Materials smart

Under the proper set of environments and circumstances all materials are smart and depict smart behavior at some point during their life cycle. 

With the inception of smart materials and structures, the world is on the brink of a new material age. Within this century the polymer age and the composite age have been experienced. These have now been followed by the smart material age. The implementation of smart materials into smart structures describes the smart material age more accurately. 

Piezoelectric materials are materials that exhibit a linear relationship between electric and mechanical variables. Electric polarization is proportional to mechanical stress. The direct piezoelectric effect can be described as the ability of materials to convert mechanical stress into an electric field, and the reverse, to convert an electric field into a mechanical stress. The use of the piezoelectric effect in sensors is based on the latter property. For materials to exhibit the piezoelectric effect, the materials must be anisotropic and electrically poled ie, there must be a spontaneous electric field maintained in a particular direction throughout the material. A key feature of a piezoelectric material involves this spontaneous electric field and its disappearance above the Curie point. Only solids without a center of symmetry show this piezoelectric effect, a third-rank tensor property (14,15). 

There are two principal types of materials that can function as piezoelectrics the ceramics and polymers. The piezoelectric materials most widely used are the piezoceramics based on the lead zirconate titanate, PZT, formations, mixed sodium and potassium niobates, lithium niobate, and quartz. The advantages of these piezoceramics are that they have a high piezoelectric activity and they can be fabricated in many different shapes. 

A new class of materials called smart tagged composites has been developed for structural health monitoring applications. These composites consist of PZT-5A particles embedded into the matrix resin (unsaturated polyester) of the composite (16). 

Pie2oelectric materials are used in many different types of sensing—actuating devices. A few appHcations include printing, monitoring of performance behavior of adhesive joints, and intelligent processing. 

Electrostrictive materials are materials that exhibit a quadratic relationship between mechanical stress and the square of the electric polari2ation (14,15). Electrostriction can occur in any material. Whenever an electric field is appHed, the induced charges attract each other, thus, causing a compressive force. This attraction is independent of the sign of the electric field and can be approximated by 

Further, PHAs harbouring special building blocks can be applied as so-called functional materials for different niche applications. Here, they can act as heat sensitive adhesives, latex materials, or smart gels [110]. Of special importance is the utilization of PHA as basic material to be connected by Unkers with biologically active substances. As an example, Hany and colleagues produced an md-PHAs-based carrier matrix linked with zosteric acid this material can be used on the surface of ships and boats to avoid bio-fouling [25]. 

A more fundamental view is reflected in the second approach, however, where sol-gel encapsulation science is divided into sections related to molecular confinement studies, the use of sol-gel encapsulation as a synthetic intermediate, and the structural studies. The majority of the articles and ideas reviewed were published in 2000 and later. Earlier studies were only included if they represented a major breakthrough or bore a special significance to the field. Finally, although the following review describes applications grouped into certain sections, much of the material may bear relevance to other sections, and it is clear that the emergent science of sol-gel will only benefit from such cross-fertilization. 

The major advantages of sol-gel-derived siHcate materials for the immobilization of proteins are that  

The method must be amenable to an aqueous environment, since this is required to maintain the biological function of the biomolecules. 

The processes must occur close to room temperature in order to maintain the proteins in their native conformation. 

The gel must have a pore structure sufficiently small to prevent leaching of the biomolecule, but simultaneously sufficiently large to allow rapid diffusion of the analyte. 

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Smallpox vaccine Smalt Smaltite SMA resins SMART Smart catalysts Smart gels Smart hydrogels Smart material Smart materials... 

This class of smart materials is the mechanical equivalent of electrostrictive and magnetostrictive materials. Elastorestrictive materials exhibit high hysteresis between strain and stress (14,15). This hysteresis can be caused by motion of ferroelastic domain walls. This behavior is more compHcated and complex near a martensitic phase transformation. At this transformation, both crystal stmctural changes iaduced by mechanical stress and by domain wall motion occur. Martensitic shape memory alloys have broad, diffuse phase transformations and coexisting high and low temperature phases. The domain wall movements disappear with fully transformation to the high temperature austentic (paraelastic) phase. 

The smart materials /stmctures field is new. As these materials are better understood, better devices can designed with them and the quaHty of life may be enhanced. 

The design of smart materials and adaptive stmctures has required the development of constitutive equations that describe the temperature, stress, strain, and percentage of martensite volume transformation of a shape-memory alloy. These equations can be integrated with similar constitutive equations for composite materials to make possible the quantitative design of stmctures having embedded sensors and actuators for vibration control. The constitutive equations for one-dimensional systems as well as a three-dimensional representation have been developed (7). 

Smart materials have active responses to external stimuh and can serve as sensors and actuators... 

Source Bar-Cohen, Y. et al., Low-mass muscle actuators using elecfroactive polymers (EAP), SPIE Conference on Smart Materials Technologies, San Diego, Cahfomia, March 1998, SPIE Vol. 3324, 0277-786X/98. 

Prahlad, H., Kombluh, R., Pelrine, R., Stanford, S., Eckerle, J., and Oh, S. Polymer power Dielectric elastomers and their applications in distributed actuation and power generation. Proceedings of ISSS International Conference on Smart Materials, Structures and Systems, Bangalore, India, July 28-30, 2005, SA-13, pp. 100-107. 

Cortie, M., Xu, X., Zareie, H., Chowdhury, H. and Smith, G.(12th-15th Dec 2005) Plasmonic heating of gold nanoparticles and its exploitation, presented at Smart Materials, Nano-, and Micro-Smart Systems 11, Sydney, Australia, SPIE, 5649, pp. 565-573. 

Z. L. Wang, Z. C. Kang, Functional and Smart Materials -Structural Evolution and Structure Analysis, Chapter 6, Plenum Press, New York, 1988. 

Piezoelectric ceramics, which depend on lead compounds, are used to produce transducers and sensors which make possible ultrasound technologies used in wide-ranging medical and commercial applications, guidance and sensing systems used in defense and commerce, and in addition, new "smart materials" research projects. 

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