Thickness Shear Mode Quartz Resonator Research Articles

An acoustic prion assay

An acoustic prion assay has been demonstrated for sheep brain samples. Only five false positives and no false negatives were observed in a test of 45 positive and 45 negative samples. The acoustic prion sensor was constructed using a thickness shear mode quartz resonator coated with a covalently bound recombinant prion protein. The characteristic indicator of a scrapie infected sheep brain sample was an observed shoulder in the frequency decrease in response to a sample.The response of the sensor aligns with a conformational shift in the surface protein and with the propagation mechanism of the disease. This alignment is evident in the response timing and shape, dependence on concentration, cross species behaviour and impact of blood plasma. This alignment is far from sufficient to prove the mechanism of the sensor but it does offer the possibility of a rapid and inexpensive additional tool to explore prion disease.

Characterization of functionally graded elastic materials using a thickness-shear mode quartz resonator

We propose the use of a quartz crystal plate thickness-shear (TSh) mode resonator to measure material property variations in a functionally graded material (FGM). A theoretical analysis is performed on TSh vibrations of an AT-cut quartz plate carrying a layer of an FGM whose density and stiffness vary along its thickness. The effect of the material property gradient on the resonant frequencies of the two-layer plate as a compound resonator is examined. It is shown that this effect may be used to measure the material property gradient of the FGM.

Patterned Electrodes for Thickness Shear Mode Quartz Resonators to Achieve Uniform Mass Sensitivity Distribution

Development of an electrode-modified thickness shear mode (TSM) quartz resonator that is responsive to nanogram mass loadings, while exhibiting a mass sensitivity profile that is independent of material placement on the sensor platform, is the aim of this study. The resulting nanogram balance would greatly enhance the field of mass measurement and become useful in applications such as droplet gravimetry, the study of nonvolatile residue (NVR) contamination in solvents. A ring electrode design predicted by an analytical theory for sensitivity distribution to achieve the desired uniform mass sensitivity distribution is presented in this work. Using a microvalve capable of depositing nanogram droplets of a polymer solution, and a linear stepping stage for radial positioning of these droplets across the sensor platform, measurements of the mass sensitivity distributions were conducted and are presented. The measurements agree well with theory. Further improvements are possible and are identified to achieve better uniformity and to reduce the instability in the resonant frequency of these devices. Additionally, droplet gravimetric results for NVR in methanol droplets using the modified TSM devices are presented, which compare well with determinations made by evaporation of larger volumes of the stock solutions.

Effects of electrodes with continuously varying thickness on energy trapping in thickness-shear mode quartz resonators

We study the effects of electrodes of nonuniform thickness on thickness-shear vibration frequencies and mode shapes of quartz resonators. This paper extends a previous paper from electrodes of stepped thickness to continuously varying thickness. Numerical results for electrodes of linearly varying thickness are presented. The results show that strong energy trapping can be achieved and adjusted using electrodes with variable thickness.

Comparing a 10 MHz thickness–shear mode quartz resonator with a commercial process viscometer in monitoring resol manufacture process

This study deals with the applicability of a 10 MHz piezoelectric thickness–shear mode (TSM) quartz resonator in monitoring of an industrial resol manufacture process. The quartz resonator is compared with a commercial process viscometer. Thirteen process batches were monitored concurrently with the two on-line instruments. At the isothermal phase of the manufacturing process, prior to process cut-off, signals from both measuring devices show measurable change in reaction rate. Correlation between the signals of the two instruments was 0.776. In all batch measurements, but one the resonator’s signal was more linear and/or less disturbed than the viscometer’s signal.

The evaluation of quality of post-harvest oranges and apples by means of an electronic nose

The measure of quality of post-harvest fruits is considered a promising application field for electronic nose technology such as the detection of defects. Among the possible defects present in fruits those due to post-harvest treatment are particularly important. Among them defects like mealiness (due to post-harvest over-ripening), skin damage (due to mechanical or temperature stresses), and infections affect strongly the perception of consumers. They have to be avoided in order to achieve high quality products. In this paper, the study of the variations of aroma of oranges, during the storage, and apples, due to the presence of mealiness and skin damage by means of a thickness shear mode quartz resonators- (TSMR) based electronic nose, is illustrated and discussed. Results have evidenced that the electronic nose has enough sensitivity and resolution to distinguish among the various classes and to correctly predict the amount of defects (for apples) and storage days (for oranges).

Review of thickness-shear mode quartz resonator sensors for temperature and pressure

This work reviews the use of thickness shear mode resonators for temperature sensing and pressure measurement. Advantages of such sensors include inherently digital format, high resolution, high accuracy, and long-term stability. This work reviews the physical principles involved in the operation of the devices along with quoted sensor performance results. The earliest commercially available temperature sensors were stand-alone units. Their use and commercial success evolved through different stages depending in part on ancillary electronics available at the time. A number of temperature-sensing applications are ancillary to other thickness shear resonator sensors. Two main categories are separate resonator for temperature compensation and dual-mode operation of a single thickness shear resonator. Dual-mode oper- ation subdivides into use of two modes from different thickness shear mode families or two modes from the same thickness shear mode family. A variety of pressure sensors use the fact that the frequency of a thickness shear resonator changes with stress bias. Such applica- tions divide conveniently into categories dependent on the pattern of stress bias used.

Monitoring of biofilm growth with thickness-shear mode quartz resonators in different flow and nutrition conditions

Monitoring of microbial biofilm growth with 10 MHz thickness-shear mode (TSM) resonators in aqueous systems with different fluid flow speed and nutrition environments was studied. Biofilm grew even on a polished gold surface of the resonator. Admittance magnitude of the resonator was found to be a robust electrical quantity to monitor, since the pressure shocks generated by the fluid pumps seem to add considerable noise only to resonance frequency. Microbial biofilm growth has not been earlier reported as a function of admittance magnitude of a TSM resonator.

Real-time detection of organic compounds in liquid environments using polymer-coated thickness shear mode quartz resonators

The selection of sensitive coatings is a critical task in the design and implementation of chemical sensors using coated thickness shear mode quartz crystal resonators (QCRs) for detection in liquid environments. This design or selection is performed through a study of the sorption process in terms of the partition coefficients of the analytes in the coatings. The partition coefficient, which is controlled by the chemical and physical properties of the coating materials, determines the inherent selectivity and sensitivity toward analyte molecules. The selection of the coatings is logically determined by the interactions between coating and target analyte molecules, but can also be made through a systematic variation of the coating's properties. The determination of the partition coefficients is only accurate if all contributions to the total measured frequency shifts, deltafs, of the coated QCR can be established. While mass loading is often assumed to be the dominant factor used in determining partition coefficients, viscoelastic effects may also contribute to deltafs. Both the effect of viscoelastic properties and the effect of mass loading on the sensor responses are investigated by using a network analyzer and oscillator circuit and by characterizing the total mechanical impedance of the loaded sensor. Different types of coatings including rubbery and glassy polymers are investigated, and the targeted analytes include classes of polar compounds (methanol), nonpolar compounds (toluene, xylenes), and chlorinated hydrocarbons (trichloroethylene, tetrachloroethylene, etc). It is seen that changes in viscoelastic properties due to analyte sorption may be significant enough to place the sensor in the nongravimetric regime. However, for most applications involving the detection of relatively low concentrations of organic compounds and the use of acoustically thin films, changes in the complex shear modulus of the coatings contribute less than 5% of the total shift in the series resonant frequency, depending on the coating. In that case, the measured deltafs and, hence, the calculated approximate classification and selection of the coatings for operation in a complex solution of water/analyte molecules.

Experimental evidence for mode shape influence on acceleration-induced frequency shifts in quartz resonators

Experimental results are presented to support the hypothesis that the shape and location of the active region of vibration in a thickness shear mode quartz resonator are the dominant factors in determining the acceleration sensitivity of the resonator. The shape and location of the mode in a real world resonator vary sufficiently from unit to unit (due to material and processing variations) that all other considerations are overwhelmed. It is shown experimentally that the mode shape and/or location can be trimmed with energy trapping by judicious addition or subtraction of mass to produce resonators with improved acceleration sensitivity.

Anharmonic Properties of Ultrasounds in Diamond-Type Crystals and Quartz Plate under an Intense Exicitation

The harmonic generation due to the third-order elastic (TOE) constants in germanium and gallium arsenide, and the nonlinear current-jump effect due to the fourth-order elastic constants in a quartz plate have been investigated. The complete TOE constants were determined from the measurement using an optical interferometer and from the values derived from the valence-force field theory. They showed a good agreement with those obtained by other experimental techniques. A phenomenon analogous to the hybride optical bistability was observed in a thickness-shear mode quartz resonator, and this was analyzed in terms of an equivalent nonlinear network.