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International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

Figure 1. Development of screw extrusion-type 3D bioprinter. (a) Structure of screw extruder. (b) Design of 3D bioprinter. (c) Screw-type 3D bioprinter.

3D bioprinter with a screw extruder was developed 3.2. Physical properties
(Table 3). By controlling the temperature and the rotational In order to evaluate the precision of the developed
speed of the screw, it is able to print materials with various screw-type bioprinter, the minimum layer thickness was
thermal properties and viscosities. It has a minimum observed. After measuring the size of the printed structure
moving distance of 12.5 µm and a high printing speed of up by setting it to a thickness of 50 µm, we found that it had a
to 10 mm/s. Existing bioprinters usually use a pneumatic high precision up to 45.60 ± 0.57 µm (Figure 2b).
pressure-type extruder. Although the pneumatic extrusion The weight per unit volume of the printed single layer
has the advantage of a simple configuration, it requires an was analyzed. The layer printed by the screw-type was
additional air compressor. The pneumatic extrusion has a about 14% heavier than the layer printed by the pneumatic
disadvantage, which is the pressure is lowered when the pressure-type. Figure 1c shows that the structures are
capacity of the air compressor is low, so that the extrusion stacked in uniform layers to form a porous multilayer
amount would change. In addition, another disadvantage structure.
is that the high-viscosity material cannot be printed
because the pressure is weak. To solve this problem, a Samples were prepared with the same conditions for
screw extruder system was introduced. Figure 1a shows comparative evaluation of constructs prepared by two
the structure of the screw extruder. It rotates a screw with types of printers.
a spiral screw blade and applies pressure in the downward 3.3. Thermal and mechanical properties
direction to print the material. Since it uses the power The enthalpy and crystallinity of PCL before and after 3D
of a motor, the amount of extrusion is constant and the printing in the screw-type samples were 68.39 ± 1.77 J/g
extrusion force is strong .
[16]
and 50.43%, respectively, corresponding to reductions of
There are two types of conveying methods: conveying 6.21% and 3.52% less than those of the raw material. For
through a lead screw and conveying using a gt2 belt. The the samples prepared by the pneumatic pressure-type
lead screw has the advantage of being able to move precisely, bioprinting, the enthalpy and crystallinity were reduced
but it has the disadvantage of slow printing speed. On the by 11.86% and 14.32%, respectively, compared to those
other hand, the gt2 belt has a fast printing speed and has a of the raw material (60.28 ± 5.09 J/g and 43.21 ± 3.65%,
minimum movement interval of 12.5 µm. respectively). Thus, this showed that deterioration of the
Their applicability was evaluated by analyzing the thermal properties of the screw-type sample has been
characteristics of PCL grafts prepared with a screw-type prevented.
bioprinter having a constant extrusion amount and strong The tensile strength of single layers fabricated by two
extrusion force. types of 3D printer was investigated. As a result, the tensile

Volume 9 Issue 2 (2023) 42 https://doi.org/10.18063/ijb.v9i2.652