Biomedical Engineering Reference
In-Depth Information
the softening and melting temperatures of the polymers. Therefore, it is
difficult to impossible to deposit ultra-thin ceramic films inside the pores as
well as on the surface of the porous polymers by CVD methods. ALD is an
ideal method for this kind of coating.
A process to synthesize a porous polymer ceramic composite material has
been demonstrated and the properties of the composite materials have been
investigated for a variety of applications (Liang et al., 2007, 2009). Highly
porous polystyrene divinyl benzene (PS-DVB) particles (Fig. 8.9(a)) were
successfully coated with alumina ALD films at the atomic level in an FBR at
33
C. This fabrication technique was considered to be novel since it allowed
for the ceramic layers to form on any surface site the gaseous molecules
could reach, meaning that Al 2 O 3 was successfully deposited on the external
surface and along all of the internal pore walls of the particles. A cross-
sectional TEM image of the Al 2 O 3 ALD films deposited along the walls of
the porous polymer is shown in Fig. 8.9(b). The dark lines along the edges
are Al 2 O 3 layers, and the lightest gray areas are the pores. This
functionalized nanocomposite system can be utilized for a variety of
applications, many of which can be enabling in the field of biotechnology.
Ultra-thin alumina films can increase the bioactivity of the polymer
substrate. The ability of a biomaterial to induce hydroxyapatite formation
on its surface is one criterion for designing a scaffold for bone regeneration
(Neo et al., 1992; Suchanek and Yoshimura, 1998). To examine the ability
8
￿ ￿ ￿ ￿ ￿ ￿
8.9
Cross-sectional SEM image of one uncoated highly porous PS-DVB
particle (a) and TEM image of one PS-DVB particle coated with 50 cycles
of alumina by ALD (b) (Liang
et al
., 2007). Reproduced by permission of
American Chemical Society.
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