Biomedical Engineering Reference
In-Depth Information
12.5.6 Solid Freeform Fabrication
Solid freeform fabrication techniques are a collection of techniques that
can build objects in almost any net shape, by depositing material layer
by layer. The method is often also known as rapid prototyping. The
advantage of these techniques over foaming is that the scaffold structure
is dictated by a computer that controls the device that lays down the
material. This means that scaffolds can theoretically be produced in
any design as dictated by a computer-aided design (CAD) file. The
CAD file could even be generated from a computer-assisted tomography
(CAT) scan of a tissue, allowing complete replication of the structure
of a tissue. However, in reality, not all materials can be used directly
in solid freeform fabrication. Thanks to new melt-derived bioactive
glass compositions, bioactive glass scaffolds are produced by a printing
process called robocasting. The scaffolds produced had thick struts (
>
50
μ
m (Figure 12.13 and see Figure 13
in colour section). The alignment of the rows of struts was so accurate
that compressive strengths of more than 150MPa were achieved in the
direction of the pore channels (three times that perpendicular to the pore
channel directions), with 60% porosity. This is similar to the strength
of cortical bone. The composition used was 6P53B (51.9mol% SiO
2
,
9.8mol% Na
2
O, 1.8mol% K
2
O, 15.0mol% MgO, 19.0mol% CaO,
2.5mol% P
2
O
5
), with a particle size of
D
50
=
m) and pores in excess of 500
μ
m. Inks were created
by mixing 30 vol% glass particles in 20wt% Pluronic F-127 solution.
1.2
μ
(a)
(b)
Figure 12.13
Bioactive glass scaffolds produced by the robocasting solid freeform
fabrication method: (a) X-ray microtomography image and (b) SEM image. (Image
provided courtesy of E. Saiz and Q. Fu. Copyright (2012) E. Saiz and Q. Fu.)
