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Liu, et al.
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Figure 1. (A) Three sources of bioprinting power. From left to right: Rotation dispensing by screw driven, air pressure dispensing by
pneumatic, and force dispensing by piston driven. (B) Schematic illustration of computer vision-aided trajectory error assessment and
correction in bioprinting.

Despite the numerous advantages of bioprinting, low Poor process control and feedback during the
printing resolution is a critical issue limiting bioprinting printing by extrusion-based bioprinting devices is the
development and utilization. It should be noted that principal factor of the low resolution of extrusion-
bioprinting resolution is a decisive factor affecting based bioprinting, which is a primary limitation of this
the overall quality of printing [11,12] . A lower resolution printing process [14] . The actual printing trajectory often
substantially reduces the accuracy in the bioprinting does not reflect according to the originally designed
model, thereby resulting in tremendous hidden dangers reference trajectories, and some error remains between
which affect treatment procedure and the overall success the designed reference trajectories. The deviation error
of organ transplantation. For instance, studies have shown between the actual trajectory and the reference trajectory
that the survival rate and differentiation of osteoblasts is small during the straight-line printing scheme, while
in the lattice area are higher than those in the film area the deviation error significantly increases during the
in the bioprinting experiment. In the same printing printing process of bending and curving structures [15,16] .
environment, the low printing resolution leads to fading Many organ bioprinting models, including ear
and the blur between the lattice area and the film area that bioprinting model, have been proposed in recent studies [17,18] .
finally will induce ambiguity and problems in the final The ear is a typical three-dimensional (3D) organ with a
cell survival rate and classification status . Furthermore, curved structure. A computer vision system was never used
[13]
recent studies on the bioprinting of the human heart to achieve process control in most of the studies, which
have indicated that the resolution of utilized bioprinting means the error between the actual printing trajectory and the
technology has a significant impact on the formation of reference trajectory during the printing process remains and
blood vessels in the heart . affects the final product, reducing the resolution of ears .
[4]
[19]
International Journal of Bioprinting (2022)–Volume 8, Issue 2 175