Periodic microstructures, applications

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. 

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). 

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.,... 

Fig. 5.7 Macroscopic damage modes that occur during the tensile and flexural creep of fiber-reinforced ceramics. It is assumed that matrix or fiber damage is avoided during initial application of the creep load (see discussion of loading rate effects in the next section). Periodic fiber fracture can occur if the creep rate of the matrix exceeds that of the fibers. Periodic matrix fracture is common when the matrix has a higher creep resistance than the fibers. In this figure, it is assumed that initial microstructural damage is avoided during application of the creep load.

Periodic and aperiodic microstructures prepared by lithography form the basis for a vast number of applications such as electronic circuits, sensors, actuators, etc. (1,2). As the dimensions of the structures are pushed to ever smaller limits, size dependent quantum effects are encountered opening new fields of interesting physics and... 

In 1971, LeMeur et al. [62] reported that dilute (6-9 wt%) solutions of a symmetric poly sty rene-polyisoprene diblock copolymer (molecular weight 1,400,000) in toluene and styrene exhibited anisotropic diffraction of (ultraviolet) light after application of either mechanical shear or a 15 kV/cm electric field. The diffracting element had a repeat distance of about 360 nm. Light diffraction from this solution shows that even this dilute solution exhibits a periodic structure. It is reasonable that this periodic element is the lamellar microstructure with a large period resulting from swelling by the solvent. 

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