Biomedical Engineering Reference
In-Depth Information
H
2
O
Air
Surfactant molecule
Hydrophilic polar end
Non-polar end
Figure 12.7
Schematic on the role of surfactant in stabilising air bubbles in agitated
water.
Particle
slurry
Surfactant
stabilises
bubbles
Gelled foam
in moulds
Vigorous
agitation
Pour
Initiator,
monomer,
cross-linker
(gelling
agent)
+
surfactant
In situ
polymerisation
(curing of
the polymer)
Sintering
Drying
Figure 12.8
Schematic of the gel-cast foaming process for bioactive glass scaffold
production.
mixing with an initiator and catalyst. As the polymerisation progresses,
the viscosity increases until a gel (a solid covalent network containing
water) forms. Just prior to gelation, the foam is poured into a mould.
The pouring window is short: too early, and the foam cannot hold its
own weight and will collapse; too late, and it will gel in the foaming
vessel. The surfactant must be of suitable type and be homogeneously
dispersed to obtain spherical pores. To obtain an interconnected pore
