Besides electrodes, the low proton conductivity of electrolytes is another
challenge to overcome. BCP-derived ordered solid electrolytes may improve
the proton conductivities of random polymeric architectures [59]. More in-depth
discussion of this issue can be found in the literature [59].
These examples suggest that BCP SA can be a powerful approach for designing
better electrodes and electrolytes for fuel cell applications. Although BCP research
is not yet regarded as mainstream in fuel cell materials research, its importance for
improving fuel cell device performance is most likely going to grow in the future.
6.2 Photonic Crystals and Metamaterials
A photonic crystal is a periodic material that strongly interacts with external
electromagnetic fields and exhibits unusual optical phenomena such as a photonic
band gap, i.e., a range of frequencies in which the propagation of electromagnetic
waves is prohibited [60]. A photonic crystal effect that we utilize in our daily life is
the coating of substrates with multilayered thin films (i.e., 1D photonic crystals)
that provide anti-reflective or highly reflective properties. The constructive or
destructive interference of photons in photonic crystals controls the flow of light.
Such interference depends on the wavelength of light and the structural dimensions
of the photonic crystals. In a finite range of frequencies, some photonic crystals
disallow the existence of any photons and reflect all incoming light irrespective of
the incident angle. Such photonic crystals are called complete photonic band gap
materials. Complete photonic band gap materials have attracted much attention for
their useful applications in such things as lasers and waveguides [60].
A metamaterial is an engineered material that exhibits unusual optical phenomena
that may not be found in nature. In this review, we use “metamaterial” as a narrower
definition for a periodic metallic material. Metamaterials are attractive in that they
enable sub-diffraction-limited photonic applications [61, 62]. The diffraction limit of
light originates from the loss of evanescent waves in the far field [63]. Evanescent
waves carry the high spatial frequency information that defines small objects. Due to
the loss of evanescent waves in the far field, the resolution of objects that can be
observed by optical lens systems is limited to the order of the wavelength of light
used to image the object.
In theory, a lens system made of a material with a negative refractive index
enables unlimited resolution imaging [64]. That is because the loss of evanescent
waves in regular materials with positive refractive index is compensated in negative
refractive index materials. Thus, evanescent waves can be delivered through such
materials. Due to this exciting phenomenon, designing a negative refractive index
material, in particular for the frequency range of visible light, has been the subject of
significant efforts in metamaterials research for the past decade. A further severe
challenge in metamaterials research is the low-cost fabrication of 3D metamaterials at
Design and Applications of Multiscale Organic–Inorganic Hybrid Materials. . .
283
challenge to overcome. BCP-derived ordered solid electrolytes may improve
the proton conductivities of random polymeric architectures [59]. More in-depth
discussion of this issue can be found in the literature [59].
These examples suggest that BCP SA can be a powerful approach for designing
better electrodes and electrolytes for fuel cell applications. Although BCP research
is not yet regarded as mainstream in fuel cell materials research, its importance for
improving fuel cell device performance is most likely going to grow in the future.
6.2 Photonic Crystals and Metamaterials
A photonic crystal is a periodic material that strongly interacts with external
electromagnetic fields and exhibits unusual optical phenomena such as a photonic
band gap, i.e., a range of frequencies in which the propagation of electromagnetic
waves is prohibited [60]. A photonic crystal effect that we utilize in our daily life is
the coating of substrates with multilayered thin films (i.e., 1D photonic crystals)
that provide anti-reflective or highly reflective properties. The constructive or
destructive interference of photons in photonic crystals controls the flow of light.
Such interference depends on the wavelength of light and the structural dimensions
of the photonic crystals. In a finite range of frequencies, some photonic crystals
disallow the existence of any photons and reflect all incoming light irrespective of
the incident angle. Such photonic crystals are called complete photonic band gap
materials. Complete photonic band gap materials have attracted much attention for
their useful applications in such things as lasers and waveguides [60].
A metamaterial is an engineered material that exhibits unusual optical phenomena
that may not be found in nature. In this review, we use “metamaterial” as a narrower
definition for a periodic metallic material. Metamaterials are attractive in that they
enable sub-diffraction-limited photonic applications [61, 62]. The diffraction limit of
light originates from the loss of evanescent waves in the far field [63]. Evanescent
waves carry the high spatial frequency information that defines small objects. Due to
the loss of evanescent waves in the far field, the resolution of objects that can be
observed by optical lens systems is limited to the order of the wavelength of light
used to image the object.
In theory, a lens system made of a material with a negative refractive index
enables unlimited resolution imaging [64]. That is because the loss of evanescent
waves in regular materials with positive refractive index is compensated in negative
refractive index materials. Thus, evanescent waves can be delivered through such
materials. Due to this exciting phenomenon, designing a negative refractive index
material, in particular for the frequency range of visible light, has been the subject of
significant efforts in metamaterials research for the past decade. A further severe
challenge in metamaterials research is the low-cost fabrication of 3D metamaterials at
Design and Applications of Multiscale Organic–Inorganic Hybrid Materials. . .
283