Biomedical Engineering Reference
In-Depth Information
unique optical properties of natural structural color through a simple process. One
promising way is to construct photonic crystals with two PBGs to get the desired
double reflection. On the other hand, the growing demand for optical interfaces
and sensors for biomedical applications is a motivating research toward realizing
biocompatible photonic components that offer a seamless interface between the
optical and biological worlds. Therefore, another key issue in this field is how to
mimic the double reflection effect using biocompatible and biodegradable materials.
We notice that the double reflection has its biological function. For instance,
there are three major photoreceptors in the compound eyes of
Heliconius erato
with spectral sensitivity peaks at 370, 470, and 560-570 nm, allowing the detection
of ultraviolet colors, and they distinguish the spectral properties of visible light
[
175
]. It follows that the double reflection of butterfly wings giving rise to both
visible and UV reflections may serve for communication and mating signals in
butterfly kingdom [
174
-
176
]. Thus, investigating the correlation between the optical
properties and the structures may help to explain the innate behaviors of the butterfly
kingdom. Investigating the coloration mechanisms of these optical properties and
the corresponding structures also has crucial implications for biomimicry, including
color-stimulus synthesis, display technologies, and various polarization applications
[
116
,
181
].
7.5
Conclusive Remarks
As can be seen from the results presented in this chapter, almost all fundamental
aspects of crystallization in biomineralization can be examined in terms of the
AEF-controlled 2D colloidal crystallization system. For instance, the initial stage
of nucleation may not be exactly the same as we expected. Unlike the assumption
that both the embryos and the bulk crystals share the same structure, the structures
of the embryos are supersaturation dependent. Such a deviation would be beneficial
in lowering the nucleation barrier and then facilitating the nucleation kinetics at low
supersaturations. From the point of view of solid-fluid interface, the above “experi-
mental modeling” can also provide some unique and extremely relevant information,
which is capable of updating our knowledge in crystallization in general. Notice
that the effect of supersaturation-driven structure mismatch has been put forward,
but never been visualized directly before. The templated 2D colloidal nucleation
provides the first observation of this effect. Such an experimental modeling system
has been successfully applied to examine many other crystallization processes,
i.e., MSC, roughening transition, adatomic step integration, defects generation and
migration kinetics, etc., which have never been examined quantitatively before at
the single particle level. Note that the key advantage of the experimental modeling
system is the combination of the visualization and the quantitative treatment,
which can transfer our knowledge to a new phase. As the colloidal crystallization
system displays the phase behaviors similar to normal crystalline materials, and the
crystallization condition can be controlled easily and precisely, it can be foreseen
that this approach will become a powerful tool to study the science and technology
