Biomedical Engineering Reference
In-Depth Information
9.4 Schematic diagram of the fabrication process of a hierarchical 3D porous
titanium based metal scaffold. (Adapted and redrawn fromWu et al. [34].)
reaction between native titanium oxide and sodium hydroxide. As time elapsed,
some titanate nano-belts and nano-wires nucleated and grew on the skeleton and,
finally, a hierarchical titanium-based metal scaffold was formed. It was found
that such surface features on the nanometer scale dramatically improved the
bioactivity of typical cell adhesive proteins (such as fibronectin and vitronectin)
to accelerate cell attachment and proliferation [34].
Wet chemistry etching of titanium is very efficient to produce nano-rough
surface features on titanium at low cost with little equipment required. However,
the etching process and resulting surface features are not controllable and are
often quite random. In contrast, using a Temescal electron beam evaporator is
complex but produces desired thickness and exact nano-roughness morphologies
on metals. As shown in Fig. 9.5, during this process, the electron beam is
generated by an electron gun that uses the thermo-ionic emission of electrons
produced by an incandescent filament. A magnet focuses and bends the electron
trajectory so that the beam is accelerated towards a graphite crucible containing
the source material. As the beam rotates and hits the surface of the source
material, heating and vaporization occur, enabling the atoms and molecules to
