Piezoelectricity An Introduction

Cady, W. G. Piezoelectricity. An Introduction to the Theory and Applications of Electromechanical Phenomena in Crystals. McGraw-Hill New York and London (1946). Revised edn. Dover Publications New York (1964). 

In Part II, we discuss the essential elements of STM instrumentation. Except for a few cross-references, all the chapters can be read independently. The chapter on piezodrives starts with an introduction to piezoelectricity and piezoelectric ceramics at the general physics level. Three major types of piezodrives, the tripod, the bimorph, and the tube, are analyzed in detail. The chapter on vibration isolation starts with general concepts and vibration meas-... 

Figure 6.28 Schematic illustration of the piezoelectric effect that occurs in (a) an unstressed and (b) stressed piezoelectric material. Mechanical deformation can also occur when (c) a voltage is applied to a piezoelectric material. From K. M. Ralls, T. H. Courtney, and J. Wulff, Introduction to Materials Science and Engineering. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission John Wiley Sons, Inc.

The advent of new receptors based on nucleic acids, called aptamers, is a new challenge in piezoelectric sensing, not based on the hybridization reaction. The development of aptasensors has analogies to the introduction of immunosensing almost two decades ago the direct detection of analytes in complex matrices by immobilizing an optimized receptor on the sensing surface. 

The symmetry of tensors for strain and stress and the related reduction in the number of coordinates has given rise to the introduction of an abbreviated notation and a representation of these quantities by matrices. This abbreviated matrix notation is almost exclusively in use in the literature on piezoelectricity and in the... 

Theory and Physics of Piezoelectricity. The discussion that follows constitutes a very brief introduction to the theoretical formulation of the physical properties of crystals. If a solid is piezoelectric (and therefore also anisotropic), acoustic displacement and strain will result in electrical polarization of the solid material along certain of its dimensions. The nature and extent of the changes are related to the relationships between the electric field (E) and electric polarization (P). which are treated as vectors, and such elastic factors as stress Tand strain (S), which are treated as tensors. In piezoelectric crystals an applied stress produces an electric polarization. Assuming Ihe dependence is linear, the direct piezoelectric effect can be described by the equation ... 

Few applications based on flow analysis can be found for the automated and direct determination of gaseous sulfur dioxide [8,9] or hydrogen sulfide [10] in atmospheric samples. This is mainly due to the difficulty encountered in the online sampling of gases, which has been partially overcome with the use of chromatomembrane cells or tubular and planar permeation denuders and diffusion cells for the collection of the analyte from air into an absorbing solution and its introduction into the flow manifold, followed by conductivity, potentiometric, piezoelectric, or spectrophotometric detection. 

In this chapter, fundamental aspects of piezoelectricity and electrostriction in dielectric materials and especially in polymers will be outlined. In order to make the introduction into the subject easier to access, basic and schematic ways of describing the complex matter have been chosen instead of an elaborate or comprehensive theoretical approach. For more detailed and more precise information, the interested reader is referred to the large volume of available original and review hterature and to other relevant ehapters of this book. 

Liquid crystalline elastomers are produced by the introduction of cross linking into liquid crystal polymer systems. This cross linking results in materials with a number of unusual properties, for example, stress-induced phase transitions and spontaneous ekmgatioo of samples in the liquid crystelline phase. When they contain chiral units. Sr elastomers are formed. For such materials piezoelectricity was predicted by Brand 103]. The helical structure of those systems can be untwisted by applicatioo of a mechanical stress, generating an electrical signal. This possibility provi the basis for the developnient of materials with piezoelectric properties. Such materials are of comaderablc interest, since the basis for their piezoelec c properties is rather different from that in the best-known piezoelectric polymer, poly(vinylidenefluoride) (PVDF). There exists rather more scope for the modification of their properties for example, the nature of the chiral unit may be varied to alter the helkal superstructure, or differences in cross link density can change the mechanical properties of the sample. 

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