Periodic microstructure

Fine-scale, spatially periodic microstructures are characteristic of spinodal decomposition. In elastically anisotropic crystalline solutions, spinodal microstructures are aligned along elastically soft directions to minimize elastic energy. Microstructures resulting from continuous ordering contain interfaces called antiphase boundaries which coarsen slowly in comparison to the rate of the ordering transformation. 

Periodic microstructures can be corroborated by observations of wavevectors /3 in transmission electron microscope (TEM) images, particularly if the sample is oriented with the modulation waves directed perpendicular to the electron-beam direction (e.g., with the beam along [001] for a crystal with (100) modulations). 

The polymerization of one or more components of a lyotropic liquid crys in such a way as to preserve and fixate the microstructure has recently been successfully performed. This opens up new avenues for the study and technological application of these periodic microstructures. Of particular importance are the so-called bicontinuous cubic phases, having triply-periodic microstructures in which aqueous and hydrocarbon components are simultaneously continuous. It is shown that the polymerization of one of these components, followed by removal of the liquid components, leads to the first microporous polymeric material exhibiting a continuous, triply-periodic porespace with monodisperse, nanometer-sized pores. It is also shown that proteins can be immobilized inside of polymmzed cubic phases to create a reaction medium allowing continuous flow of reactants and products, and providing a natural lipid environment for the proteins. 

Dunn, K.-J., and Bergmann, D. J. (1995). Self diffusion of nuclear spins in a porous medium with a periodic microstructure. J. Chem. Phys. 102, 3041-3054. 

In many applications, the polarization state of gnided light can be fixed in a particular direction and only the passive optical guiding characteristics of a PBG material come into play. Two-dimensional (2D) periodic microstructures are often sufficient for such applications. For 2D periodic dielectrics, advanced planar microstructuring techniques borrowed from semiconductor technology can greatly simplify the fabrication process. Such structures are referred to as photonic crystals exhibiting a 2D PBG. The aspect ratio of a 2D PBG material is defined as the ratio of the sample depth (vertical direction) to the lattice constant (transverse direction). 

Yablonovitch E., Gmitter T.I., Leung K.M. Photonic band structure the face-centered-cubic case emplo3dng nonspherical atoms. Phys. Rev. Lett. 1991 67 2295-2298 Yamabi S., Imai H., Awazu K. Biomimetic approach for exact control of Ti02 periodic microstructures. Chem. Lett. 2002 714-715... 

Classical physics defines three states of matter solid, liquid, and gas. It provides adequate models of gaseous and solid states. The liquid state is somewhat more difficult to characterize, due to several critical obstacles. In addition, little attention has previously been paid to boundary states (coexistence of any two or even all three states at certain thermodynamic conditions). Different sciencific disciplines created separate terminologies such as metamaterials, which properties derive from artificially created periodic microstructure. Concepts such as multiphase heterogeneous or particularly ordered media or complex materials have appeared. Finally the Nobel winner in physics J.-P. de Germes (de Gennes, 1992) united all terminologies under a common term soft materials ... 

Niino, H., Kawabata, Y, and Yabe, A. (1989) Application of excimer laser polymer ablation to alignment of liquid crystals periodic microstructure on polyefhersulfone. Jpn. J. Appl. Phys.,... 

In these relations angular brackets denote volume averages of the Cauchy stress tensor and the small strain tensor, respectively. For the correct use of volmne and ensemble averages in connection with random and periodic microstructures the reader should consult [Torquato... 

HPDLCs have periodic refractive index distribution by polymer-rich layer and LC-rich layer, so they can be used as DFB laser cavities. In the DFB laser cavity, the light feedback for lasing modes relies on Bragg scattering by the periodic microstructures [78,79]. The DFB lasing wavelength from the device should satisfy Bragg condition [80]... 

An interesting variation on template deposition is to self-assanble ordered nanostructures (e.g., surfactants) and microstructures (e.g., polystyrene or Si02 beads) on the surface of an electrode and then electrodeposit into the self-assembled pores. The order in the resulting nanostructure is imposed by the self-assembled layer, not by the substrate. Schwartz and coworkers have extended this idea to the use of crystalline protein masks to produce ordered nanostructures of metals (such as Ni, Pt, Pd, and Co) and metal oxides (such as Cu20). Braun and coworkers have used the electrodeposition of materials into self-assembled colloidal crystals or silica or polymer opals. The template is then removed (see Figure 17.11) to produce an inverse opal. This type of templating produces periodic microstructures that can be used to produce functional photonics. Figure 17.11 shows the production of CdSe and Ni inverse opals by electrodeposition into a colloidal crystal with subsequent removal of the colloidal crystal template. ... 

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