Biomedical Engineering Reference
In-Depth Information
10.2 Electron micrographs and three-dimensional reconstructions of
microcomputed tomography (CT) scans comparing a scaffold made using
particulate-leaching techniques (a), (c) and three-dimensional fabrication
techniques (b), (d). Scale bar represents 1mm (Malda et al., 2005).
matrix layer by layer (Fig. 10.2). There are three general categories of SFF
devices: laser-based, printing or nozzle-based systems. Regardless of the
solidification mechanism, the device contains some type of lift or fabrication
piston enabling the SFF setup to work in the x±y plane in iterative z-plane steps.
These methods differ in how they accomplish the goal of creating a solid two-
dimensional structure in each z-plane. Laser methods use electromagnetic
energy to selectively polymerize or solidify a monomer solution or powdered
material. Printing systems use chemical binders to create structures out of a
powder bed or using wax deposition, and nozzle systems extrude a thin
chemically or thermally treated material that then solidifies on the collecting
base in iterative z-planes (Hollister, 2005; Lee et al., 2008).
Computer-aided techniques have shown promise as a method to fabricate
matrices for various tissue engineering applications. SFF manufactured matrices
have been shown to perform better as vehicles for cartilage growth than matrices
created using compression molding and particulate-leaching (Malda et al.,
2005). With the use of SFF manufacturing, it is also now possible to create a
porated polymer matrix with almost identical stress mechanics as native
cartilage (Kemppaien and Hollister, 2010). Currently, the primary drawback of
computational matrix fabrication is that the technology does not currently exist
to control manufacturing on a submicron scale (Hollister, 2005). The use of
nanoscale characteristics has been repeatedly shown to increase the biological
activity of matrices and currently SFF scaffolds can only be engineered to have
features as small as 100m. Until SFF techniques are improved, post-production
processing using other methods for surface modifications will have to suffice to
create smaller features (Koegler and Griffith, 2004).
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