Biomedical Engineering Reference
In-Depth Information
Fig. 6.11
Fabrication of 3DOM calcite single crystals by templating colloidal crystals of P(St-
MMA-AA) spheres carrying a carboxylate corona. (Reproduced from [
86
], Copyright © 2008,
Wiley)
well-defined 3DOM structure and controlled crystal orientation via specific surface
functionalization of the colloidal crystal template. Based on the experimental
results, they found that the calcite single crystals that formed in the colloidal crystal
template evolved form small patches to large symmetric dendrites up to several
tens of micrometers in size as the amount of ACC was enhanced. In particular,
two factors play key roles in the formation of the calcite single crystals, that is, the
vacuum-assisted filtration process which induces the filling of ACC in the interstices
of the template, and the surface-functionalized template which provided the affinity
to ACC [
86
]. In a typical experimental procedure, the 3D calcite single crystals were
achieved by infiltration of the ACC precursor into polymer colloidal crystals with
subsequent drying, dissolving in THF, and heated at 723 K as shown in Fig.
6.11
[
86
]. Monodisperse poly-(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-
AA)) colloidal spheres, which have a polystyrene (PS) core and a carboxylate
corona [
87
], were assembled into 3D colloidal crystal on a filter membrane. Then,
a freshly obtained ACC dispersion was added dropwise to the colloidal crystal film
mounted under vacuum, leading to the deposition and crystallization of ACC within
the interstices of the colloidal crystals. These experimental results suggest a general
strategy for the design and fabrication of functional single-crystalline materials with
desired shapes, orientations, and nanopatterns.
Moreover, single crystals of calcite with regular patterned surfaces compris-
ing close-packed arrays of hemispherical cavities ordomes can be prepared by
crystallization on colloidal monolayers or polydimethylsiloxane replicas of these
monolayers, respectively [
88
]. This study demonstrates that crystallization within a
mould provides a general route to produce single crystals with unusual morpholo-
gies and curved surfaces.
