Piezoelectric resonance

A schematic diagram of a bulk acoustic wave (BAW) chemical sensor is composed of a BAW piezoelectric resonator with one or both surfaces covered by a membrane (CIM) (fig. 14). 

Benes E, Groschl M, Burger W, Schmid M. Sensors based on piezoelectric resonators. Sens Actuat A 1995 48 1-21. 

Fawcett NC, Evans JA, Chien LC, Flowers N (1988) Nucleic-acid hybridization detected by piezoelectric resonance. Anal Lett 21 1099-1114... 

A tubular sonicatlon device was recently reported by Borthwick et al. [93] (see Fig. 3.9). The device requires the addition of no chemical, enzyme or particles that might complicate the subsequent determination step. Furthermore, denaturatlon of target DMA or proteins for detection Is minimized as the device tolerates moderate temperature rises this allows the use of sensitive and specific Immunological detection methods on sonicated biological materials. Because the tubular device Is composed of a piezoelectric resonator made of several material layers, selection of an appropriate operating frequency Is essential to ensure proper performance (i.e. acceptable cell disruption efficiency). This device can be used for batchwise treatment of small sample volumes or In flow systems without the risk of hazardous aerosol formation inherent in probe sonloators. 

Figure 7.9. Change in resonant oscillation frequency of a piezoelectric transducer (a) with, and (b) without poly(A) immobilized to the surface. Step 1 is surface modification with copolymer, Step 2 is poly(A) immobilization, and Step 3 is hybridization to target poly(U).10 [Reprinted, with permission, from N. C. Fawcett, J. A. Evans, L.-C. Chien, and N. Flowers, Anal. Lett. 21, 1988, 1099-1114. Nucleic Acid Hybridization Detected by Piezoelectric Resonance . Copyright 1988 by Marcel Dekker, Inc.]...

Attempts have been made to correlate the outstanding electric properties (piezoelectricity, pyroelectricity) of PVDF with parameters obtained from wideline NMR experiments. Samples processed by different electric methods have been included in NMR experiments. Wideline NMR studies of irreversible effects induced by relatively high static electric fields have been reported by several authors. The results of wideline NMR ( H) have been used [53] in a combined investigation with a piezoelectric resonance method to find any effects of electric poling (0.78 MV/cm at 120°C) on structure and/or orientation. However, no indications of structural or orientational changes have been found. 

Another resonant-frequency thermometer is the quartz crystal resonator (Benjaminson and Rowland, 1972), which, if the crystal is properly cut, is quite linear from about 190 to 525 K. Although this thermometer has excellent resolution, it does exhibit hysteresis and drift. The principle of quartz crystal thermometry is based on the temperature dependence of the piezoelectric resonant frequency of a quartz crystal wafer of a given dimension. The angle of cut of the quartz crystal is selected to give as nearly a linear and yet sensitive correspondence between resonant frequency and temperature as possible. This angle of cut is referred to as an LC (linear coefficient) cut. The temperature sensitivity of the quartz crystal thermometer is about 1000 Hz/°C. 

A number of technology developments can be identified that promise to advance the applications of QCM and related piezoelectric resonance techniques. These involve modifications in the QCM device, the crystal, as well as in the systems under study and their methods of analysis. Some of these approaches have already begun to be studied and implemented. The specific areas of these improvements include increasing mass sensitivity, hybrid devices and novel resonance techniques, enabling determination of the kinetics of processes, use of cells as information-rich sensing elements, and applying data mining techniques to provide accurate analyses and outputs from complex sensor inputs in future devices. We briefly discuss each of these below. 

Thus, efficient decoupler operation is crucial especially at the higher frequencies where certain samples may absorb more power than at the lower frequencies. Sample heating effects for ionic solutions have been discussed by Led and Petersen (1978) and by Bock, et al. (1980) and a more efficient coil design by Alderman and Grant (1979). A key fact to remember is that ionic heating is an electric field effect like the piezoelectric resonance discussed in VI.B.5. so that some sort of an electrostatic shielding as described there should work here, too. 

A second possible cause of spurious ringing which is limited only to some solids is piezoelectric resonance of the sample. (Of course the cause need not be limited to a sample. More on this later.) A piezoelectric crystal has the property that a mechanical deformation of the material takes place in the presence of an electric field. Therefore, an acoustic ringing can be induced in a piezoelectric material located within an NMR probe by the rf electric field associated with the rf magnetic field. Such a ringing due to piezoelectricity has the distinguishing property that it is independent of the applied magnetic field intensity in contrast with the magnetic field induced effect described in the first part of this section. 

Gibson and Raab (1972) found that piezoelectric resonances of the NMR sample can be attenuated in one of two... 

As hinted above, piezoelectric resonance can occur in some probe parts besides the sample so that it could even affect probes for solution NMR. Therefore, if there seems to be a problem with a magnetic field independent spurious ringing, check for possible piezoelectricity of a component in the probe. Remember that quartz is very piezoelectric. In addition to the obvious uses as tubes and whatnot, quartz is also used sometimes as a filler in epoxy. 

Amorphous LiNbOs films made by sol-gel processing were subjected to a series of characterizations [57]. It was found that an amorphous LiNbOs film obtained by heating the gel film at 100°C for 2 h showed P-E hysteresis with remnant polarization Pr = 10 pC/cm2 and coercive field Ec= 110 kV/cm. Electron diffraction of such film showed a diffuse ring pattern characteristic of an amorphous nature. These are shown in Fig. 6 in which the scale for E is 147 kV/cm division and that for P is 5.6 pC/cm2 division. Further measurement showed a pyroelectric coefficient of 8 pC/cm2 K at 28°C. Note that for singlecrystal LiNbOa, Pr = 50 pC/cm2 and the pyroelectric coefficient was reported to be 20 pC/cm2 K [1]. Further, a piezoelectric resonance was observed at similar frequency range for both amorphous and crystalline LiNbOa, characteristic of a ferroelectric material [57]. 

Benes, E. Groschl, M. Burger, W. Schmidt, M. Sensors Based on Piezoelectric Resonators. Sens. Actuators A 1995, 48, 1-21. 

At room temperature the crystals of M(C6H5)4 (M = Si to Pb) are temperature-insensitive insulators having a relative dielectric constant of 10 and an electric resistivity over 10 ° ohm-cm. The electrical-mechanical coupling coefficient parallel to the c axis is 5 to 10%. The crystals exhibit moderately strong piezoelectric resonances [24]. 

Calorimetric/Enthalpimetric Chemically Modified Electrodes Microorganism-Based Photometric Piezoelectric Resonators Tissue-Based. 

See also-. Ion-Selective Electrodes Overview. Process Analysis Sensors. Sensors Amperometric Oxygen Sensors Chemically Modified Electrodes Piezoelectric Resonators. 

Piezoelectric resonators are sensor devices that respond to changes in temperature, pressure, and, most importantly, to changes in the physical properties of... 

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