Piezoelectric plates

Components include an energy source (gas, electrical), a site of energy input to solution (capillary tubes, piezoelectric plate), a means of removing large droplets (baffle plate), and tubing and a face mask to deliver aerosol. 

Fig. 1.41. Micropositioning assembly in the MIM tunneling experiment. In an aluminum block (1), two gold electrode.s (2) are contained. The right electrode is attached to a pair of membranes (3), and actuated by a stack of piezoelectric plates (4). The left electrode is actuated by a differential screw (5) for coarse positioning. The entire assembly is enclosed in a thermostat and then a vacuum chamber. (After Teague, 1978.)...

Fig. 9.8. Deflection of a bimorph. Two long, thin plates of piezoelectric material are glued together, with a metal film sandwiched in between. Two more metal films cover the outer surfaces. Both piezoelectric plates are poled along the same direction, perpendicular to the large surface, labeled z. (A) By applying a voltage, stress of opposite sign is developed in both plates, which generates a torque. (B) The bimorph flexes to generate a stress to compensate the torque. The neutral plane, where the stress is zero, lies at hi i from the central plane.

The piezoelectric stepper, nicknamed the louse, was the first successful stepper used in UHV STM (Binnig and Rohrer, 1982). A schematic of the louse is shown in Fig. 12.1. As shown, the actuating element of the louse is a piezoelectric plate (PP), which can be expanded or contracted by applying a voltage (100 to 1000 V). It is resting on three metal feet (MF), separated by high-dielectric-constant insulators (I) from the metal ground plate (GP). 

Fig. 12.2. The pocket-size STM. Vibration isolation and damping are achieved by a stack of stainless-steel plates separated by viton O rings (not shown) in between. On the top metal plate are the louse and the piezoelectric tripod. 1, A metal plate with the sample holder, with only one of the three screws tightened. 2, Piezoelectric plate. 3, Annodized aluminum feet. 4, Tip holder. 5, The current lead. Viton pieces on the edges of the metal plates are used for isolating the vibration transmitted through the wires. (After Gerber et al., 1986.)...

These actuators consist of the piezoelectric plates and metal electrodes. Since disk type actuators can be easily glued with resin to the structure, these are used in the micropumps. The disk and cantilever type show a large deformation and fast response although the generated pressure is not large. 

To generate large pressure, a stack structure of many piezoelectric plates and metal electrodes is used. Pressures greater than 350 kgf/cm2 are obtained. The maximum stroke is, however, small. The stroke to length of the actuator is smaller than 10 3. A high applied voltage of over 100 V and a small current are features of this actuator. 

If a piezoelectric plate (Fig. 6.1), polarized in the direction indicated by P, carries electrodes over its two flat faces, then a compressive stress causes a transient current to flow in the external circuit a tensile stress produces current in the opposite sense (Fig. 6.1(a)). Conversely, the application of an electric field produces strain in the crystal, say a negative strain reversal of the field causes a positive strain (Fig. 6.1(b)). The changes in polarization which accompany the direct piezoelectric effect manifest themselves in the appearance of charges on the crystal surface (see Eq. (2.71)) and, in the case of a closed circuit, in a current. 

Figure 337 Change in APM velocity due to the acousloelectric interaction between electric fields generated in the piezoelectric plate and ions in solution solid lines are calculated from Equations 3.67, while points are measured. (Reprinted with pennission. See Ref. (S9]. 1988 American Inslitute of Physics.)...

Tiersten, H. In Linear Piezoelectric Plate Vibrations-, Plenum New York, Chap. 10... 

The devices are reasonably simple to construct as their dimensions are not critical. Unfortunately the maximum oscillation will occur at the junction of the optical element and the piezoelectric plate. This can cause adhesion problems leading to static strain in the optical element and joint disruption during modulation. 

The MASIF (measurements and analysis of surface interaction and forces) force measuring device is based on a bimorph force sensor [47]. The bimorph consists of two piezoelectric plates glued together with opposing... 

The derivation above ignores piezoelectricity (Sect. 6). The theory of the piezoelectric plate has been worked out by Tiersten [56]. Kanazawa has applied this theory rigorously to the case of a crystal loaded with a liquid or a viscoelastic film [54]. These treatments are equivalent to the treatment with equivalent circuits (Sect. 6), and we therefore defer the discussion of piezoelectricity to that section. 

Fig. 6 Equivalent circuits of a a viscoelastic layer of thickness 2h, b two viscoelastic layers of thickness 2hi and 2h2 (where 1 denotes the quartz crystal and 2 denotes the film), and c a piezoelectric plate loaded on one side with a load AZi. The parameter h is half of the thickness of the respective layer...

The Curie brothers [1] are accredited with being the first to describe the phenomenon of piezoelectricity. However, piezoelectricity remained a scientific curiosity until the war in 1914, when the echo method utilizing piezoelectric plates was developed to explore the ocean bottom. The development of other devices using crystals as control elements followed and eventually the art of crystals became one of the cornerstones of the network of communication systems. 

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]. 

Since the original piezotransformer was proposed by Rosen [25], there have been a variety of such transformers investigated. Figure 4.1.17 shows a fundamental structure where two differently poled parts coexist in one piezoelectric plate. A standing wave with a wavelength equal to the sample length is excited,... 

This connectivity pattern (Fig. 7.26) is practically used in ID-arrays for the medical ultrasound probes. Composites of this particular type are easier to make by dicing and filhng technique or by the alignment of the piezoelectric plates. Again the composite s pohng is enabled by the connectivity of the piezoelectrically active phase in the pohng direction (Cao et al. 1993,1995). 

Because both coefficients J33 and J31 for PZT ceramics exhibit different signs, the uniaxially reinforced and TP 2-2 composites could reach the highest effective hydrostatic coefficient values. It is interesting, that the effective FOM in Eq. (7.37) does not depend on the aspect ratio (i.e. on the ratio of the composite s thickness T vs. the piezoelectric plate thickness t) but the value of (Eq. (7.38)) does (Fig. 7.28). 

A nonelectrochemical distance control for SECM tips that permits simultaneous acquisition of topographic and electrochemical information can be used (4, 65). Briefly, two piezoelectric plates are attached to the shaft of the SECM tips. One of the plates vibrates the tip at resonance and the second plate detects the amplitude and phase of the tip oscillation. This technique can also constantly regulate the tip to sample separation during imaging experiments. 

Two major processes contribute to detection with a SAW device generation and change of surface waves on a piezoelectric plate, and the sorption/desorption of chemicals on the surface. 

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