Page 247 - IJB-9-3

International Journal of Bioprinting Multi-material bioprinting with OCT imaging

layer . Our previous work also used OCT to realize real- plane was shown in Figure 1A. In the red box of XY
[32]
time multi-parameter quantization and feedback during plane in the figure, along the X direction, we counted the
the bioprinting process for mono-material , which number of a pixel value of 1 in the Y direction (Num ) at
[33]
i
shows superiority in data collecting as feedback in the each position (X ) and the filament pixel size was ∑ Num i .
bioprinting process. Thus, in situ volumetric imaging, error i ∑ i
detection, and 3D reconstruction can be realized by OCT, In the XZ plane, the pixel layer thickness was Z -Z ,
which provides a comprehensive method for print quality top bottom
assessment, paving the way to establish establishing high- Z was the pixel coordinate with pixel values greater than
top
precision registration procedure for improving the printing 0 appearing first at the top in the Z direction, and Z bottom
accuracy. was the pixel coordinate in the Z direction at the bottom.
In this study, the multi-material static model and the Thus, the filament size was Num i 19 4. μm and the layer
time-related control model were built with the benefit of i
OCT technology to achieve high-accuracy multi-material thickness was top Z bottom 58. μm.
Z
printing. Specifically, the static model was adopted to i
quickly determine the printing parameters for different In this study, we focused on the silica gel materials
materials under the required filament size or layer thickness, which are commonly used in the bioprinting field. Two
realizing the registration of different materials. The control different silica gels with different viscosity properties,
model determines the time-relevant response of nozzles silica gel-B and silica gel-W, were used in our study to
for each material at the starting or ending points and may experimentally demonstrate different printing materials,
automatically correct for errors in one or two correction namely paste type and semi-flowing type, respectively. The
cycles, which can improve both the registration precision extrusion rate of semi-flowing silica gel was greater than
at connection points and the overall printing efficiency. that of paste silica gel, and the surface drying time of paste
In the end, these models are used to printed single-layer silica gel was less than that of semi-flowing silica gel. In
scaffold and multi-layer scaffold, and these experiments Figure 1B, the material on the left was silica gel-B, and the
results show that different material printing paths have the material on the right was silica gel-W.
same layer thickness, and materials are precisely extruded
at the connection point between different nozzles. 2.2. Multi-material static model
Experiments were conducted to demonstrate the feasibility Due to the different rheological properties between
of the proposed method. In other words, the method is materials, the same printing parameters will lead to
helpful to improve the printing accuracy and efficiency of different printed filament metrics (i.e., filament size and
multi-material and multi-nozzle printing. layer thickness), causing mismatch between the printed
structure and the target structure. If the nonadditive
2. Materials and methods effect and interaction between different materials during
2.1. Bioprinting system and printing materials bioprinting can be omitted, a static printing model can be
In this study, we adopted the self-developed 3D bioprinting established to provide a feasible range for the one material
system (Regenovo Bio-Architect PX, Hangzhou Regenovo and reveal the relationship between filament metrics and
Biotechnology Co, Ltd.) based on optical coherence the printing parameters.
tomography . The 3D bioprinting system integrated with During a certain printing process, speed and pressure
[34]
a swept-source OCT (SS-OCT) model whose probe was play the most important role in controlling the filament
mounted next to the extrusion nozzle for on-site process metrics among all the potential printing parameters .
[35]
monitoring. Specifically, a swept laser source (HSL-20- The two silica gel materials selected in this experiment
50-M, Santec) was adopted with a central wavelength can be cured at normal atmospheric temperature, and the
of 1310 nm, a bandwidth of 105 nm, a scanning rate of small-diameter nozzle is more capable of printing delicate
50 KHz, and an axial resolution of 7.2 μm in the air . The structures . Thus, we selected a 0.26 mm nozzle for
[34]
[36]
sensitivity of the system was about 68 dB . The maximum printing, and studied the effect of speed and pressure on
[34]
axial range of the system was 6 mm (z) in the air, and the the filament metrics with different silica gel. Then, both
transverse field-of-view was 19 mm (x) × 19 mm (y). The silica gel materials were used within a pressure range of
actual sizes of a pixel in transverse and axial directions 0.15–0.40 Mpa with an interval of 0.05 Mpa, a speed range
were 19.4 μm and 5.8 μm, respectively. of 1–22 mm/s with the interval of 1 mm/s to print a series
The 2D projection view restored from the 3D OCT data of filaments with a length of 8 mm. The same parameters
was used to analyze the filament size and layer thickness. were applied in three groups. Actual printing results are
The projection of the filament on the XY plane and XZ shown in Figure 1C. Through observation, the printing

Volume 9 Issue 3 (2023) 239 https://doi.org/10.18063/ijb.707