Biomedical Engineering Reference
In-Depth Information
b
a
200
ยต
m
c
d
FIGURE 1.9
Typical structures of porous biocomposites by various techniques: (a) solvent casting or parti-
cle leaching [146,150], (b) phase separation or freeze-drying [145], (c) microsphere sintering [143], (d) polymer
coating of Bioglass foam [177].
is formed based on this method combined with particle leaching and microsphere packing. This
method shares similar advantages and disadvantages with the solvent casting technique. Details
of the method are presented in Ref. 65.
1.4.2.3
Thermally Induced Phase Separation or Freeze-Drying
Three-dimensional porous structures can also be achieved through phase separation and evapora-
tion. An approach to induce phase separation is to lower the temperature of the suspension of poly-
mer and ceramic materials. The solvent is solidifi ed fi rst, forcing the polymer and ceramic mixture
into the interstitial spaces. The frozen mixture is then lyophilized using a freeze dryer in which the
ice solvent evaporates [109,144,145].
1.4.2.4 Microsphere Sintering
In this process, microspheres of a ceramic and polymer composite are synthesized fi rst, using emul-
sion or solvent evaporation technique. Sintering the composite microspheres yields a 3-D porous
scaffold [142,143].
1.4.2.5 Foam Coating
An alternative approach to address the combination of polymeric and ceramic materials is to coat
bioactive ceramics onto polymeric foams [220-222]. The inverse method, known as polymer-coated
ceramic scaffolds, has also been investigated [173,177,223], as discussed in Section 1.4.1.1.2.
