Stretchable Structure

Superior mechanical properties of CNTs can be used to fabricate noble devices having special properties. The formation of macroscopic assemblies of CNTs while retaining their excellent intrinsic properties is challenging. 

Application of CNTs as reinforcement in composite materials is the most studied approach towards their macroscopic applications. However, in composites the resultant properties are governed by the individual properties of the matrix and the CNT-matrix interaction. Moreover, excellent properties of CNTs such as high thermal and electronic conductivities cannot be utilized effectively. To attain the intrinsic CNT properties at macroscale, CNT assemblies such as CNT films, fibers, sheets, mats, foams, etc., have been proposed. Such structures mainly rely on the van der Waals interaction between individual CNTs. Alternatively, at the cost of some of the CNT properties, a small amount of binder can be used to improve the binding. Low density and highly flexible CNT foams and aerogels, and viscoelastic rubbers are some such materials consisting of macroscopic CNT assembly. 

In the span of more than two decades, CNT research has witnessed significant advancements. Starting from controlled, easy and large-scale synthesis, purification and an xmderstanding of their physical properties 

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The tight y turn215 and the proline-containing P turn shown in Fig. 2-24 are thought to be major components of the secondary structure of elastin.216-218 This stretchable polymer, which consists largely of nonpolar amino acids, is the most abundant protein of the elastic fibers of skin, lungs, and arteries. The... 

The (3-strand sequences are stretched out conformations of these polypeptide sections and are typically stabilized by inter-strand hydrogen bonds between keto (C = 0) oxygens and peptide bond NHs, the strands being arrayed in an antiparallel fashion. This type of secondary structure is favoured by amino acid residues with small R groups (such as Gly, Ala and Ser) that minimize steric overlap between chains. Thus a well-known protein having this type of secondary structure is silk fibroin that has a high proportion of repeated sequences involving Gly, Ala and Ser and an extensive antiparallel (3-pleated sheet structure. The macroscopic properties of silk fibroin (flexibility but lack of stretchability) reflect this type of secondary structure at the molecular level. 

Structure. Collagen is a widespread protein that provides a structural framework of intercellular tissue support in connective tissue, cartilage, bone and other tissues. Elastin is a stretchable support protein. Keratin is the tough protein of fingemails and hair. 

In this section, we describe a solution that employs a net-shaped structure to make flexible electronic film devices conformable to three-dimensional surfaces [18]. Although the base films we presently use are of polyimide and poly(ethylenenaph-thalate) (PEN) — materials that are stiff and not inherently stretchable in a rubberlike sense — our solution includes struts of network structures that twist with the application of tension, as can be seen in Figure 6.3.7. Due to this three-dimensional strut deformation, the whole network structure functions electrically with a unidirectional extension of 25%. We have implemented the pressure sensor network on the surface of an egg and have obtained pressure images in this configuration. 

Lee and JGm examined the effect of lamellar structure of the dispersed EVA phase on the gas permeability of LDPE/EVA blends produced by film blowing (Lee and Kim, 1995, 1996). The viscosity ratio and dispersed domains size had a predominant influence on the formation of lamellae. An addition of LDPE-g-MA as a compatibilizer increased the number of particles and reduced the thickness of the layers. Between 5 and 6 wt% of compatibilizer produced a dispersed phase size of around 5 pm and the best oxygen permeability reduction (by a factor of 1600). Above this optimum concentration, the particle size becomes too small, resulting in shorter and thinner, and less effective, lamellae. Dispersed phase stretchability increased when a compatibilizer is present and when the viscosity ratio decreases, but it was not affected by the initial particle size. 

Cheddaring involves the development of a fibrous curd structure, but this occurs only at a curd pH 5.8 and is a consequence of the loss of calcium from the protein matrix (Lawrence and Gilles, 1982). Optimum stretchability of Mozzarella occurs at pH 5.2-5.4. 

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