Page 51 - IJB-9-2

International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

Figure 2. Physical properties of 3D-printed PCL grafts. (a) Appearance of 3D-printed PCL grafts fabricated by screw-type bioprinter; scale bar = 1 cm. (b)
Minimum thickness of layer fabricated by screw-type; scale bar = 50 µm. (c) Scanning electron microscopy image of surface of the PCL grafts fabricated by
screw-type; scale bar = 1 mm. (d) Density of mono fiber extruded by pneumatic pressure-type and screw-type. (f) Characteristics of PCL grafts. * P < 0.05.
strength of the layer prepared by the screw-type bioprinter strength than the layer printed by the pneumatic pressure
was 29.18 ± 2.10 MPa, which was about 34.76% higher method due to the shear force of the screw.
than that of layer prepared by the pneumatic pressure-type The adhesive force between the layers of the PCL graft
bioprinter, which was 21.65 ± 1.11 MPa.
fabricated by the two types of bioprinter was measured. As
In polymer processing, a shear force affects the a result, the sample fabricated by the screw-type was 3.15
orientation and crystallinity of the polymer chain. ± 0.30 MPa, which was about 2.72 times higher than the
Jariyavidyanont et al. reported that the shear force induces value of the sample prepared by the pneumatic pressure-
the crystallization of polyamide 11. They observed that the type, 1.16 ± 0.13 MPa.
polymer chains formed a repeated unit structure due to the As shown in Figure 4, the tensile strength of PCL
shear force . Additionally, Gao et al. studied the effect of a grafts prepared under the same conditions was measured.
[17]
shear force on the material orientation, crystallization, and As a result, it was confirmed that the tensile strength of
mechanical properties. They showed that the crystallinity the sample prepared by screw-type was 6.18 ± 0.15 MPa,
of the material increased in the dynamic condition which was about 29.89% higher than that of the sample
compared to that in the static condition; consequently, the fabricated by pneumatic pressure-type, which was 4.76 ±
tensile strength and e-modulus of the material improved . 0.63 MPa. The reason for the higher tensile strength of the
[18]
As shown in Figure 3(b), despite the PCL being melted, PCL graft fabricated by screw-type is thought to be that
the crystallinity of the PCL fiber printed by screw-type the higher density and tensile strength of the single fiber
bioprinting decreased by about 3.50%, so it was similar constituting it were reflected in the physical properties of
to that of the raw material. However, the crystallinity was the final product.
16.72% higher than that of the PCL fiber printed by the
pneumatic type bioprinter. Based on the thermal properties As shown in Figure 4d, the bending strength of the
of polymer materials, it is considered that the layer printed grafts prepared by the screw-type method was 7.99 ± 1.60
by the screw-extrusion method has a higher mechanical MPa, which was about 67.76% higher than that of the grafts

Volume 9 Issue 2 (2023) 43 https://doi.org/10.18063/ijb.v9i2.652