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Error Correction for Bioprinting

Figure 9. The error between the corrected printing helix trajectory and the reference trajectory was mapped to the helix trajectory; the darker
blue represents higher level of error. The error value of each helix was shown in the color column on the right.

Table 1. Error results before and after correction for each helix
Helix 1 Helix 2 Helix 3
Average error (mm) 1.06 1.15 1.58
Corrected error (mm) 0.36 0.25 0.48
Average error (mm) 2.33 2.34 2.15
(high error range)
Corrected error (mm) 0.21 0.19 0.25
(high error range)

Computer vision technology is applied to the consistent with the reference trajectory, and the helix
experimental operation to obtain the point cloud data of error in the two-dimensional (2D) space has been
the printing helix and realize the process control. A non- significantly reduced with computer vision processing.
contact camera is placed directly above the printing In the future work, an extension of the 2D space to the
platform and records the entire printing of the helix entire 3D space to evaluate and correct the errors of
images during the bioprinting process. The recorded other 3D organs should be attempted. However, the
helix images will be transferred from the camera to study was afflicted with a few challenges. For example,
the computer system, the edges of the helix will be the current computer vision is beneficial in processing
identified and extracted by the Sobel operator. The flat images, but in the case of a target object with a
estimated value of the printing helix centerline can be 3D image, the limitations of computer vision will
calculated by the edges of the helix, which represents be magnified. Furthermore, the error definition will
the printing helix trajectory. In the future, computer also shift from 2D space to 3D space. Hence, further
vision will play an important role in process control investigations are required on this topic.
with the development of computer science, including
more accurate measurement of the printed components’ 5. Conclusions
size. More precise centerline data accurately reflect the
printing helix trajectory, and the modified reference The main limitation for high-precision bioprinting is the
trajectory could be exactly expressed by the normal low resolution caused by the lack of process control, which
vector approach, which indirectly improves the accuracy is reflected in the printing trajectory as a deviation from
of correction. the original reference trajectory. The error caused by this
At present, the position of the printed helix deviation is one of the reasons that affect the resolution
trajectory is adjusted as much as possible to be of extrusion-based bioprinting. In this study, computer

182 International Journal of Bioprinting (2022)–Volume 8, Issue 2