed
robots that use similar mechanisms for movement, and they fine integrity, superficial lubrication, and nutrient supply
[48]
tend to move delicately and precisely. Since each joint of the within deep layers . The dual-factor releasing and
end effector is directly controlled by multiple arms, these gradient-structured cartilage scaffold demonstrated better
robots have high efficiency with respect to their moving repairing effect in the rabbit knee cartilage defect model
speed . Other advantages of the parallel configuration in vivo (Figure 4A). Ma et al. developed a 6-DOF robot for
[43]
include simple structure design and easy installation. in situ 3D bioprinting to regenerate cartilage and explored

Volume 9 Issue 1 (2023) 102 https://doi.org/10.18063/ijb.v9i1.629