Shape-responsive materials

Stimuli-responsive materials, shape-memory polymers as, 22 355-356 Stirling cycle, 8 43 Stirred autoclave, 14 89, 92t Stirred autoclave reactor, 20 216 Stirred batch RO unit, 21 644 Stirred mills, 16 615 Stirred tank bioreactors, 1 737-740 oxygen transfer driving force, 1 734 Stirred tank electrochemical reactor (STER), 9 660-662... 

The size, shape, and material of the electrode can be tailored to the application. Problems of response time, for example, often can be solved by using a smaller electrode. The use of new electrode materials, including possibilities for modification of the electrode surfaces, could lead to new measurement caDa ilities. Thi. mol i sizes tl itid r ce f the de el d-... 

But the day of dumb buildings is on its way out, just as is the day of dumb cars, dumb airplanes, dumb weapons, dumb satellites, and just about any other kind of dumb structure you can imagine. The day of smart structures built with smart materials has just about arrived in the developed world. Smart materials have been defined as materials that respond to environmental stimuli by making some change in their physical characteristics, such as their size, shape, electrical or magnetic conductivity, or optical properties. Because they respond to change in the surrounding environment, smart materials are also sometimes called responsive materials. 

The limiting or mass transport limited current As soon as the potential is reached when [A]j,=o = 0, the current reaches a fixed limiting current value that is determined by the mass transport of material to the electrode surface. Under these conditions, material is continuously replenished at the electrode surface by convection, in contrast to the situation in a CV where depletion occurs and a peak-shaped response is observed. Table 5 gives the analytically derived expressions for the limiting currents obtained at the three electrode types discussed in this section. 

Electrocatalytic processes at carbon materials have been widely studied. First of all, it should be noted that porous carbons and nanotube systems are able to enhance voltammetric signals recorded at conventional metal or carbon electrodes because of the increase in specihc surface area. This can be seen in Figure 7.17, which shows the CVs recorded at unmodihed and SWNT-modified glassy carbon electrodes in contact with a dopamine solution in aqueous phosphate buffer. The voltammetric profile is essentially identical, but a general increase of the currents is observed at the nanotube-modihed electrode, accompanied by large capacitive current, as denoted by the background box-shaped response. 

The material is more responsive to the ffuctuation s than to the uniform mean value Sq. Because response to s includes self-diffusion along x as well as change of shape, the material behaves with a smaller apparent viscosity or greater apparent mobility, by the factor (1 +j R /2). 

Stimuli-responsive polymers have gained increasing interest and served in a vast number of medical and/or pharmaceutical applications such as implants, medical devices or controlled drug delivery systems, enzyme immobilization, immune-diagnosis, sensors, sutures, adhesives, adsorbents, coatings, contact lenses, renal dialyzers, concentration and extraction of metals, for enhanced oil recovery, and other specialized systems (Chen and Hsu 1997 Chen et al. 1997 Wu and Zhou 1997 Yuk et al. 1997 Bayhan and Tuncel 1998 Tuncel 1999 Tuncel and Ozdemir 2000 Hoffman 2002 en and Sari 2005 Fong et al. 2009). Some novel applications in the biomedical field using stimuli-responsive materials in bulk or just at the surface are shape-memory (i.e., devices that can adapt shape to facilitate the implantation and recover their conformation within the body to... 

In contra.st to their interaction with applied electric, magnetic or electromagnetic fields, porphyrins and metalloporphyrins can also interact with other chemical species. One might view such interactions as chemo-responsive rather than field-responsive. The development of chemo-responsive materials based on porphyrins, however, is somewhat less advanced. One example of such applications is that porphyrin solids, being highly porous, are involved in the current development of molecularly based molecular sieves or shape-selective solid catalysts. Porphyrins and metalloporphyrins have also been examined for a variety of sensor applications, further proving their importance as a class of chemo-responsive materials. 

Stimuli-responsive materials have sparked enormous interest in recent years due to their potential applications in micro-machines, soft robots, biomedical systems, etc. [1-6]. A variety of intelligent polymeric materials such as shape memory polymers [7, 8], polymer gels [9, 10], conducting polymers [11, 12], and dielectric elastomers [13,14] have been developed for these applications. Compared to other stimulus-driven methods including pressure [15], heat [16, 17], electric field... 

In the literature, the constitutive equation for both the amorphous polymer and crystalline polymer has been well established. Therefore, we can direcdy use these relations to model the amorphous phase and crystalline phase of the SMPFs. We then need to consider the cychc texture change of both subphases because the mechanical behaviors of the individual microconstituents may vary when they are packed in a multiphase material system and a certain deviation in their mechanical responses may exist between the individual and their assembled configurations. Since this is a shape memory material, we also need to model the shape recovery behavior. After that, we can use the above micromechanics relation to assemble the macroscopic constitutive relation. In order to determine the parameters used in the constitutive model, we need to consider the kinematic relations under large deformation. Finally, we will discuss the numerical scheme to solve the coupled equations. 

Keywords Inorganic nanocomposite Shape memory polymer Smart composite Stimuli-responsive material... 

Sun L, et al. Stimulus-responsive shape memory materials a review. Mater Des 2012 33 577-640. 

Sun, L., Huang, W.M., Ding, Z., Zhao, Y., Wang, C.C., PumawaU, H., Tang, C., 2011. Stimulus-responsive shape memory materials a review. Materials and Design 33, 577-640. 

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