3.2 Geometry
Preparation
The geometry consisted in a prism of squared base. The CAD
model was designed with a commercially available CAD software:
1. Sketch a square of 2 Â 2 cm.
2. Extrude it along the vertical axis for 0.4 cm.
3. Save the file in .STL format.
3.3 Start Fabrication
The techniques of choice used to fabricate scaffolds were fused
deposition modelling (FDM), 3D-fiber deposition (3DF), and
bioextrusion. As a representative case, the machines used were,
respectively, Hyrel 3D 30M, EnvisionTEC V1.0 Bioplotter, and
SysEng BioScaffolder. All three machines require some preliminary
steps before actively manufacturing. These include assembling the
extrusion head (see Note 10), calibrating the working distance (see
Note 11), preparing the code, and loading the material. The
devices can be seen in Fig. 3, while Fig. 4 shows a picture of the
extrusion heads and the nozzles used. For a quality assessment,
check the scaffolds under a light microscope, and adjust the printing parameters according to the specific technique used (temperature, pressure or screw speed or rollers speed, deposition speed) to
get the desired quality, and manufacture again (see Note 12 for
further information about the choice of the right parameters).
Table 1 lists a set of optimized parameters for the materials
described here. A summary of all the main features of the three
different techniques can be found in Table 3.
3.3.1 Fused Deposition
Modelling
Printing with Hyrel 3D 30M printer (Fig. 3c) is described here as
an example of FDM. To manufacture the thermoplastic material
necessary for this printer, a step on conversion of the pellets into
filament is performed using a twin-screw extruder:
1. Mount the 1.5 mm die.
2. Set the temperature of the machine to 140
C and wait for it to
stabilize. See Notes 13–15 for recommendations about the
choice of the right temperature for deposition.
3. Start the motor by setting the rpm to 100.
4. Pour progressively up to 7 g of material in the hopper and push
it with the specific tool.
5. Mix for 5 min, open the bypass valve, and collect the filament
extruded through the die on aluminum foil, avoiding the different sections to fuse together.
6. Cut any nonuniform sections of the filament.
7. Store the filament in a vacuum-sealed bag in a dry and dark
place.
To perform the scaffold fabrication with the Hyrel AM System,
install first the two-roller extruder head (Fig. 4c left) and set the
AM of Thermoplastics for Tissue Engineering
81
Preparation
The geometry consisted in a prism of squared base. The CAD
model was designed with a commercially available CAD software:
1. Sketch a square of 2 Â 2 cm.
2. Extrude it along the vertical axis for 0.4 cm.
3. Save the file in .STL format.
3.3 Start Fabrication
The techniques of choice used to fabricate scaffolds were fused
deposition modelling (FDM), 3D-fiber deposition (3DF), and
bioextrusion. As a representative case, the machines used were,
respectively, Hyrel 3D 30M, EnvisionTEC V1.0 Bioplotter, and
SysEng BioScaffolder. All three machines require some preliminary
steps before actively manufacturing. These include assembling the
extrusion head (see Note 10), calibrating the working distance (see
Note 11), preparing the code, and loading the material. The
devices can be seen in Fig. 3, while Fig. 4 shows a picture of the
extrusion heads and the nozzles used. For a quality assessment,
check the scaffolds under a light microscope, and adjust the printing parameters according to the specific technique used (temperature, pressure or screw speed or rollers speed, deposition speed) to
get the desired quality, and manufacture again (see Note 12 for
further information about the choice of the right parameters).
Table 1 lists a set of optimized parameters for the materials
described here. A summary of all the main features of the three
different techniques can be found in Table 3.
3.3.1 Fused Deposition
Modelling
Printing with Hyrel 3D 30M printer (Fig. 3c) is described here as
an example of FDM. To manufacture the thermoplastic material
necessary for this printer, a step on conversion of the pellets into
filament is performed using a twin-screw extruder:
1. Mount the 1.5 mm die.
2. Set the temperature of the machine to 140
C and wait for it to
stabilize. See Notes 13–15 for recommendations about the
choice of the right temperature for deposition.
3. Start the motor by setting the rpm to 100.
4. Pour progressively up to 7 g of material in the hopper and push
it with the specific tool.
5. Mix for 5 min, open the bypass valve, and collect the filament
extruded through the die on aluminum foil, avoiding the different sections to fuse together.
6. Cut any nonuniform sections of the filament.
7. Store the filament in a vacuum-sealed bag in a dry and dark
place.
To perform the scaffold fabrication with the Hyrel AM System,
install first the two-roller extruder head (Fig. 4c left) and set the
AM of Thermoplastics for Tissue Engineering
81