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International Journal of Bioprinting Multi-material bioprinting with OCT imaging

material accumulation occurs in area 2. After the nozzle 5. Conclusion
control optimization, the printing results were obtained In this paper, a multi-material static model and a time-related
and are shown in Figure 12C and F, where no material control model were proposed to improve the accuracy
accumulation or gap was observed.
for multi-material scaffold bioprinting and the printing
In the proposed method, the static model for materials efficiency. Both models were experimentally established
is established before the actual printing task and without via OCT imaging data. The multi-material static model
prior knowledge of the printing task, and it works as a provides feasible printing parameter ranges for different
database for the materials. But the nozzle control modal materials to achieve accurate mutual matching of filament
is task-related, thus it may have off-line or on-line size or layer thickness and printing requirements with
applications. In the off-line application, pre-experiments different materials. The time-related nozzle control model
with first one or few layers of the scaffold are performed, and could modify nozzle control parameters efficiently and
the optimal nozzle control parameters can be optimized, improve the printing accuracy of different materials at the
as discussed in section 2.4. When the optimal parameters connection point in the face of different printing methods
were obtained, the actual printing task was performed. of multi-nozzles. Experiments were correspondingly
Its performance is shown in both the three-layer scaffold conducted to verify the proposed models and the method,
experiment and the nine-layer scaffold in section 3.4. On and accuracy improvement using the models was observed.
the other hand, the nozzle control parameter optimization In the future, we will explore more complicated structures
can be integrated into the actual printing process, which and establish an intellectual program for parameter
is the on-line application, and the parameter is updated determination in the multi-material bioprinters.
each time a new layer is finished. In most pre-experiments,
including those in section 3.4, it was noted that material Acknowledgments
accumulation or gap can be eliminated within 1 cycle of
nozzle control parameter correction, which shows the None.
high efficiency in correction. In addition, in the nine-layer
scaffold printing experiment, the same nozzle control Funding
parameter set was adopted for the connection points at The authors thankfully acknowledge the financial support
different positions, which shows the tolerance performance listed as follows: National Natural Science Foundation of
of the parameter set. Thus, this method has the potential in China (No. 31927801); Key Research and Development
on-line applications where no considerable changes occur Foundation, Science and Technology Department of
in neighboring layers’ trajectories. Zhejiang Province (No. 2022C01123).
At present, we have realized the printing of scaffolds
with the same layer thickness, where the layer thickness Conflict of interest
of silica gel materials with different properties were The authors declare no conflict of interests.
accurately registered, as shown in Figures 9–11. In the
future work, a wider collection of biological materials Author contributions
(e.g., hydrogel materials and PCL materials), more
complicated scaffold structures (e.g., circular structures Conceptualization: Jin Wang, Ling Wang, Mingen Xu
and tubular structures), and more filament control means Formal analysis: Jin Wang, Shanshan Yang
(e.g., needle shape) could be further explored to expand Investigation: Jin Wang, Chen Xu
the application scenarios and enhance the flexibility of Methodology: Jin Wang, Chen Xu, Shanshan Yang
filament size and layer thickness control. In addition, Supervision: Mingen Xu
although we have ensured the accuracy of the result Writing – original draft: Jin Wang, Chen Xu
through the model with pre-experiments, there is still Writing – review & editing: Shanshan Yang, Ling Wang
room for improvement in the modeling process. First, All authors have given approval to the final version of
OCT technology has poor imaging effect on the internal the manuscript.
structure of the multi-layer transparent material printing
scaffolds, and the signal-to-noise ratio of the image can Ethics approval and consent to participate
be further enhanced by adding a contrast agent into the Not applicable.
transparent material. Second, an intelligent software
program can be made to predict the optimal nozzle Consent for publication
control parameters of multi-material bioprinting using
deep learning or other methods [39,40] . Not applicable.

Volume 9 Issue 3 (2023) 253 https://doi.org/10.18063/ijb.707