Uses of piezoelectric materials

Scaiming probe microscopies have become the most conspicuous surface analysis tecimiques since their invention in the mid-1980s and the awarding of the 1986 Nobel Prize in Physics [71, 72]- The basic idea behind these tecimiques is to move an extremely fine tip close to a surface and to monitor a signal as a fiinction of the tip s position above the surface. The tip is moved with the use of piezoelectric materials, which can control the position of a tip to a sub-Angstrom accuracy, while a signal is measured that is indicative of the surface topography. These tecimiques are described in detail in section BI.20. 

Mass Sensitive Applications. Uses of piezoelectric materials in mass-sensitive oscillators encompass several configurations (Fig. 2). Mechanical oscillations propagated perpendicularly between the parallel faces of a thin quartz crystal... 

Electrical Stimuli. Electrically active materials have also been used to encourage tissue growth. The use of piezoelectric materials made of vinyUdene fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] enhanced peripheral nerve regeneration in vivo (Fine et al., 1991), and when PC12 cells were cultured on oxidized polypyrrole, the application of an electrical stimulus resulted in enhanced neurite extension (Schmidt et al., 1997), as shown in Fig. 16.3. Implant vascularization was enhanced when bilayer films of polypyrrole-hyaluronic acid and polypyrrole-poly(styrenesulfonate) were implanted subcutaneously (Collier et al., 2000). These types of electrical stimuli can be used in conjunction with a biomaterial to promote tissue regrowth. 

Osteocytes and osteoblasts are essential for mechanosensing and mechanotransduc-tion, and cell response depends on strain and loading frequency (Kadow-Romacker et al., 2009 Mosley et al., 1997). We explored the use of piezoelectric materials as a mean of directly straining bone cells by converse piezoelectric effect. 

The use of piezoelectric material based actuators to produce bone mechanical stimulation seems promising in theory and the present in vitro and in vivo studies were a first step towards the validation of the eoneept. 

Energy harvesting is a very important application in the modem world, and it can be used as an alternative to conventional batteries in many applications. One common method of energy harvesting is the use of piezoelectric materials to interchange electrical energy and mechanical deformation (Figure 16.16). 

Since discovering and making use of the piezoelectric effect in naturally occurring crystals such as quartz and Rochelle salts, scientists have produced a wide range of piezoelectric materials in the laboratoi y. An early example is barium titanate, used in an electrical component called a capacitor. Currently, most piezoelectric materials are oxide materials based on lead oxide, zirconate oxide, and titanium. These very hard piezoelectric materials are termed piezoceramics. 

The compounds K5Nb3OFi8 and Rb5Nb3OFi8 display promising properties for their application in electronics and optics. The compounds can be used as piezoelectric and pyroelectric elements due to sufficient piezo- and pyroelectric coefficients coupled with very low dielectric permittivity. In addition, the materials can successfully be applied in optic and optoelectronic systems due to their wide transparency range. High transparency in the ultraviolet region enables use of the materials as multipliers of laser radiation frequencies up to the second, and even fourth optical harmonic generation. 

In his work, Wallace [12] formed inkjet printheads from the rectangular blocks made of piezoelectric material. A diamond saw is used to create fluid channel grooves and channel actuator structures. These grooves are approximately 1 pm apart, 360 pm deep and 170 pm wide. Next, a cover plate is attached to the top of the grooves to form an enclosed rectangle channel for the working fluids. A polymer orifice plate (see Fig. 11.3) with many 40 pm diameter orifices is attached to the other end of the grooves. 

A variety of piezoelectric transducers have been employed for PAC. Ceramic transducers, usually lead zirconate titanate, are most commonly employed because of their sensitivity, time resolution and commercial availability. However, their acoustic response is often dominated by their own resonance, and so polymeric film detectors, such as polyvinylidenedifluoride, are often used. These piezoelectric materials are non-resonant, but not as sensitive as the ceramic detectors. Again, each detector has its own advantages (and disadvantages).14,15... 

The use of such different types of piezoelectric materials permits the building of ultrasonic generators of different powers and frequencies for a range of applications. 

The use of biological materials as coatings for piezoelectric crystals was first demonstrated by Shons et al. [237], who immobilized bovine serum albumin (BSA) on a crystal precoated with a 30% solution of Nyebar C, a low-surface energy plastic. The rationale of using this solution as the coating material is that proteins adsorbed on low-energy surfaces retain their antigenic properties. Exposure of the BSA-coated crystal to a solution... 

However, nowadays a piezo tube is more commonly used. In this geometry, the inner and outer surfaces of a tube of piezoelectric material are coated with... 

Sensitive, selective detection of biochemically active compounds can be achieved by employing antigen-antibody, enzyme-substrate, and other receptor-protein pairs, several of which have been utilized in the development of piezoelectric immunoassay devices. The potential analytical uses of these materials has been reviewed, particularly with respect to the development of biochemical sensors [221-224], The receptor protein (e.g., enzyme, antibody) can be immobilized directly on the sensor surface, or it can be suspended in a suitable film or membrane. An example of the sensitivity and response range that can be... 

With the aid of a particular class of materials (thin-film piezoelectrics), incorporation of AW devices and conventional integrated circuit components on the same silicon substrate is in fact possible. Under the proper conditions, a number of piezoelectric materials can be deposited in thin-film form, typically by RF sputtering, and retain their piezoelectric nature. For this to occur, the crystallites that grow during deposition must be predominantly oriented in a single, piezo-electrically active crystallographic direction. Two such materials are 2 0 and AIN the former has been used as an overlayer on Si wafers to fabricate all of the FPW devices studied for sensor applications to date, and also for SAW resonators. Because extremely thin piezoelectric films are readily fabricated, both ZnO and AIN have been used to make bulk resonators that operate at much higher... 

In this chapter, the emphasis is upon dielectric and ferroelectric perovskites. As ferroelectrics are also piezoelectrics and pyroelectrics, it is found that most important applications for both piezoelectric and pyroelectric perovskites make use of ferroelectric materials. 

Moreover, SH-APM devices require additional processing timing their fabricatimi of the thin plates with respect to the IDT periodicity. Thin slices of piezoelectric materials such as quartz are often used. The whole procedure permits researchers to choose the correct crystallographic orientation for generating the desired shear waves. Despite this improvement, SH-APM devices remain less sensitive than SAW devices for two reasons. First, energy of the wave does not reach a maximum at the surface. Second, similar to TSM, SH-APM is restrained by a minimum thickness of piezoelectric plate [2, 7]. 

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