Page 53 - IJB-9-2

International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

prepared by the pneumatic pressure-type method. This result Since this mechanism can apply a constant force to the
is probably due to the higher strength of the monolayer and extruded material, the amount and shape of the layers can
inter-layer adhesion force of the screw-type samples. be controlled, and for this reason, a structure with high

When the weight per unit volume of a single layer is uniformity can be fabricated.
heavy and the tensile strength is high, the 3D structure Reducing the defective rate is a very important issue
would have a mechanical strength above a certain in the manufacturing industry. We have reduced the
level and high porosity at the same time. In the case defective rate of our products by improving the uniformity.
of a scaffold for regeneration, this characteristic is an The picture on the left of Figure 6(b) is a defect that occur
important factor because the induction and integration
rate of the surrounding tissue are high only when it has
high porosity. In addition, 3D printing is a layer stacking
method, and the adhesion force between layers affects the
durability of the final product. The PCL graft fabricated
by the screw-type has high interlayer adhesion and thus
has high structural stability; therefore, it is stable against
external forces, such as movement. Considering these
points, the PCL graft prepared by screw-type can have
high performance in the body.
3.4. Accuracy of the 3D constructs
In order to evaluate the accuracy of printing, the degree
of concordance with the original image of the 3D
structure was observed. The 3D structure was prepared by
designing a complex shape with a curved surface. Based
on the analysis, the degree of concordance between the
3D structure and the original computer-aided design
(CAD) image was about 98.35% (Figure 5). Accuracy in
3D printing is a very important factor because it affects the
size, shape, and microstructure of the implant.
3.5. Uniformity and defective rate
Uniformity and defective rate were set and investigated
as indicators of quality improvement and productivity
of the PCL graft. The distance between the layers of the
printed samples was measured by setting to 500 µm. As a
result, it had an average value of 485.2 µm and a standard
deviation of 0.004919, which corresponds to 99.5% to
101.8% of the set value, confirming that it has a very high
uniformity. The uniformity of the layer structure is an
important factor influencing the physical properties of the Figure 5. Concordance with the original image of the graft. (a) Design.
graft and its performance in the body. While printing, the (b) PCL graft fabricated by screw-type bioprinter. (c) Scan image of the
screw is rotated at a constant speed to eject the material. PCL graft. Scale bar = 1 cm.

Figure 6. (a) Uniformity of PCL grafts fabricated by screw-type bioprinter; scale bar = 1 mm. (b) Defect rate of printed sample.

Volume 9 Issue 2 (2023) 45 https://doi.org/10.18063/ijb.v9i2.652